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    Another Look at Vapor Vacuum (145 Posts)

  • Dave in QCA Dave in QCA @ 12:03 AM
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    Another Look at Vapor Vacuum

    I had originally written this post on another thread on hoffman #2 vents.  However, there seems to be quite a lot of confersation on vacuum systems in the last few days and I thought I'd repost this as it might have gotten lost.

    Thoughts on the Subject of Vapor Vacuum Heating

    Is Vapor Vacuum Only For Coal Firing?


    I think part of the mystery of vapor / vacuum has to do with coal firing, how it worked and how it was regulated. Coal burning in a boiler or a furnace with reasonable good quality draft and check dampers did not burn uncontrolled like wood or coal in a fireplace. While some of us are familiar with how wood can be controlled in an airtight stove, coal is much more easy to regulate, especially after the initial gassing period when all that is left is a glowing pile of carbon. The draft can be shut down and the burning coal will nearly extinguish, producing little usable heat at all. It may appear as if the fire has gone out, but a small core of burning coal will remain in the center. A fire can be held like this for quite a period of time, 30 minutes to several hours. When the draft is thrown open, within a few minutes, the entire mound of coals will again glowing bright red with red - blue flames licking up out of it. A coal furnace, stove, or boiler can essentially be turned off and on by the movement of the draft.

    Dunham actually shows diagrams of electrical control of coal-fired steam boilers where a room thermostat operated a damper motor, connected to the both the draft and check dampers by little chains. This would allow completely automatic control of the firing of the boiler and would produce steam cycles not unlike what we see today on gas or oil fired boilers.

    On most other vapor systems, I see special controls that operate off of very low pressures, say 8 ounces or below. Some of these systems describe that steam is maintained in the mains at all time and the regulation of heat in the building is via the proportional radiator valves. Thus, if it were mild outside, the rad valves would be mostly closed, or perhaps all closed. This would cause the boiler firing to adjust down to a very low point, that held a few ounces of steam pressure in a static condition.

    Even in these types of automatic damper control, there is the ability for manual adjustment that would turn down the draft and let pressures drop.

    Steam vs Hot Water vs Vapor/Vacuum

    In the time around 1890 - 1900, the options for quality heating were pretty much between steam and hot-water. Steam had the reputation of being noisy, hard to regulate, annoying vents, and in many cases, the heat was on too much of the time. When the steam went down, the radiators cooled quickly, resulting in the feeling that the heat was off, and a phenomenon known as "cold 70". Thus, the on/off character of steam was seen as undesirable. Hot water was mild and even. But the downfall of water was that it was slow. If you let the space cool down, it took a long time to get the system warmed up and even longer to get the space warmed up. The radiators were also out of necessity, quite large, and the initial cost of installation was high. And so, the battles between cheap hard to control steam and expensive comfortable hot water waged on.

    Then, around 1905, someone realized that if you let a steam system fall into vacuum, you could boil water at a lower temperature, the steam would not be as hot and the same for the radiators. With the ability to modulate the temperature of steam, a vapor / vacuum system could mimic the operation of a hot water system, with its inherent ability to produce modulating radiator temperatures. Also, since many vapor systems operated with a separate return line, there was no need to have a hissing vent in your bedroom or living room. Since the temperature of steam could be reduced, the piping losses to unheated spaces were reduced as well. Most importantly, it seems that vapor/vacuum operation provided a much better ability to control the delivery of heat to the space and thereby prevent overheating and wasted fuel. The ability to improve distribution meant the the heated space was much more balanced, and this too prevented overheating of individual rooms and the waste of fuel. And, in addition, unlike slow hot water systems, vacuum/vapor could be up to temperature and steaming in a matter of minutes.

    Many Vapor Vacuum systems and components were invented by numerous engineering companies and they flooded the market. It must have seemed like a modern miracle, that steam heat, which had the public misconception of high pressures and danger could actually operate under a vacuum and cooler than the temperature of boiling water! WOW! A Modern Miracle!

    Now, 60 years after most coal boilers were taken out of service or converted to natural gas and oil, we find ourselves in a time where we wonder about the knowledge of the dead men. Dan Holohan has done an amazing job of learning what the dead men knew and of compiling about every piece of published information on the subject of steam heat that ever existed. He has put it all together into a packaged form that makes it easy to understand, and it's organized at our fingertips. Absolutely Amazing! I cannot begin to explain the importance of his work,not only in the present, but even more so in the future.

    But, there is something that gnaws at my curiosity, and it will continue to do so until I am able to experiment on my own, make observations and tabulate findings. This is on the subject of Vapor Vacuum. I know that Dan does not make stuff up, and neither to the knowledgeable pros, who contribute so much to this site. But here is the reason that I am skeptical about the accuracy of the statement, Vapor/vacuum is for coal only". It seems to be an accepted truth. But, Dunham very clearly stated that their vapor vacuum systems were good for any kind of firing, whether coal, oil, or gas. A number of other vapor/vacuum equipment producers said the same thing. Were they wrong? Were they lying? I doubt it. Was the idea that vacuum operation would save money, just an elaborate marketing hoax? I don't think so, it sounds to logical.

    So, where did "vacuum is for coal" come from? I know that Dan doesn't make stuff up because I have accidentally found a number of his citations and specific information in other old and hard to find publications. Some of them I found in the Heating Help library and others in Google Books or other places. The thing that is missing, or at least that I have been unable to find, is factual justification of the statement "vapor vacuum is only for coal." But, I have found one statement to this effect. It is not substantiated, and no explanation is given as to why. But, in the Hoffman Specialty vent selection guidelines it states,
    "Determine if the vent is to be installed in a vacuum system. The Model 76 Main Vent is for vacuum service.
    It should be used on systems with a vacuum pump or a vapor system with a coal or wood fired boiler.
    Systems converted from coal or wood fired to oil or gas should use non-vacuum vents such as the Model 75."
    Perhaps this is the source of the commonly accepted truism? I don't really know, but it's the only source I have been able to find.

    So, if this is the source of this directive, why would they say it? Perhaps, they thought that with very precise thermostatic controls that were now available, combined with the use of the #75 main vent and #40 radiator vent, that they felt that very even delivery of steam throughout the system was now possible, even on a very short steam cycle in moderate weather where only one or two sections of a 15 section radiator would heat. Perhaps, because they were so confident in their vents combined with good thermostatic controls, that they thought temperature control would be perfectly acceptable. If that is what they were thinking, they were pretty much correct. And since fuel was so cheap back in those days when the conversions were taking place, the added economy of keeping the vapor vacuum system in good operation seemed unimportant, and things could be simplified by forgetting about vacuum altogether.

    Am I right? I don't know. Maybe? Maybe not! But, over the next year or two, I'm going to give it a good try, and I'm going to get my 1909 Dunham system to operate in a vacuum and see how it works.

    Assuming that my guesses as to why Hoffman made the statements that Vacuum doesn't run on gas or oil unless there is a vacuum pump are right. I have to remember that much of the savings produced by vapor/vacuum operation were because of good control of the heat and the elimination of waste. But, there are a few other factors that are left on the table.

    When steam operates at 212, every time steam comes up, it has to raise the distribution piping to 212F. Even on insulated piping, the losses of pipes at 212 are going to higher than losses at 180F. The efficiency of the boiler, boiling water at 212 is going to be very slightly less than boiling water at 180F. And then, there is the whole venting thing. So much effort goes into getting the air out of the system as fast as possible to that the steam can travel around unimpeded. Then when the boiler shuts off, we want to relieve the vacuum as fast as possible and get that air back in there... and we do it as fast as possible. Every time the air comes in, we just have to take it out again. Every time that atmosphere comes in contact with water, it oxygenates it and causes corrosion. The CO2 in the air also forms a very week dilute amounts of carbonic acid, that causes corrosion in the wet piping. Why are we so eager for this to occur? Why not have vapor vacuum with gas and oil?

    Greening Steam

    It seems to me, that we may wait along time for the boiler companies to give us what we want in the form of 3 pass gas fired boilers with all heating surfaces below the water line, and so many other improvements that would improve the economies of steam heat. These things should be done, and will be done, but when, is the major question. In the mean time, it appears to me that vapor/vacuum is worth another look. We know we're not going to find 45% savings like some of the old brochures stated. We have probably got most of that just by having better controls. But, we don't have all of the savings that vacuum operation can provide, and it seems to me like it would make good sense to go after it.

    We've got some pretty darned smart pros on this site, and of course Dan ain't chopped liver either! These people are the leading minds in American steam heat today. Look at what has been accomplished in new advancements such as dropped headers, steam mini-tube, maximized venting, actual tabulated flow capacities of dozens of vents, main vents, and traps. etc.

    I accept that my thinking on this subject may be all wrong, and there is not one penny to be gained. I also accept the possibility that more study and thinking on the subject is in order. And who better to do it than all of the people who contribute to this site and work on steam heat.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
    This post was edited by an admin on January 18, 2012 12:17 AM.
  • Rod Rod @ 1:53 AM
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    Vapor Vacuuum

    Hi Dave- Thanks for taking the time to outline the vacuum steam situation.   The statement that vapor vacuum is only good for coal firing is correct as only wood/coal through control of the draft is the only firing method at the residential level that is capable (at this moment) of being modulated. At the present time gas and oil burners for the most part are similar to military flamethrowers, that is ,either fully  ON  or OFF. To replicate the coal wood burner what is needed is a fully modulating burner in both oil and gas along with a control system that works on both temperature and pressure. You would also need a control system that would use both steam pressure and temperature and outdoor reset.
    Due to the small steam market , the complexity of setting up the controls and the fact that you are trying to incorporate this into present systems, a lot of which are old enough to collect social security,  I’m afraid I don’t see this happening.

    From what I can see vacuum has two distinct benefits. One is the rapid distribution of steam and two is  using vacuum’s lower temperature advantages to produce steam.  At this moment  using vacuum for quicker steam distribution is probably the most doable/ practical application.  Developing a vacuum /variable low temperature steam system might be more practical if it was applied to  Gerry Gill’s wonderful mini tube system though it seems to work well enough just as it is.  Gerry, If you are reading this,  have you ever considered incorporating vacuum into your system?

    Long Beach Ed recently mentioned using a taco pump and a venturi to create a vacuum. I hadn’t heard of this before and I think it has great possibilities. It’s quiet , relatively cheap and other than the pump, has few moving parts. Using a variable or two speed pump you could raise and lower the vacuum as desired.
    Carlin  was supposed to be working on a 2 stage burner that could be used in smaller residential but I haven’t heard anything on that in a while. Maybe with the cost of fuel beginning to rise again we will see something develop.
    - Rod
  • Dave in QCA Dave in QCA @ 11:07 AM
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    Modulating Burners

    Rod, Modulating burners would be a great advancement.  I think that Powerflame has a high turn-down model, but it may be a bit large for most residential applications.  It seems to me that Carlin has a modulation gas burner as well. 

    In my understanding of vapor / vacuum systems, (which may be flawed) a modulating burner would bring great advantage, but is not necessarily required.  Dunham described their system as working perfectly well with on/off firing of oil and gas burners, and that the benefits of the manner in which the system operated would reduce the on/off heating characteristics of the system to which it (vapor/vacuum) was applied.

    One description of the operation of a Vapor Vacuum system, written by Alfred King, goes as follows. First, the system is brought up to full temperature at which point all of the mains and radiators are fully charged with steam and all of the air has been exhausted.  At this point, all vents are closed and steam is moving throughout the system, from the boiler to the radiators where it is being condensed.  The pressure of the boiler and piping is say, as an example, 8 oz., the system is in equilibrium with steam flowing throughout and condensate flowing back to the boiler.  Then the fire is cut off.  Boiling slows, but does not cease, as the radiators are still condensing, drawing steam from the boiler.  The 8oz pressure drops into the vacuum range and even though no heat is being applied to the boiler, it continues to boil and vapor is produced. (Because the pressure has dropped)  Vacuum essentially links the radiators to the boiler, through the link of the vapor in a sealed system.  As the temperature falls because heat is given off at the radiators, they draw more vapor to them, deepening the vacuum and further lowering the boiling point of the water in the boiler.   Thus, the temperature of the radiators, the vapor, and the water in the boiler continue to cool at the same rate, with mild boiling in the boiler and flow of vapor all the while.   (Remember, this is all happening with NO fire.)  King further describes that at a temperature of around 150F, flow of vapor will cease.  ( This no doubt corresponds to the completeness of the vacuum drawn.) 
    After a period of time, if the boiler fires again, vapor will begin to flow throughout the system almost immediately.  If some amount of time has elapsed, the temperature of the boiler must first be raised to the point where vapor production ceased, (150F was the example)  Now, with vapor flowing at a vacuum condition, heat is again being delivered to the radiators.  As the temperature of the radiators and the rest of the system is slowly increased, the strength of the vacuum is decreased, i.e.,( pressure increases), and as this occurs the boiling temperature of the water in the boiler increases. 

    Thus, when heat is applied to the boiler setting in vacuum, vapor begins to flow and the temperature of the entire system climbs at the same time.    The boiling temperature in the boiler is dependent on the pressure or vacuum.  The only way you can raise the boiling point is to reduce the vacuum.  The only way you can reduce the vacuum is the increase the temperature of the entire system. 

    So, it seems quite likely that in a mild weather condition, a boiler setting in 22 in Hg vacuum, when fire is applied will begin to boil at about 150F and vapor will flow throughout the system.  As the temperature of the system climbs, vacuum decreases, etc., etc., the firing cycle, it is plausible to think that the system may come up to a temperature of 180 or 190 in 15 minutes, at which time the thermostat may be satisfied.  The fire shuts off, and the cycle repeats, all running at temperatures much lower than conventional steam. 

    Now, if we had a fully modulating burner, it could be possible to modulate that firing rate down to more closely match the heating load of the building and thus allow continuous, or nearly continuous firing of the boiler and and flow of sub-atmospheric vapor.  However, constant state operation is not necessary according to the "Vacuum" Dead Men.

    I have paraphrased quite a bit, but this my understanding of the operating of vapor/vacuum heat as King described it ca. 1905-1908.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • twopipe twopipe @ 8:55 AM
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    vapor on gas system

    I have a 1908 Webster two-pipe system in my house and over the last year I restored it to operate as a vapor-vacuum system as it was originally designed.  The system was originally coal, then oil, and now it has a modern Burnham gas boiler.  This was actually gainst the advice of my heating guy but I'm an engineer and based on discussion on this board last year I couldn't figure out why the recommendation to avoid vacuum made sense.  And I had to replace the traps and fix leaks anyway, so as long as it was being restored why not give it a try?
    So last winter it mostly ran at atmosphere as is the conventional recommendation, and this year it is being run as a vapor-vacuum system.  Had to replace some leaky return lines (these were mostly okay under atmosphere operation but they had noticable leaks under vacuum) and replace the small vacuum ball valve- there is no vacuum pump. 
    As a vapor-vacuum system it runs very quietly and evenly.  When firing it builds up an ounce or two of pressure, and then when the boiler stops firing it drops down about 16-20oz of vacuum (if my gauge is accurate).   The system maintains vacuum from cycle to cycle, and therefore the venting is typically quite short- just a few seconds.  Steam also seems to come up faster, probably because the water starts boiling faster under vacuum and there is less resistance to its movement in the pipe.  The only thing I noticed is that I have time my weekly cleanout of the LWCO to be during a firing cycle, otherwise the vacuum just pulls air into the system.
    I really see no negatives to operating this way- the system runs great and my house is very comfortable.  As for positives- I'll have to wait until the end of the season to see how the heating bills compare with last year.
  • Dave in QCA Dave in QCA @ 11:15 AM
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    U Hah!

    I knew it!  I suspected that there were others out there, secretly operating vapor - vacuum systems, in spite all advice to the contrary.

    Your observation of having to blow down your LWCO while the system is operating at pressure is to be expected, and it is also a good double check because it lets you confirm that the device actually shut the burner down as it's supposed to.

    I'd like to know more about your system.  Have you experimented with running up a higher cycle of steam... fully heating up all of the radiators, etc., and seeing if that produce a greater vacuum?  Maybe that is the way your system operates anyway.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • twopipe twopipe @ 9:59 PM
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    Some more on my system

    I have been running this way all winter so, yes, it has run on days where the boiler fires for a long cycle. The vacuum never goes above 2lbs- not sure why or what it is supposed to get to on the system. The ball valve that is used as a check valve is probably not perfect, and the sytem probably has small leaks somewhere.

    But i am not sure it matters, the objective is to keep the steam from condensing a little while longer so that the latent heat in the steam gets to the radiators inatead of the pipes. Dropping the boiling point by a couple of degrees gives it quite a while at the speeds the steam is moving. So not sure that a higher vacuum would really bring much more benefit.


    One thing i did do was change the setting on my thermostat from "gravity return" to "hot water" which increases the allowable cycles per hour. By allowing more frequent cycling the vacuum is maintained.
  • Dave in QCA Dave in QCA @ 10:20 PM
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    And the dead men said ?

    I recall many descriptions of vapor vacuum claiming that it had all of the benefits of hot water and all of the benefits of steam, combined together.  So, since even at a mild vacuum, you are able to distribute steam very quickly when the boiler starts to fire, a hot water setting seems reasonable.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • Enreynolds Enreynolds @ 1:02 PM
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    I think

    that we are not comparing apples to apple here.  Vacuum on a one pipe steam system is totally different than on a two pipe system, and need to be considered separately
    Consider, if you will, a two pipe system complete with vacuum air vents, and of course, a tight system.  On the first firing of the system, all of the air is purged from the steam carrying pipes and radiators.  The returns will still have some air in them as is normal.  Now the boiler shuts down, and vacuum begins to form as the steam condenses, causing the boiling point of the water in the boiler to lower.  Thus the boiler continues to create steam, even though the burner is now off.  This steam continues to create the pressure differential to move the steam to the lower pressure areas of the system, namely the radiators.  Once the system creates an equilibrium temp/vacuum pressure, steam creation ceases, and stays in a vacuum state. End of first cycle.
    Now we move on to the next cycle.  Burner starts, and boiler water begins to heat.  Steam begins to form earlier because of the vacuum and starts to move toward the lower pressure  radiators.  Steam moves faster now, because it does not have to push the air out of the way, out of the vents. The system will cycle up to its normal operating pressure, meet the thermostats call for heat and repeat.  Cycle after cycle.
    Changing the system pressure in a two pipe system should not vary the distribution characteristics of the system, but might uncover some flaws.
    I am planning on replacing the crossover traps in our Webster system, and experimenting with returning it to its original vapor/vacuum glory, and hopefully enjoying some reduced heating costs.  We will see.
  • Dave in QCA Dave in QCA @ 2:11 PM
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    Exactly where I am

    En, you successfully described what I was also trying to describe, but somehow you used about 1/10th of the words that I used.  

    I too am just getting ready to remove my main vents and install crossover traps to the return piping.  Next, I'll remove the condensate return pump and reconnect for a gravity return.  I plan on venting everything through a main vent point on the return piping.  Since I am controlling with a vaporstat, an air eliminator or return trap is not necessary and they were removed from the system and discarded long ago.  I Just need a check device and am planning on simly using a 1/2" or 3/4" swing check valve.   Dunham showed this configuration in one of their drawings.   Also, Dunham showed an equalizer between the steam main and the return piping, with a check valve allowing flow from the returns to the steam main.  This would have allowed a fast transfer of the vacuum to the return piping alleviating any tendancy for condensate to be pulled backwards as the steam mains and rads pull a vacuum.

    Keep us informated of your progress and results.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
    This post was edited by an admin on January 18, 2012 2:38 PM.
  • Enreynolds Enreynolds @ 2:48 PM
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    Just ordered

    Four Watson McDaniel F&T traps for the crossovers, should be here by the 20th.  I am looking at a little more high tech check valve for the system from [u][size=8][color=#0066cc]www.fcgilbert.com[/size][/color][/u].  Their Series 200 has a cracking pressure of 1.6 oz (.1 PSI), and boasts 0 leakage.  Waiting for a call right now as to pricing.
  • Dave in QCA Dave in QCA @ 2:59 PM
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    Using Mepco 1E

    I happen to have 3 Mepco 1E straight configured traps that I am going to use.  I actaully removed one antler of 2 Gorton #2 and intalled one 1E venting to the room.  It is actually venting much better than the Gortons were because of the fact that my mains retain enough warmth so that the Gorton does not fully open on any cycle except a cold start.  

    Let me know how you make out with that super check. 
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • twopipe twopipe @ 4:46 PM
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    vaporstat with vapor-steam

    I've thought about using a vaporstat with my vapor-vacuum system but I can't quite figure if it would work.  What do I set the cut-in and cutout pressures to be?  Will the vaporstat cut in if the system is pulling vacuum?  The pressure drops pretty fast when the boiler stops firing, so not sure if it would just be cycling on and off very quickly. 
  • Dave in QCA Dave in QCA @ 5:27 PM
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    vapor stat

    Remember, a vapor stat is a limit device.  It won't make your boiler do anything by itself.  Just like a pressure stat shut the fire off if the pressure exceeds the cut out pressure, the same is true for a vapor stat.  The only difference is that the vapor stat is intended for a much lower pressure range.

    I set my vapor stat at 10 oz.  I sized my inlet orifices that I installed on all of the radiators for 8 oz operation.  My boiler is down-fired, but still greatly over sized, so I let the pressure climb up to 10 oz.  If the pressure exceeds 10 oz, it will cut out the burner until it drops to 6 oz. (the cut-in) and the vapor stat allows the boiler to fire.  If the thermostat had ended its call for heat, the vapor-stat will not make the boiler fire.  If the boiler falls into a vacuum after firing, the vapor-stat is not effected and has not effect on the boiler.  Vacuum does not hurt the vapor stat and the vapor stat will not "make" the boiler fire.

    It is similar in operation to any other limit device.  For example, think of a low water cut out.  If the water level goes to low, it will shut off the boiler if it is firing and/or prevent the boiler from firing until the water level is bought back to normal.  However, the LWCO does not force the boiler to fire just because the water level is correct.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • twopipe twopipe @ 4:46 PM
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    vaporstat with vapor-steam

    I've thought about using a vaporstat with my vapor-vacuum system but I can't quite figure if it would work.  What do I set the cut-in and cutout pressures to be?  Will the vaporstat cut in if the system is pulling vacuum?  The pressure drops pretty fast when the boiler stops firing, so not sure if it would just be cycling on and off very quickly. 
  • twopipe twopipe @ 4:46 PM
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    vaporstat with vapor-steam

    I've thought about using a vaporstat with my vapor-vacuum system but I can't quite figure if it would work.  What do I set the cut-in and cutout pressures to be?  Will the vaporstat cut in if the system is pulling vacuum?  The pressure drops pretty fast when the boiler stops firing, so not sure if it would just be cycling on and off very quickly. 
  • Enreynolds Enreynolds @ 3:10 PM
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    So It looks like

    There  may be a glut of Gorton #2 s on the barter page soon?!?
  • Dave in QCA Dave in QCA @ 5:29 PM
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    Two steps forward, one step back.

    Yes, I hate to undo "improvements" that I have already made and that have cost good money, but....    I will have 4 spare Gortons, 2 Hoffman 75s and a handful of Heattimer varivales that I had installed as riser vents.  They won't do me much good setting on the shelf!      I'd like to get something out of them.  Ebay can be a good place for such items as well.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
    This post was edited by an admin on January 18, 2012 5:32 PM.
  • ttekushan ttekushan @ 8:15 PM
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    Vacuum experiments

    The only setting I had at my disposal in the past for experimenting with vacuum was in an old building with store fronts and 2 floors of apartments above.  The boiler room was in a sub basement on one side of the building, feeding a long main with three drip stations, each station being at a transition in the elevation of the main.  I rented a store in the middle of the line and had one of the drips in my basement.  I had access to the boiler room and to my own basement only, so anything done had to be in one of those spaces.  Anyway, it was a basic two-pipe system with traps at the drip stations with one dry return, gravity return.  [We took the system back to gravity when the boiler feed pump failed]

    So it was a long, linear system with a significant time delay between heating of the tail end versus the beginning.  The room temp diff from one end to the other was about 7 or 8 degrees F if I recall correctly.  Noteworthy was the delay in the steam getting past the "hump" at the drip station in my basement.

    The purpose of the experiment was to see if I could even out the steam distribution and speed the pick-up time given that the boiler was slightly undersized.

    Enter SHOP VAC and hoffman 76's vacuum main vents.  Now, this system was NOT tight by any means (valve packings mostly) but I couldn't control that.  Therefore, the vac did not run all the time the boiler was running, but only triggered by a thermal switch somewhere along the main and operated on an adjustable time delay relay.

    The thermal switch was located in my basement on an uninsulated radiator riser.  The boiler would fire, begin producing steam, and when the steam made its way part way down the main, the shop vac (attached below the return vent through a swing check) would turn on.  The boiling at the boiler became audibly vigorous, and the steam would now charge its way down the rest of the main and up the risers.  The timer was adjusted to allow the vac to run long enough for a section or two of each radiator to heat. 

    This was quite instructive as it proved that the balance of the system was maintained in the absence of vacuum, so long as each radiator started condensing at the same time.  I think this is the key to the Paul system as it both does some of the "pick up" work and gets all the radiators on equal footing early in the cycle.

    Once the boiler shut off, a mild vacuum (maybe 2" Hg)  would develop for long enough to cool the boiler some.  A further evening out of the room temps would occur at this time.  The temperature differential from coolest to warmest dropped to 1.5 to 2 degrees F.

    The experiment proved three things:  1)  That vacuum return evens out temperatures, 2) Vacuum return shortens the "pick up" time required and total boiler run time, 3) The building temp could be dropped a bit since no one was cold anymore, and 4) I wanted to learn a lot more about vacuum (including both naturally induced and subatmospheric) operation of steam systems.

    ===

    In the absence of a vacuum pump, it seems to me that the system would have to be pretty tight for naturally induced vacuum to produce even temperatures as running the system to saturation (all rads filled with steam) to get the vacuum initiated.

    So this brings me to an idea that I had regarding Gerry Gill's mini tube steam system (I'll cross post this to that thread when I get a chance):  What if we introduce a pressure vessel akin to a reservoir tank whose sole function is not to collect condensate but to be an air/vacuum moderating chamber, say, large enough to limit the depth of the naturally induced vacuum created by the system without readmitting any air.  At this point we may be able to achieve a system with hermetic characteristics and the benefits thereof.  I would really like to not have to blow down a boiler anymore!
    terry
  • Dave in QCA Dave in QCA @ 9:14 PM
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    AMAZING!

    It is absolutely amazing that you were able to achieve such amazing results with a relatively low level of vacuum, produced by a shop vac no less!
    WOW
    Thanks for posting this!
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • Abracadabra Abracadabra @ 11:41 PM
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    shop vac

    uhm.. wow... just wow..





    This is making me itch to throw a vacuum pump/shop vac on a building with a cold stack of 3 apartments.  I think if I could get steam there quicker, I'd make a bunch of people happy.
  • jumper jumper @ 2:26 PM
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    stuff

    >>Many Vapor Vacuum systems and components were invented by numerous engineering companies and they flooded the market. It must have seemed like a modern miracle, that steam heat, which had the public misconception of high pressures and danger could actually operate under a vacuum and cooler than the temperature of boiling water! WOW! A Modern Miracle!
  • PMJ PMJ @ 6:30 PM
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    Vapor/Vacuum

    Not just for coal.
    I have been running my 1926 2 pipe gas system with vacuum for about 10 years. It fires on and off from one main wall thermostat like any residential system. I removed all the radiator vents and have only a 1oz check valve vent on the main return line. Water boils for about 4 minutes after the burner goes off and the vacuum works up to about 20-30"H20 between cycles as the steam collapses. Of course boiling starts much more quickly when the burner fires again because of the vacuum. There was really no change to the steam distribution throughout the house except that it gets there faster. All radiators heat just as evenly as before if not more so.
     I have been in the house 20 years and my experience has been that the biggest problem with steam is the time lag from the call for heat to the satisfaction at the thermostat  and that causes too much overshooting. I smoothed this out by installing a simple PLC that spreads out the boiler run/off times and gives the warming radiators time to put heat in the room. In other words even though there is a continuous call for heat the PLC is cycling the boiler and will not let it run flat out. The PLC monitors the total call time and gradually increases the %on vs %off time of the cycles until temperature is reached. It also monitors total time off with no call and runs the burner longer on 1st start up when necessary. I do not ever remember walking by the thermostat and not seeing it exactly on target.   Love this system. You couldn't convince me to go back to letting all that air back in every cycle.
    This post was edited by an admin on January 21, 2012 8:20 AM.
  • Ban Ban @ 6:10 PM
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    PLC

    What is the PLC that you used?
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
  • vaporvac vaporvac @ 8:33 PM
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    Trand VaporVac for Gas

    Hello everyone,
    First time back for this heating season and thought I'd pipe in with my 2 cents.  My house has a Trane vacuum system that was originally installed for GAS in 1914.  There was a coal furnace, but this was installed as a back-up as apparently gas was not always reliably available back then.  I have the original specs to the house which called for a gas furnace and states that the coal was for back-up and to be installed at the owner's extra expense, and have spoken with the owner's sons many years ago, and they verified that gas was original.  It also states in the original manual that it was good for both gas and coal. So it seems apparent that this was the case for at least The Trane system.
    Although my furnace needs replacing, (see post to come), it still holds a vacuum of a few inches.  I hope this will improve with a new non-leaky boiler and a little TLC
    BTW, the old coal burner (The Behemoth) still has the "Iron Fireman" that kept it automatically filled and stoked as described by Dave. There's even an on/off switch that glowed red when turned on.  It was years before we figured out that mystery switch!
    Hopes this helps move this thread forward.  Thanks for everyone's help last year.  Unfortunately, I don't think there's any chance to make it completely through this season.  Oh, well.
    Cheers,
    Colleen
  • jumper jumper @ 1:13 PM
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    intelligent control

    Any intelligent controller like PMJ's with variable (modulating) input will improve any heating or cooling system.

    >>Many Vapor Vacuum systems and components were invented by numerous engineering companies and they flooded the market.
  • jumper jumper @ 1:14 PM
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    intelligent control

    Any intelligent controller like PMJ's with variable (modulating) input will improve any heating or cooling system.

    "Many Vapor Vacuum systems and components were invented by numerous engineering companies and they flooded the market."

    Salesmen pushed too many "steam heat improving" components. Expensive to maintain and kills the cost and simplicity advantage of steam over hot water.
  • elfie elfie @ 2:01 PM
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    vacuum pump needed?

    in an low pressure trapless/ventless radiator system with only a condensate receiver vent (ie. the only air vent in the system), it seems that installing a check valve on the vent pipe would at least eliminate the reentry of air back into system

    consequently, it becomes a closed system (assuming no pipe joint leaks, etc)

    and addition of a vacuum pump increases rate of air elimination in the system which may be of benefit (and would depend on effectiveness of the checked condensate receiver air vent)

    a fascinating thread
  • PMJ PMJ @ 5:38 PM
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    Vapor/vacuum

    Just  couple other items for those interested:

    In addition to the very low cracking pressure check valve on the main return I added an  electric solenoid valve which the PLC opens after a preset time (to make sure the benefit of the vacuum is gone) so that the return is wide open to the atmosphere dropping back pressure in the main to a minimum. This valve closes when the burner cycles off to build the vacuum again. I am planning to add one of these valves at the other far end of the system as I am sure there is some back pressure there as far away from the current main relief as it is.

    Even though this system is now 85 years old I had no trouble making it tight enough. The only leaks I found were at the radiator valves and all are still original (you know the ones with the wood handles) and I could hear the air going in on the leaky ones. A little tightening did the trick. I am sure new ones would be even tighter but the max benefit of the vacuum is during the cold periods with more frequent cycles anyway and I will see at least -20" H20 hold through 10 minute off cycles.

    It is really cool right after the burner fires and there is a full boil going (like one minute in) but still significant vacuum in the system to open a valve somewhere on the return and hear the boiling stop completely in an instant. The Dead Men really knew what they were doing.

    In my opinion the natural vacuum system is significantly more efficient and quieter with dramatically better temperature control.
  • Dave in QCA Dave in QCA @ 6:15 PM
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    clarification

    I thought I would ask for some clarification of your vacuum terms.  Did you mean inches of H2O?  Vacuum is usually measured in inches of Hg  (inches of Mercury).  Most compound boiler gauges read from minus 30' Hg to plus 30 psi.   I was wondering because pulling 20" Hg is a pretty strong vacuum, but 20" H2O -- not so much. 
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • PMJ PMJ @ 6:22 PM
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    Vacuum terms

    Dave,

    Yes, I mean inches of water and you are right it is not so much. At most I see -40inches between cycles on the coldest days. I think to get really tight all those old valves would have to go. Even at these relatively low vacuum levels the effect is rather dramatic.
  • Dave in QCA Dave in QCA @ 6:56 PM
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    very interesting

    So you have a little less than 2" Hg. A pretty mild vacuum.  It is interesting to know that your observations are that it greatly improves the operation of your system.

    I suspect that tightening your valve packing will to as much as anything, even as much as putting in new valves.  I have experienced new valves on hot water systems that become leaking in a couple of years.  Tightening the valve packing or adding a little bit more packing is an ongoing maintenance issue 
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • Ban Ban @ 4:30 PM
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    Using a solenoid

    in place of the Dunham 222 Air Eliminator air check. I was thinking I could replace the air check with a 24V DC, normally closed solenoid that would be wired to the burners or the damper. The idea would be that when the system turns on the solenoid would open and allow for maximum venting out of the AE 222; much more than the original design with only 5 holes. When the thermostat is satisfied and the system shuts down the solenoid would also close to its natural position and it would start to go into a vacuum. What are your thoughts? Any concerns?
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
  • Dave in QCA Dave in QCA @ 4:45 PM
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    PMJ is doing that

    But, don't wire it up the way you have described because it will open when there is still vacuum in the system and you don't want that.  Read the post from  PMJ February 17, 2012 @ 6:45 PM.

    Also, have you tried to get an accurate measurement of the opening diameter of the cap on your present 222 air check?  I have found a person who is making the discs for the Trane vents with similar air checks.  Maybe they are even exactly the same....   But, I suspect that he might be willing to make the discs for a much lower figure than it would cost at a machine shop.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • PMJ PMJ @ 6:45 PM
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    Using solenoid

    Dave is right - you don't want to kill the vacuum at the start of the cycle. I got a pressure switch that I have set to switch at about a quarter of an oz. I have it plumbed on the dry return right next to the solenoid valve. It opens the solenoid at the exact moment that the vacuum is gone and the return just starts to show pressure. Mine goes thru my PLC so I can see it on the computer but that is not necessary - you can just wire it direct.
    One other caution - I also have a mechanical check valve in parallel with the solenoid just in case it fails. If it did the system would be completely closed - wouldn't want that. The reason I don't just go with the mechanical one is that I can't find one with a cracking pressure less than 2-3 ounces. Why even that much pressure in the dry return.
  • jumper jumper @ 8:35 PM
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    sealing

    Air can diffuse through a water tight pipe joint. Any one you can get at should be gooped.
    Same with valve stems. Instead of cranking down on packing nut.

    If you can keep out air any condensate that doesn't drain will evaporate. So ideally no vent at all. If your radiators require traps, orifice is simplest.
  • vaporvac vaporvac @ 9:17 PM
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    Upping the vacuum

    Wow! If I'm reading this correctly, I should really see some major improvement in my vacuum when I get a new boiler that doesn't leak like a sieve. I'm currently getting at least 2" of mercury.  What other measures might one take to improve it further.  I don't have traps, mbut never found any evidence of orifices either.  I'd appreciate any input.
    Colleen
  • twopipe twopipe @ 10:18 PM
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    Finding leaks

    The best way to find out where your system leaks is to hook up to ain air compressor (when boiler not running of course) and pump the system up to 15psi or so. You'll hear and see where it leaks. That was hot i got my system fixed to run under vacuum.

    Some leaks are acceptable. You really just need the system to hold a reasonable vacuum between cycles on a typical cold day- it doesnt need to be perfect. If it can hold 10-15psi for 20 min under pressure you are probably fine Under vacuum.
  • vaporvac vaporvac @ 9:17 PM
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    Upping the vacuum

    Wow! If I'm reading this correctly, I should really see some major improvement in my vacuum when I get a new boiler that doesn't leak like a sieve. I'm currently getting at least 2" of mercury.  What other measures might one take to improve it further.  I don't have traps, mbut never found any evidence of orifices either.  I'd appreciate any input.
    Colleen
  • nicholas bonham-carter nicholas bonham-carter @ 8:13 AM
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    Green with envy

    Now I wish I had 2-pipes instead of 1-pipe!
    Colleen, how about reposting in another thread. You must have some sort of limit on your rads to admit only a portion of the steam into the rad--pictures?
    Dan what about a subcategory here for vacuum steam. Maybe if the steam only were at the top, we would not have so many steam postings on the Wall.--NBC
  • jumper jumper @ 1:26 PM
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    one pipe vacuum

    You can make a one pipe system work under negative pressure as well.
    See the recent threat on Paul conversion.
  • nz nz @ 11:41 AM
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    How to convert...

    So...assuming I wanted to convert my two-pipe Dunham Vapor system to vapor/vacuum in the future...I should:

    1. Fix my leaky packless valves (see my latest post regarding repair/replace)
    2. Fix all my traps (I'm about 50% of the way through this project)
    3. Replace my boiler room return vents (the only ones in the house) with Hoffman 76s?
    4. Add a vacuum gauge

    Is it really this easy?
  • Dave in QCA Dave in QCA @ 12:54 PM
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    That is pretty much it

    Nick, you pretty much got it.
    1., yes your valves have to be totally tight.  If you hear or see any seepage, you won't hold a vacuum more than a few minutes.
    2.  yes, traps need to be working for any operation.
    3.  Yes, replace the vent on the return line with something that does not let air back in.  Hoffman used a combination air eliminator and air check.  The air eliminator had a float in it that closed the vent port if the water level got up to the height of the air eliminator in the return line.  The air check let air go out, but not back in.  Hoffman did not protect against the possibility of escaping steam from the return lines.  It was assumed that the traps in the system would be maintained.   In lieu of the Air Eliminator which protects against rising water in the return lines, which is caused by rising pressure int he boiler, you can control with a vaporstat on the boiler so that pressure is limited at a lower pressure.  The so called Dimension B states that you must have 30" of height between the water line in the boiler and your vent port, for every 1 pound of pressure in the boiler.  If you limit at 8 -12 oz, that is plenty, then you can see that you are fine with 15-22".   I would install the vent device a little bit different than you have the G2 installed.  I would put in a loop between the existing low connection that you are using and the upper connection on the horizontal line.  In the top part of that loop, I would install a Tee, and vent from that point.  It would get you a little more height.
    Also, dunham shows an option on one of their drawings whereinsteadt of an air check, they pipe from the air eliminator to a location near a floor drain and simply use a swing check at that point.  Therefor, you could simply use a swing check for the vent.  It would have to be VERY tightly seating.  And, as long as you control your boiler pressure so that you do not have water coming up the return line, and maintain your traps so that you do not have steam, it will work fine.
    4.  As far as the vacuum gauge, your code gauge may already show vacuum.  Most do.  It is typical to see 0 in the middle, 30 psi on one side, and 30" Hg on the other side for vacuum.

    One Additional Thing.......
    One other thing that Dunham usually did was use a return line equalizer.  It was basically a 3/4" pipe that ran between the steam lines, in the area coming off of the boiler, and connected to the return lines, near the air eliminator.  In that line there would be a shutoff for servicing, and a swing check valve installed in the direction to allow flow from the return lines to the steam lines.  The purpose is to transfer the vacuum to the return lines quickly.  When the boiler shuts off, the steam carrying pipes will go into vacuum fairly quickly and the vacuum will travel throughout the system on its own.  Without the equalizer, there will be a flow of air, in a backward direction between the return lines and the steam lines and radiators.  This means the the remaining air in the return lines will be sucked up through the radiator traps and into radiators and steam lines.  This causes a slowdown of condensate flow and also an audible bubbling sound.   Look on your steam lines in the area near where your vent station is on your return line and see if you find a 3/4 or 1/2 pipe stub that is capped off.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
    This post was edited by an admin on January 30, 2012 12:56 PM.
  • nz nz @ 9:39 PM
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    Vents

    Dave,

    Do you mean like this (see pic below)? I repiped this about 6 weeks ago...I guess I would just throw two or three Hoffman 76s in lieu of the Gorton #2 and the Hoffman 75 I have there now...

    My code gauge has markings for vacuum, but it never moves - one way or another. The Wika 0-3 PSI goes into the negative during the condensing phase after the burner shuts off, and then goes back to (around) zero. I was thinking I should get a second, vacuum gauge and add it to my pigtail here (in addition to a vaporstat, which is also on the list of things to do.)

    I will look for the return line equalizer.
  • Dave in QCA Dave in QCA @ 10:05 PM
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    Perfect Piping!

    Yes, this is exactly what I meant.  Have you posted this picture before?  If not, I imagined it in my head but thought it was too hard to verbally describe.  You have it exactly correct!
    Yes, a couple of Hoffman 76 would add the vacuum capability.  If you wanted to check how tight your system is, you could try a 1/2" swing check valve and see what happens.
    The Hoffmans have a float in them, but from evidenc I have seen, they don't totally seal and tend to drip a bit.  The Gorton also has a float, but from what I have heard, they may not seat and will squirt out water, but I have not tested one myself.  
    But, like I said, the vaporstat would give you a control that would prevent water from rising to the vent level.  I plan on using a swing check valve myself, after I get my vents all repiped with crossovers, remove the condensate tank and pump, etc etc.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • nz nz @ 10:08 AM
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    Vacuum Vent vs. Check Valve

    Dave,

    Yes, I did post that pic before, but on another thread.

    For the check valve - are you suggesting I install it in front of the vents on the antler? Should I get a 3/4" since that's the size of the pipe feeding the antler?

    Would the check valve be sufficient instead of buying the Hoffman 76s?

    Also - I checked, it doesn't look like I have a return equalizer, nor stubs where one might have been...however, the pic you posted below seems very similar to my near boiler piping...so its possible it was removed when the boiler was replaced several decades ago.
  • Dave in QCA Dave in QCA @ 10:45 AM
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    check valve in lieu of

    Yes. I am suggesting using a check valve in lieu of a couple of Hoffman 76 vents.  
    If your traps are working, you will not have steam in the return piping.
    If you are controlling with a vaporstat you can control your dimension B to a level lower than the vent location, thus you won't have water in the return piping.
    So, a check valve would work.  I'd use a 1/2" size from the rational, that there is less mating surface in the check and thus more likely to seal tightly.  Also, 1/2" should give you adequate venting.

    EnReynolds has told me of a very tight spring check valve designed for vacuum service that has a cracking pressure of 1.2 oz.  Kinda pricey, but perhaps worth it if you determine that your system is tight enough but the check valve doesn't hold tight enough.  

    On the other hand, I have seen a bronze 1/2" swing check valve used as a vacuum breaker on a shell and tube steam to hot water converter.  Steam pressure operated at 5 psi.   It never leaked at all!  Remained totally sealed against steam and condensate yet opened freely when needed.  Based on that, it seems like it would work for the purposes we are talking about here.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • nz nz @ 4:53 PM
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    Check Valve

    Dave,

    I'm tightening up my system this year - replacing valves all over the place - I have 10 or 11 that leak now (small leaks, those 82 year-old packless valves are failing), those are all being replaced, some with TRVs (for the bedrooms.)

    I added a vacuum gauge to my pigtail as well.

    So - for the check valve, would this be a suitable option? I was thinking about installing it before my main vent(s) at the end of the return line (two pipe Dunham here.) However, if would need to go with a 3/4" check valve - but the same model.

    http://www.pexsupply.com/Hydrovalve-SC050T-1-2-Threaded-Swing-Check-Valve

    Nick
  • Dave in QCA Dave in QCA @ 5:06 PM
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    1/2 inch I think

    I would opt for the half inch size.  My thinking is that it is adequate for the venting and with the smaller size, I would think it is more likely to seal tight enough to hold a vacuum.
    I would install it at the end of the first horizontal nipple coming our of the tee, that is located on the vertical 1/2" line that runs between the upper and lower connections on your return piping.
    All the reasons why you don't need a vent valve are stated in the posts above this one.   Neither steam no water will ever get to this area of the piping unless something else has failed, in which case, it is good to know it so it can be corrected.  I have seen Hoffman vents on the return line vent locations and they got hot and closed because of presence of steam.  The homeowner didn't have a clue that there was something wrong.  But, one or more traps had failed and needed to be serviced.  No way to know if the symptom is shielded from view.

    There have been some other ideas posted as to the use of super duper vacuum checks that have a very low cracking pressure.  But, a swing check will open very easy.  As long as it seals tightly, it will work fine.  You will be able to see how it works.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • PMJ PMJ @ 4:55 PM
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    Check Valve

    I found it difficult to get a valve with low enough cracking pressure (less than 1oz) and seal well enough to not be the biggest leak when in vacuum. I tried several and would always hear the air coming out when it did finally open. I have a 1/2" pipe and figure if I can hear the air coming out of it I have more pressure in the dry return than I want (which is zero). I ended up with a 1/2 inch 110volt solenoid valve which seals completely. Just before it I installed a pressure switch that trips at about 1/10th of one oz which signals the PLC to open the valve. Never hear anything coming out - never any pressure in the dry return. When the burner goes off the PLC closes the valve and we go back into vacuum. Really happy with it.
  • vaporvac vaporvac @ 12:07 AM
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    What equalizer?

    Hi again,
    I'm just wondering if the equalizer on the return line is the same as the equalizer that's supposed to go from the header to the boiler.  I have a weird equalizer  that looks very differnt from most specs and am now wondering if this is actually the kind you're talking about.  It does clang alot when the boiler heats up after a cold start.
    I'm very interested in maintaining and vastly improving the vacuum in my system and had considered REMOVING that equalizer as I thought it was wrong.  I'd like to get this sorted out before putting in the new boiler. Thanks.
    Teresa
  • Dave in QCA Dave in QCA @ 8:06 AM
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    Not the Boiler Equalizer

    Vaporvac, I don't recall how your boiler equalizer is set up, but the return pipe equalizer that Dunham shows on virtually all of its combinations and types of vapor and vacuum heating is not in any way, a boiler equalizer.  I am attaching one of the Dunham drawings with a label and arrow added.  This helps to illustrate exactly what I am referring to.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
    This post was edited by an admin on January 31, 2012 8:10 AM.
  • Ban Ban @ 11:11 AM
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    Schematic above

    My system looks almost identical to this one pictured in the schematic with two noticeable differences. First, I don't see a return equalizer with stop cock and check valve on mine, and second, the top of my air eliminator check-valve is defiantly lower than the middle of the return condensate (as pictured). My plan for that was to just raise the check valve up when I make the manifold for the AE. Also, my water level is significantly lower than what is pictured in the schematic. I am fairly certain I had a boiler similar to this one pictured.
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
  • PMJ PMJ @ 6:45 PM
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    More Details

    I posted earlier about having converted my home two pipe system to vacuum some years back before I came across this site. Now that I have and have learned more (read the LAOSH book) I have added some gauges around to see what was going on a little better.
    I have a 1957 Bryant steam boiler model #7-446. It is a replacement for the unknown 1926 original. It has a rated output of 369,000btu/hr which from what I read matches pretty well with the about 1000sqft total EDR I measure from 23 radiators. I am guessing the header is original because it is larger than what the boiler manual calls for. It is 4" tapped from both sides - 90 up to about 28" over the waterline then 90 forward then 90 and 90 again to the center and tees up in a single 4"( I read this is a no-no but I have no problems) then up another 6" and 90 to the back where the 4" pipe runs about 5 feet( we are now about 32" over the waterline) into the 2-1/2" main. That main runs in a loop around the entire basement in a rectangle which is about 30' x 50'. A 1-1/2" dry return runs right next to the main all the way around too. In a far corner from the boiler both supply and return drop straight down the wall and join together about 6" below the boiler waterline and from there the wet return runs all the way back to the boiler. Two stories of rads tap off these runs all around the perimeter of the loop.
    There is no other piping at the boiler - no equalizer or anything else. There is a check valve in the wet return at the boiler but after all these years I suspect it does nothing. Now when I decided to try letting the system fall into vacuum between cycles I removed the vent from the supply main in that far corner where it dropped down and meets the return. I also removed all vents on rads wherever there were any. I also removed the vent on the far end of the dry return and replaced it with a solenoid valve I run with the PLC. My logic went this way - if the rads were sized to only fill all the way on the very coldest days (with windows open) then basically at least the big ones would never close their traps. That being the case then the supply main would always be open to the return and so venting would only be required at the end of the return. I use a pressure switch right next to that solenoid valve which trips at .05" of water pressure and signals the PLC to open the valve. That valve stays open until the burner cycles off, the valve closes, and the system sinks back into vacuum - typically 20" of water up to 40" in cold weather.
    Now to pressure. Recently I installed several compound gages to see how much steam pressure I was getting as well as the vacuum at various points. I put one next to the vaporstat on the boiler(which doesn't do anything because the pressure is so low) one at the end of the main where I removed the original vent, and one at a point in the dry return in the corner opposite the solenoid valve/vent. By the way, I never hear any air coming out of the solenoid valve which is the only place in the whole system that gets opened to the atmosphere. At the end of the steam main the most pressure I have ever seen is 1" of water. In the dry return during fire it is always 0. My only surprise is at the boiler. The vaporstat tap is about 2" above the waterline. There during full fire I am showing 1-2" of vacuum still. I know the gauge is working because if I do leave the solenoid valve closed I will see pressure build there. Can anyone explain why I see vacuum there?
    This system works flawlessly. All radiators hot, no noise anywhere of any kind except perhaps hearing an expanding pipe sliding through a wall somewhere. Originally all traps were of the small orifice elbow type - I have installed a few thermostatic ones on smaller rads. I guess I am just wondering how I am able to get away without some of the controls and piping I read is essential. I am a believer that you basically need no pressure at all to deliver the steam if the pipes are big enough. Seems I really lucked out.
    Any comments?
  • Dave in QCA Dave in QCA @ 8:50 PM
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    steaming under vacuum

    After reading your discription of the operation of your system and then the question at the end, I think I understand you to ask why the boiler is still showing a vacuum when it is making steam.  I thought that perhaps you were saying that the boiler is showing a vacuum while the end of the steam main is not, and this happens at the same time.  If that is the case, you probably have a gauge that is slightly off.
    But, to the first assumption... when your boiler shuts off and the steam condenses, and it falls into a strong vacuum.  There is vapor continuing to flow at that time.  Vacuum creates a lower boiler temperature of the water. When it gets to a certain temperature and vacuum combination, flow of vapor will cease.  When the fire comes on again, the water will begin to boil and vapor will flow at a temperature below the normal boiling point of water.  As the subatmospheric vapor flows through the system, warming the pipes and radiators, the temperature of the whole system is raised, thus causing decrease in the amount of vacuum and a gradual increase in the boiling temperture.  The longer the boiler runs, the higher the temperature/pressure will become.  If it fires long enough, the vacuum at the boiler will cease.  If it continues to fire longer, you will begin to build pressure.  However, it sounds like the firing rate or heating capacity of your boiler is closely matched to your system, and so, it may take a long time to build pressure, and may not do it at all.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • jumper jumper @ 1:50 PM
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    equalize from main?

    From your description the equalizer runs from main instead of from header ? Why shouldn't that work ? Do you know if joints are painted or otherwise sealed underneath insulation ? If air can't get in then pressure depends on boiler temperature.

    Buildings with long horizontal runs have been built with one pipe distribution but two connections to radiators so that there's parallel flow. As long as condensate can return steam continues to heat.
  • PMJ PMJ @ 4:13 PM
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    Equalize from the main

    Not sure I understand your question. Everything is insulated but I'm sure I can see all the piping. I know there is no connection at the boiler to the header down to the wet return. At the far end of the main it simply 90's down a wall below the waterline where it tee's with the same drop from the dry return. There is no trap or any other device on the main or the dry return. The lone vent for the whole system is at the end of the dry return before that drop below the waterline.
  • jumper jumper @ 8:25 PM
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    equalizer ?

    As I understand your description, I figure pressure in header = pressure in main = pressure in dry return (because they're connected) . So that's an equalizer.
  • SteamCoffee SteamCoffee @ 5:58 PM
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    Any further updates?

    This was an awesome thread, I am sure many would like to hear anything new for the upcoming heating season, good, bad or ugly! Thanks!
  • Dave in QCA Dave in QCA @ 8:27 AM
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    Other Project taking Priority

    Thanks for bringing this thread back to the top.

    My attention has been focused and stabilizing a foundation of the old garage and chauffer's apartment and putting a new roof on the main house building.  I recently sent out requests for proposals for a new boiler.  I will plan on completing my plan to install the crossover traps and a check valve in the common vent at that time.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • nz nz @ 2:43 PM
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    Took the plunge...and a bonus too!

    So, about six weeks ago, I decided to convert my Dunham two pipe system to vacuum. I took off my Gorton #2 and Hoffman #75 return vents, and put in a single 3/4" check valve.

    I had previously put a 0-30 inches of water vacuum gauge in, which never really showed a vacuum since the main vents let the air back in as quickly as the vacuum formed. However, after installing the check valve, I quickly found that a 0-30 inches of water vacuum gauge was not going to cut it, as the gauge wound around 1.5 times. I fixed two leaks, and the gauge wound itself around twice.

    I recently installed a new 30-0-30 gauge where the vacuum is measured in Hg., which seems to work better. I currently am running between 6 and 7 inches of mercury vacuum, which is fairly decent I believe. To give you an idea, if I open a trap somewhere in the system, air whooshes in to fill the vacuum for about 20 seconds.

    I've noticed that the steam does move quicker through the system. It should be boiling quicker too, since in a 6-7 in. Hg vacuum, I should be boiling water at 199-200F...however I haven't really timed it. This was all expected based on what I have read and it seems to be true in case there are any non-believers :-P

    One potential side effect I have thought about, but not actually calculated, is as I should be making 199-200F steam during the upswing of the burn cycle, there should be a reduction in effective BTUs/EDR as the steam is not as hot (initially). Towards the end of the cycle, there is a very small vacuum, or very little pressure.

    This makes me wonder two things:
    1) Should I even bother with my vaporstat? Maybe set it at the lowest pressure possible (2oz I believe)
    2) Do they even make a vacuum vaporstat, so the burner cuts out at...let's say...-1in Hg.

    This is the best vacuum/boil table I have found yet:
    http://www.accontrols.com/assets/docs/eng-resources/Water%20Boiling%20Points%20Under%20Pressure%20Tables.pdf

    I've attached a pic of the new gauge, in case anyone is curious.

    On a side note... One of the radiators in my garage has had a leak in it since I bought the house 2.5 years ago. I put a little JB weld on their last year, and reduced the leaking.

    However, since its a wall-mount unit that is 20 sections wide, it would be difficult to remove...so I was forced to put my fingers in and reach to the 4th tube in the back to get to the leak. This proved difficult because the steam would leak and the surface would be covered in water. So, I would shut off the valve and wait a day for the radiator to dry off, and then put some more JB Weld on, and wait a day, and then turn the heat back on. After 3-4 times of doing this, it was a little better - but still leaked.

    Converting to vacuum made this easy...while the steam was condensing in the rest of the system, a decent vacuum (as noted above) was produced. This caused the small leak in the radiator to make noise almost indefinitely, as the air was rushing back in through the trap. While this was happening I could apply the JB Weld with the radiator dry and cold, and actually HEAR when the hole was plugged. I'm not sure if the vacuum was enough to hold it in place, but this time I had the leak completely fixed after two attempts! Now I have (what I believe to be) a completely sealed system, and the garage heats better now too!
    This post was edited by an admin on December 7, 2012 12:26 PM.
  • Dave in QCA Dave in QCA @ 3:08 PM
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    FANTASTIC NEWS!!!!

    Nick, thanks for the update and for the very good work!  I am in the process of putting in a new boiler and within a month I hope to be able to report results that are similar to yours.

    Everything you report makes sense and is consistent to what I have read in the various Dunham publications.  Regarding your vaporstat, it is fine.  It only comes to play when you hit a maximum pressure, which 8 oz is still fine.  As you have noticed, you begin to make steam while there is still a vacuum.  Steam circulates quicker, and it is at a cooler temperature.  If the call for heat is short the boiler stops before the pressure even rises out of vacuum.  If the call for heat is longer, the pressure (and temperature) will climb higher.  If it runs long enough, the pressure will climb to the cutout on the vaporstat of 8 oz., so that is still just where you want it.

    A side benefit is that once you get the air out of your system, you're not constantly sucking all of the O2 and CO2 back into the system and therefore, oxygen corrosion and formation of carbonic acid should be minimized, lengthening the life of your boiler.

    You should take the time to measure the timing on a couple of things.  First, when the boiler has been off since its last cycle, say one hour, time how long it takes to begin to make steam.  Second, once you begin to make steam, time how long it takes to reach your crossover traps.

    Both of these times should be greatly reduced, especially the time that it takes for steam to reach the crossovers.  

    Did you ever fix the piping over your garage?  If not, has the changes to your system improved it any.

    You also had commented about the clinking sounds that your in-wall convectors on your first floor made.  Since the vapor is now coming up at a lower temperature, has the improved at all.

    Are you able to tell that vapor continues to flow in the system after the fire has shut off?  This would coincide with the cooling off of the boiler water, the result of boiling under vacuum.

    GREAT WORK!!!!
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • nz nz @ 5:36 PM
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    Other items

    I did not get the pipes above the garage fixed - yet. Still have a slight hammer there. The vacuum did not seem to have any effect on this. I had a contractor who said he would come out but now he's dodging my calls.

    The fin tube rads - the expansion noises seem to be closer together now, but no other effects. I will be experimenting with some milk jug pieces, I already started playing with one the other day.

    On a side note - I did fix some of the "ticking" of the pipes against the wood floors with pieces of a cut-up milk jug as someone suggested. I had one of the three rads in my master bedroom that ticked very loudly...no matter how much I moved the rad, it would find its way back. This helped greatly, now there is only one tick that happens (I believe its below the floor (maybe between the joists) and its much quieter, instead of 20 ticks about 1 second apart.
  • PMJ PMJ @ 3:42 PM
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    You'll love it

    Sounds great. I am sure you will love the performance.
    I don't bother with the vaporstat anymore. There is never any measurable pressure to talk about anywhere in the system. With the system in vacuum between firings your time to steam is shortened and your steam delivery to the rads is faster. Between those two things you will notice quite an improvement. 

    I have found that the real issue with steam systems is the time it takes to get steam from the call for heat. This time obviously varies with the length of time the boiler has been off since the last cycle. Anything you can do to shorten this time helps dramatically as the longer it is the more the system overshoots. Then it sits off longer and the problem repeats. Anyone who tries vacuum will find that it really does cut down time to steam from initial fire and that the vacuum speeds that steam to the rads - especially the remote ones. In sum it smooths things out considerably.

    Also about overshooting - generally speaking with a simple thermostat approach by the time the stat is satisfied the rads are already hotter than was really necessary and hence the overshoot. Built in anticipators help some, but I have really enjoyed introducing a PLC between the boiler and the stat. I monitor how long the boiler has been off and vary the next fire time accordingly. The actual fire time over the long haul has been about 1/3 of the total time the stat is actually calling for heat. I fire for a while (longer if boiler has been off longer) and then wait a while (even if the stat is still calling) to give the steam in the rads a little time to heat the rooms. Really smooths things out too. Rads end up just sort of warm all the time instead of cycling so much.
  • nz nz @ 4:50 PM
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    Overshoots

    I don't have much of a (noticeable) overshoot, as I installed TRVs in all the cast iron rads on the second floor. The first floor is all in-wall fin-tube convectors, which cool off substantially quicker.

    The first floor rads do heat up quicker though, and give off quite a bit of heat so some rooms are warmer that others.
  • nz nz @ 4:51 PM
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    Update - 8 in. Hg now!

    It's been a few days since I took that pic. I'm up to now 8 in. Hg. vacuum, so I'm boiling water around 196-197F.
    This post was edited by an admin on December 6, 2012 4:52 PM.
  • Dave in QCA Dave in QCA @ 5:29 PM
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    would be enteresting if you....

    Run the boiler until all of the rads are fully heated.  In this condition, you will have driven out the maximum amount of the air that you can.  When it cools off, it will be pulling the maximum vacuum possible via self induced vacuum.  It would be enteresting to know just how deep of a vacuum you can achieve and how low the boiling temperature will be.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • PMJ PMJ @ 10:46 AM
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    Questions

    8" hg is really good - I haven't seen that much but then all of the valves on my rads are original and I'm guessing leaking some. How long will it take in your system if the boiler stays off for the 8" to go back to room pressure?

    Also, the idea of making steam at lower temp sounds more efficient but it seems to me that the heat loss of the structure for a given outside temp is what it is and lower temp steam contains less heat so more of it will be required to heat the same space than 212F steam. Also, the vacuum is killed very quickly after the burner comes on so we are mostly at 212F steam anyway. Isn't the real advantage in the fact that the steam delivery from the call for heat is so much faster. Boiling starts a minute or so earlier in the deep vacuum so steam (though at a slightly lower temp) is moving to the radiators significantly sooner after the burner comes on. And, it continues to move several minutes after the burner goes off as the steam in the system collapses and the vacuum develops again. Basically, the total amount of time the boiler spends at full fire while delivering no heat at all to where you want it is significantly reduced. Minutes may not sound like a lot but when considered against  run cycle of 15-20 minutes it is significant.

    Maybe I miss something here - comments?
  • nz nz @ 12:25 PM
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    Answers

    The vacuum holds - until the burner kicks back on. I have my t-stat set to one cycle per hour, and depending on the temp outside, it may or may not cycle every hour. Either way, I do not appear to be losing the vacuum.

    The vacuum is eliminated once the boiler runs for a little while, however I have seen the boiler cut off (from the t-stat) while still in a vacuum.

    Your comments around the steam temperature dovetail into my comments about regarding concerns of EDR/BTU. You're correct in that once the boiler has been making steam for a few minutes, the pressure raises and so does the temperature of the steam.

    In my case...in an 8 in. Hg vacuum, going to 1 in. Hg. towards the end of the burn cycle, this isn't a noticeable issue. However I can hypothesize that in cases of an extreme vacuum, the effects could be significant (e.g. 100F steam)

    FYI I checked the gauge last night a while after a burn, and I was at around 9 in. Hg, so with each burn, it appears that I am gaining a little vacuum.
  • Ban Ban @ 2:43 PM
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    Need a new Dunham Air check

    For an Air Eliminator 220. I have been working on my Dunham Air Eliminator and when I took off the "air check" I noticed that it doesn't hold a vacuum. My question is, can I use a piece of metal to repair the air check? Can I add a new style one-way valve to operate the way Dunham advised or is there a way to purchase a NOS air-check somewhere?

    Thanks!

    Photos below are of me cleaning the Air Eliminator with Hydrogen Chloride.
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
    This post was edited by an admin on December 7, 2012 2:46 PM.
  • Dave in QCA Dave in QCA @ 2:53 PM
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    222 air check

    I have been told by a reliable source, but have not verified with MEPCO, that there is a new version of the #222 air check.  If you unthread the old one the new one should thread right in.  I understant that it may have some nylon and/or other synthetic materials in it.

    Also, for cleaning the metal parts, I would suggest that you used a lime scale remover such as LSR or Limeaway.  These are citric acid based and do a great job removing lime scale and at the same time are MUCH LESS aggressive with the metals.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • Ban Ban @ 3:23 PM
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    Please Delete

    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
    This post was edited by an admin on December 7, 2012 3:26 PM.
  • Ban Ban @ 3:25 PM
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    Hydrocloric Acid

    It is interesting you mention Citric acid. I agree with you and have used it on my potable hot water galvanized plumbing system. Regarding the steam system, I found a few years back that if I soak the thermostatic traps in Hydrocloric acid the copper acordeon diaphragm retracts almost back to its original position. I believe this to be due to the mineral deposit build-up between the fins dissolves and causes the diaphragm to act normally again. Years of build-up and no maintenance takes its toll and some 80 years later they barely work. It's amazing to see such an antique device rejuvenated just from cleaning. I will look into the new air-check. In the meantime do you think I could use a small piece of copper or aluminum?
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
  • Ban Ban @ 4:11 PM
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    Fatal Error

    It said there was a fatal error when I entered this post but it did go through. Please delete. Also, Is there a way to delete posts yourself?
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
    This post was edited by an admin on December 7, 2012 4:28 PM.
  • Ban Ban @ 4:12 PM
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    Dunham air check disk; Please delete

    It said there was a fatal error when I entered this post but it did go through. Please delete. Also, Is there a way to delete posts yourself?
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
    This post was edited by an admin on December 7, 2012 4:29 PM.
  • Ban Ban @ 4:13 PM
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    Dunham air check disk

    Here is the "air check" diagram. If you look closely you can see the disk. Any Ideas on replacing this disk? Does anyone know what the original disk looked like or could possibly take a photo of one of theirs? I looked at the MEPCO website and only found vacuum breakers. Here is the link: http://www.mepcollc.com/steamspec/vbreakers.htm
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
  • Dave in QCA Dave in QCA @ 11:45 AM
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    Disc for Dunham type 222 air check

    I would estimate the disc to be roughly 14-12 gauge metal.  It is constructed of either copper or brass.  It must be perfectly flat and smooth.  The diameter should be as large as possible and still be able to fit into the screw off cap.

    Do I understand your post that the disc is missing from your air eliminiator? 

    In my system the air eliminator is missing completely. I have found a Trane float vent that has a good sized vent port and the same type of check on top as the Dunham Air Eliminiator.  However, in my Trane vents, the disc is missing as well and I am working on finding a way to replace it.   I will let you know how that turns out. 

    Regarding the new 222 air check from Mepco, you are correct, it is not shown on their website.  The website is woefully inadequate.  But, a reliable source at RC Equipment in Marshalltown, IA, who used to work at Mepco for many years tells me that it is currently available.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
    This post was edited by an admin on December 8, 2012 11:46 AM.
  • nicholas bonham-carter nicholas bonham-carter @ 11:07 AM
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    Missing check valve?

    Shouldn't there be a check valve under the "ham", in a Dunham system?--NBC
  • jumper jumper @ 3:58 PM
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    thread makes me happy

    I'm happy to see continuing interest in vapor heating. There's an article on this website about steam heat improvements in Stuyvesant Village. I've been teasing my memory to remember details a dead man explained years ago about the design of systems he installed in Toronto fifty years ago.
  • gerry gill gerry gill @ 8:40 AM
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    This is a very fascinating thread,

    my head is spinning with its possibilities. I see more experiments taking place!
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.
  • PMJ PMJ @ 9:05 AM
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    Possibilities

    I would think as a contractor it would be tough to implement vacuum in customers homes - especially older ones where many leaks have to be found and old valves replaced. I would think it would be tough to talk people into giving you the time required.
    But as an owner able to continuously monitor and fiddle with the system I can tell you that  vacuum has transformed how I think about my heating system. The heat is dramatically more even and I am convinced 10-20% more efficient than without it. I have been in my house 20 years now.
    I have no measureable pressure anywhere in the system at any time when the burner is on and vacuum when it is off. I have no vent devices at all in the entire system except a 3/4" solenoid valve on the main dry return.
  • ChrisJ ChrisJ @ 11:51 AM
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    1 pipe

    Anyone sucessfully running a vacuum 1 pipe system?

    I feel left out of the party here.
    Weil-McLain EG-45 connected to 392sqft of radiation via two 2" risers into a 3" drop header and 2" equalizer. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures updated 6/5/14.
    https://picasaweb.google.com/thetube0a3/Boiler?authkey=Gv1sRgCImUxIqv9436MQ#
  • PMJ PMJ @ 1:27 PM
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    One Pipe Vacuum

    Just guessing but I would think each rad would need its own check valve. Obviously that makes it a considerably tougher project. Also, you want check valves that seal well but also have a very low cracking pressure. Not sure how easy that is to find.
  • Dave in QCA Dave in QCA @ 3:11 PM
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    One pipe vacuum

    There were essentially two types of one pipe vacuum. 

    One was the self induced type with vacuum checks on the vents, both the main vents and the radiator vents.  There is no longer anybody making a vacuum radiator vent, so that option is out.

    The second type of system was the Paul system.  On this, instead of normal radiator vents, they was an air service trap installed instead.  Paul type vents are still made by Hoffman Specialty.  The outlet of the Paul vent is connected to a 1/4 pipe and all of these run back to the boiler room.  Originally, the Paul System air lines were connected to a vacuum pump and the system was evacuated of air and allowed to boil at lower temperatures than atmospheric conditions. 

    I think the Paul information is in the Library, but I just looked and couldn't find it.   I have an old Dunham book with their "Air Line" system described quite well.  I could scan it an post it here as a pdf, if that would help.

    Also, I would suggest that the subject of 1-pipe vacuum be started in its own thread.  It deserves to be discussed and I think it will be better if the two-pipe and one-pipe discussions are not mixed together just because of the confusion that it may create.  Vacuum is confusing enough by it self I think. 
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • vaporvac vaporvac @ 4:11 PM
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    One-pipe vacuum:Dave Bunnell?

    I believe Dave Bunnell had a thread or article on this subject. I didn't find it under resources and he has 32+ pages of posts, so I'll leave it to someone with it at hand. Since I have 2-pipe I didn't pay too much  attention to it, as Dave so rightly states one's vacuum is confusing enough as it is!
  • nz nz @ 3:10 PM
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    Almost to 9 in. Hg vacuum now

    In case any of you were wondering, i'm making steam around 195F now :)
  • Dave in QCA Dave in QCA @ 3:25 PM
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    EXCELLENT!!!

    I am hoping I have the same results!!!!

    Also, regarding your earlier comment/question regarding the btu/edr decreasing because of the lower temperature, you are absolutly right.  That is what they were striving for, especially in pumped systems.  The goal was to be able to produce a softer modulated heat in mild weather in the same manner that a how water system does. 

    According to my tables, you're at about 195 BTU/EDR, if you were actually steaming at that vacuum, which I'd guess you're not.   However, I bet your boiling begins very quickly when the boiler starts and I bet that steam hits the rads VERY quickly!
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
    This post was edited by an admin on December 8, 2012 3:25 PM.
  • vaporvac vaporvac @ 4:19 PM
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    Additional Advantages

    Yes, Dave. I, too see that lower boiling point as an advantage beyond a lower fuel consumption. Cooler radiators mean less scalding for those without radiator covers and a softer heat. I would also think this is a way to moderate the temp for those who have upgraded the insulative value of their homes.  I'm glad this thread has come alive again!
    I am also curious about your comment on not boiling at the 195deg in a vacuum. Why would that be?  I thought that was the idea of the vacuum which got stronger as the temp decreased. What am I missing?
  • Dave in QCA Dave in QCA @ 4:38 PM
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    equilibrium

    At some point, the system comes to equilibrium.  When the fire first goes off, assuming that the system is filled with steam, the steam is collapsing and pulls a vacuum.  This lowers the boiling point of the water and since the boiler and water is at the point, or warmer, the water boils and produces vapor that circulates and condenses, etc.  As the system cools, eventually the temperature of the water is precisely at or a tiny bit lower than the boiling temperature as determined by the level of vacuum.  All of the vapor has condensed.  The vacuum is stable, the water is not boiling.  Everything is at equilibrium.  If you had a vacuum pump hooked up and turned it on an increased the level of vacuum, the water would again begin to boil and vapor would flow.  Or, conversely, you you didn't affect the level of vacuum, but instead you turned on the fire and started to increase the temperature of the water, it would immediately begin boiling and vapor would flow. 

    This equilibrium at 9" vacuum is because not all of the air has been removed.  But, enough has been removed to allow for fast circulation. The deeper the vacuum drawn, the lower the boiling point.  To get to really low temperatures requires a vacuum pump.   And then, that is what is going on with the Dunham Vari-Vac System.  They vary the level of vacuum based on out door temperature, ODR, and can effectively provide the right amount of heat to a large building based on varying the temperature of the vapo......   Just like a commercial Hot Water system does. 
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • jumper jumper @ 3:32 PM
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    one pipe vacuum

    It depends how well terminals and connexions drain. Ideally you evacuate the air and don't let anymore in. In one pipe everything is connected so why do you have to evacuate at the radiator ? I think Lost Art mentions buildings of yore that used steam ejectors to induce vacuum. The book also describes a way to use two connections on a fin tube with a one pipe system. There are other ways as well to make a terminal parallel flow with one pipe. See the Wilson patent on this site. The key is adequate drainage. Even in a two pipe system inadequate drainage causes bang and sizzle.
  • Fizz Fizz @ 10:19 AM
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    Richardson back to vacuum?

    Our steam system is old Richardson with 3 add-ons which have taditional traps.  The current piping has the loop replacing swinging check valve.  Original system called for air expeller at end of dry return with swinging check valve to control condensate.  Currently, there is a #2 Gorton replacing original air expeller, and a #1 on add-on return.  I do have vacuum vents that were replaced with current set-up.  I did re-install them, and system went into vacuum, but there is a 32oz low pressure gauge which doesn't show degree of vacuum, though it did reverse to 30oz line.  System worked well, but 2 add-ons stopped heating(only ran through 2 cycles).  What are recommendations?  Current settings on v-stat are 8 & 8.
  • elfie elfie @ 2:04 PM
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    does lower system pressure mean greater efficiency?

    for those systems where a true vacuum can not be achieved, it still seems that it still is very important to operate the system at the lowest possible PSI level.

    does a lower PSI level mean system is more efficienct?  and for larger 'low pressure' steam boilers this is more difficult to achieve because these systems tend to short cycle (even with a modulating burner)
  • PMJ PMJ @ 3:25 PM
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    Pressure

    Any pressure required in the mains to get the steam to go where you want it means there is resistance to the flow. If you can get the job done with little or no pressure anywhere that is the most efficient from an operating standpoint. However, accomplishing this requires a bigger up front cost of bigger pipes. I have read here about some people needing to use venting to slow the steam down coming out of the boiler for it to be dry enough. I would hate to have to slow steam down going to my radiators on purpose as everything I have done with vacuum is trying to speed it up! I am lucky to have an older system (1926) which has larger mains than seems to be spec today. The manifold from the original boiler is still there and the pipes are oversize for the replacement Bryant there now from the 50's. Lucky for sure.

    With vacuum the steam is literally sucked down the mains at the start of the cycle. Some of the previous posts have discussed how reducing the time from when the burner fires to when vapor is actually getting in the rads is where most of the increase in efficiency is. Obviously any time to build pressure is just more lost time.

    So yes, the lower the pressure the more efficient - provided you can actually get the steam to go where you want it to. I require no pressure at all in mine to fill the most remote radiator.
    This post was edited by an admin on December 9, 2012 3:27 PM.
  • elfie elfie @ 6:39 PM
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    pressure and latent heat

    another reason for lower steam pressure is related to latent heat

    there is a benefit to latent heat transfer (ie. release of energy from steam that causes the radiators to get hot) where latent energy transfer is more effective when pressure and steam temp are lower

    the existence of higher pressure, i guess restricts movement of free flowing steam from the boiler header pipes into the mains and radiators

    it seems counter intuitive (ie. you would think the higher pressure would cause the steam to move faster thru the system but I guess there is resistance to steam flow if the mains and rads are under higher pressure in front of approaching steam).

    the existence of a vacuum is interesting because it tends to suck the steam from the boiler (so in most systems, getting pressure as low as possible while still being able to cause rads to get hot is the best that most systems can do).

    i hope i am getting all this right
  • Ban Ban @ 10:38 AM
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    Repairing the Dunham 222 Air Eliminator

    Check valve is what I have decided to do. I nixed the solenoid for venting on the AE due to cost, complexity and the reasons Dave pointed out. If I used the solenoid I would immediately lose vacuum on firing unless a PLC was added (is that an outdoor reset?). I am still concerned about the CFM of the original check valve. I have 22 Radiators in the house and relying on 6 holes to exhaust the entire system seems iffy. Because of this I have decided to make a manifold on the top of the AE out of 3/8" black with plugs in it. This way if it is not adequate venting I can figure out a solution later (hoffman 76, solenoid, or homemade Dunham air check look alike). Attached below are the 3 materials I experimented with (brass, copper, copper with neoprene and neoprene) to repair the air-check. The solid neoprene seems to work the best with the cracking pressure very minimal. The copper and neoprene comes in second.
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
  • Dave in QCA Dave in QCA @ 11:43 AM
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    Plenty Big Enough

    The Dunham 222 Air Check was furnished on the 220 Air Eliminator.  As a unit, it was rated for up to 2,000 EDR. 
    Remember, a direct comparision to the venting capacities of modern main vents may not be accurate because of the different conditions in which they operate.  The modern main air vents will vent all of the air in the mains every time the steam cycles.

    On the first steam cycle, the Dunham air check will vent the air in the mains and some of the air in the radiators, the amount of air is dependent on how long of a cycle it is and how much of each radiator is filled with steam.  During this first cycle, you will probably hear a fair amount of hissing air being relieved from the air check, but not as much as you might imagine.  On subsequent cycles, since the air has been prevented from reentering the system, you may hear no air being exhausted at all.  It all depends on how long the cycle is and if any air has leaked back into the system.  I am told by a person that was with Dunham for many years, that on subsequent cycles, you may occaisionally hear a little burp, but most often nothing at all.

    Have you measured the diameter of the opening inside the cap.  What is the largest disc that will fit inside?
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
    This post was edited by an admin on December 11, 2012 11:44 AM.
  • SWEI SWEI @ 11:47 AM
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    subsequent cycles

    is what makes me want to experiment with a fully modulating burner.
  • Dave in QCA Dave in QCA @ 11:53 AM
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    Combine with Vari-Vac

    The combination of a fully modulating boiler with a Vari-Vac system is intreaguing and in fact, make my head spin.
    The Vari-Vac system used a modulating vacuum level assisted by a vacuum pump and a modulating steam valve supplying heat into the building mains from a fixed pressure boiler.  It stands to reason that if the boiler could modulate, that you could control that and eliminate the modulating steam valve.   WOW!
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • Ban Ban @ 11:49 AM
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    Air-check

    seems to be 3/8" I am really excited about getting this system to work in a vacuum again! I want to thank everybody for their help and knowledge.
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
  • Ban Ban @ 8:07 PM
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    I have a Vacuum!

    I finally have put my system back together. Boiler fires fine, Dunham Air Eliminator is checking the air perfectly, and my crossover traps are finally stopping the steam! I still have vacuum leaks for sure, but with 22 radiators and 90 year old pipes I am pretty happy with these preliminary results. I want to thank everybody for getting me obsessed with returning my system to its proper vacuumized status! Radiators are defiantly staying warmer longer.
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
  • Kevin_in_Denver Kevin_in_Denver @ 5:12 AM
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    Full Modulation is Possible

    Just food for thought:

    A Modulating Condensing boiler can be coupled to a steam generator with a heat exchanger. It would require the modcon to operate at 200F or higher, so you wouldn't get the benefit of flue gas condensation, but the burner would modulate.

    The steam generator is just a tank with a coil in the bottom and a gap at the top.
    It may be hard to find one that has very low mass and can handle vacuum.
    Superinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments
  • SWEI SWEI @ 10:39 AM
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    full modulation is available

    http://www.midcointernational.com/products/low_nox/ is basically a mod/con burner head setup for a conventional boiler.
  • ChrisJ ChrisJ @ 10:50 AM
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    Vacuum!

    Congrats! Glad to see you are making progress.
    Weil-McLain EG-45 connected to 392sqft of radiation via two 2" risers into a 3" drop header and 2" equalizer. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures updated 6/5/14.
    https://picasaweb.google.com/thetube0a3/Boiler?authkey=Gv1sRgCImUxIqv9436MQ#
  • Dave in QCA Dave in QCA @ 11:21 AM
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    Somewhat Dissapointing Results

    My new boiler and venting system as been in operation for close to 2 months now.  Here are my observations.

    The system will pull a vacuum of 4-5" Hg on a 20 minutes steaming cycle and 5-6" Hg on a 30 minute steaming cycle. 
    Steaming seems to begin faster, steam travels down the main faster, and while there is a little bit of air venting each time, it is a VERY SMALL amount compared to a start when the system is completely filled with air.
    I do not appear to be able to produce subatmospheric vapor in these conditions.  I am guessing that I would need to put a vacuum pump on the return system and draw it down to a deeper vacuum... Experiments will follow!

    While I thought that my system was very tight, I discovered a pinhole leak in one of the 2" end of mains that loops back to the boiler room.  Repair will be soon.  All of the radiator valves have been tightened up and do not appear to be leaking.   I do have one radiator that has a crack in it.  It is about 4" from the top and I'm sure it's leaking a bit.  There may be leaks in other pipes, but hopefully not.  All of the system risers are inside the calls.  Given that they are inside the walls, they are also insulated, which helps the overall system.

    Even If I get no additional benefit from vacuum, the fact that they system venting is through a check valve that does not allow the reentry of air when the burner shuts down does appear to reduce the burn time that is required to get the air out of the system.   Since the flow of air in and out of the system is reduced, on could assume that oxygen corrosion and the formation of carbonic acid would also be reduced. 
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
    This post was edited by an admin on February 5, 2013 11:22 AM.
  • PMJ PMJ @ 12:39 PM
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    This sounds very much like my results

    except you are getting more vacuum than I am. My 90 year old system has a lot of leaks and I have not replaced all the original Mouat valves which except for holding vacuum work just fine.

    I spent a lot of time dreaming about a vacuum pump but I ended up thinking that it probably was not worth the noise/electricity. The main contribution of the vacuum is as you have found - steaming is faster, the steam travels out through the system faster, and why horse all that corrosive air in and out of the system each cycle if you don't have to. I have come to really like the lack of moving parts and the natural vacuum didn't require any new ones.

    Thanks for the update and I'll be looking for more info from any additional experiments.
    Peter
     
  • Ban Ban @ 1:12 PM
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    I kind of felt the same way,

    even though I was excited to have a relatively good amount of vacuum after all of these months I ended up in some ways a bit more confused. I am trying not to get more obsessed with the system this year (my immediate thought was to pipe in a vacuum pump right away). In many ways PMJ is right, it is kinda nice hearing the subtle sounds of the Dunham Air Eliminator with no advanced electronics or complexities. My original goal was 10" of mercury with a boiling point of 192.19 degrees F.

    My results have been interesting, on average, over the past couple of days, when the burners turn off the vacuum tends to stay in the 1" - 3" of HG depending on the length of the cycle. The way it needs to be viewed is this effort proved wonderful things so far (as anticipated):

    1. The System runs much better overall and is balanced better.
    2. There is tremendously less effort to get steam to the radiators and start heating the space.
    3. Less corrosive air entering the system
    4. When the system fires back on it is in a vacuum for at least the first 25% of the cycle. This means that I am still steaming at less than 212 degrees! I can hear it start to boil almost immediately after the burners start!

    I am happy with my results for this year. My goal for the rest of the heating season is to find all of my leaks. I have found four so far due to the action I have taken on the system. One of the leaks I found destroyed part of the sub-flooring over the years. I would have never known if I hadn't done this. Out of curiosity I used a shop vac to pull the system into more of a vacuum on the return side. The most I could get with it was 6.4"hg.
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
    This post was edited by an admin on February 5, 2013 1:18 PM.
  • ChrisJ ChrisJ @ 1:41 PM
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    Wonder

    If I could ever experiment with vacuum.  If I vent too fast I end up with cold radiators due to lack of steam.  Does this mean with vacuum I'd constantly have radiators starved of steam?
    Weil-McLain EG-45 connected to 392sqft of radiation via two 2" risers into a 3" drop header and 2" equalizer. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures updated 6/5/14.
    https://picasaweb.google.com/thetube0a3/Boiler?authkey=Gv1sRgCImUxIqv9436MQ#
  • Eastman Eastman @ 2:45 PM
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    Dave

    Dave, there is no vent on the return?
  • Dave in QCA Dave in QCA @ 3:10 PM
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    No Vent Device

    There is a vent through a 1/2 pipe and a swing check valve, but no typical vent device such as a Hoffman 75 or Gorton 2.

    The original Dunham system would have used and air eliminator and an air check or a swing check on their larger systems.  The air eliminator had a float guarded against rising water in the returns due to pressure in the boiler.  There was not protection against steam because unless a trap in the system fail, there is no steam in the return.  If a trap fails, the system should not mask the condition, you want to see the steam. 
    This installation is guarded against rising water in the returns with a Vapor Stat to limit the boiler pressure.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • Ban Ban @ 3:42 PM
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    Vent on the return

    Looks like this: http://www.heatinghelp.com/forum-thread/144863/Restoration-of-my-Dunham-Air-Eliminator

    (Dunham system)
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
  • Dave in QCA Dave in QCA @ 3:47 PM
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    My Vent

    Looks like this.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
    This post was edited by an admin on February 5, 2013 3:49 PM.
  • PMJ PMJ @ 6:10 PM
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    Cracking Pressure

    What is the cracking pressure of that swing check valve? In that size I would think at least 6 oz or even more. That is why I ended up running a solenoid valve - the entire system pressure is raised whatever the cracking pressure is. I wanted zero resistance at the vent.
  • Dave in QCA Dave in QCA @ 6:17 PM
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    to small to measure

    On the ounces gauge on the boiler, the needle is still resting on the peg when the check opens and vents. If I run it on high fire, it will come up to two ounces while venting and the check is open and blowing pretty hard.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • PMJ PMJ @ 7:33 PM
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    Pressure at the boiler

    For some reason which I never understood I don't show anything at the boiler either but I show maybe 1/2 an oz at the place where I removed the vent from the steam main at the farthest point of the loop away from the boiler. In theory there has to be more pressure right at the boiler and a drop to that point but I never can see it on a gauge. ?????
    I can barely hear or feel anything coming out of the vent valve on the dry return on full fire well after the vacuum is gone. My thinking is if it makes noise coming out then there is unwanted pressure in there and the vent hole isn't big enough.
  • Eastman Eastman @ 7:47 PM
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    At what point in the cycle does this happen?

    At what point in the cycle does this happen?
  • PMJ PMJ @ 9:44 AM
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    It takes about 2-3 minutes

    after the burner comes on at the start of the cycle for all the vacuum to be gone and the vent opens. Is that what you were asking about?
  • Eastman Eastman @ 11:52 AM
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    pressure conundrum

    The boiler gauge reads zero, and yet there is 1/2 psi at the end of the steam main.
  • PMJ PMJ @ 12:38 PM
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    It is 1/2 an ounce at the end of the main

    (or at least not sitting on the pin). Dave said his boiler ounce gage is resting on the pin too when it takes some pressure at the far end to open his check valve. I don't get it either.
  • Eastman Eastman @ 12:47 PM
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    stack effect?

    stack effect?
  • Dave in QCA Dave in QCA @ 12:53 PM
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    cracking pressure is low

    In my case, the cracking pressure is less than an ounce. If the swing check was mounted vertically, it would take more to open it. Mounted horizontally, it requires next to nothing to crack the swing plate open far enough to allow venting to take place.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • PMJ PMJ @ 1:37 PM
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    Swing Check Cracking Pressure

    Not trying to be argumentative Dave but I spent some time looking for check valves and couldn't find any as low as you say. Looking at a catalogue now for bronze check valves the lowest cracking pressure I see is 8 ounces. Did you put your gauge right before the check to see what it took to open it? Anyway the catalogue number is probably worst case so you are probably lower than that with your mounting as you say.
    Since we are already at single digit ounces it seemed to me that every ounce of back pressure at the vent point I got rid of was significant. That is how I ended up with just opening the pipe with a solenoid valve. I never put a gauge there because I really don't hear anything coming out. Maybe I will just to see what it is.
  • Eastman Eastman @ 4:34 PM
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    ?

    How does the Duhnham function on a one pipe system?
  • Dave in QCA Dave in QCA @ 5:34 PM
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    2-pipe Only

    The Dunham Air Eliminiator, The Dunham Air Check, and any other device that does not have the capability to close on steam are all only for return pipe venting on a 2-Pipe system.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • Eastman Eastman @ 6:23 PM
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    That's what I thought, but...

    I thought Ban has a one piper.  Ban?
  • Ban Ban @ 9:24 PM
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    Yes but,

    my home is a 2-pipe Dunham. I have apartment buildings which have one-pipe systems. We are always trying to make things more efficient so knowing as much about vacuum has been very important to me. The check valve that I made for the Maid-O-Mist air vent is partially based on the Dunham Air-eliminator assembly, by the way.
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
  • Ban Ban @ 11:00 AM
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    I need more, I want more,

    Vacuum! I can't seem to get more than 5 inhg. I am on a desperate quest for more and it has really made me look at the system precisely. I found leaks everywhere, just think if you were going to convert the 2-pipe steam to forced hot water, what a hot mess that would be. My strangest leak is in the casting of a radiator, a Burnham base board to be exact, which has not been repaired yet. Any suggestions on this in general? Any suggestions on the repair of the cast iron radiator leak?
    Richard Ban


    Detroit, Michigan (Dunham 2-pipe vacuum)
  • nicholas bonham-carter nicholas bonham-carter @ 11:21 AM
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    Much ado about nothing!

    I noticed what seems to be a missing check-valve under your ham, as a result of studying all the Dunham literature, in preparation for re steaming my cemetery chapel Dunham system. In that system, the check valve was turned upside down, so I wonder-on purpose, or by accident. Also I wonder what purpose it serves.
    I can see why they introduced the vacuum pump, as all the dry return piping will still have some air in there, unless some way could be found to briefly use steam to push out the air, and then cut off. An alternative could be a very large header on the boiler which could serve as an accumulator as the burner cuts off, and the system drops into vacuum.
    Could a cheap air compressor serve as a vacuum pump?
    This is now the most fascinating subject on the wall!!--NBC
  • nicholas bonham-carter nicholas bonham-carter @ 12:44 PM
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    Deep vacuum

    If the vacuum were deep enough, could the water in the wet returns boil?
    I think we need a separate subsection for vacuum steam here-Dan?--NBC
  • ChrisJ ChrisJ @ 12:47 PM
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    Yep

    I'd love a section for vacuum systems.
    If someone proves a single pipe system can work with vacuum I'd convert mine for sure.

    I don't think our pets would be happy though. When the two cats and chihuahua hear the Gorton's chirping they all run for a radiator. :)
    Weil-McLain EG-45 connected to 392sqft of radiation via two 2" risers into a 3" drop header and 2" equalizer. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures updated 6/5/14.
    https://picasaweb.google.com/thetube0a3/Boiler?authkey=Gv1sRgCImUxIqv9436MQ#
  • ttekushan ttekushan @ 1:37 PM
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    two cats and a chihuahua

    That's so cute!

    But it's the same instinct that's always drawn me to steam radiators too!

    I think a primal need is satisfied when our heat sources are actually hot. ;-)
    terry
  • Dave in QCA Dave in QCA @ 1:15 PM
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    Interesting...

    Nicholas, you bring up an interesting point that I had not considered before. However, in thinking about it, the wet return lines most likely would be at or about the level of the bottom of the boiler. The water at the bottom of the boiler as well as the wet returns would have a higher pressure then the water at the top of the boiler, which would be subjected only to the pressure of the pressure of the air/vacuum above the water. This would create a differential of about 1.8" Hg with the water on the bottom of the boiler and in the return lines being exposed to less vacuum or higher pressure. This is because of the weight of the water above. In this case, I don't think the water in the return line would boil with the exception of the top few inches in the point where the line drops below the NWL of the boiler.

    Different vacuum systems are set up with different control scenarios. From what I understand, many of the current operating systems are simply set up so that the pumps start when the call for heat occurs and will continue to run until the vacuum drops to around 8"Hg. However, the systems that run on a differential, the pump will continue to operate until a differential of 1" Hg is established, this is equal to 8 oz of pressure differential between the steam and return lines. At either of this conditions, I don't think it is likely that the water in a wet return would boil. However, if you ran a pump that was capable of producing a vacuum that was well below that which was necessary to cause the boiler to begin to boil, I think that the entire boiler and return lines would be boiling very rapidly.... of course until the vapor filled the system and then the vacuum pump would have to continue removing vapor to prevent the system from coming to equilibrium.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
    This post was edited by an admin on January 16, 2014 1:17 PM.
  • ttekushan ttekushan @ 1:32 PM
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    vapor filling the system

    Dave in QCA, you said, ".... of course until the vapor filled the system " and I think that's the key. My hunch is that if return temps are high enough for reboil, vapor will already have filled the system. And regardless, the highest temperature water in the system, as you also said, being at the top of the boiler would preferentially supply the vapor. It would boil off first and maintain the vapor flow in the preferred direction.

    I suspect that return water boiling wouldn't be a significant issue, since that hot kettle of water can supply vapor faster than the returns could.

    Of course, introduce a motorized zone valve with separate vacuum returns and all bets are off!
    terry
  • Dave in QCA Dave in QCA @ 1:39 PM
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    Very Good Point

    tte, you make a very good point and I agree with you completely. I was thinking in terms of an absolute condition with a cold boiler and very deep vacuum.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • ChrisJ ChrisJ @ 1:30 PM
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    Dumb question

    I have what may be a dumb question but I need to ask because I want to know.

    What was the original purpose of the hartford loop? Is it to keep the pressure at the input and output of the boiler about equal so water doesn't get pushed out via the return from pressure?

    Is it even necessary with a vacuum system?
    Weil-McLain EG-45 connected to 392sqft of radiation via two 2" risers into a 3" drop header and 2" equalizer. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures updated 6/5/14.
    https://picasaweb.google.com/thetube0a3/Boiler?authkey=Gv1sRgCImUxIqv9436MQ#
    This post was edited by an admin on January 16, 2014 1:32 PM.
  • Dave in QCA Dave in QCA @ 1:36 PM
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    Hartford Loop

    The Hartford loop is defined as the turning up of the wet return and its connection to the equalizer about an inch below the normal boiler water line. The purpose of this was to prevent accidental draining of the boiler. For example, if a return line suddenly broke, the boiler with a Hartford loop will drain down only to the point of the Hartford connection. If the wet return connected directly to the bottom of the boiler, the entire boiler would suddenly drain. And.... then you've got a huge problem!

    The equalizer is intended to make the pressure at the boiler outlet and inlet be subject to the same pressure, and yes, so pressure in the boiler does not push water up into a return where the pressure might be less.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • ChrisJ ChrisJ @ 1:44 PM
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    Hartford

    Dave,

    So with a boiler that has a fuel burner and a LWCO doesn't that make the hartford loop pretty much obsolete and unnecessary?

    I realize that even a LWCO can fail, but in that case the boiler will still slowly drain via condensate loss as return water comes back and leaks out.
    Weil-McLain EG-45 connected to 392sqft of radiation via two 2" risers into a 3" drop header and 2" equalizer. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures updated 6/5/14.
    https://picasaweb.google.com/thetube0a3/Boiler?authkey=Gv1sRgCImUxIqv9436MQ#
  • Dave in QCA Dave in QCA @ 1:56 PM
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    An added measure of safety

    Given modern firing that can be immediately shut off operating with a primary and a secondary LWCO, it is a pretty safe bet that the LWCO would shut of the flame. But, we all know that LWCO devices fail because we still have dry fired boilers from time to time. But, lets assume that a wet return pipe broke and quickly dumped out the contents of the boiler, and at that time the LWCO shut the boiler down, The heat the might remain in the firing surfaces of the cast iron, refractory walls of combustion chambers, etc., might be enough to damage the boiler. The bottom line is that if you have a broken wet return you don't want the boiler to dump its contents on the boiler room floor. The Hartford loop is a simple piping scenario. Of all the stupid things that can happen to controls, intentionally or be neglect, there is not much that can be done to the Hartford loop once it has been built in the piping.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
    http://grandviewdavenport.com
  • ttekushan ttekushan @ 1:57 PM
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    I'm going to go out on a limb

    and say "yes. it is obsolete."

    Larger systems with separate boiler feed pumps do not utilize a hartford loop, only a check valve.

    Electric controls have obviated that, and as you point out, the hartford connection doesn't prevent a "dry fire" condition should the controls fail.

    ---
    I'll add that the hartford connection also tends to hold condensate back when the water level drops and exposes the return connection to equalizer steam pressure. So it works the other way too. The water can't return until the fire stops or is reduced. This is why a hartford connection that's above the normal water line can cause boiler flooding with float operated auto fills and can also exhibit hammering at the end of the cycle a minute after the fire stops.

    After all that, I think they should still be properly installed. A little tradition never hurt anybody. And as D in QCA just pointed out before I could post this one, it's so simple and reliable it makes no sense to leave it out of the picture.
    terry
    This post was edited by an admin on January 16, 2014 2:01 PM.
  • ChrisJ ChrisJ @ 2:28 PM
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    ok

    I agree, just wanted to make sure I complete understand its function. Besides the fact its a backup safety think code in most if not all areas.


    Back onto topic, what problems would the wet return boiling possibly cause?
    Weil-McLain EG-45 connected to 392sqft of radiation via two 2" risers into a 3" drop header and 2" equalizer. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures updated 6/5/14.
    https://picasaweb.google.com/thetube0a3/Boiler?authkey=Gv1sRgCImUxIqv9436MQ#
  • PMJ PMJ @ 4:22 PM
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    Energy Savings and Vacuum

    I'm not seeing the great benefit from and energy standpoint of paying for mechanical means to achieve a lot of vacuum. The main energy consumption here is the heat required to change the state of the water from liquid to vapor - and this is 1000btu/lb regardless of the boiling point. As we know it is this heat that is delivered to the room when the steam condenses back into water at the radiator. And, though we can lower the initial temperature that boiling starts at with a vacuum the boiling point very quickly rises to 212 as the steam quickly kills the vacuum and we are again stuck with the 1btu/lb/degreeF we need to raise the returning condensate all the way back to 212 anyway during the firing cycle.
    When I initially converted my system back to natural vacuum between cycles I had ideas about possible great savings with a mechanically induced vacuum. Now I don't think so. I think the real benefit is just in starting the boiling quickly and in speeding the steam to the farthest places and this is achieved quite satisfactorily with the free natural vacuum. I also believe that while the initial boiling point is lowered by lower pressure, the heat of vaporization is actually raised as vacuum is increased and works against you.
  • ttekushan ttekushan @ 5:43 PM
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    Heat of vaporization

    Latent heat does increase. And it is delivered to the radiators, not lost. The steam also has less density at lower pressure thereby reducing the amount of total heat in the radiator, lower radiator temperature and reduced resistance to circulation. Mechanically induced vacuum return allows the reduction of boiler size due to the easing of "pick-up" factor requirements.

    Your point is well taken, however, since there are many ways of eliminating the pick up factor in steam heating. Off the top of my head, there's: Orifice vapor systems, Minitube with tiny piping, conversion to fin-tube (including cast iron fin) radiators, naturally induced vacuum on very tight systems, mechanically induced vacuum, and of course, any and all combinations of above.

    I really like the vacuum operation where it's an existing installation with the requisite big pipes and radiators and with an undersized boiler that can't muster equal steam distribution since it lacks adequate headroom. We can then turn an energy pig of a system into a highly efficient one. That possibility alone makes the discussion worthwhile to me.
    terry
  • PMJ PMJ @ 6:55 PM
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    Pick up factor etc

    I have one of those big pipe vapor systems but with a big boiler too. And I see pick up factor as only a small issue when it is warm outside and not much heat is needed anyway.  When I actually need heat the boiler is still warm and is never more than single digit minutes from steam anyway. When I really need heat steaming begins immediately at fire in the natural vacuum. Last I checked that big boiler that I paid to heat up is still inside my house with all its heat and warming the floor above it.
    Do we agree that vacuum does something at startup but a minute or two into any firing would be completely gone? It seems to me that the overwhelming majority of the heating process is going to go on at atmospheric conditions anyway.
  • ttekushan ttekushan @ 12:28 AM
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    I don't think we actually disagree.

    . . . unless you really want to. :-)

    " It seems to me that the overwhelming majority of the heating process is going
    to go on at atmospheric conditions anyway."

    Very true. I think the gray area is that the ancients of steam heating used at least three different meanings of vacuum steam heating, one of which overlaps with vapor heating. The one that overlaps vapor heating is naturally induced vacuum. The others are vacuum return assistance and the third is true subatmospheric operation. The last two require pumps. And in particular, subatmospheric operation requires a fairly high HP liquid ring vacuum pump that can maintain below atmospheric pressure on supply and return under all conditions. You're not going to find subatmospheric in a home (nor just about anywhere else these days) so, nope, when the heating gets going, it'll be pretty much atmospheric.

    I think mechanically assisted return can result in shorter run times during milder weather, where the heating industry seems to focus its attention. But my experiments have shown that a jet pump operating with a 1/25th HP motor can have great benefit for very little electrical use.

    I'll defer to Nash Jennings' and Oak Services' case studies on vacuum return improving seasonal fuel consumption by 30%. If a 3 HP motor can reduce fuel consumption that much on a 5 million BTU heating plant, it seems worthwhile.
    My own jet pump vacuum assist pumping station (using a cheap generic hydronic pump, 1/25th HP) has been working very well for 2 years, but the application is a 400 EDR area within a much MUCH larger heating system and all I was trying to achieve was even heating without a flooding subheader and violent water hammer in a problematic part of the system. Which it does. But any impact on fuel consumption is impossible to assess.
    Currently, another such pumping station of similar design is about to be implemented in a 600 EDR two pipe system with undersized boiler and slow return problems. Nothing else will change and a 1/12th HP pump will be used to drive it. We have a much better chance of measuring fuel consumption differences this way. The design is such that the system will function with or without the pump and without affecting performance with the pump disabled. I really want to find out how this affects seasonal fuel usage.

    "Last I checked that big boiler that I paid to heat up is still inside my house
    with all its heat and warming the floor above it."

    Yes. And the pipe too. That it's in the home is why that heat loss (if you can keep most of it from going up the chimney) is not really a loss. Steam is erroneously knocked for the issue of warm pipes and boiler. But still, if we can limit run times, then we're saving.

    "When I really need heat steaming begins immediately at fire in the natural vacuum."

    Actually, I find this true of atmospheric operation too. The larger systems I've dealt with actually will puff air out of the vented condensate receivers within moments of when the power burners light on low flame. I don't know where steam's detractors get away with implying that a boiler has to heat for 10 minutes ever single cycle.

    The question becomes, whether mechanically assisted venting and return creates a net savings of energy between electricity and fuel and whether that combination exceeds the total efficiency of other heating media. We already know that steam's advantage is its latent heat, and the more the better per pound of steam generated.
    Unless there are intractable problems, the simplest is what you are doing. And probably the best under many circumstances. There is value in a finely tuned yet simple system.

    My last sentence on this thread
    http://www.heatinghelp.com/forum-thread/140419/Why-hot-water-and-not-steam#p1322681
    sums up where I stand on the fundamental issue.
    terry
    This post was edited by an admin on January 17, 2014 12:40 AM.
  • PMJ PMJ @ 6:05 AM
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    We don't disagree

    Everything you say here looks right to me. I would like to learn more about this. I've read the claims about the 30% savings on a system that took 8psi to push steam where it needed to go and then took only 2psi with a small vacuum pump. To me, big systems mean big total leaks which were actually sort of vents in the first place? I admit l am probably missing something and would love to learn what it is. It doesn't ever take 2oz to fill my 1000 edr system so I can only assume that the pipes are too small in a heating system that needs 8. I also run a 6 million btu process steam boiler at 12 psi but that is needed to push condensate up out of tanks it heats a whole floor above it.
  • jumper jumper @ 6:24 PM
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    lots of ways

    There are a lot of ways to make steam heating work at less than 0 psig. Including one pipe.
    And even with single rate burners. There are payoffs in large industrial buildings. On a house the real question is is it worth it? I'm somewhat familiar with one pipe vacuum. Here are some numbers. A cold radiator under vacuum has an absolute pressure of about one third psia. Boiler water cooled to even 100° has a pressure of about one psia. That difference will hold 18 inches of condensate. And it may be a bad idea to let your boiler get that cold.
  • jumper jumper @ 11:54 PM
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    depends as usual

    PMJ asks pertinent questions. Big single stage goes to cut out quickly. Is that good or bad? Well it depends as usual. For example finned tube terminals also heat up quickly. But big fat radiators don't. One of vapor heating's goal is that terminals provide less heat for longer periods during mild weather.
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