Heating Help

135 square foot apartments

@ December 5, 2009 7:12 PM in Steam boiler dry fire, huge fuel savings with new boiler and piping

I never realized Denver had such a great market for 9'x15' apartments with one air vent near the ceiling!

Of course, I neglected to consider that 135 square feet near seal level expands when lifted to Denver's altitude. Imagine what these 12 suites could bring in at that elevation.

But then our steam savings might expand too :-)

-Terry

actually a good approach but

@ December 5, 2009 2:22 PM in Undersized Boiler Problem

put the petcocks on all the radiators. This will get the mains to act as a true manifold. Make sure the mains are very well vented first. Then begin turning down the petcocks on the warmest rooms first, then a little on the next warmest rooms, then back to the warmest, until you reach the now-formerly "cool" rooms. Touch up the formerly cool rooms until they are evenly heated.At this point your boiler will match the amount of steam radiation it can "see." The radiators will be "virtually downsized." This is actually the most efficient way to run any heating system. You will find that fuel consumption is good. The rating on the boiler in "square feet of steam" is your new effective EDR of the system. When a new boiler is installed, this is what you should use as your guide. Once you've balanced the system, you might want to lock those petcocks in position in some way.If the unlikely event that the system can't keep up with heat loss in the coldest weather, insulate the place and add extra storm windows. Its the right thing to do!-Terry

An additional note, your system shouldn't really need any more than about 6 or 8 ounces of steam pressure to do the trick. That's not a misprint. Install a Vaporstat that can control the steam pressure from 0 to 16 ounces. This goes in place of or in electrical series with the provided Pressuretrol. You can get a 0-3 lb. gage and set the pressure accordingly. If pressure builds so quickly that the boiler begins to cycle on and off on pressure, you will need to open all petcocks slightly. You'll get the feel of it.

Steam boiler dry fire, huge fuel savings with new boiler and piping

@ December 5, 2009 2:08 PM in Steam boiler dry fire, huge fuel savings with new boiler and piping

This a reminder that blowing down float controls and actually testing their operation are two different things. A client found this out the hard way. I hadn't been out in a couple of years since the 1970 Bryant was running "fine" although it was a gas pig. A few weeks ago I got a panicked call, "The boiler room is 500 degrees!" A bit of an exaggeration, but its a darn good thing he didn't have paints and solvents near that boiler. The jackets had acquired that attractive ashen white look. He put a glove on to pull the electric shut-off since the handle was too hot to touch!

Though that old bryant and a Dunkirk D248 may appear nearly identical, the D248 is a far more effective and efficient boiler. Several years ago I did a complete water and fire side cleaning of the bryant to get control over the high stack temps and terrible fuel consumption. One apartment ran cool from the day that boiler was installed, and somewhere along the line the boiler was slightly over fired to compensate. The terrible near boiler piping didn't help any (no effective steam drying at all) nor did the added yet unnecessary condensate pump, F&T traps, formerly wet returns now dry and trapped, etc.

Due to space and cost constraints we went with the D248 of similar I=B=R output which nearly matched EDR. We installed a proper header and equalizer, eliminated the pump and traps, reinstated the wet return concept with Hartford loop. Its back to a traditional single pipe system.

Wow. With the Tekmar 269 set at its previous calibration, the building temp was 80 degrees and rising! The "cold" apartment is now the same as everywhere else in the building.

The client has long kept a log of run times to keep control of fuel use. For a typical 25 degree evening, the old boiler ran 32 minutes on, 37 minutes off.

After recalibration of the Tekmar and under the same weather conditions, the new Dunkirk runs 12 minutes and is off 47 minutes. The "steam established" sensor heats up in about 4 minutes now instead of 13 minutes on a hot start.

After clocking the gas meter with the new boiler and comparing it with past records, we've determined that the new boiler consumes about 10% less fuel while running.

Crunching the numbers and correcting for the differing number of cycles, run times and boiler gas consumption, the new boiler uses 44% of the old boiler's use during a day with the same weather conditions and achieved interior temperature plus the cold apartment now at 70 instead of 60 degrees. Same system. Better boiler, better piping.
We'll continue tracking this one throughout the season to see if the 56% holds true.

-----

II- On-topic digression:

This particular system seemed like it had been running "fine" even thought there were some "quirks." Yeah, there was uneven heat and high fuel bills. "That's just the way steam is." Right? So we changed the boiler and piping, removed a number of "improvements" etc. and achieved huge savings. I've gotten 50+% fuel use/DD reductions in a significant number of cases before this. Enough not to be surprised this time.

I've said it before, but I'll say it again: outrageous fuel consumption on a steam system should be viewed as a symptom of a problem somewhere, not a characteristic of the medium. It could be the envelope. Often its the boiler. Sometimes something is amiss in the heating system even though it appears "fine." Usually a little of everything.

But suppose we tore out the system and converted to air or hot water and got the very same 56% savings? The inevitable conclusion would be that steam heating is hopelessly inefficient. We would never have known any differently. The influence of well publicized steam-to-whatever conversion projects that have attained similar savings prevents most of us from considering the possibility that a well executed "sprucing up" of the steam system can garner similar results.

"BoilerPro" has a great article on some of the ways this can be done with single pipe systems and undoubtedly will continue with two - pipe methods. We use the slowest radiator vents available and vent the daylights out of the main. On two-pipe, we use orifice plates or Barnes & Jones adjustable orifice valves in order to perform a "virtual downsizing" of the radiation in old homes and buildings. Its really an elegant solution that prevents you from removing sections of radiators or changing radiators, etc. The icing on the cake is that radiator steam traps last forever if they necessary at all.
I look forward to BoilerPro's next articles on two-pipe downsizing and its effect on boiler sizing.

Oh. My cell phone pictures of the boiler room were lousy, but one came out okay- its a picture of a PVC drain line in the vicinity of the dry-fired boiler.

-Terry

I second what Steamhead said.

@ November 28, 2009 1:25 AM in Vibration / Chatter On 3 PSI Gauge And Vaporstat.

Vaporstat chatter has always been due to oily contamination of the boiler water, in my experience. Skimming or surface blowoff is called for in these instances.

-Terry

Utica/Dunkirk, ECR

@ November 28, 2009 1:15 AM in Old Bryant Boiler

Embossed on the jacket on the right side near the Bryant nameplate is a manufacturer identification. Its driving me crazy but I used to know the name. It was probably a manufacturer that wound up with Utica and then ECR. Your boiler has sections and burners that are identical to the ECR Dunkirk D247 with the exception that your gas train is on the outside of the jacket on one side. The ECR Utica JD series and the ECR Dunkirk D248 are very similar, but with refinements on the flue collector and cast iron section designs.

Your boiler runs only at about 69% where ever I've dealt with them. The ECR product is a direct replacement for the Bryant series you have. The new ECRs are more effective and efficient boilers that the one you have, despite the striking similarities.

-Terry

what NBC said

@ November 13, 2009 11:02 PM in Water Hammer Arrestor

about starting a new thread and the boiler water is probably contaminated from the installation. And about that installation. We need pictures. In a new thread. We'd be glad to help.

-Terry

16 storey downfeed riser

@ November 13, 2009 10:50 PM in Steam pipe keeps breaking

Interesting. It may be helpful to go to the top of that riser and determine if it appears to have slipped downward at all. I'm not sure how that downfeed riser is suspended and at what intervals. If a clamp allowed the pipe to slip or if a clamp has broken, it seems likely that the expansion downward is allowing excessive stress on the section of pipe in question. Also possible is an expansion joint assembly that has stuck or collapsed so there is no longer relief of expansion. In other words, there is some means of "absorbing" the full expansion of that riser and to prevent its expansion from multiplying floor to floor. If there weren't, you'd have pipes inexplicably breaking. Oh wait. You do. That's your clue.

It seems to me that something has changed to cause the breakage of a tried and true steam line --and its replacement. Not too much there to fail other than supports and expansion arrangements and/or prefab expansion joints.

My concern with putting in various elbows, etc. is that you could cause condensate drainage problems, and if you don't have the elbows at full pipe size and arranged in a swing arm configuration, you may find yourself breaking the new arrangement at a fitting instead. Not much improvement! If at all practical, find the source of the lost expansion capacity.

-Terry

Remember not to burn yourself

@ November 13, 2009 12:33 PM in Hotter than HELL!!

Things that are not ordinarily hot can give you a burn if you've shut one of these down recently.

I just looked at a dry fired steamer a couple of days ago and the floor in front of the boiler was certainly hotter than I expected it to be!

At least there weren't any spray paint cans etc. in the same room. Phew.

-Terry

violent water line 'n foam

@ November 9, 2009 1:13 PM in Violent noise/not simply waterhammer

Foam is NOT normal. There is some kind of contamination creating the foam. Blowing out the base of the boiler will never remove a buoyant contaminant as it stays on the top of the water surface. Skimming the boiler is a good start.

Better yet, find the skim port and install a nipple, elbow and a service valve, perhaps with a hose bib so you can run a straight length of decent hose to a floor drain. You may also choose to run some cool water into the floor drain to temper what is about to go into it. Skim the boiler first as per Library articles on this subject. Next, I would do a surface blow off, explaining the hose and the tempering water. Simply run the boiler normally with the valve partially opened and add water as necessary to keep it running normally. Eventually the the remainder of the contaminants driven into the system will return to the boiler and out the surface valve. Many industrial boilers run with some level of continuous surface blow off for the purposes of maintaining foam-free dry steam. In your case, you should find a point where the water line becomes stable and the system quiets down. Close the valve and cap the bib to prevent wayward hands from opening it under steam.

Then you can determine if the system has any other issues.

-Terry

Hi Mel,

@ November 5, 2009 11:14 PM in Steam EDR compromise

Glad to see that downsizing worked out for you. A job well done. Nice, isn't it? Except for that boredom part...

Terry

is the tank new?

@ November 5, 2009 10:33 PM in Two pipe steam system issues

air bubbling in the tank sounds like its higher than the dry returns. As others have said, what else did you change? There should be no vents on the radiators if there are traps. As far as the boiler back filling the tank, install a motorized zone valve in the boiler feed line. The feed control on the boiler will open the valve and the contacts on the valve will operate the feed pump through a relay. I've seen this done on several installations and it works out fine. Water can't be sucked into the boiler this way, either.

Bear in mind that the water level in the tank must be below the lowest point of the dry returns as this tank is a vented receiver to vent the system's air and provide vacuum relief during cool-down.

Is there a condensate pump somewhere in the building that you're unaware of? If one of those fails, you can have all sorts of weird problems that depend on its location and elevation.
Was there a vacuum breaker on the old boiler? Here's why I ask: Its possible that the original tank installation height was screwed up from the get-go and higher steam pressure was used to drive the air through the water in the tank. The high water level of the HRT would actually have to be held back from the feed tank by the in-line check valve. In this scenario, a vacuum breaker on or near the boiler might have existed to deal with the incorrect height of the receiver tank. In addition to all of this, the absolute strangest reason for such a hypothetical arrangement would be that the tank was elevated to condense steam from the returns caused by both high supply pressures and bad steam traps! Stranger things have happened. And it all sort of works until you change the boiler and leave out a tiny vacuum breaker that was there to deal with a symptom. Hypothetically.

A pro out there as Steamhead says should be able to figure it out.

-Terry

Hi Mark

@ November 3, 2009 11:26 AM in Legionnaires Disease and Hot Water Tank Temp

I remember your posts of your LD experiences vividly. Your posts alone changed how I advise clients from that point on. The fact that it is an inhalation problem and that the most vulnerable among us have issues with lungs/brachia, to recommend low water temps is simply irresponsible.

140° water temps aren't ridiculous. Given a choice between a mild scald from 140° water (assuming no tempering) and a miserable illness/death, I'll choose the former. I'm strange that way.

I always used 140° anyway for the dishwasher and winter cold water tempering. I never could determine any difference in gas usage regardless of water heater temperature.

I can't put my finger on the study right now, perhaps others here know of it (I saw it on the Wall to begin with): It determines that fuel consumption difference for water heating @ 120° vs 140° with a standard water heater to be quite small.

Anyway, we like you around here Mark. Keep that water heater turned up!

-Terry

8-Way

@ November 3, 2009 10:47 AM in Boiler Surging / Any help for this boiler?

8-Way is a good product. Its not a particularly fast descaling product, but it releases the muck that sits at the bottom of boiler sections and elsewhere. It provides good scale control and is a good oxygen scavenger/anticorrosive agent. Just don't use too much. Pale purple/pink in the sight glass is fine. You may find extra muck at each blowdown. This is good since it is slowly releasing deeply accumulated stuff.However, 8-Way can actually cause surging in low water content boilers if a) the concentration is too strong, or b) there are contaminants on the water's surface. If the boiler wasn't properly skimmed at installation or if piping work of any kind was done in the system, these contaminants can remain there indefinitely until skimmed off. The skimming idea described by S.G. above with the 8-Way in there will improve your results. Now, there are simply some boilers models that bounce more than others and this is normal. Other things: The lower the water content/EDR output, the greater the chances of boiler flooding between cycles. Also beware of overfiring of such boilers since the water line will always be violent when given more heat than their design allows. Check manifold pressures. Finally, you may find that with certain boilers the 8-Way may have to be practically at trace amounts for a minimum-bounce water line, assuming you've done a good skimming.-Terry

orrrr. . .

@ November 3, 2009 10:24 AM in Steam EDR compromise

You could simply run a steam line to a neighbor's house to heat their home as well. The boiler will cease to short cycle. And you could charge for your steam generating services and come out ahead.

I'm just a fount of great ideas today.

-Terry

P.S. depending on the design and burner type on your boiler, you could choose a less ambitious route and have it downfired to match the EDR. This would stop the short cycling but energy savings would be dependent on the boiler/burner design if any savings are had at all. Creative and more effective ways of downsizing a boiler exist, but you may find it difficult to find someone willing to do them.

Thermal Energy

@ October 31, 2009 6:09 PM in district heating

Thanks for the link. Informative video. A great way to do things.

Terry

Fuel savings.

@ October 29, 2009 12:42 PM in Vapor system conversion to hot water condensing boiler

Out of tune steam systems can use tremendous amounts of fuel. Unlike modern equipment which is just as likely to lock out and leave you with no heat, the old steam system will continue to operate in what may appear to be a proper manner while out of tune. Everything may appear normal. The excess fuel consumption is often the only symptom in evidence. Excess fuel consumption is more a symptom than it is a characteristic of steam heating, unless it is a self fulfilling prophecy created by decades-long habits. "Normal" becomes "Proper" in the mind. Its amazing how many times i've heard this from maintenance people and even steam service technicians, verbatim: "thats just the way steam is." B.S.I.M.O.

My last two church jobs involved minimal parts replacement but cleaning, balancing, control, load matching, venting rate manipulation and boiler timing/pressure control. One is a 1948 system with steel boiler, convectors, pneumatic control system. Major boiler cleaning & adjustments along with repair of the pneumatic system were all that was necessary. Reattached the wing to the steam heating system that was running with rooftop units for a decade. . . . The other church has an 1885 two-pipe with air vent system with a standard two pipe wing added along with two zone controls. The building was heavily insulated about 10 years ago. Together with oversized radiation, it was discovered that design temp for each wing could be maintained with a 50% duty cycle. So I downsized boiler, adjusted variable firing rates, restored two pipe air vent original building to original spec. Utilized two existing 4" zone valves to operate the zones sequentially with an "or" logic configuration so that auxiliary switches enable one of two different steam pressures depending on the zone in operation: either a firing rate controlling vaporstat for the original section (4 oz steam pressure) or a firing rate vaporstat @ 16 oz to allow slow pressure rise at low fire) for the newer piping. The usual 1.5 lb and upper limit pressuretrols remain as safeties. Isolation of returns is handled by a vented receiver. The 1885 section uses only float traps in the returns, venting being handled at the radiator vents.

The buildings' fuel consumption/DD dropped 50% and 55% respectively. If I were prone to using the term "Greenest Solution," now would be a good time to use it. Unless referring to the capital expenditure required of the churches involved. The payback period was less that one year in one case and about one year in the other. "Not a lot of Green," in these cases.

-Terry

Rod, on those valves,

@ October 26, 2009 1:06 AM in Install Pics and Hissing Radiator

I very much agree with your point of capping those, but my choice is using a gate valve there for its full port but slow opening characteristics and leaving it installed. But FIRMLY capped at the outlet. On some of today's low water content/high turbulence boilers I like to be able to do a surface blow off occasionally.

On some occasions I leave a nipple with a brass cap instead. I just don't like the idea of putting a steel pipe plug in the casting since they seem so prone to getting impossibly stuck and being a real pain for any future needs for skimming/surface blowoff.

Just my 2¢. But a good call for safety's sake.

-Terry

Paul vents, a pump, and a regulator.

@ October 26, 2009 12:41 AM in Paul system retrofit

My ears were burning, so I looked around the Wall and...

Thanks for the vote of confidence, Frank. I also know Gerry wants to fully restore a Paul type system.

Mike, I would forget about the steam powered pump capable of moving that volume of air out of the system. Use an electric one. It won't use that much power, especially considering the potential for fuel savings. I've heard of up to 30% fuel reductions, but I don't know how reliable that information is. IMO, if you got a 20% reduction that would be the minimum and quite delightful.

Some vacuum systems use a liquid ring pump, but it might not be a good choice in this application. It must be primed as these pumps are typically used in two pipe vacuum systems where they are necessarily pumping both condensate and air. When the pumped fluids rise above 140F the pump becomes less efficient. I'm thinking a vortex blower/vac might be a good choice for this particular application.

The ideal radiator vents are the Hoffman #3. Pricey but available. About $68 apiece if I recall correctly.

Regarding the depth of the vacuum, that is a much more complicated topic. You could merely set the vacuum level to a nominal level for evacuating air. This is fine and all you really need. But it would be interesting to be able to vary the vacuum level based on demand and outdoor temperature. The ancients were able to do so, but adapting modern controls to achieve the same goal might be too daunting. To really control steam temperature and volume, the vacuum must also communicate back to the supply to lower the system (supply and vent) below atmospheric pressure while maintaining a pressure differential to allow steam circulation regardless of their absolute pressure. There I go again, complexifying things before getting off the ground... Certainly its too daunting to start out with! We don't want to discourage this project!

Lets just stick to a fixed vacuum like a pound or two (2-3" Hg vacuum). It'll be a night and day difference.

Lets continue this. Perhaps Gerry can pipe up too ;-)

-Terry

inlet orifice doesn't work on single pipe but

@ October 23, 2009 8:08 PM in High-Efficiency Steam boiler thought experiment

you get the same effect with proportional venting of the radiators. Gorton has a good chart, as does Jacobus Maid-o-Mist. Also look at balancing a steam system with proportional venting by Gill and Pajek, here on heatinghelp.

Yow. 50% more?

@ October 22, 2009 11:44 PM in High-Efficiency Steam boiler thought experiment

OK, nevermind all that nifty heat extraction stuff for now. There's a lot of low fruit on the tree to harvest first! You have a point about steady state efficiency and all, but the cast iron of the boiler can't absorb 50% of the heat intended for heating a building and make it go somewhere. Were that true, think what we could do with such a compact thermal storage unit!

Do you know how that boiler is sized with regard to the existing load?

Is the boiler firing at its ratings? Is excess air out of control?

Is the chimney sized for a coal boiler and sucking the burner's heat right through the passages? This should be checked with a Manometer or analyzer. Baffle the flue pipe until draft is within proper range, -.02 to -.04" W.C. (for gas burners).

What are the combustion numbers from when it was last serviced? Please tell me it gets serviced and that a combustion analysis is done.

If there is no LWCO, what else is missing or incorrect? Is there something about the way it is piped and/or vented that is could cause this trouble? [remember a LWCO can be incorporated into a boiler feed pump control if you have that arrangement.]

I recommend a carefully sized and carefully chosen boiler, but are there other symptoms that we should know about? For example, does one portion of the building have to get very hot radiators before others begin to heat?

Take a typical apartment and cross reference the radiators and determine their EDR and figure how that relates to the size of the apartment and other heat loss considerations. Does it seem disproportionately high for your location?

What is the condition of the rest of the system, like traps and vents?

Do you actually have a vapor system whose operation is being ruined by excessive steam pressure or excessive boiler size? Do some radiators have "special" looking valves and traps but others do not, as though they've been replaced?

Does the steam main run through the basements with upfeed risers or through an uninsulated attic space with downfeed risers? If downfeed, what is the condition of its insulation? Someone must actually look! Record breaking icicles can be a good indicator. Once troublesome building I tend to has just this problem. The insulation has fallen from the overhead mains. This place is right on lake Erie and the winter winds exhaust tremendous amounts of heat from that space. As a matter of fact, if gentle breezes come from certain directions and lock the heat up there, top floor apartments will run about 78F with the radiators closed. Yes, they have the biggest, most dangerous icicles in town.

Conversely, does the boiler run all the time just to keep the place comfortable at all? An undersized boiler in a large unbalanced system can begin to run continuously without ever reaching a temp setpoint. I'm guessing you don't have this problem given the pressures you mention.

What I'm getting at is that even a new boiler can be sized and piped into a system with various issues such that it will still consume far too much energy. I've got a number of clients with steam heated buildings of the 24 to 28 apartment size. Most fall into a fuel consumption range that I would expect for a building of that type.

However, there are a few others that just suck up natural gas like you wouldn't believe. The outdoor temperatures have only a marginal effect on usage, a sure sign of large heating system inefficiencies. These are the type of situations that prove that combustion efficiency and fuel-to-steam efficiency can be quite different.

Sometimes the systems are just grossly oversized. One of my gas guzzling buildings has a design temp of -45F. Thats not a typo. They don't want to spend the money rectifying the problem. $8,000 a month on gas for a 24 unit building is OK tho. It should be half that. These things often have a 2 month pay back period, sometimes less and more obviously if the boiler is being replaced as well. But I digress.

I'm a big advocate of using radiator orifice valves or inlet orifices to control the rate of steam being fed into the radiators. Here's the basic idea:

• Determine actual heat losses based on a modern heat loss model and design temp, etc;
• Determine the EDR necessary;
• Determine your operating pressure (low! and control it pretty tightly);
• Cross reference desired EDR to be heated to supply pressure;
• Adjust adjustable orifice valve or drill orifice to the proper number;
• Size any new boiler to what I call the "Virtual EDR" plus a modest pick up factor since the piping is still the same.
• I strongly suggest some form of staged firing, with the lowest stage able to maintain steam pressure under minimum load. With two stage firing the lower stage should be used to remove the pick-up factor and hold the steam pressure steady or very slowly rising under minimum load. The reason we don't want the steam pressure to drop as soon as the burner drops out of high fire is that radiators that are not yet properly heated will have their air content expand to fill the void left by the condensing steam and in the absence of enough steam output to fully replenish the steam's share of the radiator. This can cause radiators at the end of the line to run cold even with boiler running. It is a form of steam stall.
• For heaven's sake pipe the boiler properly and control the draft.

Finally, I'm trying to find an interesting study that shows that converting the average steam heating system (meaning one in decent running order, not the guzzler problem systems) has a payback period of 35 to 50 years. What a bargain.

-Terry

Reply (long, no drawings yet)

@ October 22, 2009 1:35 AM in High-Efficiency Steam boiler thought experiment

You have to remember that it is the latent heat of evaporation of water that is the primary heat transfer medium. So for every pound of water from and at 212F about 970 BTU (at sea level) are required to turn it into steam at 212F. The sensible heat remaining is only 1 degree F per pound. This is why steam moves heat and power so efficiently. It is extremely light, low resistance, fast and has an enormous heat capacity. But steam's temperature intensity is also its achilles heel in condensing tech as stack temps are always over the saturated steam temp and the heat carrying capacity of return water is miniscule if it remains in the liquid state.

If you used an economizer, or as you suggest, using returning condensate as your heat sink, you can only infuse that water with a few BTU's before it is up to 212 F water. You still have to provide it another 970 BTU before it steams.

This is why an economizer for steam usually provides a number of non steam fluid streams to absorb waste heat from the stack. A cool enough source can condense flue gasses, but you are not going to generate any steam with it unless you are extracting heat from a high pressure steam boiler such that there is enough waste heat to provide a modest amount of low pressure steam from the exhaust gas heat. This is where the unfired steam generator /waste heat recovery boiler (WHRB) is used.

Even with the condensing boiler, you would only be able to condense a minute amount of exhaust gasses because the total heat you could introduce into the system would be the difference between the return water sensible heat and about 120F with decreasing flue gas condensing above that. Then you have to introduce 970 times that heat to water already at 212F to produce steam. You wouldn't get any steam with the proposed arrangement unless you fire the original boiler. And considering the minute rise in efficiency by warming the return water in a residential heating application, the losses incurred by running the condensing boiler would probably increase your total energy consumption especially if compared to waste heat extraction with a traditional stack economizer.

This is not to suggest that we can't consider a fairly practical means of extracting waste heat from a steam boiler, which at its best may condense a little, or at its worst allow the exiting heat to be little more than the saturated steam temp. At this point we are adopting the philosophy of water boiler manufacturers like System 2000 or perhaps Thermal Solutions non condensing boilers that run at about 88% efficiency (not thermal efficiency) in the interests of longevity and product reliability.

I'll get into the deeper specifics of this alternative idea another time, but this is the basic idea: using your low efficiency high mass boiler as a WHRB remains as you originally proposed -only you fire with a decent efficiency steamer next to it, not a condensing water boiler. The fundamental design is a CI steam (primary) boiler exhausted without a draft hood into a power venter and down into the waste heat (secondary) boiler's flue outlet. The waste heat boiler exhausts out the bottom and up into a side wall vent or lined chimney. There are no burners in the secondary boiler. The secondary/waste heat boiler would be set up as a Mestek Ray where the combustion gasses move downward, cooling as they reach the bottom. Should there be any condensation of flue gasses water will drop into a bottom tray where the burner would ordinarily be on a regular CI steamer. If there is condensation, let the CI rot. It might still last 30 years.

The secondary "boiler" should have a side steam outlet rather than a top and here's why. Stay with me here. Picture the two boilers side by side, with the exhaust gasses of the active boiler being blown downward through the secondary, unfired boiler. The bottom is the exhaust on the secondary boiler, remember. They look like boilers piped in tandem through two hartfords but are interconnected THROUGH THE TOP OUTLETS ONLY. The bottoms are not piped together at all. System return / fill water enters the secondary boiler at the bottom and completely fills it to the side outlet tappings where water cascades into the hartford of the primary boiler. The top of the boilers are piped in parallel. In other words, the steam side is connected such that the boilers are in parallel and the water side is connected with the boilers in series.

As return water enters the bottom of the secondary "boiler" it rises as it is heated by the exhaust gas flow from the primary boiler in counterflow. The water warms, rises within the secondary boiler and slowly feeds preheated water into the primary boiler by overflowing into its hartford connection. At start up and beginning of the cycle, flue gas condensing may occur. Under long run times and full system saturation, the secondary boiler may actually produce steam. This steam will be ADDED to the output of the primary boiler by virtue of the header piping arrangement. In this way, we will always have somewhere to put the heat recovered from the stack. In this worst case scenario, the flue temp will be little more than the saturated steam temp.

I am confident that this method would provide overall efficiency numbers that approach those of high efficiency non condensing hot water boilers.

Due to steam's unique circulation and energy transfer characteristics, the boosted efficiency of this arrangement should result in total fuel conservation that meets or exceeds many competitive modern installations while retaining the comfort of steam heat.

I'll post a few diagrams of this proposed system when I have a bit more time.

Terry

P.S. If Steamhead, Gordo, Gerry, or Steve Pajek (though not exclusively!) are reading this, this is the most practical short term solution to my condensing steam boiler design project of this summer. The condensing steam boiler is currently beyond my $ supply and has tested my engineering abilities, but suffice it to say that it has just enough higher maintenance components that its additional cost may be a difficult sell. It works in theory, and the estimated numbers look good in addition to doing away with the concept of a traditional boiler entirely. Scale sized system subset tests are encouraging, but introduce nearly as many questions as they answer! Its electrical power consumption is on the high side of normal for off the shelf components, but at least the heat generated therefrom gets directly applied to the steam output. It should theoretically condense under all heating loads, but is confined to low pressure applications. I'll give it a try again next year.

Ahhh, you are in Cleveland

@ October 14, 2009 10:09 PM in Bang, Bang

You are in good hands here, if I don't say so myself.

You are also in the company of vapor system and SelecTemp experts! [check out the library under unusual equipment/systems]

-Terry