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    Bypass with thermostatic valve? (24 Posts)

  • AJ AJ @ 12:20 PM
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    Bypass with thermostatic valve?

    Ok this is one of those DIY’er questions so bear with me…
    Background: Peerless WBV-03 connected to old cast iron rads.  System water volume is approx. 100gal. No zones. New parallel piping to radiators (i.e. not gravity).

    I’d like to install some boiler protection because of the high water content(although there is no mention of this in the Peerless manual???).  P/S piping doesn’t make much sense to me because there wouldn’t be any zones on the secondary so essentially the P/S would act like a system bypass.  That is, assuming both pumps came on at the same time.

    I was thinking of a system bypass, with a manual globe valve in the bypass followed by a thermostatic valve with a remote sensor attached to the return. I read about this somewhere but can’t find it again. The TV would close off the bypass as return temps came up and the manual valve would throttle the bypass loop so there would be some system flow initially.

    What are the down sides to this setup?
    Where do I find a simple thermostatic valve with remote sensor? I can only find the 3-way mixing type.
    Thanks.
  • Ironman Ironman @ 1:22 PM
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    More Info

    Can we back up and get a little more info? Usually this type of scenario (gravity converted  to forced flow) will allow you a significant increase in efficiency in designed correctly from the start.

    1. Have you done a heat loss on the house? If so, what was the total?

    2. What was the btu's of the old boiler?

    3. What's the btu rating of the new one?

    4. What's the EDR (btu output of your radiation)?

    5. What size are the main supply and return lines?

    You're on the right track by considering boiler protection, but having the requested info will help in advising what options there are.
    Bob Boan



    You can choose to do what you want, but you cannot choose the consequences.
    This post was edited by an admin on December 1, 2010 1:24 PM.
  • AJ AJ @ 1:59 PM
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    >>>

    1.       The house is a work in progress but the heat loss be between 68 and 80k depending on infiltration, insulation etc.. This is with Slant/fin heat loss software.
    2.       No old boiler. This is a new install with salvaged radiators…. because I’m insane.
    3.       New boiler is 85 to 103 depending on firing ???
    4.       EDR was matched pretty close to the upper limit of the heat loss so figure 470 ish. Not sure if that’s the right way but it’s what I did with what I knew at the time. I can add radiators if needed.
    5.       1 ¼ mains with 1” branch that then splits to ¾” to the rads. All black pipe.
     
    Basically this is an old large one-room schoolhouse. Brick construction with no insulation. 14ft ceilings, attic will be well insulated. Infiltration will be average( single pane windows with storms). Heat loss is high for sq/ft. 4 huge antique rads and a couple other small ones. This is a side project that I could never afford to pay someone to do so any help is much appreciated.
  • AJ AJ @ 6:00 PM
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    Question simplified......

    I found the original post that  mentions the thermostatic valve in the bypass....
    "On residential size jobs, I do this by installing a full-size bypass and equipping it with a thermostatic valve that has a remote bulb and capillary tube. The bulb goes in a well on the return pipe, right at the boiler. When cold-starting, most of the flow goes through the bypass. As the system warms up, the thermostatic valve starts closing and will modulate to the return temperature you set. Needs only one pump. Failure mode will be valve open, so boiler is always protected. In residential radiant systems,"

    I just need a source for a thermostatic valve and remote bulb sensor that will work. Preferably 1 1/4"
    Thanks


     "
  • zacmobile zacmobile @ 6:54 PM
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  • Ironman Ironman @ 7:36 PM
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    Hydraulic Separation

    Is an issue that a bypass won't address. The bypass will address the temp issue,but not the issue of different flow rates required for the boiler and heating loop(s).

    The boiler needs a 20 -30 deg. delta T, while the radiation will work best with a 20 deg. delta T. The bypass would be constantly varying the flow rate in the radiation while attempting to protect the boiler until it reached 140 + deg. This can lead to uneven performance in different parts of the radiation. How much in your case? I can't say for sure, but the larger the water volume in the radiation, the greater that I would be concerned.

    By providing some means of hydraulic separation (such as primary/secondary), this issue is removed from the equation.

    I would recommend that you pipe the boiler supply connection straight to the boiler return connection to form a primary loop. Place a Taco 007 or Grundfos UPS15-58 circ in this line near the boiler return. Place two closely spaced pri/sec. tees in the loop to form a secondary loop for the radiators with its own properly sized circ. Now the boiler can have its own required flow and the radiators will maintain their own flow rate independently.

    If you want precise control of the boiler water temp to get it to 140 deg. as fast as possible, you could then add an additional aquastat that senses boiler temp in the primary loop and holds the secondary pump off until the boiler reaches 140 deg. Or an even better setup would be to use a variable speed delta T pump like the Taco 008-VDTF6 in the primary loop.

    If choose to use an indirect, then pipe it as another secondary loop and give it priority by using the necessary pump control. No need to hold its pump off til 140 deg. though. You're not dealing with a cold, high mass like you have with the radiators.

    This should work much better than thermostatic bypass and it's the arrangement more engineers are recommending now.

    I'd also recommend that you install a boiler reset control. It could very easily save you 10 - 15% in fuel usage.

    Best Wishes
    Bob Boan



    You can choose to do what you want, but you cannot choose the consequences.
  • AJ AJ @ 9:21 PM
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    more questions

    Thank you very much for the reply. I have more questions. Sorry if this is dumb but….
    The thing I don’t understand about P/S is…. on a secondary with no zones (i.e. 1 big zone)and no TRV’s on the radiators, there will be no real variation on what the secondary is pulling from the primary right. So essentially a certain fixed amount of flow will be pulled to the secondary and a certain amount will bypass the tee’s and continue to circulate through the primary. This doesn’t seem to be that different from a fixed ’system bypass’.

    If you want precise control of the boiler water temp to get it to 140 deg. as fast as possible, you could then add an additional aquastat that senses boiler temp in the primary loop and holds the secondary pump off until the boiler reaches 140 deg.

    But, assuming approx. 12 gal of water in the primary and 90 gal in the secondary(old cast iron rads.), when the secondary kicks on, wouldn’t it overwhelm the primary with cooler water anyway?

    Or an even better setup would be to use a variable speed delta T pump like the Taco 008-VDTF6 in the primary loop.

    If I were going to use a variable speed delta T pump on a system without zones would I even need P/S piping? What would be wrong with just standard piping, no bypass or P/S, and a variable speed delta T pump.
    This post was edited by an admin on December 2, 2010 9:22 PM.
  • Mike Kusiak Mike Kusiak @ 8:08 PM
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    P/S and low temp protection

    Bob, I understand how the P/S setup will allow both loops to have their own optimum flow rate, but won't there still be the issue of thermal shock and low boiler temperature? This is something I have always wondered about. Even if you hold the circulator in the system loop off until the boiler reaches 140F, when the system loop starts it will be mixing a large volume of cold water into the boiler loop and suddenly lowering its temperature. I guess it depends on the relative thermal masses of the two loops, but with 100 gallons of water in the system loop I would think it could rapidly cool the smaller volume of water in the boiler.

    What about some type of motorized mixing valve setup with an outdoor reset controller where you could control the relative volume of water mixing dependent on outdoor and return water temperature?
  • Ironman Ironman @ 9:54 PM
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    Depends...

    Mike,

    I would think that it would be more dependent on the mixing (heat balance) ratio. You'd be back to calculating using the universal hydronics formula. In this case, without calculating, it's probably about equal depending on pump selection and pipe sizing.

    The bypass could still be added, but I'd do it with valves, not the thermostatic one. It doesn't begin to open to the system until 160 deg. and has to reach 180 deg. to fully open. You'd have to look at system reset then instead of boiler reset, but that would be a better choice any way. The thermostatic one is sold by Danfoss.

    I agree that a control that could do all this would be ideal, but we could be driving the price higher than some would want to pay who purchase low to mid range boilers.

    I'm gonna take a look at my Tekmar catalogue and see what they offer. Maybe someone else could chime in on this if they know of anything better.
    Bob Boan



    You can choose to do what you want, but you cannot choose the consequences.
  • AJ AJ @ 9:27 PM
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    Mike

    Mike..thats what I was thinking, you posted while I was typing.
  • Mark Eatherton Mark Eatherton @ 11:12 PM
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    Oventrop...

    I just put a 1-1/4" 3 way with a remote bulb, cap tube and thermostat. It works like a champ. Dead nuts on proportional control.

    The have a set of instructions for using the same rig as a boiler protection scheme.

    http://www.oventrop-na.com/us/index.asp?sprache=US

    Great products.

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • AJ AJ @ 1:36 PM
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    more...

    I don’t really understand the need for a 3-way valve. It seems like a standard valve (like a TRV for example) placed inline in the bypass would work without complicating the flow of the return piping/adding pressure drop, etc…
     I was thinking of just putting a 1 ¼ TRV in a system bypass line and adjusting it so the room temperature in the boiler room closes the bypass at approximately the time when the return temps are greater than 140.  It would be much easier if the valve could sense the return temp directly though.
    This post was edited by an admin on December 3, 2010 1:59 PM.
  • hot rod hot rod @ 3:33 PM
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    a number of options

    to protect the boiler from low return temperatures. It can be done with valves or pumps. The important thing is that you have a means to sense the temperature returning to the boiler.

    A 3 way thermostatic valve, a motorized valve with a controller, a valve with a remote sensing bulb, can do this, a pump with variable speed and a control that watches return temperature can do this.

    But just a pump, bypass pipe or manual valves cannot assure return protection as they do not have a means to detect the temperature and respond.

    Here is a link to a manual that you may download and read up on the concept and methods of mixing. It shows concepts and products dating back to the 1940's from B&G and others, up to the current methods and components.


    www.caleffi.us/caleffi/en_US/Site/Technical_library/Idraulica_magazine/args/detail/~Details~Magazines~magazine_detail_0000093/type/magazine/index.sdo

    hr
  • kev kev @ 4:54 PM
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    boiler protection

    I have tried the thermostatic three ways valves and they work great. If you call DANFOSS they will help you with the location of the pumps and layout. It does involve a lot of fittings, flanges, tees etc.  I wish somebody would sell an affordable pre-piped gizmo that would be easy to connect to a simple cast iron boiler that you could then pipe your heating loops off while giving the boiler the protection it needs.
  • AJ AJ @ 9:16 PM
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    how is this drawing?

    I realize that this is a very simple piping setup but I just want to make sure the there are no problems.
    This will be a system bypass, probably with a 140 deg. ESBE mixing valve on the return/bypass connection.
    Is it ok for the pump to be so close to the 90 right before it?
    Is it ok for the bypass and then the first branch circuit to be so close (downstream) from the pump?
    Thanks
  • Mark Eatherton Mark Eatherton @ 9:55 PM
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    Sure...

    That would work, and to guarantee no condensation during normal operation, you could put a 2 way non electric thermostatic valve on the by pass with the remote bulb sensor at the return line going into the boiler. Just make certain that the actuator that you use for controlling is capable of a higher set point operation. Set it for 140 and let 'er rip.

    The location of the two close branches are not an issue. They are looking for a pressure differential that will dictate where and how much they flow. Distance between tees is more critical in primary secondary piping schemes, which this is not.

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
    This post was edited by an admin on December 4, 2010 9:58 PM.
  • AJ AJ @ 10:07 PM
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    Mark

    Mark,
    Could you point me towards a 2 way thermostatic valve with remote bulb sensor?
    Make and model number would be great. The only thing I can find are the 3-way mixing type.  Thanks
  • Mark Eatherton Mark Eatherton @ 10:26 PM
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    Oventrop...

    Not sure how I missed this question, but Oventrop makes a 2 way with a 10 meter max length cap tube.

    Check with Oventrop North America and they can give you a part number.

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • CTGuy CTGuy @ 10:08 PM
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    Do I need a bypass valve?

    I am adding an old wood "water jacket" boiler to my existing system.  My oil boiler is an old American Standard which has a domestic hot water coil. A layout is attached.  As you can see, I have plumbed the boilers in series.  I did so because I need to keep the coil hot at all times.  The idea, obviously, is to allow me to burn wood and run the heat through the oil boiler, and when the wood burns down, the oil will kick in.  The wood boiler's circulation pump will kick in once the water in the wood boiler reaches the desired temp. The question is: Do I need to use a bypass valve on the wood boiler?  Normally, I would say, yes, but when I think about it, I have my doubts.  Since the boilers are plumbed in series, and the oil boiler will always be hot, the water returning to the wood boiler should also always be hot, right?  If the purpose for the bypass valve is to prevent cold return water entering the hot wood boiler, do I need one?  I have included one on the layout plan (just above the wood boiler) to show what I had originally had in mind.
  • Mark Eatherton Mark Eatherton @ 9:13 AM
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    Drawings didn't come through...

    Try posting them as JPEG instead of PDF format.

    The manufacturer of the solid fuel boiler should have given you an idea of acceptable piping manners and methods. They don't like to see long term condensation potentials because it can cause problems with creosote fur in the flue gas passage ways.

    Generally speaking, it is not a good idea to pipe boilers in series, because when in the off mode, the off boiler becomes a heat emitter. You can do freeze protection by cycling a pump with the boiler set up as a secondary item.

    RT*M... Follow the manufacturers recommendations and avoid problems.

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • CTGuy CTGuy @ 11:07 AM
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    Here is the layout in jpg format

    Sorry.  Here it is in jpg format.  Since I have a separate circ pump and flo check on the wood boiler circuit, do you think I will get much back flow through the wood boiler when it is cold?
  • CTGuy CTGuy @ 11:14 AM
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    Ok - I'll try to post the JPG again

    I made it smaller. Maybe it will work this time.
  • CTGuy CTGuy @ 11:30 AM
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    Ok, here it is.

    It worked this time I think. Do I need the thermostatic bypass valve on the return to the wood boiler?  The wood boiler is old.  I don't have an owner's manual, and can't even find a model or manufacturers' name anywhere on it.
    This post was edited by an admin on January 19, 2011 11:59 AM.
  • Tranberg Tranberg @ 8:33 AM
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    Laddomat

    Google Laddomat    (charge-o-matic in swedish)

    http://www.laddomat.se/images/laddomat_urval.jpg

    http://www.laddomat.eu/index.php?lang=en
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