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ODR with fireplace

will close when they satisfy so no system water will flow through them. This can happen even when you are not using the fireplace. The TRV's are your "indoor sensors".

Be sure that there is some type of by-pass to prevent your circulator from dead-heading when this happens.

Hope this helps.

Mark H


  • Dave_4
    Dave_4 Member Posts: 1,405
    ODR with Fireplace

    Will have panel radiators, with TRV's, on constant circulation with outdoor reset. I have a new woodburning fireplace BIS Tradition that is capable of putting out 80K BTU/hr., which is more than enough to heat the house when it gets cooking.

    I am concerned that with the boiler ODR and fireplace not talking to one another, the boiler will not shut down and we will overheat the house when the fireplace is being used.

    I think I need some type of inside sensor/reset. What controls can I add to prevent this from happening?

  • Dave_4
    Dave_4 Member Posts: 1,405
    What about the boiler

    I understand that the TRV's based on room temperature are what will shut off the panels.

    However, the boiler will be controled through an ODR which, is based on an outside temperature. So how do I let the boiler know not to fire when it is cold outside and the fireplace is heating the house?

    Or am I misunderstanding how an ODR functions.

  • Mark Hunt_3
    Mark Hunt_3 Member Posts: 184

    is telling your boiler to run now?

    If the "TT" terminals at the boiler are jumped out and the boiler rides the reset curve until the warm weather shut-down kicks in, you could install a simple toggle switch to open or close that circuit. If you want something that is more "automatic", a master thermostat could also be installed in a central area that would open or close the same circuit.

    TRV systems typically run on constant circulation meaning that the boiler is maintaining whatever temp the ODR control tells it to and the circulator is running whether the TRV's are open or closed. During the periods of time that all of the TRV's are closed the temperature drop across the system will be VERY low so the boiler will seldom fire. BUT, it will fire from time to time. It is supposed to, otherwise there would be no heat available for any TRV that opened.

    The ODR just controls what the water temp is going out to the system based on OD temp. Colder weather, warmer water. Warmer weather, cooler water. All of the ODR controls that I have seen have the "Warm Weather Shut-down" feature which will prevent the boiler from firing during warmer seasons.(Domestic hot water production is not affected by the WWSD)

    We would need a bit more info on exactly what type of control strategy was used with your system in order to give more detailed answers. Boiler model, ODR control etc....

    Pictures would be a plus.

    Just shutting off the boiler while the stove is firing would eliminate your hot water IF the boiler is responsible for its production.

    Mark H

  • Dave_4
    Dave_4 Member Posts: 1,405
    Still in the planning stage

    The system is still in the planning / design stage. However, I need to get moving before winter sets in. Heating with wood is cheap, but alot of work.

    There will be two zones with panels covering about 2100 S.F. One of these zones will be directly affected by any heat output from the fireplace. The second zone is isolated from the room with the fireplace and also has insulated walls, so the heat from the fireplace in the second zone would be minimal.

    An indirect HW tank will also be installed.

    There will be future expansion of the system that, budget allowing, will include; heated basement 600 s.f. and garage 550 s.f. (radiant floor tubing installed), attic 1600 s.f. conversion (panels), remote shop 830 s.f. (fan coil).

    My thought on a boiler is a mod/con such as Weil Ultra, Buderus GB142 or NTI Trinity. The ODR control is part of the manufacturers boiler system.

    I did not understand that the ODR controls the water temperature at the boiler, I thought the ODR controled whether or not it fired and controled the heat output.

    I want it to be an automated control, not requiring any switching by myself, so the toggle switch is not an option. A centrally located thermostat in the first zone is definitely an option and it keeps things simple. I was thinking it would be more complicated than just a thermostat.

  • Mike T., Swampeast MO

    TRVs get along very well with other heat sources. Remember that one of the best virtues of TRVs is their ability to deal with solar gain. The sun is a heat source...

    With constant circulation, TRVs and reset the boiler will fire to meet the current reset target. As TRVs throttle down (or even close) the load on the system will be reduced and while the boiler will still fire to target it will take less and less boiler energy to meet the target.

    Unless your home was very carefully designed to allow a single fireplace to heat the entire place fairly evenly, your radiators in rooms not close to the fireplace will still require heat unless you intentionally set the TRVs low.

    If you're using a conventional thermostat as a "master" DO NOT locate it in a space that receives much heat from the fireplace unless you FULLY expect that the fireplace can heat the ENTIRE home!!

    Presuming you're using a mod-con (generally the heat source of choice for such a system) you might want to include a thermostat-like device located in the space with the fireplace as an "external disable" control. Set such slightly higher than your desired room temperature and with the fireplace "cooking" it will shut down the entire system. Do this ONLY if you are 100% absolutely positively certain that freeze-up anywhere in the system in any weather conditions is impossible! Should you do this you must accept the possibility of significantly lower room temps in spaces not well-heated by the fireplace.
  • Dave_4
    Dave_4 Member Posts: 1,405

    not totally clear on the ODR, but I trust you guys as professionals. In any case my contractor will be installing the boiler, Indirect HW and controls and should know the issues and how to deal with them.

    The fireplace was an after thought in the house remodel/addition and the heat output will not be evenly distributed through the house.

    Thanks to all for the comments and help, you guys are great and very generous with the info you offer.

    Thanks Pete

  • ODR does only determine what water temperature the boiler fires to when it is asked to fire, and it may determine when the whole system turns off (warm weather shutdown).

    In a constant circ system though, you are likely jumping out the system the boiler thinks there is always a heat demand, and it maintains a circuit at a temperature determined by ODR. This is required or you don't have constant circulation.

    You do NOT want a thermostat in the fireplace zone turning off your heat demand. If you did that, then no other emitters would get heat either, even the ones NOT in the fireplace zone.

    You either do not want a constant circulation system, instead using a regular thermostatic on/off zoning strategy, or you should let the system continue to circulate as it wishes, and deal with the fact that you are maintaining a circuit temperature even with the fireplace running.

  • jp_2
    jp_2 Member Posts: 1,935
    it shouldn't matter??

    if the wood stove over heats the house shouldn't the trvs just shut down then the boiler return is roughly the same as the supply and it shuts down also? or at least short cycles like crazy?

  • pretty much, though certainly the circuit loses heat you don't need to lose as well. If you are using the wood heat most of the time, for example, you'd probably be better off with a zoning strategy so the back rooms can just call when they actually want heat.
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