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TRV, Balancing Valve, or Both?

Scott_Mountain_View_CA Member Posts: 202
edited November 2014 in Radiant Heating
I'm designing a radiant heating system for my small home. Runtal rads and most likely direct return piping. Reading Siegenthaler's book, I'm not clear how from a functional perspective a TRV differs from a manually adjusted balancing valve. Both control the flow through the emitter. It's a given that I'm installing TRV's on all rads.


  • SWEI
    SWEI Member Posts: 7,356
    A TRV adjusts flow based on the temperature in the space it is mounted. A balancing valve adjusts flow based on how you adjust it, and then stays there.

    You should seriously consider a reverse return layout if that is at all practical.
  • I understand the difference between the 2 valves. What I was asking is FROM A PRACTICAL PERSPECTIVE, how do they differ...in other words, both valves constrain the flow through an individual rad. What I don't understand is the interplay between a balancing valve and a TRV.
  • OK, I may have answered my own question...I found a website that describes balancing a hydronic rad system:

    1. open wide all TRV's
    2. balance the system by taking temperature measurements for each rad and adjusting the balance valves until all rads have a similar temp (+/- 20 F was their recommendation....seems it should be tighter than that?)
    3. set TRV's on each rad to a desired temp.

    Is this more or less correct?

    Here's the website: http://www.shadlock.co.uk/energy/heat/chbal.htm
  • Bump
  • SWEI
    SWEI Member Posts: 7,356
    OK, it seems like you are asking about TRV's on one end of the radiator and balancing valves either at the other end of the radiator or on a manifold. The balancing instructions you posted are close, but the important thing is that the rooms have similar temperatures, not the radiators. I would expand this a bit and say that you should also turn any thermostats (if you have them) up to about 85˚F and then take the opportunity to adjust your ODR parameters once the balancing valves are set so that room temps are even. The ODR parameters should be tuned so that all rooms are as warm as you will ever need them (think visiting parents, sick children, etc.) Once this is done, set the TRVs to a comfortable temperature. This will give each of your TRVs a reasonable operating range.
  • What are ODR parameters?
  • SWEI
    SWEI Member Posts: 7,356
    OutDoor Reset