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Thermostatic Radiator Valves

Mike Cory
Mike Cory Member Posts: 1
in THE MAIN WALL
I have a gas hydronic system with cast iron radiators. It is piped in parallel an only 1 zone. I was considering adding thermostsatic radiator valves to 5 of the 10 radiators that overheat. Boiler capacity 100,000 btus.

My questions are:
Can I use the existing circulator on constant circulation with bypass piping and a differential pressure valve or do I need a secondary pump for the bypass piping?

Do I have to put the radiator valves on all radiators?

Can the radiator valves be installed on the the return side of a radiator?

Thanks,
Mike Cory

Comments

  • Ken_8
    Ken_8 Member Posts: 1,640
    I assume when you say parallel...

    You mean 2-pipe reverse return?

    And yes; a head sensitive bypass valve would be in order - if you do fit out more than ½ of the units with TRV's. Depending on a whole magilla of other factors (pipe size, existing circulator charateristics etc.) you may not need any bypass at all. Especially of you have a S-100 circulator already in place.



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  • Paul Pollets
    Paul Pollets Member Posts: 3,665
    Careful...

    You'll want to do all the radiators (revalve) when the system is dry. You'll be disapointed not to have ultimate control over the heat output in the few radiators you leave un-valved. It's very hard to keep the system balanced when TRV's are not on all the rads. Yes, a pressure bypass differential is highly recommended. It only matters that the TRV's are on the same side on all the rads. I usually put them on the return. If you mix, they will make a thumping or banging sound. Keep the valving consistent.

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  • Ken_8
    Ken_8 Member Posts: 1,640
    Paul's right.

    I never heard of anyone installing a few TRV's that didn't regret not doing them all.

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  • DWood
    DWood Member Posts: 60
    What tends to happen

    when you only put TRV's on some of the radiators (usually the one's that overheat first) is that the TRV's on these radiators modulate down or shut off and the heat flow is force to the radiators that are open, ie. the ones without the TRV's. You'll probably end up with TRV's on all radiators at the end of the project. And I agree, a differential pressure bypass valve would be recommended.
    Good Luck
    DWood
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