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Rads and TRVs

Hello Everyone!

I'm planning an installation where iron rads will be installed in various places around a home, and I'll be controlling them with TRVs. I understand how these valves start and stop water flow depending on room temperature, but I'm thinking that I should probably be plumbing in some kind of balancing valve for each rad, too. An unavoidable part of this installation connects very different lengths of pipe to each rad. I'm afraid that if/when all the rads call for heat, it'll all flow through the rads with the least pipe leading to them. Should I not flow balance the system with the TRVs all wide open, then let room conditions and the TRVs control the flow? And if I should be installing balancing valves, what kind? Are ball or gate valves going to wear or erode in strange ways over time if water is flowing through them when they're partially closed? Is there some kind of visual flow meter that I could possibly plumb into the various branches to help me balance them? Sort of like the flow meters in an infloor hydronic system?

Also, what's the best brand of outdoor air temperature sensor to use to control the circulator pump for a TRV rad installation? What's the best brand of flow control valve that bypasses the rad lines when all the TRVs are closed?

Thanks very much for your help!



  • furnacefigher15
    furnacefigher15 Member Posts: 514

    What kind of piping layout will you be using?
  • zacmobile
    zacmobile Member Posts: 211
    edited April 2012
    piping layout

    They forgot a manifold system, while it uses the most pipe is the easiest to install & balance. If you use a typical radiant manifold it will normally have balancing valves built-in, fancier ones have visual flow meters which make it a dream to balance your system.

    For circulation I would use a variable speed smart pump, then there is no need for a bypass; if all the TRV"s are closed the circulator will sit & idle. Nothing needed to control it either, it just "sees" when valves are opening (ie. heat is required) & begins ramping up to the appropriate speed.
  • Paul48
    Paul48 Member Posts: 4,469

    If you're referring to the link I posted, a couple are manifold systems. The reverse return provides the most self-balancing ability.
  • Henry
    Henry Member Posts: 995

    You need a pro to come up with a proper P/S and possibly a smart pump on the main reverse return, something like a Grundfos Alpha. I have seen a few DIY manifold systems on cast iron rads. DISASTER! I will have to post one when I get back to the office next week.
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