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TRV retrofit

Paul Pollets
Paul Pollets Member Posts: 3,656
A pressure bypass differential valve is used when TRV's are installed. It will make the pump work more efficiently and extend its service life. Usually, we leave off the TRV in the room where the thermostat is located, and use a reg wheeled valve.

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  • Andrew_6
    Andrew_6 Member Posts: 6

    I am retrofitting TRVs to my cast iron radiators, and I had a couple of questions.

    First, most of my rads have enclosures/covers, so I figure that I need to use remote sensing operators, otherwise the head would be placed vertically. My real question, though, is do I need to put a TRV on every rad? I plan on putting a Tekmar 256 on the boiler (Burnahm Series 2, 130Mbh input) with constant circulation. I have 4 rads in bedrooms, one small one in a powder room, and then one in the living room, one under a window seat in the dining room, and one in the front hall. The thermostat is currently on the second floor landing.

    The second question is in regards to the boiler piping. Currently there is no bypass or pressure activated bypass. There is, though, a single pipe loop of 3 panel rads on the third floor fed by Oventrop bypass radiator valves. Would this be sufficient to provide a bypass for the boiler if all the TRV's (8 cast iron rads) close? I'm just trying to minimize the work around the boiler. If it is not sufficient, would a bypass with a globe valve help, while also raising boiler water temps?

    Thanks for any feedback.
  • jeff_51
    jeff_51 Member Posts: 545
    better control (balance)

    if you install trv on all rads, and without looking, prolly will have enough bypass. Also, you may want to consider leaving either the powder room or front hall as a "wild" rad, no trv, just for extra heat, more loss at front door and everyone likes a warm bath. You can always add them later if those areas ore too hot, will also help for bypass if needed. Note, we use nothing but ball valves on hot water.
  • Andrew_6
    Andrew_6 Member Posts: 6

    Leaving the TRV off the powder room makes sense. It is a corner room with no insulation, and was always cold last winter. I will probably put one on the front hall rad, though, and maybe just leave the temperature setting high on that TRV. I'd prefer to avoid draining and refilling the system another time. Jeff, would you still recommend piping in a (non-pressure differential) bypass next to the boiler?
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