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TRVs for paired hot water radiators?

Farian Member Posts: 4
I have recently had the boiler on a gravity hot water system replaced with a circulating boiler (Buderus GC144/5 ) and I’m having trouble getting the system balanced. Basically, the downstairs rooms are not warm enough and the upstairs rooms are too warm. I’ve tried closing the valves on the upstairs radiators and fully opening the valves on the downstairs radiators (as advised by the installers) but there’s still a difference of 4 to 5 degrees F between upstairs and downstairs. I’m thinking a possible solution might be to put TRVs on the upstairs radiators but I’m not sure if that would work in my situation.

The house is a 2-storey brick house built 1913, approximately 1,600 square feet. Many years ago, the house was divided into two apartments, upstairs and downstairs. Each apartment has 5 cast iron radiators. The heat is controlled by a single thermostat, located in the upstairs apartment, where I live. I was thinking I could use a thermostat like the Ecobee, with a remote sensor that I would put in the downstairs apartment. The thermostat could be programmed to work off the downstairs sensor, thereby ensuring that the tenants stay warm enough, and then I could regulate the upstairs with TRVs. But…

It appears to me that the piping of the heating system is a hybrid of supply & return system and single pipe. Basically, there’s a main supply that has several single pipe loops coming off of it. Within each of these loops, the return of an upstairs radiator serves as the supply for the downstairs radiator below it. There’s a main return that collects the returns from the various individual loops. The large iron supply pipes (and some of the returns) run through the rooms of the downstairs apartment, so also serve as a heat source to some extent.

I don’t really understand how water flows through the radiators in these single pipe loops. If the valve is closed on an upstairs radiator (whether it’s a manual valve or a TRV) won’t that restrict the water that’s able to reach the downstairs radiator below it, thereby making the situation worse? If so, is there any solution to this situation? I also don’t understand why there’s such a difference between upstairs and downstairs temperatures now, with the circulating boiler, compared to the more even heat we had with the gravity system. Any insights on this would be greatly appreciated!


    EBEBRATT-Ed Member Posts: 15,840
    Maybe you could post some pictures and or a piping diagram.

    In most cases upstairs radiator returns should not become the supply to the downstairs radiators unless you have some configuration of a "series loop system" which may nor work well in your application. Need pics or diagram to help
  • jumper
    jumper Member Posts: 2,333
    Usually it's the other way around. Lower floor on gravity doesn't get warm enough. But I've encountered the opposite situation. When new boiler & circulator come in usually these problems are solved. Sometimes an extra dedicated circulator is installed to make certain lowest circuit gets enough heat.
  • Farian
    Farian Member Posts: 4
    Thank you much, Ed and Jumper for replying. I've tried to do a drawing to explain the piping. I hope it makes some sense! I'll also attach a photo of the 1st floor bedroom that shows the supply pipe (at the far right) coming in from the utility room, and then going to the upstairs radiator, from whence it comes dow to the radiator in this bedroom. The front rooms of the house all have this arrangement and it's these rooms that are out of balance (too warm upstairs, too cool downstairs). If other photos would be helpful please let me know. Thanks again!