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Hot Water Radiant Heat - Balancing with Smart Thermostat with Remote Sensors

Hello! I’m a new homeowner in need some advice with balancing our hot water rad system.

A little background:
2 storey detached brick house built in 1917 with radiant heating. Each floor contains it’s own unit, as well as 3rd smaller unit in the basement.

The thermostat that is connected to the boiler is on the main floor. Trying to figure out which the approach for balancing the system.

My current thinking is as follows:
* ECOBEE 4 with remote sensors.
* Main unit installed in boiler room, acting as only a master,
* remote sensor on each floor
* Setup so boiler runs only when the average temperature across sensors dips below setting
* Further, rads have thermostatic valves, independent of the ecobee unit, which we can adjust accordingly
* Bathroom rads with manual valve: i’ve read to avoid thermostatic valves in bathrooms

Wondering if I’m on the right track here?


  • Jamie Hall
    Jamie Hall Member Posts: 19,380
    This is three independent units? Can or is the piping arranged so that it can be divided into three zones? If so, the tenants will be much happier if that were done.

    Your idea of thermostatic valves will work -- but only under one condition: that the radiators are piped with independent supplies and returns. Monoflo? No work. Series? No work. Also, you will want to have a pump which responds to the varying flow demand.

    I'm not sure I'd set the thermostat to respond to the average. That ensures that at least one of the units will be colder than is wanted. I would think you would want it so that if any unit wanted heat, they could get it.

    What's the problem with thermostatic valves in a bathroom? Hadn't heard that one.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ironman
    Ironman Member Posts: 6,900
    TRVs, constant circulation and ONE thermostat in the coldest room to act as a high limit. If you have a mo/con boiler, get the ODR curve setup and adjusted properly.

    You don’t want multiple thermostats trying to interact with TRVs.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Zman
    Zman Member Posts: 7,372
    There are literally hundreds of system types and variations out there.
    If it is a hot water radiator system from 1917, it is likely a gravity conversion.
    Some pictures of the radiators as well as the boiler and surrounding piping would be really helpful.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ninjasong
    ninjasong Member Posts: 2
    Thanks for your comments! I've had to do some research to understand your questions, but I think got it. let me try to address everything.

    Separating supplies to rads by each units isn't really an option, (and also we, and another couple who we own the house with, are living in 2 of 3 units)

    I can confirm likely it is a gravity conversion system, as we got some pipes that go into the ceiling of the second floor at the back of the house, that are capped.

    I see 5 pairs of supply+returns coming out of the boiler room. It appears the 5 zones. I can't confirm with 100% accuracy which pipes feed what parts of the house.

    I will say that it is definitely more than psossible that each supply/return is not serving one rad each. We suspect it's vertical slices of the house.

    ie. Zone A is the back of the house for 1st+2nd floor.

    I have some pictures here of the equipment in the boiler room:

  • Ironman
    Ironman Member Posts: 6,900
    It definitely looks like a converted gravity system, but I really can’t tell what’s going on there from your pics.

    We need better pics from further back that show all of the near boiler piping.

    That being said, I’d still recommend what I posted before.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.