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Master Temperature Control of Rooms
We live in an area where a private Geothermal company provides pressurized hot water to the house. This neighborhood (and the house) has been using this company for over 100 years. We bought the house a couple of years ago and want to do some upgrading.
A couple of things to note:
1. The water comes into the house at 165 deg F.
2. It is an open system. Once we use the water we dump it into a creek behind the house.
3. The setup is unique for the neighborhood as our radiators are not in series. We have a supply line and a return line. Each room has its own supply and return. Most rooms have only one radiator but several of the larger rooms have two radiators. In the rooms with two radiators, those radiators are in series.
4. The whole house is controlled by an old mercury thermostat in the dining room. This thermostat feeds a Honeywell mercury switch relay that opens a valve that is situated at the end of the return line (just before it exits the house and dumps into the creek).
5. We live in the U.S.
The main issue: The dining room dictates when the whole house heating will be turned off. This creates hot spots (primarily upstairs) and cold spots in the house. With the rooms having their own supply and return we would prefer to control each room individually.
I had considered the Honeywell Evohome system. It looks perfect; a master controller using Bluetooth to control each room. However, it appears I would have to use US to UK voltage converters in order to operate the hardware. I don't believe I want to do that.
I cannot find where I can get the same system in the U.S.; a master controller to control each room. The best I can see is using a Nest or Ecobee in each room to control a valve on the return line from each room. However, this requires a thermostat in each room plus wiring to a relay. This is an old house with lathe and plaster and I prefer to not run any wires.
I have also found Bluetooth TRVs that I could place in each room and control via my phone. But I don't want to control it via my phone; I would prefer a master house controller.