Boiler AND AC control via thermostat

Other Devices & Integrations Climate Control & Temperature Sensors
1

Hello all. Long time reader, first time poster.

I’ve just purchased a home and want to put in a full control system. I have a fairly oddball HVAC system for the US market and as such I’m having difficulty finding a controllable thermostat. Currently I have a old school two zone hot water boiler. Each floor has a old style two wire mercury thermostat.

Now I have the following upgrades coming to the home:

  1. Central Air. One of the reasons I liked this house is that it had no preexisting AC unit. As such I could start fresh and have it done right. I’m looking into a spacepak based system that should work with any thermostat.

  2. A new high efficiency boiler. The current boiler is maybe 60% efficient if I’m lucky. I was told by the inspector that the boiler is at the end of it’s life. As such I’m going to upgrade it to a new 90% efficient boiler.

What I’m looking for is a thermostat that can handle a wide range of setups from 2 wire to 6 wire. Everything I’ve seen that is supposed to be compatible states quite clearly on the box that they won’t work with a boiler. Any help would be appreciated.

2

Any Z-Wave Thermostat can control one Heat Zone and the AC … You will need at least 4+NumberOfCoolStages thermostat wires for this.
If you were Single Zone … this would control the Boiler/Zone valve directly.
There are many boiler setups … depending on which you use you may or may not need a 24v relay to interface to you boiler/zone controller.

If you want to Z-Wave control the 2nd Zone, you still need at least 3 thermostat wires to the 2nd thermostat. I do not know of any heat only z-wave thermostats. So this will have some extra unused features … however with automation you can utilize them. Here you may also need a 24V relay to interface with your boiler controller.

If you tell your installer you want to design this for generic programmable thermostats for the two zones … he will explain your options.

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What you can do with Automation is that if the Up Stairs Thermostat does not get the temperature you desire … you can have it nudge the lower level set points so the average of the two zones goes to the desired temperature.

3

Don’t feel constrained to Z-Wave thermostats – there are a number of wi-fi - controllable thermostats that work well with Vera and other HA systems and have excellent feature sets.

watou