Hi there - one thing I would like to add to my Home Assistant instance when I move home would be a smart heating system. Before trying out HA and moving to my current rental, I previously used Hive (I am based in the UK) smart thermostat in a small flat via Alexa and the Hive app, and it worked pretty well, but I didn’t have any automation interact with it i.e it was effectively a self-contained system.
However, we’ll be moving to a slightly larger home and I’d ideally like something that had connections to radiator valves that track temperature in a specific room/area (or could respond to automations that check temperature sensors elsewhere). I probably can’t afford to have smart valves on every radiator, so would likely use the thermostat in the large open-plan living space, with valves in my bedroom and my daughter’s bedroom.
Question 1: Does anyone have recommendations for systems that can be controlled locally (not necessary via manufacturer cloud, as I’d intend to do that via HA Cloud perhaps) and play nice with HA?
Question 2: If they all connect to HA, can you mix and match thermostat manufacturer with a different one for the valves?
Question 3: Has anyone had problems with logic around these?
Example 1: Valve 1 is below the target temperature, but because the master thermostat is above it, no heat is delivered despite the need for it in one room.
Example 2: If heat is being delivered to heat up one room, will the valves in rooms already above the target temp turn down in response to a slight creep above?
Question 4: With connected thermostat, valves, sensors etc, can you simply craft manual logic in HA to control all this? Obviously I’d like something that just works, or gets me 90% of the way there without this, but I’m happy to try if nothing meets the needs above.
If I work backwards, with a smart home system while you can use HA to do the smart stuff, it will become quite time consuming to setup, because a smart system learns how a room warms up. They work on the basis of a target temp and target time, so if you want 20c by 5pm, then it works out how much time is required to get there, which could mean the heating comes on at 4pm for example. While you could do the maths yourself, there are a lot of variable (starting temp for example) and if you start it too early you are wasting energy.
Similarly, with a proper smart heating system, there is no master thermostat. There will be a central controller, which is used to control the entire system. That central controller in a lot of cases can also be used as an external sensor for a specific room, but it doesn’t override the TRVs calling heat. TRVs respond to the temperature of he room, whether that comes from their own heat or something else. For example, I have air conditioning in the house as well as radiators and we will sometimes use that to top up the room or bring the system up from a cold start as it does it quicker than the radiators.
With regards to your question about thermostats and TRVs, the whole point of HA is being able to mix and match. However it does depend on what system you use. Personally I went for a standalone system which I can integrate as I have a policy that nothing in my house must be dependant on HA. If I lose HA then the most that happens is a few additional lights don’t work and I have to press manual buttons on other things, but there is nothing critical like heating control lost.
Which brings me to your first question - a recommendation. I have had Evohome for over eight years. It controls a TRV in every room and it just works. I touch it twice a year (turn it on in the Autumn and off in the Sping). HA monitors it, could control it, but doesn’t.
For HA integration there is a native integration which polls the cloud, however the interface between the TRVs, boiler controller and the main controller has been reverse engineers and there is an HACS package called ramses_cc which can provide you with all of the control you need. It just requires a low cost custom USB stick to listen to the packets. This is the very long thread on the subject: Honeywell CH/DHW via RF - evohome, sundial, hometronics, chronotherm - I suggest reading up from the end as there are over 4000 posts and only the last couple of 100 are now relevant.
This tool has reached the point where it can fake an external sensor, allowing you to have a temp sensor away from the TRV without having to use the Evohome ones, which can be useful if you have furniture in front of the TRV and get inaccurate readings.
The key money saver is boiler control, so if the budget it limited I would get the boiler control, hot water control and one of the starter kits in place first, which will give you the general control.