Best Underfloor Heating control?

I’m looking to control my water-based underfloor heating. It’s on the same loop as the rest of the house, so currently, if I only want to heat the bedroom radiator, the whole underfloor heating downstairs needs to be on too!
I’ve done a lot of reading and watching, but don’t feel I’ve found the right solution.
(Here’s a good “Underfloor Heating Explained” video, if you’re starting in the same position as me: )

Below is my best understanding of what I’ve got.

  • Purple is the inlet, with an injection value like this one. I don’t believe I should touch this because it regulates the temperature of water going into the floor.
  • Red are valves for the four individual pipes. Ignore the two white TRVs - I was just testing them out on there.
  • Yellow is the return to the boiler.
  • The pump is always plugged in, and always seems to be running.

I see three options:

1. Put actuators on the four valves (red circle). This would give the most granular control.

  • Another user asked about Homematic, but no responses on that thread, and it’s likely to be €300 for that solution, which sounds steep!
  • Alternatively, I guess I could put 4 smart TRVs on each valve? But that doesn’t feel right.

2. Put a Smart TRV in the yellow circle. This seems the best solution, but requires some plumbing to add a thermostatic valve in.

3. Add a smart plug to the circulator pump. If I want the underfloor heating off, I assume I can just turn that smart plug off?

I am not a plumber, but experimenting with the same thing this winter (i.e. trying to optimize an old unregulated floor heating with HA)

My thoughts on Option 3: I don’t think that the purple circle is your pump. It’s rather the mixing valve that regulates your inlet temperature. Changing the inlet temperature makes a whole lot of sense if the outdoor temperature substantially changes; but it wont help you controlling the temperature in each room individually.

Neither will Option 2, a valve at the yellow circle, as this will only control the entire return flow from all rooms, not individually. Also that screw nut there might be not just a nut but a flow limiter which may be part of the hydraulic equalization of your entire heating system. So I’d not plumb there without consulting a real plumber first.

So what remains is Option 1. One option could be the Homematic controller. But since they do not officially support Home Assistant, I shied away from paying 300+€ too. I actually put Zigbee TRVs there. Obviously not just like that, because these TRVs measure the surrounding temperature in the manifoldbox, not the temperature in the actual rooms. But if you sync them (technicall speaking: offset them) with normal temperature sensors to be placed in the rooms, it can work. There is a custom integration in HA called Better Thermostat (check which does exaclty that (and more). Better Thermostat is intended for radiator heaters, so using it for a floor heater is a rather odd experimental tinkering solution. But so far it works surprizingly well for me. Hysteresis usually stays around +/- 0.5 ° C, which is pretty fair in my opinion.

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just a short message from me (for now). You can’t just put smart TRVs on there (I suppose you are talking about those which are supposed to go on room radiators!?) These have an integrated temperature measurement and heating control logic.

My personal recommendation is the system from Homematic. Their products are excellent and high quality. Amongst other products they are also relatively cheap. I have yet to find components with Zigbee which are even close to the quality and function/control the HM products offer… Home Assistant integration is more than excellent, you just need to look in the right direction :slight_smile: GitHub - danielperna84/custom_homematic: Custom Home Assistant Component for HomeMatic

@Uberkeyser thanks for sharing your experience. This was also news to me.

I will share with you my solution, maybe you are interested in copying it. It is zigbee based.

First of all, definitely go with one valve per circuit, the cost/complexity is way worth it when you can turn on/off the heat for each room. The valves are cheap and you can probably buy them cheaper online than in a hardware store. Take a picture of the mechanical interface where you put RTL valve, and send to a plumber with heating experience, he’ll tell you what valve you need. They are simple on/off valves controlled by electricity. Remember there are 12VDC, 24VDC, 120VDC and 230VDC variants. Just be careful to pick the right voltage for your conutry if you choose AC version, and if you go with DC version remember you need compatible power supply.

Here is the 4 channel relay controller I used, you can buy it on aliexpress, details on zigbee2mqtt here.

You use one relay output for each of your circuits valve. If you have more than one circuit for one room, you combine them on the same relay/channel. If you end up with a spare channel, you can use it to switch the pump on and off if you like. It will increase the pump lifespan to turn it off when all valves are closed.

Now put one temperature channel in each room you want to heat.

Then go to home assistant and create a thermostat/climate entity for each room. The input to each thermostat is the temperature sensor and the set temperature you choose in HA. The output is the corresponding relay to your valves. Here’s a quick sketch

You can see I combined the two middle channels to one bigger room with two water circuits, which left one channel spare for the pump.

I only use three relays, plus one for pump. Here is a screenshot of how the thermostats are displayed in home assistant:

If you find the solution interesting just ping me for details where/when you need them,

Just to be precise: The thermostat now lies within home assistant software. There are no external thermostats or backup solution if HA goes down. The relay module I used has though buttons to control the relays manually, meaning you can turn on/off valves individually if you need to.