Electric underfloor heating thermostat

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Wondering if anyone had experience with using the Wifi MQTT Relay thermostat with Underfloor heating (

Or recommendations for another that can be controlled through EmonCMS/Node-Red and provides a way of tracking consumption.
I guess for energy consumption, might be able to use a Shelly or Sonoff, but good to track time heating is on etc.

Someone did ask a couple of years ago about modifying the Relay Thermostat, but can probably work around that with a node-red dashboard and a cheap tablet :smile:

You can use any wifi switch to do so such as the Sonoff devices.

I’m using ‘dumb’ wifi relays and managing the temperatures and schedules through Home Assistant (generic climate integration). You can then add in more complex conditions such as outside temperature and presence detection.

/me facepalm

dawning of realisation that they are all relay controllers but some with power monitoring…

Thanks for making the penny drop

No bother. Sonoff now have a ‘DIY’ mode so you can OTA flash something like ESPHome or Tasmota to make the integration with HA easier.

The one advantage some of these other relays have is that they offer a Normally Closed (NC or Normally Open (NO) option i.e. the relay defaults (no power to relay) open circuit or closed.

I’m putting a relay override on my mechanical tank thermostat so I can make the boiler heat the tank more or less depending on conditions. However, I’m using 2 relays one NC and one NO so if the relays lose power it reverts to the mechanical thermostat.

I’ve also set up my heating so I have not removed the ‘wall’ thermostat, just override it (relay is in parallel), so again, if the control system goes AWOL, it reverts to the wall themostat.


I’m actually using the Wifi MQTT Relay thermostat for my central heating but only for wire connection to trigger boiler heating and as temperature sensor, the actual heating schedule/conditions is setup in NodeRed dashboard using heating node.

Interesting what you say about having the old “dumb” thermostat in parallel, hadn’t thought of that, I also left the old one on the wall as backup, just in case, but having it in parallel could make sense, especially if get house sitters

I was using sonoff Pow to “smarten” up the old boiler, but changed to Shelly 1PM (with stock firmware but MQTT enabled) as it actually fits in junction box rather than messy plug setup.
So I have node-red turn on boiler when heating comes on and so forth.

For the underfloor heating, as I understand it, temperature sensor should be under the heating elements (under/in the screed) so would need a very long wired DS18B20!
I’ve not seen any articles about successfully adding temp sensor to a Sonoff Pow R2, but that would do the job, though would have to work out where to put it as too big for back boxes – unlike the Shelly devices.
I’ve still got a Sonoff Pow running Tasmota to keep an eye on garden cabin power consumption and see if heater comes on. I could see if I manage to wire up DS18B20 to that I guess.

I’ve purchased Shelly 1 with Tasmota loaded from Flashed Firmware successfully before, not much more expensive and just makes life easier. Maybe I’ll grab a Sonoff Pow R2 from there to try out.

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If you haven’t looked at HA, do. It is getting really smart!

Thanks for the Flashed Firmware tip - CC2531 dongle for 15EU is a good price.

Sonoff have the OTA DIY mode now so easy to flash yourself.

I did setup HA a few years ago, at the time I think I was having issues maintaining the config yaml file a bit, then found that nodered and it’s dashboard alongside emoncms did everything I needed.
A colleague was saying it was much more straightforward, I will revisit, but barely time to maintain/fix/improve nodered stuff atm with house renovations.

Yeah I went there specifically for the CC2531, probably grab a few Xiaomi temp sensors (not much more than elsewhere but free & fast shipping as it’s within Europe).
I wish they did a Shelly 1pm flashed with Tasmota as I am preferring them over Sonoff these days.

I flashed my Sonoff Pows using the Tasmota-OTA which sounds like it’s redundant now if Sonoff support it directly, that’s good to know.

I have just realised my my EmonTx will be in the new kitchen (main fuse board is there) but that doesn’t help me.

Your setup of having a simple thermostat as backup for the underfloor heating might be sensible, though I’d probably want to run 2 temperature sensors under the floor…

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