I currently have a Nest Thermostat controlling the heating but I am looking at moving over to some sort of TRV setup and controlling the boiler via HA.
The call for heat is just a no voltage switch which in theory should be simple to replace but I cannot find a Zigbee product that does the job. I have seen that lots of door sensors can be hacked to do the job but ideally I would want this to be mains powered to give a little more resilience and keep the heating working.
Everything I have seen is either wifi, live contacts, involve soldering PCBS or one had £50 shipping to UK for a £20 switch…
Failing that is there a way I can get the Nest Link to do the triggering via Zigbee (wasn’t sure whether I could add a switch into the currently unused thermostat wiring but I think that is 12V so I guess that is still an issue)
Normal is to use “contactor” for switching high-load products such as heating (boilers/heat-pumps), and electric motors. The contactor itself is controlled can be controlled with any mains-powered smart switch
The circuit doesn’t actually switch the boiler but controls the contactor inside the boiler which does. I believe the circuit is either 12v or 24v with very little current and when the circuit is made (thermostat is triggered) the boiler is fired up.
My concern with a lot of smart switches (designed for lights) is that they look to be passing through voltage to the switch
Is there any reason you only want to use ZigBee ? The esp01 WiFi relay board with esphome would only be ÂŁ2 ish. I use several of these and they work fine for dry contact applications
No probably not. I have always found WiFi devices are less stable (partly in implementation and partly just WiFi itself) but this is probably just my preconceptions.
I have over 80 WiFi HA devices and they hardly ever cause me a headache. Unlike ZigBee that drop connections regularly for me so have replaced any I can with WiFi. Mostly battery sensors remain.
I was looking again last week but there doesn’t seem to be a nice Zigbee solution. I have seen people rewiring SONOFF controllers and a few hacks or custom builds but nothing off the shelf.
I am currently just bodging the nest controller by setting the heating right up when I want it on. It is working by virtue of the TRV settings so the kitchen where the thermostat is doesn’t get much warmer but the rooms that are still cold get heated. I will look again at some point but the WiFi options switches are the only ones that will work and I am still very wary of WiFi IOT stuff in terms of security and privacy
I am always wary of Aliexpress… It looks great when you click through and it says £4.24 but that is only for the remote fob. The board is £10.39 which is still quite a lot cheaper than the £18.87 on Amazon.
The case does look interesting however it doesn’t actually allow you to use the USB power socket so I would need an additional transformer too. Also way (having been stung like this before on Aliexpress) whether you are actually getting the case and board or just the case…
Might do a bit more digging on Aliexpress and see if there are other ones with cases that actually fit the USB (although I suspect they will all be the same as this one)
I know this is a few years old but for anyone in the UK (and other parts), I have been using a Zigbee Salus Relay (SR600) with Zigbee2MQTT. Salus SR600 Smart Switching Relay 16A - Screwfix
The relay has dry contacts and is suitable for controlling a boiler.
I use Node Red for my automation, controlling the Salus Relay (Boiler) using TRV heating zones.
I have a Nest Thermostat located in the Living Room which turns the Living Room TRV on (40°C) and off (0°C) based on whether its calling for heat but it will also adjust all of the other TRVs temperatures (only if they’ve not been turned off manually) to be set inline with the rest of the house when changed.
