Turn on heater

[gizmolo]

Hi everyone,

I have a gas boiler connected to a thermostat with two wires, carrying 23 Vdc.

Is it possibile to substitute the thermostat with a Shelly 1PM Plus? If so, how should I wire it?

I just want to be able to turn on and off the boiler from Home Assistant, I don't care about using also the thermostat. I want to keep only the Shelly.

Thank you!

 

[thgoebel]

Please add product names of boiler and thermostat or post a link! Most likely, the signal between thermostat and boiler is transmitted over a bus protocol…

[gizmolo]

mmm, i don't think so. the boiler is an Immergas Vitrix Exa (i'm based in Italy) and the thermostat is a generic one with batteries. It works with 2 AA 1.5V batteries, and when the external temperature goes below the threshold it just close the circuit between those two wires with a relè. Wires togheter = boiler start heating.

[gizmolo]

The thermostat is this one (albeit mine seems a little different, it has "CRONOGYR REV22" printed on the front while the one in the manual doesn't): https://www.manua.ls/siemens/rev-22/manual

[thgoebel]

Ok. Assuming you’re right, this diagram could help:

 

As thermostat I would recommend a Shelly BLU H&T.

[gizmolo]

Ok, so as I feared it's not possible with the Shelly 1PM, I have to use one with dry contacts like the one you mentioned and find a solution to bring L and N wires to it for power.

Thanks a lot!

[wooly]

I have used a different approach: using an UNI I used one of the output to connect the input of the boiler to be able to start the boiler indipendently from the thermostat [labeled "accensione caldaia" and the other output in series with the lined from thermostat labeled "abilita riscaldamento", so i can either leave the original thermostat active (actually to disable the heating when i want] or force the start of boiler even if according the thermostat would not be necessary.
Much more versatile than the Sh1 [also you can put some thermometers on the UNI, without having to buy a costly and poorly efficient H&T separate device]

Edited November 20 by wooly