Replacing a basic room stat.

Phill Most Chill

Phill Most Chill

Phill Most Chill

Associate
Joined
22 Nov 2023
Posts
5
Location
UK
Hello
I am trying to replace old mechanic Honeywell thermostat for what the manufacturer says is a universal Honeywell DT90E and should be suitable for all boilers. However after swapping the stats, DT90E did not communicate with the boiler and I had to swap back to the old stat. The manual states that DT90E is either 24V or 230V. Therefore I just left the DT90E connected to the 24V connection on PCB board as it was with the old stat, please open the link: https://drive.google.com/file/d/1VF8SHWkA6Et-bOvm_1psXnU82OBj1Jr2/view?usp=sharing. Yellow circled is the white "24V terminal" connection. Sadly for some reason there is no communication between the DT90E the boiler, with this connection. Thinking about wiring it to 230V terminal right next to it, encircled in green. Now I am not sure which terminals on brown, 230V box to use. On the 24V both wires are connected to two RT terminals. But on 230V there is only one RTterminal. Does that mean I have to use L and N terminals? Any ideas why is it not working on 24V? The Boiler is Thema Condens F30E if that helps. Thank you very much for your help and wisdom...
 
Yes, of course. I f you are asking me if I know where the other end of the cable is, then yes. I already tried and swapped the stats. But it did not work...
Re-reading what I wrote in my first post, I think I should have made myself clearer: "Therefore I just left the DT90E connected to the 24V connection on the boiler's PCB board as it was with the old stat" and as seen on the picture. So on the boiler's side I had left the wires as they were and on stat's side connected them accordingly to the manual provided which is just L to terminal A and N to terminal B really. No idea why it is not working...
 
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