DIY Doctor UK DIY Forums

Help. Have a Danfoss room thermostat for underfloor heating that no longer seems to be programmable. Want to replace with a smart thermostat. Got a ProTouch Smart.
The old Danfoss had 3 wires connecting. Grey into (N)eutral, Black into NC/Normally Closed and Brown into (L)ive.
The new Protouch has Neutral, Live, NO/Normally Open and COM contact points.
I assumed to wire it, it would be Grey/Neutral, Brown/Live... and the Black into either the COMM or the NO. Whilst the thermometer powers up and connects to WIFI ok, it doesn't trigger the boiler to heat the room. I will call an electrician in, but posting here in case there is an obvious solution. Thanks in advance.

Hi kpgristy
There should be two connections either side of the com connection. One should be nc and the other no. You may have to provide a live feed to the com connection but refer to the installation instructions.
Regards S

Thanks Stoneyboy. Alas there are just the 4 points and no NC. See image. Live and neutral connect fine... thermostat lights up, connects to WI-FI and is programmable. It’s just that when it calls for heat from the boiler, it gets none. Boiler etc are ok as the previous thermostat call for heat fine. Is the issue purely that I have no NC contact... which would mean the thermostat is essentially incompatible?

Hi kpgristy
Suggest you wire the stat as shown in the ‘switching mains voltage’ diagram and fit the black wire into the NO connection.
Regards S

Thanks again for responding. I did try that first time around, which ultimately led me to raise this post. I may try again this weekend just in case there was a loose wire, but I’m not holding out much hope.

As said new needs link, where old one link internal. So Brown into (L)ine and (Com)mon.

Thanks both.... worked a treat. Appreciate your guidance.