Help needed - Replacing Danfoss Tp4000 with Nest Smart Learning Thermostat

[0xen]

Hello all, I bought myself a new thermostat after doing a online compatibility test and proceeded to try the install. My previous unit had two cables coming from it, COM and N/O, this lead me to believe i had a two wire system. After looking around I found that with two wire systems Im meant to plug the cables into W1 and Rh of the nest unit. I did this and after powering on my boiler and letting everything settle I noticed that even after setting the thermostat to 9C it would keep the radiators on and is clearly not working. Have I missed anything? Images included below

 

[flameport]

What country are you in, and where did you get that Nest from?

 

[CBW]

As above questions, and I think you’d still need power to it.

 

[0xen]

What country are you in, and where did you get that Nest from?

England, got it from Screwfix

 

[flameport]

England, got it from Screwfix

The product shown is not intended for use in the UK, and isn't compatible with UK heating systems.

 

[0xen]

The product shown is not intended for use in the UK, and isn't compatible with UK heating systems.

I see! I just found this which shows the difference. If I got a replacement one that is the "UK" one, could the 2 wire solution work do you think? https://support.google.com/googlenest/answer/9256506?hl=en-GB

 

[CBW]

Th only 2 wire Nest you will get to work is the Nest E. If you want Nest learning thermostat, then you could use the 2 wires for the T1 and T2 connections for heat link and wire in the rest at the boiler or wiring center

 

[ericmark]

The USA Nest can use sensors in different rooms, but the Europe Nest is a single stand alone unit, there are two for the UK the Gen 3 will work DHW as well and comes as two parts, and the Nest e not used but is two wire only, in fact only wireless thermostat I have seen which is two wire. How you have got a USA version I don't know.

The normal idea is with a wireless thermostat the base goes near boiler or motorised valves and the sensing head goes where you want to sample the heat. With the Nest Gen 3 you can power the head from the base using two wires, this is what I have, but not sure what Nest Gen 3 was designed for, as it seems to be the odd one out for smart thermostats in that it does not connect to any TRV heads or sensors, so unless a open plan home, they are a bit useless.

Most expensive thermostats link to TRV heads, Hive, Wiser, EvoHome, Tado all have a system where the TRV heads can tell the wall thermostat heat is required, and so it can fire up the boiler. Also most except for Hive, have the option of working with OpenTherm, however not all boilers have OpenTherm option.

I have Nest Gen 3, and am now considering replacing it with Wiser, as the Hall where it is fitted cools slower than the Living room, but can't fit thermostat in Living rooms as one there is an open fire in the room, two there are outside doors in the room, and three which is the biggest reason there is no way to power it from the boiler supply if moved to living room, so central heating would stop working if we got a power cut, nearly all the other systems the wireless head is battery powered so no problems getting power to them.