Nest Thermostat 3rd Generation UK. Only get heat when hot water is on.

[Mark991]

I have the Nest Thermostat 3rd Generation in the UK just installed by my electrician. I have a system boiler with on/off for heating and hot water. After initial installation it worked fine for heating/hot water but at the end of the first day I could not get the heat to turn off at all either using the thermostat or the app. I then did a factory reset on the thermostat which fixed the heating issue (now able to turn off/on via the thermostat and the app no problem) but since then whenever I turn the hot water on only the radiators heat up (even with the heat off) and I get no hot water into the tank whatsoever. Google phone support offered no solution and advised me to get an engineer out. Should I perform another factory reset? Thanks.

[Frustratedddd]

You could always try another factory reset, as you have nothing to loose.

You say the system was working correctly after installation, are you sure you tested everything and the installation is correct?

Are you saying, when NO call for heat just water [heat turned of] rads warm up, and no water at all?

Are you saying when calling for heat and NO hot water [water of] just heat, rads get warm?

Do you have a motorised valve in the system, if so check that is working ?

[Mark991]

I ran another factory reset and same issue. Not sure if the system was working 100% correctly after installation to be honest but we had hot water on the first day.

Yes when no call for heat just water (heat turned off) rads warm up and no hot water at all. 

Yes when calling for heat and no hot water (water off) just heat, rads get warm.

I presume the valve is working since I can still get hot water if I use the old controller (slide switch to cont.), the nest is just wired into the old controller.

Thanks.

[Frustratedddd]

The description you say points to the water contacts not connected or switching or crossed.

Sounds like the installation has failed, but might be wrong.

Why run through an old programmer, when the Nest does everything?

Can you upload a picture of the Heat Link wiring?