Boiler not firing up after for upstairs Nest Thermostat

[gallagheri]

Hello all

Hopefully I can get some help here - as this situation now is driving me a bit nuts. 

My setup is as follows:

1. Two installed Nest Learning Thermostat (upstairs and downstairs). 
2. Combi boiler downstairs.
3. Hot water tank/cylinder upstars (300L).
4. Two heatlink connected to each thermostat. The downstairs heatlink connects to the combi boiler, and the upstair heatlink connects to the hot water cylinder/tank.
5. Radiators in all rooms.

The problem seems to be to happen only after certain conditions, which I'll try to outline below alongside the problem description itself.

Problem:  I turn the upstairs thermostat temp above the current temp of the room, the thermostat shows "heating" in orange, but nothign really happens, AKA radiators do not get hot, the boiler doesn't fire up, and I assume the cylinder does not provide hot water to the radiators. The zone valve clicks and shows to be "on" (so I discarded the issue), but nothing happens when you touch the radiators. Turning the heat up on the downstairs thermostat though does fire up the boiler immediately, and this works for the upstair radiators too, provided the temp upstairs is set up higher than the current temp (meaning the zone valve is open upstairs).

Now, if I put the hot water cylinder thermostat temp up to 65c degrees (from say, 60c) this will make the problem go away - meaning if I bump up the temp of the upstairs radiators, hot water flows to the radiators heating up the room. However,  when I do this I notice something that I haven't noticed before: the hot water indicator downstairs stays constantly "on" and in orange colour, meaning its continuosly heating up water. This did not happen before (I've used these thermostats for 3 years now), which makes me think it's really not working as before.

I've run out of ideas on what could be the issue. Has anyone gone through a similar issue?

Thanks

[Vladut]

Hi there, thank you so much for reaching out. Based on what you've described so far it might be related to a wiring behavior. Did you have any plumbing or electrical work recently?

[gallagheri]

Hi Vladut,

Not really, the nest have been installed 5 years ago and we never had an issue. My suspects, at teh moment, are the thermostat from the hot water cylinder, which may be acting up.

[LarisaL]

Hi there! This might be happening because of various reasons and in situations like this we perform a click test to determine if the issue is related to your thermostat or to another part of your heating system like a valve, wires or with the boiler itself. That being said, please go near your Heat Link and turn the heating on from the app and let me know if you hear a click. You should hear a click when you turn on the heating and another click when you turn it off. Just to make sure that the relay is working properly, please try that 5 or 6 times and let me know if you hear a click at every command. Let me know how it goes. 
 

[Vladut]

Hi there, just checking in with you. Did you manage to check the last message my colleague sent?

[TudorL]

Hi there, since me or my colleagues haven't heard from you in a while, we'll need to close this thread, but you can always open a new one if there's any active issue. Have a good one and stay safe!