Nest thermostat not communicating with Heat Link

[Banstead17]

The Nest Thermostat has been running well for several years, but in the last couple of weeks there has been an intermittent problem whereby the Nest thermostat isn't always communicating with the Heat Link. The Nest Thermostat has the usual orange screen with target temperature and no error codes, but the Heat Link doesn't then switch the heating system/boiler on. The Heat Link has a green light and has no apparent issues either and my only solution in the interim is to manually turn on the Heat Link by pressing it's button. This successfully turns on the heating. I've reset the Nest Thermostat and reset the Heat Link several times, but this doesn't solve the issue. Could there be a problem with the wireless connection between the Nest Thermostat and the Heat Link and how can this be investigated and resolved? When I look at setting on Nest app is states that the Heat Link connection is "Wired".

[Frustratedddd · Accepted solution]

This sounds like the thermostat is working fine, and that points usually to a valve.

Yes checking the app is fine, but to double check always take information from the display, just in case.

The Heat Link switches through the boiler to the valves, but if faulty and you press manual mode that overides eveything and can by pass the valves.

I would suggest you get them checked

[Frustratedddd]

When you call for heat do you hear a click at the Heat link?

[Banstead17]

Thanks for responding. Yes I do hear a click at the Heat Link when calling for heat. 

[Frustratedddd]

That would suggest the Display is talking to the Heat Link, and that could say there is a problem at the boiler end.

You say by pressing the Heat Link button for manual mode the system works, that also suggests the Heat Link is working. Does the display show Manual Mode when the Heat link button is pressed? Should that be yes, then that would suggest the thermostat is working.

You also say the system is a wired system, and that would say the connection does not rely on the wireless connection. You can obvioulsy try to connect the wireless connection, but that's not really an issue here. You can double check your connection at the display rather than the app also.

Do you have any motorised valves, and have you had them checked?

[Banstead17]

The thermostat display does indeed show Manual when the Heat Link button is pressed. 
When I checked the settings for the Heat Link in the Nest App it states that it is wired. 
As you state, perhaps the motorised valves need checking. Are you able to elaborate are how they interact with the Heat Link and the boiler for my own understanding? 
Would  you be able to surmise why the motorised valves may not work when the Heat Link is activated by the thermostat, by the valves do work if Heat Link is activated manually?

Many thanks. 

[Frustratedddd · Accepted solution]

This sounds like the thermostat is working fine, and that points usually to a valve.

Yes checking the app is fine, but to double check always take information from the display, just in case.

The Heat Link switches through the boiler to the valves, but if faulty and you press manual mode that overides eveything and can by pass the valves.

I would suggest you get them checked

[Banstead17]

That’s very helpful and useful information thanks. I shall certainly get them checked. 

[Banstead17]

Valves replaced and all back in working order thanks!

[Frustratedddd · Accepted solution]

Result.

You would be amazed the amount of people that blame the stat first, the are gob smacked when they find out the valve is the culprit!! Great result anyway.