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Nest Thermostat not starting heating

IanG1
Community Member

Have a 3rd gen Nest. I have a problem in that when I increase the target temperature by rotating the Nest Thermostat - even to 30 degrees centigrade the Nest does not turn on the boiler. Boiler seems to turn on normally as per the Nest schedule - just doesn't seem to work when I perform a manual override of the scheduled heating times by turning the dial on the Nest thermostat.  If I press the manual override button on the Heat Link the boiler turns on immediately so not a wiring problem. Have had the Nest installed for quite some time and worked perfectly until now. Any ideas how I can fix this problem please? 

15 REPLIES 15

AlexD
Community Specialist
Community Specialist

Thank you for all the information @IanG1 . I am sorry to hear you are facing this behavior from your device and I would be happy to try and assist. 

 

Just to confirm, it follows and achieves all temperatures in your set schedule, correct? It is just the manual adjustments that don't seem to be followed, correct? 

IanG1
Community Member

Not entirely - first thing in the morning the thermostat is showing that the heating is on (orange colour) but the boiler is not on. If I press the heat link button the boiler comes on immediately. If I don't press the heat link button the boiler does eventually switch on but at a later time - so looks like some kind of delay between the scheduled heating time and the boiler actually starting - even though the thermoses is showing orange. If I turn the dial to increase the temperature during the day (when the heating is scheduled to be off) the boiler does not start even though the thermostat is showing orange. Again, if I press the heat link button the boiler fires up immediately.

AlexD
Community Specialist
Community Specialist

Thanks for clarifying. So it seems the thermostat, even though it turns orange and says the heating is on it does not seem that the boiler is actually on, until later. Although it does fire right up when using the manual mode. 

 

Let us do a test on the Heat Link using the Nest app to see how it behaves:

 

1. Go with a mobile device next to the Heat Link and open up the Nest app.

2. Make sure that the manual mode on the Heat Link is not active and if the heating is set to be on, display is orange, turn it down so it is off, black screen. 

3. Turn the temperature up until the display goes orange and listen for a clicking noise from the Heat Link.

4. Turn the temperature down until the display goes back to black and listen for a clicking noise again.

 

Let me know what the result is.

 

Also, just to confirm. Does the thermostat control both heating and hot water or just the heating at the location?

IanG1
Community Member

Hi Alex - when I perform the test by turning up the temperature on the phone app the Heat Link does click and the Honeywell motorised valve makes a buzzing sound but the boiler does not turn on. If I then press the manual override button on the heatlink the boiler immediately starts. 

DragosC
Community Specialist
Community Specialist

Understood. From the details above it seems the Heat Link does its job, it gives the command to the valve. If you want to be more certain you can perform a continuity test on the Heat Link's relays, but you'll need an electrician for that. Let me know please. 

IanG1
Community Member

OK but how can the heat link turn the heating on when I press the override button but not turn the heating on when  it's activated by the schedule on the Nest App and the thermostat is orange? It worked fine until quite recently and no changes have been made to the wiring of the Heat Link - and it's a fairly new third generation Nest.

DragosC
Community Specialist
Community Specialist

Understood. The continuity test will be able to answer that question. Either by schedule or overriding, it will tell us us if the device works or not. 

IanG1
Community Member

OK - how do I arrange that please?

 

DragosC
Community Specialist
Community Specialist

If you have a multimeter and you feel comfortable, you can do it yourself and I'll give you instructions for it. If not, you can call out an electrician to do it for you, but the callout cost won't be reimbursed. 

IanG1
Community Member

Have a multimeter so happy to test it myself 

DragosC
Community Specialist
Community Specialist

Alright. I'll send you an email with the instructions for it. Let me know how it went. 

DragosC
Community Specialist
Community Specialist

Hi there. I'm just following up on our last message. Do you still need our help? Keep us posted. 
 

IanG1
Community Member

Hi Dragos - heat link tested fine - problem turned out to be a faulty control valve on the heating system. Replaced and all working fine now - thanks for your help!

DragosC
Community Specialist
Community Specialist

Understood. Thanks for letting me know. Should anything else come up, please open another thread and we'll take it from there. Have a good one and stay safe!

IanG1
Community Member

Thanks - you too