No heating working but the hot water is working

[Btlizzard]

Hi, I have a 3rd generation nest thermostat which had been working perfectly. We’ve had a lot of house renovations which plumbing and electrical work took place. The timer/schedule is now not working on heating but it does work on hot water. How can this be?

[MattyS73]

I have the same issue.  Just noticed as the temperature has dropped.  Works on manual if the hot water is on but not independently.

[Btlizzard]

Correct :))) Anyone know why?? 

[AlexD]

Hi @MattyS73 . Please try the same test I mentioned and let me know how it goes. 

[LarisaL]

Hi there @Btlizzard and @MattyS73! Thanks for reaching out. I'm so sorry to hear about this situation. Could you tell me if the boiler is firing up if you turn on the heating from the display, manually?

[Btlizzard]

good evening, thank you for reaching out. 
if I push the button on the Nest link (the white box with the big button) then that turns on the water and heating simultaneously. This is the only way I can get heating 

[Btlizzard]

So the answer to your question is ‘yes’ the boiler fires up 

[AlexD]

Thanks for letting us know here. I want to do some tests to see how the relays in the Heat Link behave. Go next to the Heat Link and open the Nest app on a mobile device:

1. Select your thermostat to access the heating controls and make sure the screen is black, heating is off.
2. Turn up the temperature until the display goes orange, heating on, and listen for a clicking noise.
3. Turn the temperature back down until the display is black again, heating off, and listen for a clicking noise again.

I also want to check for the hot water.

1. Go to the Nest app and select the hot water control.
2. Tap on the cogwheel in the upper right corner to go into the hot water settings and toggle the first option there off. This will turn off the hot water schedule, you can enable it back after the test.
3. Boost the hot water for any amount of time and listen for a clicking noise.
4. Turn the boost off and listen for a clicking noise again.

Keep us posted here with the results. 

[Btlizzard]

I did the test above for the heating, the heating when I turned the dial on the app made a click noise, but the boiler did not fire up nor did the orange appear on the app. The same with the heating. 

[AlexD]

Thanks for letting me know. Just to check did you also turn the temperature back down and checked for a clicking noise?

Also I assume for the second part you are referring to the hot water correct? As you mentioned heating again. 

Could you take a screenshot of what did not go orange in the Nest app so I can have a look? 

[Btlizzard]

Beg your pardon I meant water. Yes, I  turned down the temperature and the clicking noise occurred. 
reference the photos, nothing turns orange 

[TudorL]

Thanks for letting me know. By any chance, do you have a system boiler with a separate water tank? 

[Btlizzard]

yes (it’s not a combi) with a separate water tank

[TudorL]

This means that there is high probability that you either have an S plan or a Y plan, but I would incline that you have a Y plan, a 3-port valve, and when you activate the valve all the way, the heating is able to come on as well. I would recommend an installer to come and check the valve, but also the wiring that has been done on it. 

[Btlizzard]

I’m a Y plan, with a the port that acts as a safety for the hot water and a 3 port. I’ve actually got an electrician here right now

[TudorL]

That's great, would he be able to check the valve now? 

[Btlizzard]

Both valves have been replaced last week. 

[AlexD]

Based on the fact that the Heat Link is clicking as expected that would indicate that the Heat Link is working as expected. Since you mentioned you had lots of work done on the system at the location it's most likely something in the system somewhere. 

However if you want, I can send you the steps to perform a continuity test on the Heat Link. This will show for sure if something is going on with the Heat Link. If you have a multimeter and are comfortable in doing so, you can perform the test though it would be best to have a installer or electrician perform it, or a Nest Pro. They can also contact us live over the phone or chat when they are there and my colleagues can walk you through all the steps. 

[Vladut]

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

[Btlizzard]

Hi, thank you for the tips. In the end up the electrician changed everything over but we never actually got to the bottom of what it was. Which is a shame as it’s always so useful to know. 
however I think it could have been the tank stat, a lose wire perhaps. 

[AlexD]

It's certainly possible. Just to confirm, is everything back on track now? 

[Btlizzard]

Yes it appears so. Thank you for all your support. 

[AlexD]

No worries. If anything else comes up, make sure to reach out again here or on any of our support channels. 

Have a great day ahead!