Nest thermostat 3rd gen not working for radiators

[Abadon9]

My nest thermostat seems to have stopped firing my boiler for heating, either in schedule or manual mode.

Having tried a reset on the nest, checking the heat link, running that manually, and turning up the thermostat to a high temperature, nothing seems to make the boiler fire for heating. It does fire for hot water, both in schedule and manual modes.

When increasing the nest heating temperature, it displays as heating, but doesn't fire the boiler at all.

But when I press heat link button, the boiler can heat for radiator.  Seems it is ok for hot water but not ok for heating.

FYI I bought this house which previous owners had the nest thermostat and they did a factory reset on it. When trying to set it up for my account I asked them what settings they had and they just said to google it/youtube it. 

my only problem is always the same, radiators are not Turning on even if I have schedule on, only hearts up when I turn hot water on. If I turn off heating completely there’s a click sound from the boiler, same way when I turn it back on, but no heating… in my area only 2 companies deal with nest pro, one of them doesn’t even answer their phone, and the other one said they haven’t done this for 2 years….. 

really frustrated at this point, will an electrician be able to solve the problem, or a plumber? 

thankss…

[Frustratedddd]

Sounds like a motorised valve issue again.

Do you have a motorised valve, and have you checked that correctly?

The first question as always is, Do you hear a click when you turn the display to call for heat at the Heat Link, and another when you turn the display back again?

[Abadon9]

Hi, 

So on the nest thermostat, if I turn the dial below the current temperature the screen will turn grey, and yes there will be a click sound on the boiler, when I turn it up over the temp, there’s another click, but no heating sent to the radiators even though the thermostat says “heating in x hours”. the radiators won’t turn on without the hot water being on. 

I actively look at the boiler (I have a viessman vitoden 100-x) system boiler, and when hot water turns on, the flame on it turns on, but when turning heating up independently no flame shows up… hope this helps. 

[Frustratedddd]

The click you are listening for is in the Heat Link, do you hear that?

Have you checked the valves if you have them?

[Abadon9]

I have no clue where the click is coming from, the heat link is literally right beside all the cables below the boiler, the click sound start and it’s like a “clock ticking” for a few seconds, clicks after clicks. Sounds really loud so I think it’s from the boiler? I’m not 100% sure 

[Frustratedddd]

You can tell where the click is coming from by a simple method. Put your hand on the front cover of the Heat Link, then get someone to call for heat at the display. You will feel a slight vibration which is the click. Do that a few times to confirm. Failing that put you ear next to the cover if you can get to the Heat Link.!!! There will be only one click, if you turn the display up, then another when back down.

This is important to know if the relay inside the Heat Link is switching. The boiler isn't important at present.

[GabrielaG]

Hi @Abadon9,

Thanks for posting in the Google Nest Community. I'm sorry to hear that your Nest Thermostat isn't activating your boiler in either schedule or manual mode. I appreciate the troubleshooting steps you’ve already taken, and I understand how frustrating this situation is, and I’m glad to assist you.

Thank you for your help @Frustratedddd.

To help us diagnose this, could you let us know:

• Have you experienced any recent power outages?
• Have you tried activating the heating using the app?
• What is the status of the LED light on the Heat Link? Is it solid, pulsing, or off, and what color is it?

Looking forward to your response.

Regards,

Gabriela