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Nest 3rd Gen with Heatlink (Europe), radiators are heating even if it is hot outside

MN74
Community Member

Hi, I am having trouble with heating, I use the Nest 3rd gen thermostat that is wired and connected to Heatlink (we are in Central Europe). For heating, I use a condensing boiler—Viessmann (supporting opentherm). After its installation (November 2024) everything was ok until just recently when the hot weather arrived. The problem is that I use Nest to regulate radiators, which worked perfectly fine; they turned on once the temperature dropped. But now, I realize that the radiators are heating when I turn the hot water on, for instance, while in the shower, the radiators turn on. Since then I've turned the autosense off; all smart features on Nest that I know of are disabled, and the temperature is set to 13°C/55°F, but from time to time I can still feel that the radiators are heating. I have no idea what to do. Any thoughts? Here is a picture of how the Heatlink is wired. IMG_1696.JPG

3 REPLIES 3

Frustratedddd
Community Member

The first thing I would do is switch the system off NOW and get the installer back immediately!!!

Reason, cross polarity will NOT help!!! [See Picture] - Live Neutral round the WRONG way!!!

When they come back, ask them to put the cable inside the Heat Link rather than leaving the cores outside!!

You could also ask them to perhaps connect an earth wire, as the feed looks just a 2 core, but that could be incorrect on my part as I cannot see the cable 100%!

 

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virnab
Community Specialist
Community Specialist

Hi MN74,

 

Thank you for posting in the community.

I understand that your radiators are heating up even when you only intend to use hot water, despite your 3rd gen Nest Learning Thermostat (NLT) being set to a low temperature and smart features disabled. I appreciate the important details of your installation you've provided and the picture of how the Heat Link is wired. No worries, help is here.

Thank you Frustratedddd for your contribution.

Before I start providing assistance, I would appreciate it if you could answer the following questions:

  • Are you getting any error messages or code on your 3rd gen Nest Learning Thermostat (NLT) display?
  • Has there been any recent work done on your thermostat(s) or heating system? If yes:
    • What kind of work was done?
    • How long was the power off for?
  • Were there any power outages? If yes:
    • When was the latest power outage?
    • How long did it last?
    • Has the thermostat been off since then?
    • Did the thermostat and Heat Link work before the outage?
  • Does the thermostat call for heat?
  • Does the display show a water droplet? This icon indicates whether hot water or bacteria prevention is activated.

Please keep me posted.

 

Best regards,

Virna

@virnabAre you serious? Look at the connection polarity!!