Hot water ignores timer

[StellasBrother]

3rd generation Nest Learning thermostat.

When timer says hot water is off, increasing the setting on the hot water thermostat causes the boiler to run.  But central heating behaves properly.  Is it possible to mis-wire the Nest thermostat to cause this problem?  Or is the Nest thermostat faulty?  How do I solve this problem?

[Derickf]

Hi @StellasBrother,

Thank you for posting in the community. I'm sorry to hear that you are having trouble with your Nest Learning Thermostat (3rd gen) because even when the timer says hot water is off, it will run the boiler if you increase the heating. I understand how difficult this could be. I'm happy to assist.

To gather the necessary information, please answer the following questions:

1. Do you have a system or a combi boiler?
2. What's the status of the Heat Link's LED light?
3. When did the issue start?
4. Has there been any recent work done on your Nest Learning Thermostat (3rd gen) or heating system?
5. Does the display show a water droplet inside of a circle?

I'll be waiting for your reply.

Best regards,

Derick.

[StellasBrother]

Nest was installed sometime in 2019. Problem was apparent immediately.

Boiler is system and was replaced August 2024. So problem is not with boiler.

Heat Link's LED light is green. Currently HW timer is off and CH timer is ON.

No work done on Nest since its installation; boiler replaced as explained above.

Display does not show water droplet in circle. Changed setting to "boost", red water droplet now shows. Will note tomorrow what the display shows when the timer calls for HW.

[StellasBrother]

StellasBrother here:  found the problem.  it has a Bacteria Prevention feature which I found by googling for "nest thermostat 3rd generation water droplet" see:

https://support.google.com/googlenest/answer/9256656?hl=en#:~:text=Your%20Nest%20thermostat%20will%2...