Nest hot water not turning on at right time or sometimes at all

[Emmer]

I’ve had a 3rd generation Nest thermostat for years and never had any issues, it has recently stopped heating my water when the schedule says. Sometimes we wake up and its been on in the night, but not at a scheduled time. 

The boiler fires and heats the water if I use boost but does not appear to heat when the schedule calls for it. 

This morning my schedule should have heated the hot water in the morning between 6.30 and 7.30 , at 7.30 when I got up, I had no hot water and the boiler was cold and not firing, I hit boost for 30mins and the boiler fired up. This is a regular occurance. 

I thought I might have an issue with either the hot water tank thermostat or motorised valve but the fact boosting works makes me think there is a problem with either the heat link or the connection. 

I've seen lots of similar posts over the years, but no solid resolution. I have deleted and reset the water schedule. I have reset the heat link. I have checked the wiring in the heatlink. I hear the click when I turn the water on and off. 

What is the next step? 

[sicsacol]

Hi @Emmer,

Thanks for reaching out to the community. I understand your Nest Learning Thermostat (3rd gen) has stopped heating your hot water at the scheduled time, even though the boiler fires and heats the water when you use the boost function. I know this must be concerning since you've tried multiple troubleshooting steps with no success. I appreciate the detailed information you shared and your troubleshooting efforts. No worries, let's work together to get this resolved. To better assist you, I have some questions for you:

• What's the status light in your Heat Link? For more information about your Heat Link's light, please check out the next article: Heat Link lights and what they mean.
• Has there been any recent work done on your Nest Thermostat or heating system?
• Were there any power outages?

Any additional details you can provide will be helpful.

Cheers,
Jonathan