Nest Thermostat - Cannot turn Hot water heating off

[fredu1]

Hi

I cannot seem to find settings to control (turn on/off or defer to my schedule for example) my hot water control. Its always on.

Clearly, my boiler is constantly 'topping up', 24 hours a day. Not very efficient.

Is there a way to have this linked to my heating schedule please, or at least allow me to take control manually via Home Assistant.

System Description: Nest Thermostat -> Viessmann Vitodens combi boiler opentherm connection. Radiators, and hot water on demand

[Paul_R]

Hi there, thanks for reaching out. If you have a combi boiler you cannot control your hot water separately, because as you mentioned yourself, it's hot water on demand, thus the boiler heats the water when you open the tap. You can't set a hot water schedule either, as that is available for system boilers only, and the same goes for the on/off switch for hot water. And as for the boiler working non-stop, it is normal as that is what Open Therm means, water is constantly circulated through the system with the goal to save as much energy as possible. Please let me know if I misunderstood anything about your set-up, or if you need any further clarifications or information.

[fredu1]

Hi Paul, thanks for the reply. 

The boiler I have tries to maintain whatever water (hot water in the reserve tank, not the heating circuit) temperature the Nest Thermostat tells it to set, so is constantly trying to maintain this by sawtoothing (Burner activity to maintain temperature in the reserve tank). 

I don't want this feature and am happy to wait for hot water to arrive.

It looks to me like its the Nest Device that is constraining this, by not allowing 'hot water' to be schedule constrained. I have tried to attach a picture, not sure its worked though 😉

[fredu1]

[Paul_R]

The "sawtoothing" that you describe is exactly the Open Therm system functioning correctly. The only thing that happens when you open the tap for hot water is that the valve closes for the water that's circulated through the radiators, so it doesn't get mixed with the water coming to your taps. Otherwise, the thermostat and the Open Therm system look like they're working just as intended.

[fredu1]

Thanks.

So, I guess there is no provision within the Nest Thermostat to turn this excessive waste cycle off whilst we are sleeping, or out shopping for the entire day. I do believe however that if Geofencing is enabled, this does turn off after two days. That's a shame really, having this would:

• Reduce the flame startup frequency and preserve life within the boiler (starting circuits etc)
• Reduce gas consumption (I don't know by how much but over the year, probably quite a considerable saving)

Incidentally, there are two separate piping circuits within the boiler. If even a small amount of water from the radiator heating circuit (there are chemical additives in there) were to seep into and pollute the domestic water supply, could be trouble.

[OannaCG]

Thanks for your feedback! Our engineering team will take it into account, we're always looking to improve our services. Should there be any updates, we'll make sure we'll post them on our official channels. Please let me know if there's anything else I can help you with. 

[fredu1]

I would say they need to do more than 'consider this'. Nest in general are already on thin ice (my opinion), and a lot of Nest Fanboy people I talk to are seriously advising other, far superior technical products (tado, etc). The Nest/Google ecosystem has been far from an easy journey for me imo

[OannaCG]

Thanks for sharing your thoughts with us. We'll definitely send this feedback to our senior colleagues. We can't promise anything, though, as it's up on our engineering team, but as I previously mentioned we're always looking for ways to improve our services and products and we really appreciate your feedback. 

[AlexD]

If you have any more feedback or suggestions make sure to let us know. I will go ahead and close this thread for now. Thank you for all the interest in our product.