Nest Schedule for HW overriden by HW Cylinder Stat

[Jon_S1]

Hi

Trying to resolve a long running issue with the control of my HW.

My configuration is a Nest Gen 3 Thermostat running a Vaillant EcoTec 428 Plus conventional boiler via a Nest Heat Link and Cylinder Stat for the HW.

CH works fine and runs correctly from my programmed CH schedule, BUT the HW seems to ignore the programmed HW schedule on NEST, calling for heat only when the cylinder stat call for heating. This means the boiler fires sporadically (approx. 5misns every hour) throughout the night and the pump runs for 95% (but not 100% - it has short breaks).

Not surprisingly, what i am seeking is a configuration where the calls (from cylinder stat) ONLY result in heat being supplied during the period when the Nest Schedule is ON.

On a previous Nest installation i was able to i achieve exactly this mode of working, but for some reason I can’t get it working this way on my current installation.

Not sure of its a wiring issue somewhere, a Nest setting issue or something else. Several plumbers have taken a look but not been able to resolve.

Thanks in advance of anyone’s assistance 

Jon

[maedacortez]

Hi Jon_S1,

Thanks for reaching out. I understand that the hot water isn't following the schedule you set up, and I'm happy to help. To better understand the situation, I'd like to ask a few questions:

• When did this issue start?
• Have you recently made any changes to your HVAC system?
• Do you have a system or a combi boiler? Is the control On/Off or OpenTherm?
• Could you please send me pictures of the wire labels on your Google Nest Thermostat 3rd Gen and your control board?

I look forward to your response.

Regards,

Manuel