Best Thermostat permanently runs my boiler

[Jpc2302]

After 2 years of no problems, my Nest thermostat now doesn’t switch off my boiler at the required temperature on the display. There are no error messages displayed on the thermostat or the boiler and the in a green LED on the link.

The only change I have made in the house recently is to change WiFi routers. The thermostat appears to be connected to the new router ok.

Does anybody have any ideas on a solution?

[Houptee]

Probably the boiler controller is bad where the wires connect.

[Jhonleanmel]

Hey folks, 

Thanks for lending a hand, @Houptee.
@Jpc2302, I wanted to follow up and see if you are still in need of any help. Please let me know if you are still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.

Thanks,
Mel

[Markjosephp]

Hi Jpc2302,

I'm checking back in — how's it going with your Nest Thermostat? Still need our help? Let us know so we can assist you right away.

Regards,
Mark

[Jpc2302]

Hi Mark, thanks for checking in.

Unfortunately the thermostat is still not controlling the boiler which I’m turning on/off manually to heat the house/water.

If I leave it on the boiler just continually heats and doesn’t switch when the thermostat set point is reached.

The Nest display looks normal to me and the Nest receiver connected to my boiler has a green LED inductor (which I’m assuming is good)

Any help would be appreciated.

Regards

Jeremy

[Markjosephp]

Hi there,

I'm sorry to hear the issue still persists. To isolate, could you tell us the type of Nest Thermostat you have? Here's your point of reference. Also, please check the power readouts on your thermostat's technical into settings.

I'll look forward to your response.

Thanks,

Mark

[Jpc2302]

Hi Mark,

It's a gen 3 2018 v3.4

Software version 5.9.5-2

Battery 3.956v

Vusb 5.13v

Vin 0.00v

Iin

200 mA (c)

Regards

Jeremy

[Houptee]

You have no power getting to the Nest see where it says Vin 0.00volts

The power comes from the R wire and the C wire.

If you know how to use a mutlimeter to test for AC voltage you can go to the boiler and locate the R and C wires and put the lest leads from the meter on the R and C terminals with the meter set to read AC voltage (not DC) and see if you detect 24-30V AC.

If not you have a problem with the transformer in the boiler.  Or the 120 volts AC power to the boiler transformer is off not giving power to the transformer.

You can buy a multi-meter for under 20 bucks at Harbor Freight Tools or Home Depot or Lowes or Amazon.

[Jpc2302]

Hi, 

The problem is now fixed. It was the 3 way valve controller that wasn't working (easy to fit a new one) and the Nest thermostat is now working correctly.

Thanks for the advice.