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Connect Google Nest to boiler, 2 yellow wire boiler

Bigwheelz
Community Member

Dunkirk Quantum 90 Hot Water, natural gas boiler

System is heat only

Worked fine with a Honeywell thermostat (want the ability to control the temperature remotely)

The boiler has only two yellow wires for the thermostat.  These wires have 28v AC voltage.

The Nest Thermostat gives an an error message: N260 and “low battery”.  There is no C wire terminal on the boiler board.  There are no red or white wires on the boiler board.  There are only the two, apparently identical, yellow wires.

I bought a Nest Power Connector, but I cannot find a wiring diagram that applies to my situation. 

Is there a diagram for correctly wiring the Nest with a two yellow wire system?

3 REPLIES 3

Markjosephp
Community Specialist
Community Specialist

Hi Bigwheelz,

Thanks for reaching out here in the Google Nest Community Forum. I'd be happy to take a look at this for you.

Since your boiler has only two yellow wires with a 28-volt AC voltage and no C-wire terminal, it can complicate the installation process. The Nest Power Connector is a good attempt to address this, but finding the right wiring diagram is crucial. This message code is fixable with a proper installation. So please check your boiler board to see if it also has the terminal label to indicate which wire is for the power and the heater. Also, can you share with us a photo of it and your Nest Power Connector and how you installed it?

I look forward to your response.

Regards,
Mark

Thanks for your response.  The attached photo shows the two yellow wires that I have have attached to the nest.  I believe that the module on the bottom left of the board is the transformer for the thermostat.  Please let me know if you need more information.thermo1.jpg

zoeuvre
Community Specialist
Community Specialist

Hi folks,

 

Thanks for chiming in, Mark. 


@Bigwheelz, if your Dunkirk Quantum 90 Hot Water, Natural Gas boiler has two identical thermostat wires that have no distinction, I highly recommend you reach out to a Nest Pro technician to install the Nest Power Connector on your boiler professionally, as your system is considered a complex system.

 

Let us know if that helps.

 

Best,

Zoe