Nest E without a C-wire

[joetroia]

I have a non Wifi thermostat with a R and W for heating only.  Want to install the E with a 24v transformer instead of a  Nest Power Connector to act as the C-wire.  Will this connection work? 1) Connect the furnace red wire to R and the furnace white wire to W1, Then connect one of the 24v transformer to the C and the other to the R.  In this case the red wire  from the furnace and one of the 24v wires go to the R.  Thanks for your help.

[GabrielaG · Accepted solution]

Hi joetroia,

Thanks for reaching out to the community. I understand you want to install the Nest Thermostat E with a 24V transformer instead of a Nest Power Connector. I'm happy to assist you right now.

It is not advised to install a 24V transformer since you can damage both your HVAC system and your Nest thermostat. The Nest Thermostat E is compatible with 85% of 24V heating and cooling systems, such as electric, gas, heat pumps, and forced air. Although the Nest Learning Thermostat E is made to function even without a common C wire in your home, there are a few situations in which installing a new C wire or the Nest Power Connector may be necessary.

If you have more questions, please feel free to write in this post.

Regards,

Gabriela

[joetroia]

The reason I was thinking of using a plugin transformer is that no one including google support could tell me how to wire a Nest E with a Nest Power Connector for a heating system with a Honeywell Zone valve. I only have a R and W wire going to my old thermostat.  Can you let me know how I can do the wiring when having a Honeywell Zone valve?

[GabrielaG]

Hi joetroia,

Thank you for your reply.  I understand that you want a guide to how to wire a Nest E with a Nest Power Connector for a heating system with a Honeywell Zone valve. I'm happy to continue assisting you.

Nest Learning Thermostat E is made to function even without a common C wire in your home. However, there are a few situations in which installing a new C wire or the Nest Power Connector may be necessary. If you consider your HVAC system needs a Nest Power Connector, you can check this article, which includes a guide on How to install the Nest Power Connector.

If you have more questions, please feel free to write in this post.

Regards,

Gabriela