Question Wiring Thermostat

[GusMexa]

Can someone tell me why blue is labeled as C and the Black one is going to U1, What is this about?

Thanks

[Patrick_Caezza]

There is no standard on what color is for what function on thermostats. The Blue wire is mostly used for the common (C) wire. The U1 terminal is specific to the make and model of the thermostat, I would guess the Black wire is controlling an accessory such as a De-humidifier or a Humidifier, an outdoor thermometer, or a similar device

[GusMexa]

Thanks for the response, so do you consider this system would be compatible for the nest,,?

[Patrick_Caezza]

Yes, this is compatible with any of the Nest thermostats

You can try wiring it like this.

Blue - C to C

Red - R to Rc or R (jumper to Rc not needed)

White - W to W1 or W

Yellow - Y to Y1 or Y

Green - G to G

Black - U1 to (probably not needed unless you have a humidifier or dehumidifier installed and the to * or */OB)

The "or" is for the Google Nest Thermostat

[Ryan_G]

Hey GusMexa,

I just wanted to follow up and see if you're still in need of help? Please let me know, as I would be happy to answer any questions you may have.

Thanks for your help, Patrick_Caezza.

Best regards,

Ryan

[Ryan_G]

Hey there,

Just wanted to jump in here to check to make sure that you saw our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Have a great day.

Best regards,

Ryan

[Ryan_G]

Hey folks,

It looks like we haven't heard back from anyone so I'm going to go ahead and lock the thread. If you have any further questions or concerns, feel free to create a new thread.

Have a great day.

Best regards,

Ryan