I have an extra black wire labeled E with no corresponding port on the nest thermostat.

[rgaila]

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Original Poster: Craig Archer 

I have an extra black wire labeled E with no corresponding port on the nest thermostat.

[rgaila]

Hi Craig,

Thanks for reaching out to us and welcome to our community! We'd be happy to help look into this for you.

It sounds like you're describing an E connector, which some thermostats do have. The E wire turns your emergency heat on or off. Emergency heat is usually used when it’s too cold outside for your regular heater to keep your home warm. Here's more info on what this wire does and controls.

It might not be necessary to plug your Nest thermostat with your E wire. If it's affecting the use of your device, let us know and we'll troubleshoot further.

-From Garrett DS, Community Specialist.