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Additional L wire

EdR
Community Member

Third generation Nest with a Waterfurnace Premier 4.0 Geothermal system.  Hooked up the new Nest.  But was left with one wire not connected anywhere.  It was a black "L" wire.  Not sure what to do with it.  Tucked it in the wall for now.  I did enter it on the compatiablity chart and it never noted to use it.

My unit is three stage Heat, two stage cool.

Heat -  does have emergency heat and auxillary heat.  Just real worried that the black line should of been used, any advice would be wonderful.

4 REPLIES 4

Kristina1119
Community Member

Heat pumps with L wires

  • L wires are typically used to show system status, like emergency heat being on. Nest thermostats can work with systems that use Service Light (L) wires. While L wires can't be connected to the Nest thermostat, it doesn't need them. The Nest thermostat and Nest app will show you system status information without connecting L wires.

EdwardT
Community Specialist
Community Specialist

Hi folks,

 

@Kristina1119, thanks for the help!

 

@EdR, how's it going with your Nest Thermostat? Let us know if you have other questions and we'd be glad to help.

 

Thanks,

Edward

MelbaDT
Community Specialist
Community Specialist

Hey EdR, 

 

Checking back in — we hope you've got the answer you're looking for. Feel free to let us know if you have further questions in mind. 

 

Best, 

Melba

MelbaDT
Community Specialist
Community Specialist

Hi, 

 

We haven't heard from you in a while so we'll be locking this thread if there is no update within the day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the Community.

 

Best, 

Melba