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Installation Help | Nest Learning

Tmy04003
Community Member

my system has forced water radiators as well as an AC unit in the attic with fan/compressor outside (but not a heat pump to my knowledge).

Changing my main zone to the nest and uncovered this wiring from prior Honeywell thermostat (which oddly used a blue wire in a green slot).  When installed, turning on the heat now triggered the outside fan as if it was a heat pump. In addition there was no power to RH so the nest shut down after the battery ran out. 

anyone have a similar issue and solution?

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6 REPLIES 6

Houptee
Silver Product Expert
Silver Product Expert

Any spare unused wires in the cable that comes from the AC system?

If you can get a C wire connected at the Nest, and also at the AC unit, it will work correctly and only use the power from the AC system.


Houptee -- NJ Master HVAC Licensed Contractor

Tmy04003
Community Member

Thank you for the help. The 3 wires that come out from AC unit I believe are the Red hooked into RC, a blue and a green. All 3 were hooked into slots in prior thermostat and I don’t see any extras. 

Houptee
Silver Product Expert
Silver Product Expert

You must have set it up wrong and it thinks you have hot air furnace.

Set it up as a dual fuel system.

Tell it heat is radiators and Ac is forced air.


Houptee -- NJ Master HVAC Licensed Contractor

Markjosephp
Community Specialist
Community Specialist

Hello folks,

 

Thanks for the help, @Houptee.

 

@Tmy04003, I wanted to ensure that everything was covered here. How's it going with your Nest Thermostat? Have you tried reconfiguring your system? Please let us know if you need more help.

 

Regards,
Mark

Jake
Community Specialist
Community Specialist

Hey there,

 

I wanted to check in and see if you are still in need of any help. Please let me know, as I would be happy to assist, and answer any questions you may have.

Best regards,
Jake

Jake
Community Specialist
Community Specialist

Hey there,

 

I wanted to check in, and let you know that I will be locking the thread in 24 hours.

 

Best regards,

Jake