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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8266
Experience:  Furnace, A/C and heat pump specialist.
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I bought a Wi-Fi Smart thermostat and I have no "C" wire can

Customer Question

I bought a Wi-Fi Smart thermostat and I have no "C" wire can it still be connected another way?
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

Do you have an unused wire in the bundle at thermostat? If not there are a couple of options. Best to is to run a new wire with enough wires for a C.The other option will require you to give up the FAN ON option.

Customer: replied 1 year ago.
What I. want to do is run my heating and a.c. system via Wi-Fi from another location so I still will need the fan on wire connection
Expert:  airheatman replied 1 year ago.

OK now the fan ON option just allows you to turn the fan on without any heat or AC, just blower,Do you think there will be times when you want to turn on just the fan. In AUTO position, fan will cycle with the heat or AC.

Customer: replied 1 year ago.
Ok I can use the fan on wire as the "C" wire to the WiFi thermostat?
Expert:  airheatman replied 1 year ago.

Ye very few people actually use the FAN /On feature on their thermostat.As mentioned it just lets you run fan to circulate air without having HEAT or AC on. Do you ever just run your fan?

Customer: replied 1 year ago.
No never use just fan, so I can use that wire as "C" wire what letter is that wire?
Customer: replied 1 year ago.
I have 4 wires, W,Y,G and R
Expert:  airheatman replied 1 year ago.

Excellent.This is the most simple and practical way to solve your problem.All you are sacrificing is that FAN option.

Here is what we will do.

1. Move the wire currently going to G at thermostat over to C

2. In furnace do same thing.Move G wire over to C

3. Now add a small jumper either at thermostat or on furnace board from Y to G

That jumper signals blower on anytime the Y is energized for compressor in outdoor unit to come on,so fan runs on call for Cool.Fan is controlled through furnace controls in heat mode.

Customer: replied 1 year ago.
Will try hopefully you are a life saver and we'll worth the $$ THANK you I need to copy this down in writing so give me a. Minute
Expert:  airheatman replied 1 year ago.

Take your time. This will work and will solve your problem.You can rate now and return to the question for up to 30 days at no addidtional charge to follow through or you can do this and then come back to rate question.Expert is not paid for assisting you until you rate answer. Bonus always appreciated if you feel justified when finished.

Customer: replied 1 year ago.
Thank You and Happy New Year!
Expert:  airheatman replied 1 year ago.

Thank you. Now if for any reason you ever want to add that FAN ON option back, there is another way to do this.It is a little more involved and requires an adapter that costs about 25 bucks. It is called an "Add a wire" adapter. See links below for how it works and an example of where you can purchase.

But the simplest and most practical is the way explained earlier.

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