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Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3971
Experience:  Experienced in all aspects of HVAC, both residential and commercial.
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I'm trying to put a new thermostat control at my shop. When

Customer Question

I'm trying to put a new thermostat control at my shop. When I opened the old thermostat it only has three wires. One red connected to RC, a white one that is connected to Y and a brown one that I attached somewhere in the back of the plate. There is also a jumper wire that connects RH and RC together. In my new thermostat I don't have an RH. I only have an RC. Would it be okay to just connect the red wire to RC? And then connect the white wire to Y? Thanks for the help
Submitted: 2 years ago.
Category: HVAC
Expert:  Tim H. replied 2 years ago.

Hi, I'm Tim and I'm an HVAC expert here to help answer your question(s). Please provide all the information I ask for since I'm not onsite. At the end of our dialog you will be asked to rate my service, but please wait until then and all your question(s) have been answered satisfactorily. Thanks for your business!

Yes, you can connect the wire to RC. And the white would go to Y just like your old thermostat.

Customer: replied 2 years ago.
Thanks for the answer. I cannot see to find the AC switch in the breaker box. Would it be okay for me to just install it without turning off the power?
Customer: replied 2 years ago.
By the way I added a picture of the old controller wiring.
Expert:  Tim H. replied 2 years ago.

Sorry, had to step out for a service call. Did you have add'l questions on this?

Customer: replied 2 years ago.
Hello Tim,I just connected the wires to RC and Y and I have no power to the system. I saw a sign that states that the unit won't power without a C wire. Is that the brown wire?
Expert:  Tim H. replied 2 years ago.

Follow the brown wire back to the furnace or air handler that this thermostat feeds. See if it lands on a C or common terminal.

Customer: replied 2 years ago.
Unfortuantely my shop is in the mall and I cannot follow the wire to the air handler. When I unscrewed the old unit the brown wire was attached to a screw like it was a ground.
Expert:  Tim H. replied 2 years ago.

It could be a common. If you take a voltmeter and test across R to the brown wire, you should see 24 volts AC.

Customer: replied 2 years ago.
I tested it with a voltmeter and didn't get anything. I tried plugging the wire into C and it still won't power up the unit.
Expert:  Tim H. replied 2 years ago.

OK, well this may not be the best choice in thermostats then. Unless you can run a new wire.

Customer: replied 2 years ago.
Thanks Tim. I think you are correct. I was trying to install a WiFi system and apparently I have to install a C wire kit. Thanks for your help I really appreciate it.
Expert:  Tim H. replied 2 years ago.

Yes, good luck! Thanks for using Just Answer and please don't forget to rate my service as that's how experts get paid (thanks in advance for any bonus left). Otherwise experts work at their own time and expense. Feel free to post back with any additional questions.