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I would like to install the Honeywell RTH6500WF thermostat.

Customer Question
My heating system is a...
I would like to install the Honeywell RTH6500WF thermostat. My heating system is a First Co 48HBQB.
I turned off the breaker, removed the prior thermostat (Honeywell Pro 400) and labeled the 4 wires (G, W, Y, R). There was no C wire attached, but there was a blue wire wrapped around the wire bundle. The Honeywell instructions said that a C would be needed to supply 24V power to the new device, and this blue wire could be used as the C if the other end was also available at the furnace.
I removed the furnace cover, and indeed the blue wire was there, similarly wrapped. The problem is that the First Co circuit board (model CB201V) does not have a C terminal labeled. The 4 other wires are wire nutted each to an extension wire with the female end of a disconnect that then attaches to the circuit board.
Question: How do I get 24V power to the blue wire?
Thanks.
Rick
Submitted: 2 years ago.Category: HVAC
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Answered in 18 minutes by:
1/23/2016
HVAC Technician: gotoman for ac, HVAC Technician replied 2 years ago
gotoman for ac
gotoman for ac, HVAC Technician
Category: HVAC
Satisfied Customers: 5,358
Experience: 51 years of experience install design and repair of all makes and models of AC
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One moment Rick

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HVAC Technician: gotoman for ac, HVAC Technician replied 2 years ago

Rick if you have air conditioning you will have two wires going outside to unit. One will connect to Y the wire is common you can 24 volt common there. Russ

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Customer reply replied 2 years ago
Russ. No luck with power. Am I able to send you pictures?
HVAC Technician: gotoman for ac, HVAC Technician replied 2 years ago

Yes go ahead and send photo. Russ

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Customer reply replied 2 years ago
Russ:Here are the pics.Rick
Customer reply replied 2 years ago
Russ:
I am unclear where we stand on this. Am I awaiting a reply from you, or am I to repost my question?Rick
HVAC Technician: gotoman for ac, HVAC Technician replied 2 years ago

Sorry Rick great info. Take the blue and connect to the brownand white wire nut. Take yellow connect to Red and you will have it. Russ

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HVAC Technician: gotoman for ac, HVAC Technician replied 2 years ago

The brown wire going to white wire is the common or C you are looking for. Outside wire color codes differ depending on who installs them. Red and are used. Also Blue and yellow depending on make. Some use brown for common. Some Blue and some black.

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