Can I hook up common wire?


Old 06-04-20, 06:35 AM
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Can I hook up common wire?

I am trying to install a Honeywell wifi thermostat that requires the common wire. The current thermostat has the blue common wire coming out of the wall but it is not connected to the thermostat. I went into the attic and looked at the furnace/blower and the blue common wire is also there but not connected to the control panel. There is a red wire connected to the common slot on the control panel that leads to a wire nut and out to the A/C unit. I have attached a diagram. Model of the furnace/blower is Nordine GL1RA 054C-12A. A/C unit is a Frigidaire/Nortek FSA1BE4M1SN30K.

So basic question is can I connect the blue common wire to the furnace (along with the red wire already there) and then connect the blue common to the new thermostat? Just trying to not blow out the control panel on the furnace. Thank you!
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Old 06-04-20, 09:31 AM
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Yes, adding the blue wire is the right thing to do. Two wires under the C screw is fine.
PJmax voted this post useful.
Old 06-25-20, 12:05 PM
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Thanks for your help Astuff! I've been on vacation but after returning, I hooked up the common wire and all is working well. Thanks again!
Old 06-25-20, 03:57 PM
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Hi, itís best to connect the C conductor to the same wire nut splice for the condenser unit, not a good idea to have 2 conductors under 1 screw terminal unless it rated for 2.
Old 06-25-20, 08:46 PM
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With those small #18 gauge wires.... it's ok to have two under a screw.
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