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Old 04-04-2011, 11:44 AM   #1
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Thermostat Wiring-Transformer (where to?)

Hello all!

I had a complete new HVAC system installed for the downstairs portion of my house. The installation required a new t-stat since it is a 2-stage cooling system.

I really like the features on the new t-stat, and purchased one for my slightly older 1-stage upstairs HVAC system as well. One of the features I like is that it runs on household power, using the batteries for a backup. It's my understanding that I've already basically got power to the t-stat via the R wires, and that I just need to add the common to basically complete the circuit.

I looked at the wiring to the internal board, and there is a wire running to the common, which runs to a "safe-t-switch," and then continues on to somewhere I can't locate. There is a separate bundle of wires that runs to the t-stat. Can I use one of the unused wires in this bundle and ALSO connect it to the common on the board, or will that mess up the "safe-t-switch?"

System is a Frigidaire with the following model numbers:
Condenser FS3BD-030K
Furnace L1RA-054C12A
Coil C5BH-T30C-B

Circuit Board:
Thermostat Wiring-Transformer (where to?)-img_1792.jpg

Wires leaving furnace:
Thermostat Wiring-Transformer (where to?)-img_1793.jpg

Old t-stat connections (was an old Hunter t-stat):
Thermostat Wiring-Transformer (where to?)-img_1794.jpg


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Old 04-04-2011, 11:45 AM   #2
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One More thing...

The new t-stat is a Honeywell VisionPRO 8000 (TH8320U1008)


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Old 04-04-2011, 04:35 PM   #3
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Yes, you can just connect it to the furnace's common terminal.
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