C wire in wifi Thermostat form Lennox gas furnace g8d2

8150 Views 4 Replies 3 Participants Last post by yuri, Jan 10, 2016

tenteris

Discussion Starter · Jan 10, 2016

I have a Lennox gas furnace G8D2 (produced in a long time ago) and I just purchased a new Wi-Fi thermostat Honeywell TRH 6580 WF 1006/W.
The installation instruction says that wire C must be connected (to provide 20V power for the Wi-Fi thermostat, but the furnace does not have wire C (it only gas wire G).
Can anybody please advise how can I find wire C on the furnace that needs to be connected to wire C of the Thermostat?

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beenthere

· #2 · Jan 10, 2016

Post pic of furnace wiring.

Your furnace has a common. The transformer will have a common post/or wire. Look at the wiring schematic on the furnace panel.

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