Need help wiring a 2nd Generation Nest

Old 12-02-14, 10:30 PM
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Need help wiring a 2nd Generation Nest

Good evening

I have a Lennox ml193uh and i am trying to wire a nest thermostat.
My troubles are how to wire a common to the nest so it does not loose power. I have been reading about wiring the c to a 24v common source. I do not know where to pull that power from the board on the furnace.

Thanks in advance.

Old 12-02-14, 10:40 PM
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Welcome to the forums.

Do you know where the control board is ? It may be in the lower section of the furnace with the blower. The pic below is what you should see. The C terminal is clearly marked next to the R, W, Y and G.

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