Wi-Fi thermostat 'C' wire questions

Old 04-03-13, 09:57 AM
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Wi-Fi thermostat 'C' wire questions

Hi Folks,
I'd like to buy a Honeywell Wi-Fi thermostat, but I want to make sure I understand how it install it first.
The 'C' wire from the furnace is Common, or Ground.
But my (c. 1987) Utica Starfire II oil furnace with tankless h2o has a (Honeywell) board with no post marked C or Ground, and the power wire bundle to it has only white & black. That means the chassis is ground, right? And I can connect the thermostat to a wire terminating into the chassis? What gauge wire should I run? (The bundle to the thermostat only has hot & neutral wires, no spares. The wife won't let me buy a stand-alone transformer for the tstat 'cause she doesn't want a wire running down the wall.)

Old 04-04-13, 12:19 PM
Join Date: Oct 2002
Location: Hamilton County, Ohio
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I'm not sure what you are referring to when you say chassis. A common wire would run from the furnace, attached to a ground potential part such as the frame of the furnace. 18 gauge wire is fine for this application.

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