Where does the thermostat wire go?

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Old 07-19-15, 12:47 PM
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Where does the thermostat wire go?

I want to install a Honeywell wireless thermostat, but my current stat does not have a C wire. Elsewhere I saw that I can swap the G wire for the C wire, if I am willing to sacrifice the use of the "fan-only" setting.

My furnace and air handler are separated. Furnace on the ground floor, air handler (also A/C) is in the attic. The system was installed in the 1990s. The furnace is a hydronic unit with a Honeywell hydrostat attached, but only 2 wires go into that. There are 2 other zones, but I am not concerned with them.

Will the wire from the thermostat most likely go to the air handler in the attic, or to the furnace? (Attic access is slightly easier than furnace).

Thanks,
JimR
 
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Old 07-19-15, 01:41 PM
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C comes from the cooling transformer.
 
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Old 07-19-15, 06:16 PM
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Ok, I think that tells me where I have to connect to, but what I need to know right now is where should I look for the cable that originates at the thermostat? In the boiler room, or in the attic?
 
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Old 07-19-15, 07:07 PM
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If a single thermostat is controlling the boiler and cooling...

R(h) and W runs from the boiler to the stat.
G, Y, Rc and C runs from the cooling air handler to the stat.
 
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Old 07-19-15, 08:34 PM
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Stellar information, thanks.
 
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