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Replacing Thermostat - no labeled panel on furnace?

Posted by lifesupport4u (My Page) on
Mon, Jul 28, 14 at 12:57

I replaced my home thermostat with a wifi system. It works great.

A friend asked me to do the same. He has an old analog thermostat (no digital display) and a 4 wire system.

However, at his furnace the wires are all spliced and appear to run to various places. I could not find one labeled panel like mine had.

My understanding with a 4 wire system is you have to jumper the fan wire. I am not sure how to do this without a panel.

Any advice or help would be great.

Follow-Up Postings:

RE: Replacing Thermostat - no labeled panel on furnace?

Is his system a combination heat/AC unit? The typical four wires on a 24v controlled combination system are:
Red (power)
White (heat control)
Yellow (cool control)
Green (fan control)
The thermostats I've used in my last three houses have not required any type of separate jumper, although some thermostats may have had that function built in.


RE: Replacing Thermostat - no labeled panel on furnace?

Does this thermostat need a C connection? Here a YouTube video explaining how to use the G wire as the C wire. The C (common) wire is the ground connection. You will have to find this connection at the furnace.

Here is a link that might be useful: Substitute G-Wire for C-Wire -- DIY Installation

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