Installed a digital thermostat... or so I thought...


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Old 03-30-04, 12:50 PM
D
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Installed a digital thermostat... or so I thought...

Hi all.

I recently bought a digital thermostat to replace our old terrible one. I disconnected four wires, red, blue, green, and white and attached them to the same spots as labeled on the new thermostat.

The new thermostat, has a RC, and RH labeling. I'm imagining that it's Red Cold and Red Hot... either way it's a moot point. There is also a connecting wire that came with the unit, that connects RH and RC together.

The problem is that my heat doesn't work. Air conditioning seems to be fine because the blower is on, but the heat... nada. I am not sure where to hook up the red wire, whether I should use the connecting wire, etc...

Any help is appreciated.
 
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Old 03-30-04, 01:11 PM
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What do the directions that came with the thermostat and with the furnace indicate?

I would start there.
 
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Old 03-30-04, 01:13 PM
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That's assuming I still have the directions for the furnace..

The thermostat said to hook it up to RH, and use the jumper wire to hook into RC... but no luck so far
 
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Old 03-30-04, 01:23 PM
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Make and model and type of furnace?
Make and model of air conditioner?
Make and model of thermostat?
 
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Old 03-30-04, 01:41 PM
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Originally posted by John Nelson
Make and model and type of furnace?
Make and model of air conditioner?
Make and model of thermostat?
I'll let you know when I get home... ETA 2 hours
 
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Old 03-30-04, 02:20 PM
noxx
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Using the "standard" thermostat color coding, one assumes that your wiring is as follows.

red +v
White - heat
Blue - cool
Green - fan


On an older four wire system it's likely that the standard colors are used and haven't been molested too many times. Often when replacing a standard stat with a digital, you will encounter problems because there is no ground, and the digital will only operate on batteries.

When you get home, pop open your furnace and inspect the wiring coming back from the stat. The green and white wires should land at terminals at the furnace, and the blue wire may either terminate or be spliced directly to the 2-wire cable going to your compressor.

Without seeing it myself there are so many variables it difficult to pin down the problem, it may be that the fan is not interlocking properly because your wiring/ xmfr size doesn't suppoort your new stat, it could be a misplaced terminal, could be a half dozen things.

Let us know a little more in detail and we'll get you all worked out.
 
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Old 03-30-04, 02:26 PM
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If I take a picture and post it, will that help at all? I can take pictures of both the furnace and thermostat (and its connections).

I'll do that as soon as I get home.
 
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Old 03-30-04, 03:36 PM
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Wahoo! I fixed it! I swapped the blue wire onto the C (for Cyan... *sigh*) post and the heat kicked right on.

Thanks for the help folks!
 
 

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