Nest wiring with 8 wire Carrier heat pump

Old 05-17-17, 04:31 PM
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Nest wiring with 8 wire Carrier heat pump

Has anyone had experience with this setup? It is a single stage cool/dual stage heat. I have tried EVERY combination and have had no luck.

My wires are:

Any help would be truly appreciated
Old 05-17-17, 04:52 PM
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Welcome to the forums.

We need the model number of the old stat and what color wires were on which terminals.
Guessing can lead to damaged equipment.
Old 05-17-17, 04:55 PM
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If you forgot to write down the old thermostat to wire combination that was in use, take some pictures of the wire connections at the air handler.

The fuse will also require replacement.
Old 05-21-17, 11:08 AM
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Yeah 8 wires is not standard. For 2H/1C heat pump it would be 5 (6 with a common).

The "standard" hookup would be

RH (Power In) - Red
Y1 (Compressor) - Yellow
G (Fan) - Green
W1 (2nd stage/Electric heat) - White
O/B (Reversing Valve) - Usually orange, sometimes brown
C (Common) - Blue

But yeah you do need to check what the connections are on the air handler, and you did most likely blow the fuse trying different combinations.
Old 05-21-17, 08:52 PM
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Wow. I just checked and there are over 40,000 possibilities for arranging eight wires.
Old 05-22-17, 02:10 PM
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Way more than that.. It's 8^8, which is over 16.7 million. However when you subtract the known givens (red, white, yellow, and green) that correspond with letter terminals, it's only 4^4 or 256

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