Black wires to both air handlers

Old 02-10-19, 10:26 AM
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Black wires to both air handlers

I have 2 air handlers, a Goodman for the downstairs and a Lenoxx for the upstairs. There is PVC running across the attic floor with 2 black thermostat wires running between the 2 units. Can anyone guess why this would be? I have to go up there tonight and I can see what they are attached to, I don't remember off the top of my head. I think it was from the "R" of the upstairs over to the downstairs unit and vice versa. It doesn't make much sense to me, by I am no electrical genius.

I am replacing my RAM 3MC4 board with a 19W94 later this week so I would like to get a full grasp on the wiring before I tackle it.

I am having an issue with the Nest E "no power to the "R" wire" thing. It happened a couple weeks ago and I went up to check all the wires. I think it was a short somewhere because I got it working somehow. I am going to look at it tonight, so I may have more questions coming. 😁
Old 02-10-19, 06:30 PM
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Welcome to the forums.

With the 19W94 make sure you get the connectors/adapters needed for your furnace.
I'd need some pictures of where the wires connected. There shouldn't be any common connection between air handlers and furnaces. They run on different transformers.


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