Wiring Aprilaire humidifier to Nest 3rd gen thermostat

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Old 12-03-19, 07:14 AM
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Question Wiring Aprilaire humidifier to Nest 3rd gen thermostat

Hello all,

I have a Aprilaire 760 humidifier that has worked well with its own humidistat for several years. I have recently purchased a Nest 3rd generation thermostat and am attempting to wire the humidifier to the Nest. I have read several other posts on this site and have followed similar instructions that resulted in positive outcomes. Unfortunately, that is not the case for me.

A piece of information I took away from other posts is that I needed an additional relay. I purchased a 6AZU2 relay. You can see from the images how I installed it.

I then connected the wiring to the Nest. I originally inserted a wire into the * and the other into the C. I immediately ran into problems. While troubleshooting from the Nest website I was told that C is not often required. So I pulled the C. Then it errored again telling me I should move the power from Rh to Rc. So I tried that. I tried every conceivable configuration. Switching the * and C wires, only in * but moving power wire, on and on and on.

Reading this and reviewing the photos does anyone have any suggestions?

Thanks in advance.

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Last edited by PJmax; 12-04-19 at 12:03 AM. Reason: imported/converted pdf's/pics/label
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Old 12-04-19, 12:06 AM
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Welcome to the forums.

You don't need the 50 switch anymore. Save it for the future.
I labeled the relay. My colors used are just an example.
The two green wires go directly to the humidifier.
The blue wire connects to C on the furnace board.
The pink wire goes to the * terminal on the nest.

That's it.
 
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Old 12-10-19, 08:44 AM
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Thank you for the feedback. I've finally been able to look at your photo compared to the wiring and I have a question for clarification.

By taking the relay out that I installed, that will leave the blue and brown with a gap between them. Do I need to reconnect them to each other? I'm sorry if that is a basic question, I just don't want to destroy anything.
 
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Old 12-10-19, 06:15 PM
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You need the relay. I drew where the wires connect to from the relay.
The nest sends 24vAC on the pink wire. That and the blue wire supply 24vAC to the coil.
The two green wires go directly to humidifier. When the coil gets power..... the switch closes and those two green wires become shorted.
 
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Old 12-11-19, 08:31 AM
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That did it Pete. Thank you very much. Please go tell HR I said you can take an atta-boy out of petty cash.
 
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