Nest + bypass humidifier wiring setup

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Old 11-27-16, 03:10 PM
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Question Nest + bypass humidifier wiring setup

Hi all,

I've been doing a lot of reading on here before setting up my 3rd gen Nest to control my home's humidity. We have a bypass humidifier (Honeywell HE225):

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The previous owner had a humidistat next to the old thermostat, which I've now removed (you can see the two dangling wires from the humidistat next to the nest) below:

Name:  Nest with Exposed  Old Humidistat Wires.jpg
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As reference, here's the current wiring on the Nest:

Name:  Nest Wiring.jpg
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Based on my research, I'm planning to use this wiring diagram for my setup and have purchased a 6AZU2 relay:

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The question I have at this point relates to how the wires from the furnace board wire in. Here is a picture of the board:

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Here are the things I'd like to confirm before proceeding:

1. Is this the right diagram to use?Assuming yes, then....

2. Does the "HUM 24VAC" wire from my furnace board (Red arrow in photo above) equal to the red wire in the diagram that is going from "24VAC" to one of the relay switch terminals?

3. For the blue wire in the diagram going from the humidifier solenoid to the board, should this wire into the C/Common on the board (white arrow in board photo)?

4. Do I need to use the optional common wire from the nest to the board? Right now i'm not using that Common wire on the nest.

Thanks so much!

Dan
 
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Old 11-27-16, 07:57 PM
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Welcome to the forums.

The diagram (looks like one of mine) is showing a second completely independent 24vac transformer to run the humidifier. Is that what you are doing.... using a 2nd transformer?

In any case.... you will no longer be using the HUM terminal on the board.
You will be using a connection to the C terminal on the board.
You will need a wire from the * terminal of the nest to the furnace area.
 
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Old 11-29-16, 07:09 PM
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Thanks for the reply PJmax! I had no idea that was one of your diagrams too!

I am not using a second transformer. We just have the bypass humidifier. From your comments regarding the * nest terminal to the furnace, this is also different than the diagram. Do you know if there happens to be a diagram that would accurately describe the wiring I need to run? Many thanks!
 
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Old 11-29-16, 07:35 PM
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Here's a variation for you to follow. The colors for the humidifier are arbitrary. I just picked ones I like. Also... since it is 24v AC.... there is no polarity.

Name:  nestwithNONPOWEREDhumidifier.jpg
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You can always check this thread which is a similar setup to yours.
http://www.doityourself.com/forum/hu...hermostat.html
 
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Old 12-05-16, 08:10 PM
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Thanks so much for putting that together! So just to double (or triple?!) check, I definitely do not need a separate relay for this setup?
 
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Old 12-05-16, 08:23 PM
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You don't need a relay for your application.
 
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