Gen 3 Nest to American Standard HVAC & Humidifier

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Old 12-04-18, 03:52 PM
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Gen 3 Nest to American Standard HVAC & Humidifier

I'm trying to install a new Nest 3 into my HVAC system. I do IT work so I'm pretty handy with electronics and wiring, but after reading thru a bunch of forum posts, I can't find one that looks exactly like the setup I have. The main HVAC unit is a American Standard aue1b060a9361a and the humidifier is a AHUMD200ABM00B with a separate manual control on the wall. The thermostat itself has the standard W, RH, G, and Y connections, and then for the humidifier, I can see 2 cables coming off the solenoid, one goes into a transformer that connects to HUM-H and HUM-N on the board of the HVAC, then comes out of that transformer and goes to the manual humidifier control, and then appears to come back to the solenoid.

I've included a link to all the photos of the system.

https://photos.app.goo.gl/mBvQvVrJN3LtuPQR6

Any help on getting the wiring correct would be appreciated.

Thanks!
Brian
 
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Old 12-04-18, 04:00 PM
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Welcome to the forums.

I see a four wire cable between the thermostat and the control board. If you do not have any more extra wires in that cable then leave the humidifier as it's currently wired. If you want the nest to control the humidifier..... you will need an additional wire...... five total.

R - red ------------->Rh
Y - yellow ---------> Y1
G - green ---------> G
W - white -------- > W1
 
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Old 12-04-18, 04:13 PM
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I kinda assumed I could do just that and have them operate independently, but wanted to see how easy/hard it would be to have the nest control the humidifier as well. The current controllers are mounted directly next to one another on the wall, so moving over the wires for the humidistat would be very simple. Would it require additional wiring on top of just moving over those 2? If so, again the HVAC is really close and I'm sure I can pull a multi-conductor wire over if need be.

Thanks for the help and the fast response!
 
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Old 12-04-18, 04:22 PM
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No..... if you have a humidistat next to your thermostat...... that'll be fine.

At your humidifier....... one solenoid wire connects directly to the C terminal on the furnace board along with the white wire that's already there for the A/C condenser. The other solenoid wire connects to the * terminal on the nest via one of the two old wires in the humidistat cable. That's it...... the old h'stat and the transformer are no longer connected.

Since you already have red, green. yellow and white at the stat. The h'stat line will add an additional red and white wire....... I'd remark those two wires with different colors. I'd remark white as blue and use it for Common and remark red as brown and use it for *.

By converting both old h'stat wires over..... you'll now be able to control your humidifier with the nest and you will be supplying the nest with a C wire.
 
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Old 12-04-18, 05:03 PM
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Just to make sure I have it 100% correct, right now there are a red and a white wire coming from the solenoid.

The white wire is currently going directly to the humidistat. I should disconnect that from the humidistat side and connect it to "C" terminal on the HVAC board? So it essentially goes from the solenoid to the "C" on the HVAC board

Then the red cable currently runs from the solenoid thru the transformer (which connects to HUM-H and HUM-N on the HVAC board) and to the humidistat. I should disconnect the red wire from the humidistat and connect that to the * on the Nest?

So to the nest, the 4 standard cables, and * to one of the solenoid?

And the other solenoid to the "C" on the HVAC board?
And the other

Sorry, I just want to be overly clear so I don't wire any of this wrong.

Thanks again!
 
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Old 12-04-18, 05:19 PM
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So it essentially goes from the solenoid to the "C" on the HVAC board - Correct.
I should disconnect the red wire from the humidistat and connect that to the * on the Nest? - Correct.

Since you are abandoning the old h'stat...... you are going to re-purpose one of the wires to connect from the solenoid to the * terminal.

The nest can work without a C connection but since you have the second wire in the h'stat cable..... you can use that to connect the furnace C to the nest C. This will insure more reliable operation.

As a pro installer..... I don't install any thermostats that rely on power stealing. That means they "claim" to work properly with no C connection. I will change the thermostat cable first.
 
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