Wiring NEST with Goodman forced air and humidifier


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Old 01-24-17, 10:48 AM
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Wiring NEST with Goodman forced air and humidifier

Helping the mother in law...did I get myself into trouble?

She received a Nest 3 from her gas company and I offered to install it.

Doh!

Furnace model...gks90703bxad with a Generlaire whole home humidifier.

I wired the nest in what I thought was the logical way. When I turn to normal operation and turn up the heat...I get fan and humidify, but no heat, and code 2 (2 flashes red) on the furnace. The Pro-setup was done so that humidifier gets "hum+heat" and fan as "active".

I backed up a step and disconnected the humidifier (orange C and black * wires) from the Nest. I hooked up the old humidifier controller. The Nest then worked fine for heating and fan...no codes on the furnace.

Took pictures of the before and after wiring below...Any help would be appreciated. Could it have something to do with the two wires to the fan (G) on the furnace control panel? Thanks.

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Old 01-24-17, 11:51 AM
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Welcome to the forums.

You cannot connect a load to C at the nest.

Black goes to *
Orange goes to C ..... AT the furnace.

If you had a wire from C at the furnace to C at the stat then you could get C from the stat.
 
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Old 01-24-17, 03:58 PM
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Thanks for the welcome and your help Peter!

I am not clear yet what needs to change here...

The orange wire was originally C from furnace to the humidistat. I made it C at furnace to C at nest.

The black was originally from the stat to humidifier, I made it humidifier to * the Nest.
 
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Old 01-24-17, 10:00 PM
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Check where that white wire on G at the furnace goes to. My guess is that it goes back to the humidifier valve. If so it needs to move to the C furnace terminal. That way the humidifier valve gets C/common (white wire) from furnace and * (black wire) from Nest to activate.

And the Nest gets C/common (orange wire) to make it function properly.
 
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Old 01-24-17, 11:25 PM
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Ok. I see the orange has been converted to C correctly at both ends.
We can assume the black on the * goes to the humidifier.

The second wire to the humidifier needs to go to C on the furnace board.
We don't see a wire from C to the humidifier as there is only the orange on C.

So like Astuff said.... should that white wire on G be on C ?
 
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Old 01-25-17, 07:30 AM
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I don't know but am wonder if setting fan as "active" is correct for humidifier.
 
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Old 01-25-17, 09:09 AM
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Of course, now I understand what you are saying..."You cannot connect a load to C at the nest". Before the stat closed the circuit for the humidifier, the nest C connection will not do that, I believe it states the C is only to charge the nest.

I am stopping by the in-laws later today and will verify the white wire currently to G is from the humidifier...I thought I took notes/pics on that wire but I cannot find them now.

Thanks again Astuff and Pjmax.
 
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Old 01-25-17, 11:11 AM
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More complicated than I thought, I may just call someone in. Humidifier wires run one black to the nest *. The other hum wire connects with 2 yellow wires one running to an air pressure switch and the other back to the control module.

The white to G we see is actually a two wires from a relay socket with white to G and black to R ( I thought this was a shadow in my picture)

Pressure switch is the circular black thingy near the top, Holding the wire from the humidifier.
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Yellow and orange wires I am holding come from the humidifier and the air pressure switch respectfully to the control module.
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Relay socket...
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Hmmm...
 
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Old 01-25-17, 12:01 PM
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Yes, this is getting complicated. Apparently with that model furnace the yellow wire off of the pressure switch is supposed to provide switched power to the humidifier. It is hot with W and the safeties are good.

Not sure what they did with the relay and the tap off of R and G terminals. That last picture is interesting with the transformer driving the relay. It may be that they wanted the fan running whenever there was a call for humidity. I guess the 120v feed is switched somehow?

There may be some more wire hidden. You would need to properly trace all the wires as well as determine how the relay and humidifier valve are connected.

From the manual:
24 VOLT HUMIDIFIER
The yellow wire connected to the I.D. Blower pressure switch is
powered anytime the pressure switch is closed and provides 24
VAC humidifier control. Remove the yellow wire and connect a field
supplied jumper wire with a “piggyback” terminal to the pressure
switch terminal. Reconnect the yellow wire to the “piggyback” ter-
minal on the jumper wire and then connect the 24 VAC line of the
humidifier to the stripped end of the jumper wire. Using a wire nut
or a field-supplied quick connect terminal can make this connec-
tion. The wiring must conform to all local and national codes. Con-
nect the COM side of the humidifier to the B/C terminal on the
furnace control board (or to the COM side of the 24 VAC trans-
former).
DO NOT CONNECT 115V HUMIDIFIER TO THESE TERMINALS.
 

Last edited by Astuff; 01-25-17 at 12:27 PM.
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Old 01-25-17, 12:43 PM
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Also - what other wires are behind the thermostat? Normally there is a yellow, blue, and possibly brown to go with the orange.

The error/blink codes makes more sense now. When calling for humidity it was powering the pressure switch. 2 FLASHES = PRESSURE SWITCH STUCK CLOSED

So what I think you need to do is remove the black wire from the wire nut to separate it from the two yellows (put the yellows back together by themselves). Then put that black wire on the furnace's C terminal along with the orange that goes to the Nest's C. That way the humidifier valve will have one black wire going to the Nest * and one black going to C/common.
 

Last edited by Astuff; 01-25-17 at 02:01 PM.
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Old 01-25-17, 05:38 PM
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I concur with Astuff.

Ultimately you want one wire from the solenoid to C and the other solenoid wire to *.

I would say "fan active" is not what you want.
You want humidification with heat.
 
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Old 03-14-17, 07:28 AM
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Just wanted to thank those who posted here. I was using a fan relay like I used on my old Bryant / Aprilaire setup and it would not work even when wired properly. I unhooked the relay and went * and C directly to the solenoid to get my Goodman humidifier working again. Thanks!
 
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Old 03-14-17, 08:31 AM
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A fan relay would work but you'd need a second transformer to run the humidifier.
 
 

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