# Wiring Aprilaire humidifier to Honeywell thermostat



## MurphyMan (Dec 25, 2011)

Greetings.

I am installing an Aprilair model 400 humidifier into my old Carrier air handler, running off the Carrier heat pump. I have a Honeywell TH8320 thermostat. 

Here is my problem. The Aprilair destructions call out for a hook-up to W. Well, on my thermostat there is no W.

Here is the humidifier wiring diagram: http://www.aprilairepartners.com/products/category/humidifiers/83218.pdf

For the thermostat, I am using the 2H/1C connection wiring guide, shown on page 5. http://www.hydro-temp.com/help/drawings/honeywell%2069-1894ES.pdf

You can see the air handler board connections here: http://www.docs.hvacpartners.com/idc/groups/public/documents/techlit/im-fa4a-11.pdf

How should I hook this up? Should I hook it to Y, the compressor?

Sorry about all the links. :whistling2:

Thanks!

Murph


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## sammy37 (Dec 9, 2008)

Same issue I just had with my heat pump and humidifier install. I temporarily had mine hooked to a relay through the G wire and had a seperate transformer for the humdifier but have recently bought a White-Rodgers thermostat that has a humidity feature built in. 

You dont want to hook it to Y, otherwise it will run in the summer also. Same with leaving it attached to G, fine for now but will also run in the summer.


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## sammy37 (Dec 9, 2008)

Someone needs to delete the above post


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## MurphyMan (Dec 25, 2011)

Okay - I got it working. Just used Y. I can just turn it off for the summer.

The Aprilaire 400 seems to be pumping out the humidity. It's been running for 12 hours now, and it seems to be taking effect.


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## sammy37 (Dec 9, 2008)

MurphyMan said:


> Okay - I got it working. Just used Y. I can just turn it off for the summer.
> 
> The Aprilaire 400 seems to be pumping out the humidity. It's been running for 12 hours now, and it seems to be taking effect.


Did you wire in a humidistat? If you hook the humidifier to G, you will be able to run just the fan only if you need to humidify without a heating call. 

Also, did you plum it to hot water? Works better with a heat pump that way.


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## MurphyMan (Dec 25, 2011)

sammy37 said:


> Did you wire in a humidistat? If you hook the humidifier to G, you will be able to run just the fan only if you need to humidify without a heating call.
> 
> Also, did you plum it to hot water? Works better with a heat pump that way.


Yes, I wired it per Aprilaire instructions, so if humidity is called for, it will turn on the fan. Yes, I also ran the hot water to it. Now, I'm off the the hardware store to find some insulation for 1/4" copper tubing. The air handler is located in a cold garage.


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## MurphyMan (Dec 25, 2011)

Just to wrap this and to make it official, I just got a reply from Tech Support at Aprilaire:

Dear Mr. MurphyMan,
Thank you for contacting us with regards to your model 400 Humidifier. Without a W terminal, you can eliminate that wire. Y is not needed as G is still called for and accompanies any Y call. We recommend the same wiring for heat pump and heat/cool systems, otherwise.
Please let us know if you have any further questions.
Sincerely,

Brett Phillips
Technical Support
Aprilaire - Division of Research Products Corporation​
:yes:


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