Installing a Nest with a Aprilaire 760 humidifier


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Old 01-04-16, 07:05 AM
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Installing a Nest with a Aprilaire 760 humidifier

I have a nest on order that should arrive in a few days. Ive read most of the install stuff. I need help with the wiring for my humidifier. My current control looks like this.




Here's the humidifier




Here's pic of the current thermostat.



Can anyone give me info regarding how to hook up the aprilaire? I can get more pics and info if needed.


Thanks.
 
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Old 01-04-16, 09:56 AM
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http://www.doityourself.com/forum/th...e-760-a.html#b

Looks like you will need an isolation relay.
 
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Old 01-04-16, 10:11 AM
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Welcome to the forums.

There are several 760 models. You show a humidistat. Does that wiring also involve a transformer ?
 
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Old 01-04-16, 10:18 AM
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Ive read some threads regarding transformers. Can anyone give me some general guidance when it may be located if there is one. I'll poke around when I get how and see where all the wiring goes.
 
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Old 01-04-16, 10:20 AM
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Look at the base of the humidifier and trace where the wiring goes. If it goes just to that humidistat..... then you will need a relay like shown in Houston's post.
 
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Old 01-04-16, 11:18 AM
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I'll have a look tonight and report back. Thanks.
 
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Old 01-05-16, 05:22 AM
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Here's a pic of the wiring. It appears the wires come out of the humidifier and go directly up to the stat.



Red and white with brown sleeve go right up thru the floor to the stat.



Humidifier is plugged into an outlet mount on the side of the furnace.



Page 15 and 16 here have some install info for a humidifier. Looks like I need to add a relay?

It also talks about knowing if the humidifier can run without heating or cooling and if it needs the fan to operate. How would I find that out?

http://support-assets.nest.com/image...ller-Guide.pdf

Thanks again.
 
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Old 01-05-16, 09:06 AM
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I replied 2 times to this post and it wont appear?
 
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Old 01-05-16, 09:26 AM
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It got caught in the SPAM control system as you are a new member yet. Can you see it now ?

Yes.... you will need a relay. The receptacle that the humidifier is plugged in to is probably controlled to operate with the blower.

Set the Nest up to humidify only with a call for heat.
 
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Old 01-05-16, 10:49 AM
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Ok it posted now. Use the relay they referenced in the pic below? They say to use a White Rogers 90-290Q or similar.



Looking at the wiring schematic do I still need to run the "C" wire to the relay? Or is that power cord which is plugged into a wall outlet on mine?

It also talks about knowing if the humidifier can run without heating or cooling and if it needs the fan to operate. How would I find that out?

I may need some guidance on the wiring.
 
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Old 01-05-16, 11:51 AM
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The nest is programmable in that you can have it turn on the blower and humidifier without the burner. You can also program it so the humidifier only runs when the burner is on. The second method is the preferred setup method for maximum performance and least waste.

I believe it's " humidify with call for heat".

You can use any 24vac coil relay.

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Old 01-05-16, 12:17 PM
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Awesome. Thanks for the wiring pic. That will help a lot.

The "C" wire should already run from the furnace to the stat so I should be able to find that color and trace it back to where it hooks to the furnace and then run a new wire from there?
 
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Old 01-05-16, 12:19 PM
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Yes...the C wire at the stat will appear at the furnace.
 
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Old 01-05-16, 12:38 PM
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Sounds funny when you say it like that!

Thanks for the help. The nest should arrive tomorrow. If I have time I'll start putting it in.

Another silly question. Since my current stat and humistat are separate I'd like to patch one of the holes and make it look clean. Easiest way will probably be to use one of the existing furnace stats wires to pull some new wires up through the wall for the humi. What kind of wire should I get?
 
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Old 01-07-16, 09:20 AM
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GOt the Nest yesterday. Picking up the relay today. Heres a pic of the board in the furnace.



Im going to run a wire from the C screw (hard to see but its the white wire on the right) and run that to the relay like posted below.

How can I test the 2 wires currently at the humistat to see which one is the load wire? Can I test it with a meter? Should it be 12 volts?
 
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Old 01-07-16, 10:29 AM
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You don't need to identify the load wire.
Pete was showing that the normally open contacts connect to the load, which is a humidifier in this application.

The coil on the isolation relay connects to the star terminal and to furnace C.
 
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Old 01-07-16, 11:04 AM
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Ok thanks. So the 2 wires from the humidifier to the relay can be hooked up to either terminal.

You guys must laugh at some of these questions from guys like me that dont do this stuff.
 
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Old 01-07-16, 11:48 PM
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I'd rather you ask then burn something up.

Since you're dealing with AC voltage... there is no polarity in any of the wiring.
 
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Old 01-11-16, 05:10 PM
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Are any of the terminals live on the relay when its on? Trying to figure out where to mount it? On the outside of the furnace? Ceiling? Inside the furnace cabinet. Does it matter?
 
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Old 01-11-16, 05:27 PM
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This relay looks a little different from the drawing above. Want to confirm. Is 1 and 3 the C and * side and 2 and 4 the humidifier side?





And either lead can be hooked to either post? Like C and * could be swapped?
 
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Old 01-11-16, 05:32 PM
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Want to confirm. Is 1 and 3 the C and * side and 2 and 4 the humidifier side?
And either lead can be hooked to either post? Like C and * could be swapped?
Correct and correct.

Since it's low voltage on the relay..... you can mount anywhere it's convenient.
 
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Old 01-16-16, 03:21 PM
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Got everything hooked up and set up today. Working good. Thanks for the help!
 
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Old 01-16-16, 06:23 PM
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Great news......and thanks for taking the time to stop back.
 
 

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