Aprilaire 500 wiring


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Old 03-10-24, 08:50 AM
J
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Aprilaire 500 wiring

Decided that waking up dry as the desert had ran its course and purchased the Aprilaire 500 with the automatic control…

Looking at the manual I am a bit confused with the wiring and hope one of you can help me! My furnace has a HUM terminal and was wondering if wiring number 4 here is the way to go to have the humidifier run only when the heat is running and the outdoor temp is within the configured range.

some pics of my furnace




 
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Old 03-10-24, 02:43 PM
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Welcome to the forums.

The HUM terminal on that board is 120vac and cannot be connected directly to the humidifier.
You would need to connect a 120v -->24vac transformer or a 120v coil SPST relay.
Since you have two stage heating..... you cannot use the W1 or W2 stat terminals.

This diagram shows using the furnace power to run the humidifier and the separate supplied transformer for W switching to the humidistat.


You can also use a dual relay pack.... HD401. Available at amazon.
 

Last edited by PJmax; 03-10-24 at 03:04 PM.
Jrodenas voted this post useful.
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Old 03-11-24, 08:05 AM
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Thank you so much for the wiring diagram! I am always very confused with HVAC wiring so I do have a couple questions on it...
1. Since the R wire is run from the furnace to the Terminal and to the humidifier, does this mean that the water will be running constantly into the humidifier?
2. The diagram shows the transformer connected to the HUM (black cable) and to Neut (White) and on the other end to the W to the terminal and to the C in the furnace. I assume this is because the HUM terminal only gets power when the thermostat calls for heat. Does it matter which terminal in the transformer I attach the W and C?

Appreciate the help Pete and apologies if these are silly questions, I am just trying to learn as I go along.
 
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Old 03-11-24, 02:30 PM
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No apologies necessary.
You are working with sensitive and expensive equipment.
Ask away.

Yes... the HUM terminal gets 120v only when the burner is operating.
If you use a transformer..... there is no polarity.
If it has white and black 120v wires then the white is Neutral and the black is HUM.
The 24v side has no polarity. Connect in either direction.

You need to supply R (24v) an C to the humidistat to run it.
That same 24v can be used to operate the solenoid.
The transformer just supplies the W 24v which turns the humidistat on.
 
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Old 03-18-24, 06:30 AM
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Did the install over the weekend using the diagram above and it is working as expected, thanks again Pete!
 
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Old 03-18-24, 06:02 PM
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Awesome. Good job. Thanks for letting us know how you made out.
 
 

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