Question on wiring Aprilaire 500 w/electronic humidistat

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Old 12-16-18, 05:50 AM
J
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Question on wiring Aprilaire 500 w/electronic humidistat

I have installed several 700 with electronic humidistat and do not understand why the 500 wiring instructions are so different. The main difference is that the 500 humidistat is always on (backlight) since the hunidistat R and C is connected to the R/C on the furnace board and not the transformer. This has the ODT and not run in manual mode.

The transformer is wired to the solenoid not the humidistat.

Can I just wire it like the 700? And if no why not?

What am I missing?

Thanks
 
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Old 12-16-18, 10:14 AM
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Welcome to the forums.

Not really sure what you're missing.

There are two types of humidifiers..... from a wiring standpoint......
1) requires 24vAC to be applied to the solenoid wires.
2) has a built in 24vAC and requires a contact closure to operate.

The 500, 600 and 700 are pretty much all type 1.
The 760 is type 2.
If the humidifier comes with a separate transformer.... it's a type 1.
 
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Old 12-16-18, 01:33 PM
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Thanks for the reply. NVM the 700 part.

With the wiring as stated in the directions the electronic stat back-light stays lit all the time using the R/C on the furnace board per the wiring instructions. Is it designed to do that now? It is at my sons and I am trying to figure out why before I travel there again. Is it a stat problem or furnace board problem or designed that way now.

Thanks
 
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Old 12-16-18, 02:56 PM
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I'd say designed that way. The thermostat and furnace have nothing to do with it.
This is an electronic humidistat and needs continuous power.
It requires a 24vAC input to activate the humidifier. I usually use the W line to activate it.

There are examples in many of the humidifier threads if you are looking for wiring ideas.
This is the most common way of wiring.

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Old 12-16-18, 04:25 PM
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Thanks, the wiring diagram is this one: https://www.doityourself.com/forum/a...tat-wiring.jpg

Everything works fine but I am not used to having the electronic thermostat on when the furnace is not.
 
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