Wiring help: Moving from Aprilaire 760 to 700M on Trane

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Old 01-17-16, 09:22 PM
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Wiring help: Moving from Aprilaire 760 to 700M on Trane

I'm popping out my old Aprilaire 760 and its humidistat and replacing it with a 700M and its humidistat on a Trane furnace.

I need some guidance with the wiring because I know the 760 had a 24 volt transformer built into the humidifier; therefore, it had its own power. The newer 700M humidifier require 24 volt power to engage the internal relay which sends the 24 volts to the water solenoid valve and turns on the internal fan.

I know I need to switch around the wires on the board. I just don't know which wires I need to move and where I should put them.

I don't think I need to use the 24-volt transformer that was included in the box.

Like the 760, the new 700m will be plugged into a 120 volt plug.

I wasn't able to locate the exact Trane furnace model number. The installer's guide I have lists 11 different model numbers on the cover, ranging from UH2B060A9V3VA to DHD2D120A9V5VA.

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Old 01-17-16, 11:28 PM
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Welcome to the forums.

The model number can be found on an ID tag on the side wall.... inside by the burner.


In your top picture.... the HUM terminals are 120vac.

I see two cables there..... one is from the thermostat and one is from the A/C condensor.
I don't see any old wiring to be moved.

Maybe you have a switched receptacle for the humidifier. You'll need to look into that.
What will you be you using for an h'stat now ?
 
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Old 01-18-16, 12:20 PM
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Thanks for the tip on finding the location of the ID tag!

The model number is: auh2c100a9v4vac. It's an American Standard made by Trane.

I haven't installed the new Aprilaire 700m yet.

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I know I need to switch around the wires on the board. I just don't know which wires I need to move and where I should put them.

If anyone could please provide some guidance, it be much appreciated.
 
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Old 01-18-16, 11:56 PM
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Please re-read my previous post.

If there is currently wiring going to your old humidifier...... I need to know what that wiring is.
Follow the wiring from the humidifier back to the furnace.

The 760 could have been run on a switched AC receptacle.

There is no visible low voltage wiring in place for your new humidifier.
And again.... what will you be using for a humidistat ?
 
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Old 01-26-16, 01:41 PM
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Okay, sorry for the incorrect information.

I checked and there is actually no wiring currently going from the humidifier to the furnace's board. The wires from the humidifier fan box run to the humidistat.

It also seems like I'll need to use the 24-volt transformer they supplied to install this.

I'll be using the humidistat that came in the box with the Aprilaire 700M. It's the Aprilaire 4655 Manual.

So, I'd greatly appreciate some direction on how to get the 700M up and running.

I suppose, first, I need to know how to get transformer wired up. I've never done this before and don't have a clue. What kind of tools and wiring do I need to buy? How do I mount the transformer?

Let me know what pictures I need to provide.

Thanks!
 
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Old 01-27-16, 12:02 AM
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Locate the wiring junction box for the furnace. That would be the junction box where the main power connects. Open the junction box cover and see if you can locate the BK/3 wire. It should be a single capped wire.

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