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Is humidifier wired correctly?

1047 Views 4 Replies 2 Participants Last post by  surferdude2
Hi folks.

New house and I'm trying to get the (HVAC) humidifier working correctly. It's a GeneralAire 1099 and an Amana AMV90905DX two-stage.

There's a handwritten note taped to the humidifier that says "Humidifier set-up. Change to heat cycle only. Wires from humidifier source, move from "G" - Green to White "W1".

The humidifier is currently connected between "B/C" and "W1", but doesn't seem to be on the entire time the blower's on.

The furnace manual says "The furnaces integrated control module is equipped with line voltage accessory terminals for controlling power to an optional field-supplied humidifier and/or electronic air cleaner." I "think" these might be the terminals labeled "HUM" at the bottom of the board in the attached picture. The manual only has a block diagram that doesn't look like the circuit board. And, the manual covers a couple variations of the AMV9/ACV9 furnace, so I'm wondering if those accessory terminals might be an option I don't have?

I guess I'm looking for a more experienced opinion. I'm thinking I should move the humidifier to those terminals?

Appreciate any thoughts.



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The way it is wired now is a common way and not problematic. It will only run when the thermostat is calling for heat. The furnace fan runs after the call for heat ends in order to cool down the heat exchanger and get the most efficiency out of the unit. That time is adjustable on some control boards but left alone is usually best.

The note is telling you that it can be wired to the fan leg of the thermostat and it will run when you set the fan switch to "On" at the thermostat and not "Auto." I don't recommend doing that since the humidifier doesn't work very well when the heat is off and will waste lots of water.

You should check to see if it is connected to hot water (recommended) since that makes it works much better than a cold water connection.
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I'm pretty sure the H terminals on that furnace control board are 120 vac. You'd have to use a transformer to get 24 vac for the humidifier if you decide to change the wiring. I wouldn't do it... it won't work a bit differently than it does now.
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If you set the flow down too low it won't wet the entire pad surface... you'll work that out in time though. Just so it's wetting the pad all over. Normally they run with a full open valve and there is an orifice that limits the flow properly.

Thanks for the update.
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