Wiring Aprilaire 700 (Automatic) Humidifier to RUUD furnace

Problems related to residential installations.

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Wiring Aprilaire 700 (Automatic) Humidifier to RUUD furnace

Post by ApolloX » Sat Nov 17, 2012 11:12 pm

I'm in the process of connecting an Aprilaire 700 (Automatic) unit to a RUUD Furnace. It's a RUUD UGRA Achiever 90 Plus, with circuit -

Model - 1028-928A
Part - 62-24140-04

The wiring diagram for the Aprilaire 700 is as -

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The circuit board looks like the -

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Three -

1) The furnace circuit board has a HUM contact on the bottom near the center, marked as a Humidifier Relay. What exactly is the purpose of it? Can it supply the continuous 24 VAC power the Aprilaire diagram requires? Should I ignore this relay when installing this humidifier?

2) The Humidistat control panel (the digital panel that comes with the humidifier), interrupts the thermostat's blower signal. According to the diagram, you connect the G wire from the thermostat to G on the humidistat, then Gf from the humidistat to the G on the furnace. Shouldn't these wires be run in parallel to the furnace instead in serial? The only purpose I could discern is if the humidifier wanted to disable the fan signal from the thermostat, but I can't think of a scenario where this would make sense.

3) The Humidifier unit has two brown wires coming out of it, which appear to be unmarked. Does it matter which is wired to the humistat and which is wired to the 24 VAC transformer, or are they interchangeable?

PS I tried posting pictures but they appear to be blocked. Not sure how to properly post images for this topic.

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