Wiring Aprilaire 700 to a Lennox G43UF Series...

I'm in the middle of installing an Aprilaire 700 to a Lennox G43UF-36B-070 furnace and really don't want to guess the wiring.

Can anyone lend some expertise?

Thanks!

 

After more and more reading and poking around my furnace I think I've got a game plan.

My furnace has a Hum port - but it's 110 volts. So, my plan is to connect that to a transformer (and a neutral) that will step it down to 24 volts, then the 24 volts goes into R and C on my Humidistat.

The humidifier itself is then connected straight to the H ports on the humidistat via the brown wires. (Which, oddly, are twisted together in my unit from unboxing...)

If that's correct, what's up with my yellow wires? I have two that are twisted together (one from solenoid, and one from the inside power connection), one yellow coming from the 4-port connector from inside the box going nowhere and a yellow from my solenoid valve going nowhere.

I think I just answered my own question. Those two loose yellow wires need to be connected to each other - they just aren't at the factory for other installation methods....

Which, if my above ramblings are correct leaves me with one question:

Where does one get a 110volt - 24 volt tranformer to accomplish this? Is there a preferred part number I go searching for? A preferred site (or, better yet, physical store?)

 

You could do that.. But I would leave the HUM open up for the unit's 110volt power, and use R and C off the board for the humidistat power.

Correct.

Yellow wire is not used. leave that hang connected to nothing..

 

Ah, so you're suggesting that I hack the standard A/C power cord and connect it directly to the HUM port - which, would be switched if my furnace was built right - leaving me with a constant 24 volts from R and C - but as long as one was switched it doesn't matter which - correct?

If that's the case, is there a preferred location to connect the neutral and ground to the board?

 

I would call it hack the power cord... Leave that be... What I am going to suggest is get 18-2 wire, and electrical box, and an outlet socket. Mount that on the side of the furnace and plug the humidifier into that, and then wire from the outlet run a wire to HUM and Neutral wire.

HUM is switched, so it will provide power to the outlet/humidifier when the furnace is calling for heat.

There may be an open female spade on the board you can use, otherwise, wire nut it with the wire coming into the furnace.