Armstrong Furnace and Aprilaire humidifier wont shut off! HELP!

scott0949

I have an Armstrong GUK100D14-2b(about 7 years old) and an Aprilaire Model 760(same age as furnace), humidifier attached. The humidifier won't shut off. No matter what I adjust the humistat to, it keeps running, even when I turn it to off. When I unplug it, the furnace makes a loud buzzing noise for about 2 seconds and then stops. I assume it's trying to find the power for the humidifier. When I plug it in, I do hear water going into the system. I checked all the wires and they seem to be tight and connected properly. The humistat does make a "clicking" noise when I adjust it. About 6 months ago I had to replace the circuit board. I'm not sure if this is the problem, but wanted to let you experts know. When I connected the circuit borad, I did connect the wire to the board where it says "HUM". But, I was unsure about one of the wires. I can't remember which one but anyways, when the furnace blower kicks on, there's a small and quick hesitation before it starts blowing air and then it works fine (the furnace). So I'm not sure if this has anything to do with it or not. I disconnected the wire from the humidifier from the circuit board and it continues to run. Any ideas what could be wrong? I'm unemployed and I can't afford to pay someone to come out and take a look at it. But I can't afford the electricity either, to keep the humidifier running 24/7!
Thanks in advance.
Scott
P.S. - I just had the humidifier plugged in and opened it. It continued to run. Shouldn't it have shut off? It looks like to me the wires inside the "box" should have shut it off, at least for safety, if nothing else!

hvactech126

you might have burnt up the control board in the 760. the hum terminal on the control board, is most likely 120v. your 760 has an internal transformer and you probably smoked it! time for new humidifier

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scott0949

So do you think that maybe that's the wire that I didn't put in the right place? You're the expert and I did think about what you said, but if the wire is on the "hum" contact, you're saying I might still have put it on the wrong connector? If it fried the transformer, would that be the transformer inside the furnace, that the Humidifier connects to? Because I was thinking that if it was fried, that it wouldn't work at all, but I don't know!!

Jackofall1

You are correct if you let the smoke out of the Hum motor it wouldn't work. Not real sure why the furnace would shut down when you disconnect the Hum. But when you wired the Hum sensor did you put it in series with the Hum motor or parrallel.

Hum contact on control board to transformer primary L1
120 V neutral to transformer primary L2

Transformer secondary L1 to sensor/ rheostat T1
Rheostat T2 to Hum motor L1
Hum motor L1 to transformer secondary L2

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scott0949

WOW! You're way over my head! I'm handy but I'm not much on electrical. Please let me re explain, because I'm not sure my posting made sense. The Hum. continually runs when I plug it in. Even when I open the door to it, it still runs and the fan almost took my fingers off! I noticed when you open the door that it looks like based on the connections I see, that that motor should shut off. However, it just runs no matter what. It is putting water into the system, so it's humidifing the house. But the humistat will not allow me to shut it off either. It "clicks" but that's about it. So when I put in the new control board, I'm not 100% sure that I even hooked it up wrong. The furnace DOES NOT shut down when I disconnect the Hum. I just noticed that ever since I put the new board in several months ago, the furnace fires up, then has a very slight hesitation before it start blowing the air. The hesitation is maybe 1 or 2 seconds at most. Maybe it's suppose to do that, I don''t know. I just don't remember having a hesitation before I put the new board in. So it could be hooked up fine, I just don't know. I did trace the wire from the Hum. and the transformer and it is hooked onto the board where it says "HUM". I hope this explains things. It just seems strange that the only thing that will shut off the hum. is unplugging it. If I fried something I would just guess that the Hum. wouldn't even start up, let alone never shut off. Does that make sense? I don't know what you mean by the L1, L2 etc. Maybe if I knew which transformer was primary and secondary, I might be able to figure out what you mean.

hvactech126

the control board in the 760 has its own transformer. if you burn up that board, it also has relays in it. if the fan runs with the door removed, then it needs a new control board in the 760. the relay for the fan and solenoid are stuck closed. The solenoid shuts off when you take the door of the humidifier, Correct? you did not hook the 760 up properly and that is what fried the board IN THE 760 APRILAIRE HUMIDIFIER

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scott0949

You asked if the solenoid shuts off when I open the door to the humidifier. I'm not sure if you mean the fan or the actual solenoid. When I open the door, the fan continues to run. It does NOT shut off. Is that what you meant? So, if I fried the 760 board, that means the hum. is not hooked up correctly to the "main" board right? I'm unemployed and so is my wife, so money's tight. Do you know around what those boards cost for the 760?
Thanks for all your help, it is GREATLY appreciated!

hvactech126

I don't know what those boards cost. could vary greatly my area to yours. be better off going to home improvement store and getting another powered humidifier and reinstalling with wiring done properly

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scott0949

Thanks for all your help, I appreciate it!!