Gas and Oil Home Heating Furnaces - Goodman Furnace - where to wire humidifier

Hi All:

I have a goodman furnace, model GUPI075 or something very close to that (I'm in the office so I can't look to be sure but that is what I remember).

Anyway, I got a whole house humidifier, installed it and wired it to the furnace. It runs now when the burner is lit, but not when the fan is running and burner is out.

Does anyone know where I can wire it so it runs when the fan runs as opposed to the burner? I used my voltmeter to locate 26 volts when the furnace was running so that is how I wired it for now. Those volts are gone when the burner kicks out.

They say that you can wire it so it runs with the fan, so if I put the fan on from the thermostat (always on), I can keep the humidifer running. If any of you guys can help, please let me know and thanks!

I can take pictures and email them out if you want to see the setup. I am hoping that some of you are experts in this field and can tell me to wire it to this terminal or that.

Thanks again!

-=>Raja.

If there is no humidifier tap on the furnace control board, there are a few other ways to do it. One is to (assuming a 24 volt humidifier) wire the small transformer that powers the humidifier to the blower lead for heating. The possible downside is that you may fry the transformer if you run the fan on another speed for cooling. You can also buy a current sensing relay that clips on the motor lead for the blower and it will switch the humidifier on for you when the blower is running. That is the easiest way and the one I like the most but the relay is about $20. There is not much reason to keep the humidifier on when the burner is off because there won't be much evaporation going on without the heat.

Ken

I have a relay in there already, bought it years ago from Home Depot when I replaced my thermostat with a digital one. The digital one didn't like to work the heat without the relay. Not sure exactly how I wired it, I followed the directions at the time. It somehow seperated the thermostat from the furnace so it could control the heat.

I guess I need to dig around and find the manual for the relay and see what I did there.

There is a board on the furnace is the lower compartment with alot of wires and some high voltage (110v), cap and such. I think the fan runs on 110v though I'm not sure. On the top side there is a bunch of wires that come from the thermostat I believe to a box right behind the power switch/plug outlet to the furnace. There is where I found 26 volts, in some places live all the time and in another live only when the furnace is calling for heat. I wired to the live when calling for heat to run the humidifer.

I was considering changing the wiring so that if I move the switch on the thermostat to fan ON instead of AUTO it would continue to run the humidifier.

I know this is a hard question to answer when you are not there to see it. Is there anywhere I can find a wiring diagram for the furnace?

-=>Raja.

I think the first thing to do is look closely at the control board. They usually have terminals on them for EAC (electronic air cleaner), HUM (humidifier) and a few others I can't remember right now. If you see a male spade terminal and a HUM designation on the board, thats what it is for. You should check the voltage but I would recommend using that source to trigger the humidifier. It is powered with the blower in heat mode only.

Ken

If I'm not mistaken this terminal will not be powered with the fan switch on the stat set to "on". Doesn't the fan "on" power the cooling speed terminal? If the humidifier is a direct spray type with no pad or plate the humidifier should not be used with out the heat being on anyway.

Just get a A51 or A50 for 24V current sensing relay and slip it over the blower wire and your done. I dont think you should mess with the board. This way any time the blower is on the humidifier can be on. this will also let you turn just the fan on and get the humidifier to run also.

ED ;)

You probably know more about this than I but if the relay is put on the heating speed wire (presumably low), I don't think the humidifier would run if the fan were in "ON". On the other hand, if the relay were put on the cooling speed wire, the humidifier would not run with the fan in "auto". How about using an air pressure switch installed on the supply plenum? I hate humidifiers on furnaces so I don't deal with them very much. Learn me sumpthin. :wall:

It can go around all the fan wires it works just like an Amprobe is how it works you dont tap into any wires . lennox use about the same thing years ago on electric furnaces When the strips would start to come on this would turn the blower on. Worked just fine this way you could tell right away if a sequencer was stuck on cause the blower would stay on .. Sail switch get stuck to much in teh duct from dirt

ED :D

Never thought about putting one around more than one wire. I lernt sumpthin, guess you can teach old dogs new tricks. :D

Hey Grady this is an old old dog here. :D

ED ;)