Humidifiers and Dehumidifiers - Aprilaire 560 wiring Problem

Jay/Ed Imeduc,

I am trying to resovle a continous water run on Aprilaire 560. First I unhook the wire on the Hum selinor to see if the water will stop running but it didn't so I knew the selinor is bad.

I replace it and it stop. Now when the furnace start the water will not run but when I turn the Humidistat pass 35 it will click and the water start running but will not stop unless I turn it again below 35.

Question 1: If the Humidistat clicks when I turn it pass 35 is that telling me its good.

Now after tracing the wires I notice the wiring is not correct, that is the Humistat and the Humidifier are all wired to a 24volt transformer and the transformer is getting 115 volt from the safety switch on the furnace no 'sail switch.'

I want to rewired it. There is a 115 volt male HUM and 24 volt screw type Hum on the furnace board. I want eliminate the transformer and use the 24volt on the board for the Humidifer but there is no 'C'ommon terminal as far as I can tell on the board. The board has Cool Heat male terminals.

Question 2: Where can I plug in my 'C'ommon wire from the Humidifier.
No name on the furnace and the board looks like a generic board with no name.
Thanks in advance

I came across a post with ' where is my 24v common connection' after reading it looks like if I eliminated the transformer and wire it using the 24v on the board I can tie my common to where the common on the termostat goes on the board.

I just want to make sure cause the furnace is working fine and I don't want to blow the board and leave them in the cold. Its very cold out here and I am just helping.

Please confirm if am right. thanks

Question 1: If the Humidistat clicks when I turn it pass 35 is that telling me its good.
Correct, if it's doing it around 35%, then that tells us that your home is around 35% humidity. All is fine.

Now after tracing the wires I notice the wiring is not correct, that is the Humistat and the Humidifier are all wired to a 24volt transformer and the transformer is getting 115 volt from the safety switch on the furnace no 'sail switch.
Safety switch?? As in the pressure switch or flame roll out?

I want eliminate the transformer and use the 24volt on the board for the Humidifer but there is no 'C'ommon terminal as far as I can tell on the board. The board has Cool Heat male terminals.
Where's the t-stat wire meets on the board, there is no C? How about B? Where the t-stat wired up to the board, should have W,R,G,Y, C(om) or B.


No name on the furnace and the board looks like a generic board with no name.
What's the model # on the name plate inside the furnace?

Safety switch?? As in the pressure switch or flame roll out?
I mean the on and off switch on the side of the Furnance.



Where's the t-stat wire meets on the board, there is no C? How about B? Where the t-stat wired up to the board, should have W,R,G,Y, C(om) or B.

No W,R,G,Y, C(om) or B on the board. only Heat and cool I think the Heat and Cool is for the fan speed. Any wire coming from the t-stat is wire to another wire in the furnace.
Good point: I did not open the thermostat to see which wire are use and how they were used, silly me.
As in most cases in t-stat the blue wire which is mostly the C(om) is never used so is the B.

So in this case if the none of them is used what should I do.
And if one of the them is used what should I do.

I did not write down the Model # silly me again. But if you can tell me what to do with the C(om) or 'B' either used in the t-stat or not I will be happy. My friends is a little far from my house and not technical.

hope to hear from you soon. Thanks

Find the t-stat wire/low voltage wire, and trace that into the furnace.

Is this a new or old furnace?

The furnace is 15 years old. Thanks I will Update when I go there again.