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Matthew, HVAC Technician
Category: HVAC
Satisfied Customers: 2014
Experience:  14 years experience in the HVAC field of service, installation, Manual J & D calculations
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anyone have knowledgeof wiring humidifiers to furnaces

Resolved Question:

anyone have knowledgeof wiring humidifiers to furnaces?
Submitted: 6 years ago.
Category: HVAC
Expert:  Matthew replied 6 years ago.

What is the model of the humidifier?

Customer: replied 6 years ago.
bestair BA200, am I wiring it to the same transformer inside that furnace that the thermostat is wired to?
Expert:  Matthew replied 6 years ago.

I am having a hard time finding this humidifier's information so I will need just a little more information to help you.


1. What terminals are there on the humidistat


2. are there only 2 wires hanging off of the solenoid


3. Do you have any other accessories hooked to this furnace ( filter, dehumidifier, U.V. lights, Zone board)

Customer: replied 6 years ago.

very little info out there, the humidifier solenoid has 2 wires comming from it, the humidistat has 2 terminals and they are not labeled, nothing else hooked to furnace. my furnace white-rodgers circuit board has no HUM or EAC terminals. I was told by York tech support that I need to wire it to the heat cycle of the furnace. My hot or common wire will be red/yellow and my neutral white. they failed to tell me the location of these wires, so I am assuming they are on the furnace transformer, the same one the thermostat is wired to, am I right?

Expert:  Matthew replied 6 years ago.

ok here it is


one side of solenoid goes to one side of humidistat


other side of solenoid goes to the W terminal on the furnace control board


Other side of humidistat to C on the furnace control board


Now this is only if you are not using a separate transformer for the humidifier. There should be nothing between these connection just do it exactly like I described and the humidifier will power up when the heat is on and the water will flow to the solenoid if the humidistat is sensing that it needs more humidity to meet the % it is set at.

Expert:  Matthew replied 6 years ago.
If you where to hook to the 24v leads coming directly off of your transformer in the furnace the solenoid would have power all the time and water would pour through it even with the furnace off.
Customer: replied 6 years ago.

so again. where do i hook it in? it must be somewhere on the control board

Expert:  Matthew replied 6 years ago.
Follow your thermostat leads into the furnace. where they hook are these terminals I am talking about. It could be this furnace has wires that the thermostat wire nut too. If that is the case tell me the color wires that hook to your thermostat wires. Sorry but your picture did not come through it is blank.
Customer: replied 6 years ago.
Customer: replied 6 years ago.
the only other suggestion I have is to let me email you the furnace manual with wiring diagram
Expert:  Matthew replied 6 years ago.
Sorry but I still can not read it just looks like blurs can't distinguish the wires and parts. Can you not find where the thermostat wires hook up? I can not give out my email sorry
Customer: replied 6 years ago.
they hookup to the transformer inside the furnace. there is a R, W, G, Y AND C
Expert:  Matthew replied 6 years ago.

AHHHH ok you have a mounted terminal transformer sorry sorry. Yes you hook up right there W and C go right under the terminal with the wire that is already hooked there from the thermostat

Customer: replied 6 years ago.

since this transformer that the thermostat is hooking to is 24volts, can I assume I do not need to use the supplied 24 volt transformer because I am not hooking to the furnace control board which would be 120volts?

Expert:  Matthew replied 6 years ago.

correct. If you want to use the supplied transformer than you have to tie the 120v side of that transformer in with 120v coming out of an outlet somewhere or on the 120v side of the furnace voltage supply then hook the humidifier in tot he 24 side, but using the furnace transformer is perfectly fine as long as you do not have any other accessories tied into this furnace like a U.V. light, electric air cleaner, or zone boards.

Expert:  Matthew replied 6 years ago.

If you do use the supplied transformer on this furnace since it does not have a Hum terminal you would need a current sensing relay in line with the humidifier circuit to switch it on and off during a heat call. This relay hooks around the heat speed wire of the blower motor and then splits one of the 24v lines going to the humidistat or the humidifier.


Aprilaire 50 Current Sensing Relay 24v

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