Aprilaire 600 and Dual Fuel system
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Aprilaire 600 and Dual Fuel system
I have an Armstrong Air 2 stage heat pump and gas dual fuel system. A WhiteRodgers big blue thermostat runs it. The Aprilaire 600 humidifier works fine when the heat pump is running. During colder temps, when the thermostat switches over to gas the humidifier no longer comes on. Attached is a pic of the wiring on the furnace. Any help would be appreciated.

Last edited by PJmax; 01-15-18 at 08:49 PM. Reason: labeled diagram
#2
Welcome to the forums.
A lovely picture but I have no idea what I'm looking at.
What controls the humidity ?
Do you have a humidistat ?"
You'd need to have the blower circuit activate the humidistat.
OR a relay may be needed. I need more info.
A lovely picture but I have no idea what I'm looking at.
What controls the humidity ?
Do you have a humidistat ?"
You'd need to have the blower circuit activate the humidistat.
OR a relay may be needed. I need more info.
#4
I labeled the first picture. I need to know how the humidistat cable connects.
What color is on what terminal ?
What color is on what terminal ?
#6
My apology. I mislabeled the first diagram. I neglected to consider the heat pump.
That means the two wire cable is connected white to C and red to Y. Is that correct ?
Can you tell me if that cable is A or B at the h'stat ?
Does the display go out on the humidistat when not running ?
If I'm correct.... it means they are using the Y (compressor terminal) to run the humidifier. That also means that the humidifier would be active in the summer if not manually turned off.
I think we're going to need to use a relay to have both systems run the humidifier.
Can you post the part number off the control board.
That means the two wire cable is connected white to C and red to Y. Is that correct ?
Can you tell me if that cable is A or B at the h'stat ?
Does the display go out on the humidistat when not running ?
If I'm correct.... it means they are using the Y (compressor terminal) to run the humidifier. That also means that the humidifier would be active in the summer if not manually turned off.
I think we're going to need to use a relay to have both systems run the humidifier.
Can you post the part number off the control board.
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I will double check the wiring and control board part number tomorrow. Llooking at my humidistat picture below there isn’t any wires connected to A or B, can that be right? The humidistat always has a display on it. Thanks again for your input!
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I verified the white wire is connected to C and red to Y as you described. There are two numbers on the control board and I’m not sure which is the number you need. The numbers are 1170-83-21A and 1170-20 0703 47584-001. See attached photos. Thanks!
#10
That means the two wire cable is connected white to C and red to Y.
Is that correct ? - YES
Can you tell me if that cable is A or B at the h'stat ? - ???
You couldn't answer that since my picture didn't post.

There are are four cables on the h'stat. The ODT and the HUM are ok.
I need to know is the cable above (connected to R and C) connected to the location I marked A or B on the h'stat ? Can you tell me where the other one connects ? I don't see it at the board.
This is difficult since we need to find a way for two system to control one device. Thanks for posting the board info. I was hoping for a 24vac HUM connection but yours is a 120vac HUM connection and is not helpful.
Is that correct ? - YES
Can you tell me if that cable is A or B at the h'stat ? - ???
You couldn't answer that since my picture didn't post.

There are are four cables on the h'stat. The ODT and the HUM are ok.
I need to know is the cable above (connected to R and C) connected to the location I marked A or B on the h'stat ? Can you tell me where the other one connects ? I don't see it at the board.
This is difficult since we need to find a way for two system to control one device. Thanks for posting the board info. I was hoping for a 24vac HUM connection but yours is a 120vac HUM connection and is not helpful.
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That means the two wire cable is connected white to C and red to Y.
Is that correct ? - YES
Can you tell me if that cable is A or B at the h'stat ? - ???
You couldn't answer that since my picture didn't post.
Attachment 89662
There are are four cables on the h'stat. The ODT and the HUM are ok.
I need to know is the cable above (connected to R and C) connected to the location I marked A or B on the h'stat ? Can you tell me where the other one connects ? I don't see it at the board.
This is difficult since we need to find a way for two system to control one device. Thanks for posting the board info. I was hoping for a 24vac HUM connection but yours is a 120vac HUM connection and is not helpful.
Is that correct ? - YES
Can you tell me if that cable is A or B at the h'stat ? - ???
You couldn't answer that since my picture didn't post.
Attachment 89662
There are are four cables on the h'stat. The ODT and the HUM are ok.
I need to know is the cable above (connected to R and C) connected to the location I marked A or B on the h'stat ? Can you tell me where the other one connects ? I don't see it at the board.
This is difficult since we need to find a way for two system to control one device. Thanks for posting the board info. I was hoping for a 24vac HUM connection but yours is a 120vac HUM connection and is not helpful.
#12
We're getting closer. Ok..... between that and you said that the humidistat is always lit up even when the humidifier is not running which means cable A goes to a 24vac transformer or supply.
I'm thinking.
I'm thinking.
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I took another peek and the other set of wires does in fact connect to a transformer. The transformer then connects to a neutral (white wire) and line connection (black wire) to the control board pictured below.
#14
Thanks for hanging in there.
I know it's tough to see..... can you tell me what terminal the black wire is connected to ? It may be a L? terminal. The white will be on an N terminal.
Your humidifier is currently set up to only work with the heat pump. It looks like they are using the Y/compressor terminal to turn on the humidifier. Does the humidifier try to come on in the summer and you have to manually turn it off ? The humidity during the summer may be high enough to keep it from coming on.
I know it's tough to see..... can you tell me what terminal the black wire is connected to ? It may be a L? terminal. The white will be on an N terminal.
Your humidifier is currently set up to only work with the heat pump. It looks like they are using the Y/compressor terminal to turn on the humidifier. Does the humidifier try to come on in the summer and you have to manually turn it off ? The humidity during the summer may be high enough to keep it from coming on.
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The black wire connects to a terminal labeled LINE.
I recently purchased the home so I have not experienced the humidifier running when the AC is on. The humidistat was in the off position during the summer months as left by the previous owner. To be honest, I didn’t even realize I had a dual fuel system when I purchased the home because the appearance is of a split system. It was when I switched over from AC to heat for the first time that I realized the setup when the gas furnace didn’t fire up.
I recently purchased the home so I have not experienced the humidifier running when the AC is on. The humidistat was in the off position during the summer months as left by the previous owner. To be honest, I didn’t even realize I had a dual fuel system when I purchased the home because the appearance is of a split system. It was when I switched over from AC to heat for the first time that I realized the setup when the gas furnace didn’t fire up.
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Hi again - Sorry to revive an old thread, but I am still looking for a solution for my issue. I would appreciate anyone willing to review the post and provide input.