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Lennox WB2-17 Humidifier Not Working (Not getting any voltage from Trane XC95m)


dmenn's Avatar
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03-05-17, 06:23 AM   #1 (permalink)  
Lennox WB2-17 Humidifier Not Working (Not getting any voltage from Trane XC95m)

Hello - I just recently moved into a new home that has a Trane XC95m HVAC unit and a Lennox WB2-17 Humidifier. This looks like a bypass filter, not a fan controlled one. The humidifier is not working under any conditions (heat on, fan on, humidistat in various positions). I checked the voltage coming up to the solenoid/humidistat and I'm not getting any voltage. It appears the wires feeding the solenoid/humidistat are coming out of the HVAC unit. When pulling off both service panels of the XC95m, it appears the wires are coming out of a junction box (same box where the power is fed to the entire unit).

Not sure where to go from here.. I assume the wires should have ~24 volts AC coming out? I'm reading 0 volts, so could there be a faulty transformer? Not sure where that would be or what other steps I could take.

Thanks for the help!

 
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MO

03-05-17, 07:39 AM   #2 (permalink)  
Take a look at the control board and see if there is a wire connected to terminal 6 HUM H.

 
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03-06-17, 06:54 PM   #3 (permalink)  
Yes, there is a wire going into the HUM-H line (black). There is a white wire going into the plug with all of the white wires (Plug 4) that says HUM on it. I did not have time to measure voltage at those spots, but I will this weekend when I have time. Based on the schematic, that would be 120 volts. This humidifier only runs off 24 volts - the solenoid. Am I missing something, or did the previous owner have this wired incorrectly? My concern is that I'm getting 0 volts across the two lines coming out of the HVAC system up to the humidifier. Anything else I can try/test?

 
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03-06-17, 08:20 PM   #4 (permalink)  
Welcome to the forums.

Are you saying that the low voltage thermostat cable is connected to HUM and neutral ?
That would be wrong!

The HUM-H line and the white neutral is a 120vac connection that is only live when burner is active.

Since your humidifier requires 24vac..... don't connect the HUM terminal directly to the humidifier. You can install a 120v>24vac transformer but I'm curious what the previous homeowner did. Can we assume there is a two wire low voltage humidistat in the line ?

Pictures are always helpful. How to insert pictures.


~ Pete ~

 
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03-16-17, 04:54 PM   #5 (permalink)  
I will work on getting some pictures of the setup. I've done more investigation. Two wires come out of the HVAC unit (connected to the HUM lines in the junction box - which based on the schematic is 110V) and run up to the 24v solenoid/humidistat. I pulled the wires and when the heater is running I'm getting between 3 volts and 4 volts AC.

I took some thermostat wire and connected it to the control board (R and B/C connections which show 28V) and wired that to the solenoid/humidistat for testing. When I adjust the humidistat above a set humidity, the solenoid activates and water starts flowing. So, I know the solenoid and humidstat function properly when powered by the 28V AC.

So, I have no idea why this setup was connected to the HUM lines from the junction box. It appears like it was wired wrong. However, it is strange that those lines only have 3 to 4 volts.

Regardless, can I just hook up the solenoid/humidistat to connections on the control board to get the 28 volts? Would it be the W1 or W2 and B/C connections so it is only active when the heat is on?

Thanks!

 
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03-17-17, 12:05 PM   #6 (permalink)  
W1 and C would be the first choice.

It's good you've found the solenoid still ok. That means high voltage wasn't connected to it.


~ Pete ~

 
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