White Rodgers Thermostat (1F95-1291) Humidifier Wiring Help


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Old 06-03-14, 12:56 AM
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White Rodgers Thermostat (1F95-1291) Humidifier Wiring Help

Hi All,

I recently purchased a White Rodgers thermostat (1F95-1291). I am replacing a UPM303M thermostat. Most of the wires are easy to map: Y, R, G, W. When I connect them, I am able to get heat and air conditioning.

However, there are two wires on the UPM303M labeled H1 and H2 for humidity. On the White Rodgers thermostat, there is only an HM connection for humidity. When I talked to White Rodgers support, they told me to connect H1 to R and H2 to HM. When I did that, the fuse on my Carrier 58STA-STX furnace blew.

After turning off power to the furnace and replacing the fuse, I looked a bit closer at the furnace wiring to see if I could determine how the wiring worked. I noticed that the brown wire (formerly H1) was connected to the 24V COM terminal on my furnace circuit board. The orange wire (formerly H2) was connected directly to a black cable that runs to my GeneralAire 1042LH humidifier. The cable is split into two sections: one is connected to the orange wire (formerly H2) and the other is directly connected to the furnace board on a connection HUM 24VAC as shown in the attached picture.

I thought it might make sense to connect the 24V COM brown wire to the C connector on the White Rodgers thermostat. According to the White Rodgers manual, the C terminal is used for 24 V common (optional). I left the orange wired connected to HM. When I powered on the furnace, I was able to generate heat and air conditioning, however, the humidifier did not turn on when I raised the humidity. The thermostat display reported “Hum On”.

I tried a few other connections. Here were all of the outcomes:

Brown (H1) -> R
Orange (H2) -> HM
Outcome: Fuse blew

Brown (H1) -> C
Orange (H2) -> HM
Outcome: Heat and cool worked, but humidifier would not turn on even though thermostat said “Hum On”

Brown (H1) -> HM
Orange (H2) -> R
Outcome: Power turned on furnace without blowing fuse. Cooling worked. Fuse blew as soon as humidity was requested.

Brown (H1) -> Orange (H2)
Outcome: Attempting to get the humidifier to turn on. Nothing happened. Fuses okay.

Brown (H1) -> R
Orange (H2) -> HM
Outcome: Fuses blew. I tried this configuration again in case I had created a short the first time.

When I blew the fuse, did I damage my humidifier? Is there an easy way to check?
Should I connect the brown wire on my furnace to something else, perhaps R or W?

When I talked to White Rodgers support, one technician suggested that this thermostat would not support my configuration because of the H1 and H2 wires, however 3 technicians said it would be okay – I called them a lot today! I also talked to GeneralAire and they agreed that the brown and orange wires should be connected to R and HM as shown in the diagram Figure 7 at the bottom of page 4 in the White Rodgers manual. He mentioned that the polarity across the solenoid does not matter.

Here are some links to the manuals:
White Rodgers (1F95-1291): http://www.emersonclimate.com/Docume.../0037-7313.pdf
UPM 303M: http://www.upm-marketing.com/manuals/THM302M303M_E.pdf

The UPM thermostat was working and generated humidity prior to replacing it with the White Rodgers. I chose to replace the thermostat because I wanted the auto heat/cool feature on the White Rodgers thermostat instead of the mechanical switch for heat/cool on the UPM model. Typical Canadian spring – hot in the evening but freezing in the morning. I was forgetting to switch the thermostat from cool to heat at night and it would be cold in the morning!

Thank you in advance for your help!

Best,
Chris
 
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Old 06-03-14, 06:04 AM
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Move the heavy black wire from 24v hum to the furnace C terminal. (You have a digital stat capable of controlling when the humidifier should run)

Connect the orange wire to HM at the stat.

Connect the brown wire to C at the stat.
 
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Old 06-03-14, 09:13 AM
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Thanks Houston!

I don't have a C terminal on my furnace. Is that the same as the 24V COM? The same place as the brown wire is connected?

For the thick black wire, presumably I'll have to cut off the jumper end, strip it, and wire it around the screw? It appears to be strands of copper inside. I'm assuming that's not an issue.

The humidifier should still be okay despite shorting out the furnace circuit board a couple of times?

Best,
Chris
 
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Old 06-03-14, 10:21 AM
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Is that the same as the 24V COM
Yes.... that is the C terminal.

Just strip the black wire, twist the strands and stick it under the terminal with the other wires.
 
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Old 06-03-14, 12:21 PM
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Hi PJ and Houston,

Air Conditioning : Working!
Furnace : Working!
Humidifier: Working!

Super thanks!!! That was amazing! If you ever happen to be in Calgary, send me a note and we can grab a drink!

Best,
Chris
 
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Old 06-03-14, 04:48 PM
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Great you've got everything working. Thanks for letting us know.
 
 

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