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Old 03-03-2010, 04:22 AM  
python01
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Default Connecting humidifier to your furnace

Where humidifier should be connected to turn on only when the furnace is on?
I think I have seen somwhere that it can be connected to the blower motor via relay, not sure if it means that I would actually cut the cable and connect relay coil in series?
Is there a way to connect it without cutting wires?
I have trane xr90 furnace and flow through humidifier.



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Old 03-03-2010, 06:16 AM  
travelover
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On my furnace, there was a place to plug in a humidifier on the conduit board. Have you looked there? Other wise, just wire it so it runs with the blower, if you have a single speed blower.



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Old 03-03-2010, 07:43 AM  
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On my furnace, there was a place to plug in a humidifier on the conduit board. Have you looked there? Other wise, just wire it so it runs with the blower, if you have a single speed blower.
I have variable speed blower so I probably can not wire it there. What the markings would be on connector board for humidifier?
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Old 03-03-2010, 07:48 AM  
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If you connect to the blower motor circuit, you'll be running the humidifier when the A/C is on this summer. However, you could always run the wires back to the thermostat control board in the furnace.

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Old 03-03-2010, 08:13 AM  
Wuzzat?
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You may be able to use a sail switch, which is a small sail mounted in the duct that actuates a Microswitch that controls the humidifier.

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Old 03-03-2010, 10:37 AM  
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Can I get them at most home improvement stores?
What would be proper name for this type of switch?

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Old 03-03-2010, 10:40 AM  
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kok328,
I would like to run them to thermostat control board but don't know which terminals to use on that board and whether I should be using relay and how to connect that relay (series or parallel)

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Old 03-03-2010, 11:54 AM  
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To activate the water solenoid from the tstat control board, connect the hot from the solenoid to the W (white) terminal on the tstat board. Now when the heat & only heat comes on, so will the water for the humidifier.
If you are installing a humidifier kit, it should come with a humidifier controller to adjust the amount of humidity. If this is the case, the wiring will be somewhat different.

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Old 03-03-2010, 12:06 PM  
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To activate the water solenoid from the tstat control board, connect the hot from the solenoid to the W (white) terminal on the tstat board. Now when the heat & only heat comes on, so will the water for the humidifier.
If you are installing a humidifier kit, it should come with a humidifier controller to adjust the amount of humidity. If this is the case, the wiring will be somewhat different.
Yes I have to install it with humidifier controller so I would have to disrupt power to solenoid when furnace is not on and let it go on when furnace is on.
Should I connect relay coil between white and common ( I think it is marked C on the board and then use relay contacts to control the solenoid?
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Old 03-03-2010, 12:58 PM  
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Quote:
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Can I get them at most home improvement stores?
Probably not. Try HVAC supply houses in your area. If you sound business-like they might sell it to you for the wholesale price.


What would be proper name for this type of switch?
Honeywell S688A1007 Sail Switch with 5 in. Wide Sail
or you can make your own with a $2 Microswitch from Hosfelt.com or Radio Shack.

If you use this switch to control the 24vac instead of the 120v, the danger level of this project is about the same as having a meteorite hit the ground 10' in front of you.

I used homebrew logic circuitry to do this function, but my circuit must be unplugged if the AC is turned on because that puts ~2x the rated voltage into my circuit through the blower motor.
It's not widely known but it is hinted at in the humidifier installation instructions, that when you put 120v into one winding of your blower motor to select the speed, the other windings are putting out all different voltages, some of which are quite a bit higher than 120v. This motor acts like a transformer with multiple taps on the windings.


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