Humidifier 24vac furnace wiring

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Old 12-05-15, 06:07 AM
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Humidifier 24vac furnace wiring

I want to wire the humidifier drum motor to the furnace to ensure the humidifier motor only runs when the furnace is running. The humidifier is a desert spring reservoir type with a 24vac motor to turn the drum. The furnace is trane xv80. Currently, the motor is wired to an external 24vac transformer and runs whenever humidity is lower than level selected. Am I being to ambiguous?
 
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Old 12-05-15, 06:58 AM
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If the humidifier drum motor is the only load on the 24 vac transformer, you can power the 24 vac transformer from a 120 vac source in the furnace control. The best source is the relay that supplies 120 vac to the blower motor. Look at the electrical diagram inside your furnace. Find where the power source is for the blower motor. Remove, at the source, the 2 wires supplying 120 vac to the 24 vac transformer. Connect 1 lead to the 120 vac neutral and the other lead to the wire supplying 120 vac to the blower motor. If this wire connects via a friction lug, you can buy a Y lug and connect both wires to the Y. You will need to crimp a friction lug to the 24 vac transformer 120 vac input wire.
If the humidifier drum motor is not the only load on the 24 vac transformer, you will have to install a new 120/24 vac transformer. Wire the 120 vac input as suggested above and move the humidifier drum motor power wires to the 24 vac output side of the transformer. Good luck.
 
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Old 12-05-15, 07:21 AM
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Welcome to the forums.

You can also use a current sensing relay which just clamps on the blower power wire and has two wires that connect in series with your humidistat.

Current sensing relay for humidifier - amazon
 
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Old 12-07-15, 02:24 PM
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Ambiguous

Thx. Yes, the humidistat and the drum electric motor are both wired to the external 24vac transformer.
Thx Pete, I will look at buying the item you indicates. Can you be more detailed on how I now wire the electric motor to the blower on the xv80 furnace while leaving the humidistat as is?
 
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Old 12-07-15, 02:29 PM
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The sensing relay has a jaw built in that clamps right over the neutral wire to the blower.
There is no cutting into the blower wiring involved.
 
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Old 12-11-15, 10:47 AM
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Name:  xv80 wiring all c1.jpg
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Size:  49.8 KB Here is wiring for our XV80 furnace.
Name:  new wiring to furnace blower.jpg
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Size:  22.4 KB From what Beelxbob writes, this is a diagram of existing wiring and what I think the new wiring should be to ensure the drum motor only runs when the blower motor runs and the humidistat is activated. As the current wiring (top portion of this drawing) runs both humidistat and drum motor via a 24vac transformer, can't I just move the 24vac transformer inputs to the blower motor and neutral? If yes, where on my wiring diagram are the blower 120vac and neutral sources?
Is this is not correct, where do I place my 2nd 24vac transformer?
PJmax indicated a current sensing relay would work but I would prefer to use what I have if I can.
 
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Old 12-11-15, 05:43 PM
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You can't post wiring diagrams here. The board has a limit of 50kb and 600x600. That diagram is unreadable.

1) You can put it on a free hosting site and post the link here.
2) Send it to me.... full (aka BIG) size and I'll host it.
3) Post the diagram number listed in the bottom right corner.
 
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Old 12-14-15, 08:00 AM
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Here is a link to the wiring diagram for my XV80 Trane furnance.
I also included a pic of the terminals inside the furnace.
 
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Old 12-14-15, 09:30 AM
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Thanks for the large diagram. I took an excerpt from it. It looks like they have pre-wired the AC section for EAC and HUM connections. Locate the junction box where the 120vac comes into unit. You should find the 120v connections for your humidifier transformer there.

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Old 01-04-16, 05:29 AM
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Thx for the response. Found the HUM where you indicated and placed the 24 vac transformer there black to HUM and white to common wired. Now working correctly.
 
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