How to Wire a Furnace Humidifier
By their nature, a furnace will remove the moisture from the area that it heats. When the circulated air from the living space flows over and through the heat exchanger, any moisture may be "flashed off" by the contact of the hot metal tubes. To replace that moisture into the household living space, an automatic furnace humidifier may be warranted to be installed. Does this Spark an idea?
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Things You'll Need
- Screwdriver Philips or slotted
- 12 gauge braided wire
- Wire strippers
- Wire nuts (optional)
Instructions
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1
Remove the electrical power from the furnace by either shutting off the safety switch that runs the furnace or switching off the main power circuit breaker or pulling the fuse.
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2
Use the screwdriver and remove the protective cover to the electrical control box wiring area. This area will also contain the circulation fan motor relay or contactor. The motor relay or contactor should be identified by a name tag placed just below or to the side of the switching mechanism.
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3
Run two 12-gauge wires from the motor control contactor to the electrical box on the mounted humidifier. You may have to remove a knock hole for the wire to enter the electrical box on the humidifier unit. You can easily remove the round metal plug with the end of the screwdriver.
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4
Strip the ends of the two wires and attach them to the two wires of the humidifier. These two wires should be used to provide the main power to the humidifier unit. One wire will be the power wire and the other will be the neutral or ground wire for a 120VAC humidifier. A 220VAC unit will use both wires as the power. Be sure to cover all bare connections with a wire nut.
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5
Strip the ends of the wires that run to the motor contactor. A 120VAC humidifier unit will terminate to the motor contactor in the following order. The neutral or ground wire will attach directly to the neutral lug of the furnace connections. This will be identified again by a tag named "neutral or ground" and or a set of white wires. The black power wire should be connected to the bottom side of the motor contactor for the blower motor. A 220VAC unit will simply connect both power wires to the bottom side of the motor contactor. In other words, under both wiring circumstances you will want the humidifier to be tied to the wires that feed the circulation motor. This will allow the humidifier to operate only when the furnace blower is on.
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6
Replace the electrical cover on the furnace and energize the electrical power. Test the unit for proper operation of the humidifier.
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Tips & Warnings
Modern humidifiers that are part of a furnace add on will have the humidistat built into the inside of the unit itself. There will be an adjustment on the outside of the unit to set the amount of humidity in the circulated air.
