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Bypass Humidifier to Nest


Aurust's Avatar
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09-10-17, 03:16 PM   #1 (permalink)  
Bypass Humidifier to Nest

I have a bypass humidifier with 2 wires coming from the furnace, through a transformer, connected to the water solenoid, and then wired to the humidistat. I'm wonder how to wire to a nest thermostat and whether I need a relay to use the new thermostat. I'd like the humidifier to only come on with heat. I've done up a simple wiring diagram of what is install right now:

 
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NJ

09-10-17, 03:27 PM   #2 (permalink)  
Welcome to the forums.

A fairly easy installation job. You will need one extra wire in the cable from the thermostat to the furnace. One of the solenoid wires goes directly to C where the furnace low voltage connections where the thermostat wiring connects. The other wire goes to the * on the nest. Configure the nest for humidity with heat.

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~ Pete ~

 
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09-10-17, 03:48 PM   #3 (permalink)  
Thanks for the reply. I'm a little confused on the wiring still. Where does the transformer come into the wiring? Right now there is no C (common) wire from the thermostat to the furnace, just red, green and white.

 
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09-10-17, 05:16 PM   #4 (permalink)  
The wiring is just as I've shown. You don't need the transformer. BUT you need an extra wire from the furnace to the stat. One wire goes from the solenoid DIRECTLY to C on the furnace.... not the nest. The other solenoid wire goes DIRECTLY to the * terminal.

Red, green and white. What is this.... just a furnace... no A/C ?

 
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