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Wiring a two speed furnace fan motor

  • ChuckWood's Avatar
  • ChuckWood
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ChuckWood created the topic: Wiring a two speed furnace fan 21 Mar 2012 03:01 #1

I am progressing nicely on my shop ventilator and soon will be doing the electric part.

My fan has multiple speeds which I will use two. High a low or intermediate. The motor as three wires coming out of a loom a more wires. (Red, White and Black)

I found a SPDT switch today. (Single Pole, Double throw) There are three prongs on the back side of this switch. I would guess that the hot wire would go to the center prong. One of each of the remaining wires would go to either the upper or lower prong. (Switch in the upper position for high speed - switch in the lower position for the lower speed - switch in the center for off)

Ok now where to the wires from the power cord go? :unsure:

Somewhere I have seen a video on that but now that I want it I can't find it. :(

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Colin replied the topic: Re: Wiring a two speed furnace 21 Mar 2012 08:56 #2

Yeah ... hmmm - wiring, sorry, this is where I call my electrician :)
Sorry I'm no help on this part

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ChuckWood replied the topic: Re: Wiring a two speed furnace 21 Mar 2012 19:19 #3

Colin wrote: Yeah ... hmmm - wiring, sorry, this is where I call my electrician :)
Sorry I'm no help on this part


It's ok Colin. I think I have it figured out. Thanks.

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Marshall replied the topic: Re: Wiring a two speed furnace 24 Mar 2012 16:44 #4

I can honestly say that I have one of these old furnace motors and squirrel cages and it works real well , but mine was already wired for use ...........MB

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ChuckWood replied the topic: Re: Wiring a two speed furnace 24 Mar 2012 17:43 #5

Marshall wrote: I can honestly say that I have one of these old furnace motors and squirrel cages and it works real well , but mine was already wired for use ...........MB


Had a bit of a set back this morning. I went to bench test my fan before putting it into the box and after running fine for about two minuets on high I hooked it to the lower speed and after about 30 seconds the sparks flew out of the end of the motor and part of my work room was filled with smoke. That is the end of that motor.
I called the heating guy I got it from and has another fan he will get for me. Might be a day or two set back however.

Just my luck.

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Colin replied the topic: Re: Wiring a two speed furnace 25 Mar 2012 21:19 #6

Well ... good that it stopped working now while you are in the process of getting it going. I hate coming back months later to repair these things when they could have been done at the time of installation ... so, maybe it's a good thing :)

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