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I'm finally getting around to building my air filter. I picked up a furnace blower (squirrel cage fan) from a local heating guy. I have 2 questions about the electrical. (FYI - the motor is 1/3hp 1050 rpm)

1. There are White, Black, Green and Red wires coming from the motor. I was expecting white, black and green, but the red was a surprise. Why is there a red wire and what do I do with it?

2. I'm guessing this fan is going to be a bit more powerful than I actually need. What would be the best way to add "speeds" to the unit?

Thanks,
Bob
 

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It may be a 4 wire 240Vac motor or maybe it's a dual voltage motor. The name plate on the motor will tell you exactly how it should be connected. But all of my experience is industrial 3 phase, I'm sure the guys that have more residential experience than me will chime in.

The best way to speed the fan is by gearing / belt pulleys. If it's not a capacitor start motor than you can use a variac to change the speed but I'm confident that it'll have a cap start on it.
 

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Well Bob, without more info, that wiring could be one of 2 ways. 1. black and red being 2 legs of 220 v with white being neutral and of course green being ground. The other possibility is black is one speed and red is another speed of a 110 v motor, white and green as before. No label on or in the motor?
 

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Discussion Starter · #5 ·
It's a direct drive unit, so gearing thru pulleys is out.

The only plate I can see on the motor (without pulling it out) is the 1/3hp , 1050rpm plate. Looks like I'll have to pull the motor.

Thanks.
 

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I think the red is either one half of a 220 or it is a lower speed than the black. If it was me I'd take an old plug and cut the wires off the female side. Use that to "hot wire" the motor while the blower is securely mounted to something so it won't jump. Try it with just the black and then just the red and see if you notice a difference. Of course you need to be really safe. Connect the wiring while its unplugged and then step back and plug it in really carefully being ready to pull it out quickly if something crazy should happen. The only way to add speeds to a unit would be to get different gears or something. If you vary the voltage to change the speed I believe you would damage the motor as it probably wasn't made to do that. I'm no electrician so whatever I say is just from my experience. I took a motor out of an old blower once and now have it mounted in my band saw. I went through many a gear to find one that slowed it down enough to be strong and do some resawing of thick boards. Of course if you have the time and know someone who claims to be an electrician, it would be best to get them to look at it. I just don't have that luxury.

Good luck
 

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If you have a lathe, you can always turn a test pulley from hardwood until you get the speed that your looking for. Then purchase the size pulley that you need.

Oh never mind, direct drive. You said that once.

-Memory's the second thing to go, I can't remember what the first was.
 

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I have one of these rigged up for air circulation. It had a diagram for wiring the motor on the housing. I don't recall wire colors and am 50 miles from the shop, but there were two speeds based on which wires were used. If it has a manufacturer's name and model number an internet search may get you a wiring diagram.
 

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Discussion Starter · #12 ·
Just finished wiring it up. After finding a wiring diagram for the motor, the white wires are connected and then it's either black to black (for high speed) or black to red (for low speed).

Thanks for all of the replies!

Bob
 

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Most 120 v single phase blower motors have multiple speeds with different colored wires for each speed. I havce seen them with as many as 5 or 6 speeds.
 

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TopamaxSurivor is correct. One most blower moors you will find a minimum of 2 speeds (only one on a really old motor) a high speed for A/C and a lower speed for heat. More often then not you will see 3-4 speed motors. And for what it's worth, the black is usually your high speed.
 
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