Electric motor swap question

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Forum topic by coloradoHick posted 03-24-2013 09:16 AM 1039 views 0 times favorited 7 replies Add to Favorites Watch
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1 post in 2062 days

03-24-2013 09:16 AM

Topic tags/keywords: electric motor swap hp rpm

Hey folks,
I am a newbie to the forum (and woodworking in general). I have recently scored a grizzly dust collector that no longer has the 3 HP motor, but does have everything else. I have a line on a 8 gallon air compressor with a 220v 5hp 3450 rpm 7/8” shaft magnetek motor that I think will work. It is more powerful, but other than that the specs line up. I am just wondering if the impeller will be too heavy (it mounts on the motor shaft), or if there are any other differences between an air compressor motor and a dust collector motor, or having the bigger motor will cause any problems with the unit.
I should add that I am a weekend warrior, and that this dust collector will not get the amount of hours that it would in a pro shop. And I have not wired it yet so I could obviously use the correct wire and breaker size for a 5 hp motor.
Thanks for the advice!

7 replies so far

View sprucegum's profile


324 posts in 2169 days

#1 posted 03-24-2013 10:58 AM

I would go for it if the motor is free or real cheap, but thats just me, I once helped a friend put a 327 in a WW2 jeep. A little more HP is always good rite?

-- A tube of calk and a gallon of paint will make a carpenter what he ain't

View Lee Barker's profile

Lee Barker

2170 posts in 3022 days

#2 posted 03-24-2013 12:44 PM

Welcome to the forum Jon. I hope it is helpful and inspirational for you.

It sounds like you’re attentive to the possible differences between the motors but I see no mention of mounting. The key things are shaft diameter and length, rpm and mounting. If you’ve got those covered, make the move!



-- " his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View Fred Hargis's profile

Fred Hargis

5138 posts in 2665 days

#3 posted 03-24-2013 12:50 PM

Like Lee said, the mounting arrangement and the shaft size will be the key. For the record, I have a 5 HP compressor duty motor on my DC. It’s the same one that CV sells for their units…and that’s where I bought mine. But his one one is c-face, I’m guessing the one you need is a 56 frame or such.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Shawn Masterson's profile

Shawn Masterson

1325 posts in 2120 days

#4 posted 03-24-2013 01:23 PM

I will work as long as the shafts match
the only concern I have is that most compressor motor are an open frame and a DC should a sealed motor. you are sucking the dust to the impeller and any leaked dust will be sucked right into the motor, causing premature bearing and contact failure. It may last for a while not as long as it should. also I have noticed an influx of over rated motors. I had a “6.5hp” on my old compressor and there was possible way it was. It only drew 15 amps, a true 5HP should be around 22-25 amps. amp ratings are the best way to see how close a motor is to it’s rated HP.

View RussellAP's profile


3104 posts in 2458 days

#5 posted 03-24-2013 02:08 PM

A couple of basic things. Know the difference between a horizontal and a vertical motor and don’t mix them up. Some DC systems are extensive and will cause a motor with an efficient impeller to start very slowly due to back pressure. If the motor has start windings, and a centrifugal switch, it could heat up very rapidly on startup. I would think a capacitor start would be your best choice. Or maybe a system with a belt and a clutch.

-- A positive attitude will take you much further than positive thinking ever will.

View waho6o9's profile (online now)


8478 posts in 2749 days

#6 posted 03-24-2013 02:14 PM

Maybe get Grizzly tech support to give you some friendly advice
as well.

Welcome to LJ’s ColoradoHick!

View runswithscissors's profile


2869 posts in 2197 days

#7 posted 03-24-2013 09:24 PM

Typically compressor motors are very strong at startup, because they have to overcome existing pressure in the tank. That’s why many motors specify “not for compressor use.” I share Shawn’s concern about vulnerability to dust; but assuming the seal where shaft enters the impeller shroud is tight, it may not be such a problem.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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