Removing Capacitor from Dust Collector Motor

[Sandra White]

Many thanks for the additional comments - all good stuff.

Re Dan's suggestion - I tried looking for the centrifugal switch.

Doesn't look like it is on this end of the motor:

Motor 1.jpg

(I undone 3 bolts and tapped the end cover. The end cover (along with the white fan and the motor shaft) moved about an inch or less and then stopped.

Here's what it looks like from the other end:

Motor 2.jpg

Motor 3.jpg

I'm tempted to proceed just undoing stuff but thought I'd see if any one has this kind of set up.

Thanks!

[Dan Friedrichs]

Do a google image search for "centrifugal switch" so you know what you're looking for, but I'd bet it's under that black cover. Take the motor cooling fan off and see if you can remove it.

[Sandra White]

Well, its been a while but I'm back to looking at this dust collector.

To answer John's question, the original capacitor was 400 MFD 125VAC and the replacement is 400-480 MFD 110-125 VAC, so i think I'm alright with the replacement.
caps.jpg

I took out the motor - the centrifugal switch looks pristine and seems to operate with finger pressure.
Dust Collector Motor.jpg

While I was at it, I sandpapered between the contacts.
contacts.jpg

Put the motor back and fired it up without re-attaching the impeller. It ran fine. So then I re-attached the impeller - it now cuts out after a second or so, just like before, and not only that - the impeller is turning in the wrong direction!

Not sure what is going on.

PS. I was looking at a replacement centrifugal switch and this switch has an Amp Rating: 20 amp
This dust collector was sold to accept regular house voltage of 120 VAC - and states on the motor 11 amps - is that OK?

[Dan Friedrichs]

Somehow you flipped wires on the centrifugal switch when you re-assembled it, causing it to reverse rotation. See this for more detail: https://woodgears.ca/motors/reversing.html

Regarding the shutting-off behavior: what, exactly, is causing it to "cut out"? Is there a magnetic switch and overload relay?

[Mike Henderson]

Don't worry about discharging it. There is little risk of stored charge on a motor capacitor.

If you really wanted to, the way to do it would be to cut the wires and touch the exposed ends together.

I agree with Dan. I've never gotten a shock from a starting cap. Additionally, that cap has failed which is another reason it probably can't hold a charge. But if you're worried, just cut both wires at the same time.

Mike

[Sandra White]

Dan, thanks for the reply.

I'm not sure how I could have flipped the wires but I'll double check when I take it apart again.

As far as shutting off - the dust collector was tripping the circuit breaker in the main service panel.

To save time re-setting the circuit breaker in the main service panel, I've since started using a Surge Protector Power Strip (120Vac 15 Amp 50/60Hz):

surge protector.jpg

Whenever I turn on the dust collector, it runs for about a second or two, then the surge protector trips.

[Kevin Jenness]

Time to take it to a motor shop.

[Mike Cutler]

Well, its been a while but I'm back to looking at this dust collector.

To answer John's question, the original capacitor was 400 MFD 125VAC and the replacement is 400-480 MFD 110-125 VAC, so i think I'm alright with the replacement.
caps.jpg

This capacitor is fine. It is correct for the application. Unfortunately, capacitors are prone to "infant mortality". Without a capacitor checker, it's on blind faith that you believe the capacitor to still be good.

I took out the motor - the centrifugal switch looks pristine and seems to operate with finger pressure.
Dust Collector Motor.jpg

While I was at it, I sandpapered between the contacts.
contacts.jpg

Put the motor back and fired it up without re-attaching the impeller. It ran fine. So then I re-attached the impeller - it now cuts out after a second or so, just like before, and not only that - the impeller is turning in the wrong direction!

If you take the impeller off does it run properly, and how do you know the impeller is spinning backwards?

Not sure what is going on.

PS. I was looking at a replacement centrifugal switch and this switch has an Amp Rating: 20 amp
This dust collector was sold to accept regular house voltage of 120 VAC - and states on the motor 11 amps - is that OK?
Yes, it's fine. If it was the reverse, then it would be an issue.

As Kevin stated, it may be to take it to a motor shop and have it tested. Get an estimate for services first. It may be cheaper to just replace the motor.

[Dan Friedrichs]

Well, you eliminated the most likely failure by replacing the capacitor, and it looks like the centrifugal switch is good, as well.

You also found a really good piece of information in noting that the motor runs fine without the impeller, but trips the circuit breaker with the impeller in place. If the motor had a shorted winding (or something), it seems less likely that the presence/absence of the mechanical load (the impeller) would trigger this problem. So, excellent troubleshooting work, there.

Some ideas to try, next:

1) When you've been running the motor with the impeller, is it in the blower housing with ductwork and filters (etc) attached? The motor will draw maximum amps when the mechanical load is maximum, which is when there are no restrictions on the impeller. If you have the motor set out on a workbench with the impeller spinning in free air, I would definitely say to put the entire dust collector back together and see if you trip the breaker. It's possible the capacitor was bad (causing the breaker to trip, initially), and if you're overloading the motor by not having filter/duct/etc restrictions on it, it may be tripping it now, but won't once assembled.

2) The next most likely thing to check is the supply circuit. Can you try plugging it in to a different circuit/breaker? Perhaps a circuit with a 20A breaker? Is there anything (except the motor) plugged into this 15A circuit when you're testing? Could be a bad breaker, could be a few amps worth of "other stuff" (lights, etc) on this circuit is causing the total current to exceed 15A...

3) Is the run of wire from the breaker panel to the dust collector long? It's possible your voltage is drooping, which will cause the motor to draw more current. Use an AC voltmeter to measure the voltage at the motor while it's running. Less than ~110V would be concerning.

4) You could buy a clamp-on AC current meter and measure the current to the motor while running, and see if it exceeds 11A (or 15A...).

5) I wouldn't bother taking it to a motor shop. You've already replaced the only "fixable" component in this motor (the capacitor). The only other thing that could have "failed" is that there could be a short in the stator winding. No way that's economical to fix (and it's also very unlikely).

[Bill Orbine]

Well, you eliminated the most likely failure by replacing the capacitor, and it looks like the centrifugal switch is good, as well.

You also found a really good piece of information in noting that the motor runs fine without the impeller, but trips the circuit breaker with the impeller in place. If the motor had a shorted winding (or something), it seems less likely that the presence/absence of the mechanical load (the impeller) would trigger this problem. So, excellent troubleshooting work, there.

Some ideas to try, next:

1) When you've been running the motor with the impeller, is it in the blower housing with ductwork and filters (etc) attached? The motor will draw maximum amps when the mechanical load is maximum, which is when there are no restrictions on the impeller. If you have the motor set out on a workbench with the impeller spinning in free air, I would definitely say to put the entire dust collector back together and see if you trip the breaker. It's possible the capacitor was bad (causing the breaker to trip, initially), and if you're overloading the motor by not having filter/duct/etc restrictions on it, it may be tripping it now, but won't once assembled.

2) The next most likely thing to check is the supply circuit. Can you try plugging it in to a different circuit/breaker? Perhaps a circuit with a 20A breaker? Is there anything (except the motor) plugged into this 15A circuit when you're testing? Could be a bad breaker, could be a few amps worth of "other stuff" (lights, etc) on this circuit is causing the total current to exceed 15A...

3) Is the run of wire from the breaker panel to the dust collector long? It's possible your voltage is drooping, which will cause the motor to draw more current. Use an AC voltmeter to measure the voltage at the motor while it's running. Less than ~110V would be concerning.

4) You could buy a clamp-on AC current meter and measure the current to the motor while running, and see if it exceeds 11A (or 15A...).

5) I wouldn't bother taking it to a motor shop. You've already replaced the only "fixable" component in this motor (the capacitor). The only other thing that could have "failed" is that there could be a short in the stator winding. No way that's economical to fix (and it's also very unlikely).

All that and more! Also check the mechanical. I was thinking maybe something not turning freely. Bad bearing? Impeller rubbing, clogged? Such as assuming something to cause machine to start under heavier load.

[John Lanciani]

Ditch the power strip, the cheesy breaker in them is not meant to handle the inrush current of an induction motor. You likely already fixed the core problem, but you introduced another variable into the equation.

[Sandra White]

Well done, John!

I stopped using the cheesy power strip and the dust collector starts up and runs!

It's still running backwards though:
https://photos.app.goo.gl/1YB5UEayV8pGprQe9

Notice how it runs clockwise. You would think that it would run counter clockwise to use the scooping action of the vanes. Also, you see that end cap? (I think that is to prevent the key in the shaft from falling out) The end cap bolt is a left hand thread.

The only electrical change was replacing the capacitor. I don't think it matters which way the capacitor leads are hooked up.

This is very strange as I bought this dust collector new and no one has messed with it except me.

[Dan Friedrichs]

I think that's actually correct. The blades are curved to reduce noise.

[Kevin Jenness]

It's the correct rotation for the backward-inclined impeller.

[Sandra White]

Wow! Who'da thunk.

Many thanks Dan and Kevin - I guess I'm back in business!