Dust collector stopped working yesterday - bad start capacitor?

[Ian Scofield]

Not exactly sure what happened, no pops or burning smells or anything. Took a break for lunch and came back out and the dust collector wouldn't fully turn on. I pressed the on button, it sounds like it's beginning to start then it flipped the breaker. Did some googling and I'm not entirely sure but it sounds like it could be a bad start capacitor?

Here's a video of the sound:
https://www.youtube.com/watch?v=H_HN...ature=youtu.be

Does this seem like a start capacitor? Any other troubleshooting steps before I test the actual capacitor?

Side note: If it is the start capacitor, what is a good manufacturer to replace with? I know the replacement is 300mfd/125VAC but I don't want to replace it with a cheap one so I can hopefully avoid replacing down the line.

Lastly, I run my dust collector in my garage (someday I'll have it outside) and I turn it on/off kind of frequently since I don't need it running while I'm not cutting. I've read a few people post that motors like these should not be started/stopped often. Is this correct? If so, what's the number of stops/starts per hour you should try and stay under?

[James Phillips]

It is almost definitely the capacitor. If you have a safe way to reach the fan and give it a push start and it starts, you definitely have a bad cap.....

[Charles Lent]

The other possibility is the centrifugal start switch. It switches the capacitor in and out of the starting circuit. This switch is located inside the back end cover of the motor (opposite end from shaft). It should be closed when the motor is not running and open as the motor reaches 20% of it's running speed. What sometimes happens is that dirt/sawdust prevents the switch from closing as the motor slows to a stop. When the motor is started again the capacitor is not in the circuit because the switch hasn't closed, so the motor fails to start and you get the hum that you are experiencing. Sometimes the problem is the switch contacts and sometimes it's the plastic collar on the shaft. This collar needs to slide on the motor shaft. If the flyweights can't move this collar on the shaft it can't open and close the switch. Cleaning this area of the shaft and a very light lubrication is all that's usually necessary to fix it.

Charley

[Ian Scofield]

Thanks for the responses. I'll go take a look at the centrifugal switch and check with my multimeter to see if it's open/closed while the motor is off. A replacement capacitor is only $7 so I'll go pick one of those up today. I'm hoping it's just the cleaning to get that switch working again.

Just want to get back to my project....

[Mike Henderson]

I think it's a lot more likely that the cap went bad then that the centrifugal switch is causing the problem. Most of those motors are TEFC so it's tough for swarf to get in and those switches don't fail very often in the absence of swarf.

Regarding how often you can start up a motor, the problem is that during startup you get an high current flow, which causes heat. So starting a motor often will heat up the motor more than just running it. The answer to your question depends on a lot of things, including how cool the air is around the motor, the design of the motor, and whether you run the motor long enough each start to cool it off. I'd put my hand on the motor and feel the heat. As long as the motor is not HOT you should be okay.

One other comment on caps - some of those Chinese motors have very small (physically) caps, and maybe that's why they fail. If you buy a quality cap, it may not fit into the same space.

Mike

[Ian Scofield]

Took the capacitor to a motor repair shop abd they said the cap is fine. Not sure If I believe them though because their capacitance meter read 366 which seems out of tolerance for a 300mfd capacitor. Before I left I checked the leads to the start capacitor and the circuit was closed (0 ohm) so I know the centrofugal switch appears to be working.

They said it was mechanical and to disassemble and see if its binding somewhere and run it with no load on it. So that will be the next project.

This is my second dust collector in 3 months. Getting really frustrated with working on and replacing these things.

EDIT: Came back and have completely checked everything except the motor itself...way above my pay grade. I have tested both legs of the circuit (240v dust collector) and they make it all the way up to the plate outside of the motor (right side):

Now one thing seems odd to me, but I have zero experience with motors. EVERY one of those copper pads connects to each other. Seems a bit odd that everything is connected to itself on that panel, I would assume that would be a short? But it doesn't immediately pop the breaker so I'm guessing that's how it works?

I didn't have another start capacitor that matched exactly, however I had a 400mfd capacitor from the HF dust collector that no longer works due to a bad bearing I believe. Put that in and it's doing the same thing. Opened the exhaust port to see if the impeller was binding anywhere and it spins smoothly, no grinding/rubbing/etc.

As you can see here, it begins to spin, but it just never "takes off" for lack of a better term:
https://www.youtube.com/watch?v=bTKH...ature=youtu.be

[Jim Andrew]

If you don't mind, please enlighten the rest of us on the kinds of DC's you have and have had trouble with.

[Ian Scofield]

Jim,

I originally bought a HF dust collector and it worked fine for just over a few months then had a grinding noise and was having a lot of vibration on startup/shutdown. Made a thread here:
http://www.sawmillcreek.org/showthre...now&highlight=

The conscensus was possibly a bad bearing. But by the time I invested in a bearing puller, three jaw puller, etc. to remove the impeller and replace it, I had already surpassed the cost of the dust collector.

So I looked on craigslist and found a new in box grizzly G1029 dust collector. I cut the plastic off it so I know it wasn't used. The guy had a bunch of tools that he had bought since he was going to redo the cabinets in his kitchen but he just never did so he was selling everything. Worked fine for a couple months and now this.

Not sure if I'm doing something wrong to cause all these issues or if murphy's law is just hitting me hard.

[Ken Fitzgerald]

Is it hardwired or does it use a plug?

Do you have a volt meter with which you could verify incoming line voltage?

[Ken Fitzgerald]

The copper/brass pads are part of a terminal strip. Yes they are electrical shorts. This terminal strip provides the ability to connect the internal wiring of the motor to the incoming power cable.

[Ian Scofield]

Is it hardwired or does it use a plug?

Do you have a volt meter with which you could verify incoming line voltage?

Ken, I've used a volt meter and have tested the incoming line voltage. Also tested my tablesaw, jointer, and planer and they all fire up no issues on the same circuit. So unfortunately the dust collector is the culprit.

So that pad is functioning correctly then? I understand the purpose for it is connect internal wiring and incoming power, but I would assume each set of contacts would be kept separate. As in top row would connect both left and right side, but not the rest of them. For example:
1 2
3 4
5 6
Those are the contact. There is zero resistance if I connect 1 -> 2,3,4,5 or 6.

Thanks for the help!

[David L Morse]

I listened to the video. It sounds to me like the motor spins up to the point where the centrifugal switch should open but it doesn't. If the switch won't open when it's supposed to the start capacitor and start winding stay connected and the motor draws higher than full load current until the breaker opens. Getting to that switch won't be fun.

As far as your Ohmeter readings as concerned keep in mind that the DC resistance of the motor windings are about an Ohm or less so depending upon the scale and resolution of your meter you could read 0 everywhere.

[Ian Scofield]

I listened to the video. It sounds to me like the motor spins up to the point where the centrifugal switch should open but it doesn't. If the switch won't open when it's supposed to the start capacitor and start winding stay connected and the motor draws higher than full load current until the breaker opens. Getting to that switch won't be fun.

As far as your Ohmeter readings as concerned keep in mind that the DC resistance of the motor windings are about an Ohm or less so depending upon the scale and resolution of your meter you could read 0 everywhere.

David, would the centrifugal switch not opening and removing the start cap/winding prevent the motor from ramping up to normal speed?

EDIT: Here is the centrifugal switch:


There wasn't any dust or debris in there, clean as a whistle. If I pull the centrifugal switch up, I can see that it separates the contacts on the left. It doesn't seem like it's gritty when I pull it up, so I would assume it wouldn't need any lubrication. I did start the motor while watching the switch and the shaft spun, but it didn't seem like it was spinning fast enough to cause the switch to engage and open the circuit.

The 20 amp circuit it was on was tripping as it was doing it's startup. I put some lubrication on the centrifugal switch to see if that would make a difference and it still started really slow and tripped the breaker. I have a 30 amp breaker so I moved it to that and it still made the same humming sound (it never did this before all these issues started, so by the sound I can tell it's not right). It continued to start up and progressed further, as in the impeller was moving way faster than on the 20 amp circuit, I'm assuming because it was pulling more amps than it could on the 20 amp circuit. Felt kinda nervous and turned it off because it still isn't right.

Could it still be the start capacitor that's not causing the motor to spin up fast enough to trigger the centrifugal switch? I'm not convinced the capacitor has been ruled out as the motor shop just tested capacitance and said it was good. They didn't test ESR which doing some googling can determine a capacitor is bad, but capacitance may say it's good. Also they measured it as 366 which seems out of tolerance to me. I ordered a new start capacitor so hopefully that will show up before next weekend.

Thanks for the continued help.

[Ian Scofield]

Replaced start capacitor today and still not working properly.

I turned it on and it still makes that humming noise that doesn’t sound right. And it never takes off. While its spinning down if I start it again, for a half a second it sounds like it should but then goes back to its humming and slow start then trips the breaker.

Could the start winding have fried? That seems about the only piece left.