Jet JJ-12 Jointer Trips Breaker

[Jay Runde]

I have a Jet JJ-12 jointer that I haven't used in about a year as I have been upgrading my garage workshop electrical and insulation. It has a 3HP 16 Amp 240V motor in it hooked up to a 30 amp breaker. Now when I try to start up the jointer, the motor starts for a couple of seconds and then the the breaker trips. When I remove the belts from the motor, it runs fine. Any ideas what the problem might be?

Thanks
Jay

[Matt Meiser]

I have mine on a 20A circuit and its fine, so either something is wrong with your breaker or something is wrong with your machine. No answers but several questions that might help with diagnosis.

I'm not clear if you had it up and running before or if you've been storing it for a year?
You say it runs for a couple seconds--does it come up to speed fully, then shut down?
With the belts off, does everything seem to turn freely? With the planer feed engaged and disengaged?

[glenn bradley]

Since you state that with the belts off it runs fine, I would inspect the cutterhead. With the belts off does it turn completely free or is there the resistance that points to fouled grease or bearings? Could there also just be spoil in the way that has hardened over the year and is acting like a brake on the cutterhead? Breakers do age and must be replaced but, it runs well with the cutterhead out of the picture so probably not an issue there.

[ian maybury]

A dodgy connection somewhere in the wiring or in a plug can cause that sort of thing.

It may well be a problem caused by or at least worsened by some sort of stiffnening in a machine that's been laid up too, but it's worth checking the jointer manual as well to determine what the recommended size and type of breaker is. Over here it's fairly normal for machines to require a type C or slower release breaker type. That way they can handle the short duration starting surge (which can be up to 6x the plated current) without needing to be so large as compromise the protection in steady state running conditions...

ian

[Neil Brooks]

Count me in with those who say that ... no problem without the belt ... is a significant point.

The belt invokes the rollers and the bearings. I'd check everything that moves ... when the belt IS on ... and see which thing seems to be causing much more resistance than every other thing. Something's seized up, needs greasing, cleaning, replacing, new bearings, or ... similar.

You gave good info, incidentally :)

Good luck !

[Neil Brooks]

One more thing ....

If you have an ammeter ... I might START by checking the actual current draw without, and then WITH the belt on. It makes sense that -- even if everything was working properly -- it would draw slightly more power with the belt ON than off, meaning ... it COULD be a faulty breaker (or wiring issue).

I doubt it, but ... with an ammeter ... it would be a simple matter to check that, first.

EDIT: that wasn't very clear. The motor/unit should have a rated current draw, in amps. With the ammeter, you'd see whether it was drawing in excess OF its rated amperage. If it wasn't, it's wiring/circuit protection. If it IS drawing more than rated current ... and only WITH the belt on ... something's stuck/sticky.

HTH.
Neil

[Rod Sheridan]

The symptoms point to a starting capacitor issue with the motor.

If it's a capacitor start/run motor, an open start capacitor will allow the motor to start on the run capacitor, however it won't have enough torque to start rapidly enough to prevent the breaker from tripping.

Likewise if it's a starting capacitor that has reduced capacitance, same issues.

Regards, Rod.

[Jay Runde]

The jointer was running before I stored it for the past year. I don't think it is completely coming up to speed before the breaker trips. I'll check tonight if everything turns freely with the belts on/off this evening.

I don't have an ammeter. I was thinking of picking one up from Harbor Freight on the way home from work today to test things out.

[Trent Shirley]

Are you tripping the house breaker or the motor breaker? Any chance you have another 220v line you can plug into to test with?
Double check the circuits to make sure both sides of the line are properly in phase or it could try spinning the motor in reverse. Check the amp setting inside the electrical box to make sure it matches the setting listed on the motor plate.
A loose connection somewhere along the power circuit is the most common cause.
Test how much resistance you have spinning the motor over by hand with the belt in place. If there were signifcant resistance you should be able to feel it.

[Jay Runde]

It is tripping the house breaker.

I don't feel any resistance with both the belt on and off. Everything seems to be spinning smoothly.

I hooked up an ammeter and it peaks at 62 amps with both the belt on and off and runs steady around 12 amps with the belt off.

[jonathan eagle]

I would suggest you look at Rod's response.
Jonathan

[Jay Runde]

I tested the start capacitor with my meter and it is showing 0 ohms. From what I've read, it means that is bad. Going to stop by a locol motor repair shop and pick up a new capacitor either today or tomorrow to see if that helps. If that doesn't work, I guess I'll have to bring the motor in to get it checked out.

[Jerome Hanby]

If you have an analog Ohm meter, short the cap, then put the leads across it and the needle should swing towards zero then rapidly fall back towards infinity. Zero ohms is pretty much a short no mater howyou look at it and would seem to explain the problem you have been describing...

[Jay Runde]

I bought a new capacitor today, installed it, and all is well now. Thanks for the suggestions on the capacitor.

[Rod Sheridan]

You're welcome, glad to hear that it was a simple repair.....Rod.