Jointer trips gfci when turned off?

[Paul Kusnierz]

I have a Delta Shopmaster 6" jointer (JT360). The motor is a 3/4 hp, 13amp wired for 120v operation. I recently started running the jointer from a gfci protected line and every time I turn the power off, the motor trips the gfci. As it is winding down and nearly at a stop, I hear a tick sound coming from the motor which has always been normal but right after that the gfci will trip. The fact that is trips only when turned off has me confused. I have tried different outlets on the gfci line with the same result. If I plug the jointer into a non gfci protected outlet, it works fine. No other machines do this on the gfci outlets. Anyone have experience with this?

I did speak with an electrician who suggested I check the manual to see if Delta suggests the machine not be operated from a gfci. The manual says nothing about using a gfci to power the machine. From other thread searches it seems the common thing to try first would be to replace the gfci in case it's a faulty outlet, but all those problems are from tripping the gfci during use. Not when the machine is powered down like I have. Any input would be greatly appreciated.

[Ron Natalie]

That jointer appears to have a simple ON/OFF switch which I suspect only switches one pole of the power. There are two things that will trip a GFCI:
1. An imbalance between the current going out of the hot leg and returning on the neutral.
2. An interconnection between the neutral and ground.

Since there ought to be NO current flowing when the power switch is OFF, I suspect the second is the issue.
Somewhere in the thing, in the course of spinning down, there's a ground-to-neutral fault.
The tick you hear may be the centrifugal switch that connects/disconnects the start winding. It's possible that there's a fault there.

If you can't find it by inspection and correct it, one solution would be to replace the switch with a two pole switch (or a magnetic starter) that will remove the hot and the neutral legs.

[Steve Meliza]

Take a look at this thread:
http://www.sawmillcreek.org/showthre...-JT360-Jointer

[Paul Kusnierz]

Ron,

My electrical experience is limited so would replacing the start switch with this be what you are referring to? http://www.google.com/aclk?sa=L&ai=C...gpspn%3Dpla%22

[Ron Natalie]

That looks like it will work or I might be inclined to try one of the griz switches: http://www.grizzly.com/products/220V...f-Switch/H8242

[Mike Henderson]

I found that some of the older GFCI units would trip much easier than the new units. I had one that my scroll saw would always trip, every time I turned it on. I replaced the GFCI with a new one and it works perfectly.

Mike

[Tim Race]

Motors will cause GFCI to trip. There was a different ground fault device (I forget the acronym) that didn't trip at the miniscule amount of current that a GFCI does. Your neutral and ground wire do not open when you turn the machine off. When the motor is powered down, it's still rotating and creating an induced voltage and current flow, this will cause a GFCI to trip. This is why you don't put a refrigerator or deep freeze on a GFCI. IF you want the GFCI protection, I suggest you head to Grainger or somplace like that and purchase a short cord with a GFCI built into it. They don't trip as easy and you get the additional protection if the power should drop and come right back on, these will trip off and when the power comes back on it will not restart the machine. This prevents big trouble with kickbacks and dulling blades. Now these only work for 120V machines. If you run 220 volt I suggest you find someone comfortable and knowledgable about electric to install or assemble and preset holding circuit with a magnetic starter. This will keep you table saw and other big equipment for quick power drops. MAtter of fact where I worked these setups were required for OSHA.

[Mike Henderson]

Motors will cause GFCI to trip. There was a different ground fault device (I forget the acronym) that didn't trip at the miniscule amount of current that a GFCI does. Your neutral and ground wire do not open when you turn the machine off. When the motor is powered down, it's still rotating and creating an induced voltage and current flow, this will cause a GFCI to trip. This is why you don't put a refrigerator or deep freeze on a GFCI.

This is not my experience and doesn't seem to make sense from an electrical point of view. For 120V, a GFCI works by summing the current in the white and black wires. If there's no leakage to ground, the currents sum to zero. If you break the hot (black) wire, the motor cannot drive current into the white wire because there's no circuit. It would be like connecting a wire to one terminal of a battery and expecting current to flow through that wire - it won't unless there's a return to the other terminal of the battery.

Refrigerators and freezers in a garage are exempt from GFCI because a GFCI can trip for no obvious reason. If it does, the food in the frig or freezer could spoil. It has nothing to do with the motor in the frig or freezer.

Mike

[Kevin W Johnson]

I agree with Mike, I have many different tools that run on a GFCI without issue. Drill press, bandsaw, OS sander, router, scroll saw, etc...... Even my outside outlets are on a GFCI breaker, and I run my 120v mig welder (not a motor, but heh) on those outlets just fine.

[Richard Jones]

..........Refrigerators and freezers in a garage are exempt from GFCI because a GFCI can trip for no obvious reason. If it does, the food in the frig or freezer could spoil. It has nothing to do with the motor in the frig or freezer.............

Used to be you could use a single (gang, not quantity) receptacle in the garage, ostensibly for the very reason you stated. No more. Exception is gone in the 2008 NEC.

[Jim Neeley]

Is there any possibility that the switch is breaking the neutral leg, rather than the hot leg?

[Lee Schierer]

Is this problem possibly caused by the start capacitor discharging as the centrifugal switch closes as the motor spins down?

[Mike Henderson]

Used to be you could use a single (gang, not quantity) receptacle in the garage, ostensibly for the very reason you stated. No more. Exception is gone in the 2008 NEC.

Thanks for pointing that out. I wasn't aware of the change. I suppose the GFCIs are better today than they used to be.

Mike

[Tim Race]

This is the 3rd time I've tried to reply. First 2 didn't work for some reason. Go read your 2011 NEC code book article 210.8, the exceptions are back in there or should be. Test your motor and controls if all is good then maybe replace the GFCI. Welders, toasters and exterior christmas lights do not affect GFCI's like motors will. I had a lot more here for you earlier EMF, BEMF, centrifigal switches, capacitive acting wiring and the like. I spent my 33 years doing this stuff and I teach these things enough as it is in class. Be safe, have fun, make sawdust, build something nice for your Queen.

[Jim Neeley]

This is the 3rd time I've tried to reply. First 2 didn't work for some reason. Go read your 2011 NEC code book article 210.8, the exceptions are back in there or should be. Test your motor and controls if all is good then maybe replace the GFCI. Welders, toasters and exterior christmas lights do not affect GFCI's like motors will. I had a lot more here for you earlier EMF, BEMF, centrifigal switches, capacitive acting wiring and the like. I spent my 33 years doing this stuff and I teach these things enough as it is in class. Be safe, have fun, make sawdust, build something nice for your Queen.

Hi Paul,

Can your jointer be re-wired to run on 240VAC? Section 210.8(A) of the 2008 and 2001 NEC, which governs GFCI outlets and mandates their use in garages, etc., states:

Dwelling Units: All 125-volt, single phase, 15- and 20-ampere receptacles installed in the locations specified in 210.8(A)(1) through (8) shall have ground-fault-circuit-interruptor protection for personnel.

and

210.8(A)(2) states: Garages and also accessory buildings that have a floor located at or below grade level not intended as habitable rooms and limited to storage areas, work areas, and areas of similar use.

If you run a tool on 240VAC, a GFCI is not required.

Hi Tim,

As one who will be completely re-wiring my 4-car garage / shop in the immediate future I would greatly appreciate it if you would point me to the exceptions permitting exclusion of GFCI outlets on 120V 20A circuits in a garage. I would especially like to except the dedicated circuits for a fridge and freezer. Unfortunately for me I could not only not find an exception, Exhibit 210.10 in the NEC Handbook shows a freezer in a garage as an explicit example of where GFCIs ARE required.

Jim