8" JET commercial Grinder (New) in HS Welding shop.

R

RMELECT

Member
Location
New England (USA)
Occupation
Electrician
Good evening,

Just installed power to a new 8" JET Bench grinder 120v 3.5 to 7a . The existing 20a GFI trips when started. Called JET Tech support and was told that there bench grinders can not be plugged into a GFI.:LOL: Which come cord and plug ready.

I installed a 30a fused disconnect powered by a dedicated 20a circuit and fused with 15a fuses. Hardwired the grinder. Have I covered my bases?

Thank You
 
As Larry stated if GFCI protection is required for the outlet in that location then you cannot just hardwire the equipment to bypass that requirement. There also may be an issue with the grinder itself, the manufacturer would have to allow it to be hardwired. Some cord and plug equipment is not listed for hard wiring.
 
In a lot of cases tech support is not much support. I have an older Harbor Freight bench grinder that works fine on a GFCI.
 
On the plug for the grinder, with the switch ON try measuring the resistance from the pin for the line and also for the neutral to the ground pin, and see what you get. Also, try measuring the capacitance on the smallest scale if your meter has that capability.
If an open circuit to the ground is indicated, then some transient effect may be tripping the GFCI.
 
 
Just curious did you megger the grinder? A new motor should have at least 25 meg ohms to ground. Have recorded over a Gigi ohm on new 480 volt motors using 1,000 volt range on a megger.
 
busman said:
Sorry. Misspelled it. Should be Baldor. Had no idea they were so expensive now. I think mine was about $500.

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Baldor is the last US grinder manufacturer & they are proud of them bought one at a ReStore for $8 that had issues, the replacement cap & shipping, was a bit more then I paid for the grinder, the grinding wheels were $50 each & it it's never tripped the GFCI, the only one that will is a 7" Rockwell 200V 3Ø & that is because of the VFD that powers it.
 
I will agree the Jet should NOT be tripping this. This is ready made, UL and is sposed to be able to be used on legal circuits. I also have a 1 hp Baldor.
 
It seems that it wouldnt pass UL if it wasnt designed for gfci? I would think anything came plug and cord today would need to?
 
Sberry said:
It seems that it wouldnt pass UL if it wasnt designed for gfci?
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Jet is a big and popular manufacturer. Could it be that they are "putting their foot down" on the useless proliferation of GFCIs which would cost them millions to re-design some of their products that they have been selling forever? They don't need a UL listing and you don't need one to use a product. Maybe they figure that they have enough sales to people who don't care to worry about it?

-Hal
 
It never occurred this tool that comes cord and plug wasnt listed some way? (used UL generically) Cant say I have ever read a manual says if it trips gfci remove it. Really cant imagine then not fixing it if there is a regular fault?
 
Sberry said:
Really cant imagine then not fixing it if there is a regular fault?
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Just because it trips a GFCI doesn't mean that it's dangerous or a hazard to health. Look at it this way. They have been selling a grinder forever with no problem. Then all of a sudden, the NEC comes along with this new device that says they have to redesign the motor because it doesn't like their grinder. That could cost them millions. Nobody ever got shocked and testing showed no abnormal leakage.

-Hal
 
Yes but could or would you keep up production if it faulted? I didnt imply it was dangerous,,, as I mention I used one recently that tripped and I didnt fix, but I cant imagine Jet taking 1000s of calls and having the secretary tell them all that they should modify a common circuit so it will run? I would have to be convinced a guy could actually get anyone at Jet on a phone that knew much.
 
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