GFCI/grinder question

[Gregg Feldstone]

Got a jet IBG 8” VS grinder. Uses a VFD to change speeds and electric breaking. I thought it was broken but discovered that VFD‘s don’t play nice with GFCI receptacles. The machine trips the receptacle every time. Plugged it into a non-GFCI and it seems to work fine other than some wobble on one of the wheels. My question is this: if I simply replace a couple receptacles as non-GFCI will I still have a problem if several other receptacles on the same circuit ARE GFCI? The circuit breaker in the box itself appears to be a regular breaker not a GFCI.
Because I thought the grinder itself had a problem I have another one being sent and itÂ’s too late to stop. It is a bit of wobble evident in a factory supplied grinding wheel pretty normal or might I have an actual problem with the grinder itself. I do plan to replace the wheels with much finer higher quality oxide wheels for my turning tools or maybe even CBN wheels.
IÂ’m thinking of comparing the two grinders side-by-side when I get the new one but at 70 pounds itÂ’s a bit of work. What do you guys think? Thanks

[Mike Cutler]

Gregg

If it is a single circuit, with receptacles "daisy chained", and the first receptacle in the string is an GFCI, then you will still have the problem.
If these are stand alone GFCI Duplex receptacles, then yes, replacing the GFCI with a standard duplex receptacle will not effect the others.
Without knowing exactly how your branch circuit wiring is installed though, makes it very difficult to predict the effect.
Oh, and yes, VFD's are notorious for not playing well with GFCI protected branch circuits.

[roger wiegand]

It won't work if your receptacle is downstream from a GFI, as those receptacles are also GFI-protected and will be triggered by the wonkiness the VFD introduces. If there is no GFI receptacle wired between the breaker and your unprotected receptacle it should work fine even if there are GFI receptacles downstream.

There are commercial GFI's apparently that can deal with VFD's, but they cost several hundred dollars. In a situation where I had no choice but to plug a VFD into a GFI protected circuit I ended up installing an isolation transformer between the VFD and the outlet. That, combined with shielded power cables, works fine.

[Tom M King]

Swap the GFCI receptacle with the next one in the circuit, and use the first one, with the new, non-GFCI receptacle. No doubt someone will say that makes it non conforming to the code, but I wouldn't lose a bit of sleep over it. Swap them back if you sell the house.

[John K Jordan]

...It is a bit of wobble evident in a factory supplied grinding wheel pretty normal or might I have an actual problem with the grinder itself. I do plan to replace the wheels with much finer higher quality oxide wheels for my turning tools or maybe even CBN wheels...

It's not that uncommon to have a bit of wobble in a standard grinding wheel, especially an inexpensive one. Most of the time the wheel can be dressed to run true. Before I switched to CBN wheels I had some good quality Norton wheels on one grinder which although ran true after dressing one or both had some vibration. I added the OneWay balancing system which solved the problem; used that for years. I see these are about $70 now.

If you suspect wobble from the grinder you might be able to measure the runout with a dial indicator at the base of the shaft where it's not threaded, turned by hand with the wheels removed.

Since a CBN wheel can't be trued, it has to run true from the start. A common cause of a bit of wobble is non-precision washers. I like to use the spherical washer set that Woodturners Wonders sells which so far has eliminated any minor wobble on my grinders with CBN. For a CBN on a Tormak there wasn't enough room on the shaft for the spherical washer but I found some precision machined washers which did the trick.

(BTW, I ran separate non-GFCI circuits for my lathes with VFDs.)

[Gregg Feldstone]

Thanks to all who posted. I believe the receptacle IS the first in the chain since it’s closest to the breaker box. The next two are also GFCI . I really want to get rid of all of them since I plan to use the grinder in a different location in the future. This is all in my garage. Anyone know why a garage would require GFCI receptacles? Could it possibly be a code requirement in Texas?
I have no running water there except the water heater,which is elevated 2 feet off the floor with a good pan.
Mike mentioned “stand alone GFCI” receptacle. Do you mean by this a receptacle attached to the breaker with no other receptacles in between? A dedicated circuit? Thanks

[Gregg Feldstone]

I also ran across a thread of people reviewing the grinder on Amazon. One person mentioned that Jet told him to install a GFPE. I am not sure if they meant a GFPE breaker or a GFPE receptacle, if that exists. Does this make any sense? I understand GFPE is to protect equipment and has a higher amperage threshold before tripping. Does a GFPE work with equipment with VFD’s? What benefits would I get from replacing the circuit breakers with GFPE breakers? This of course after I get rid of the GFCI receptacles. Thanks

[Rod Sheridan]

It’s a code requirement because of conductive floors in garages...Rod

[Mike Cutler]

Thanks to all who posted. I believe the receptacle IS the first in the chain since it’s closest to the breaker box. The next two are also GFCI . I really want to get rid of all of them since I plan to use the grinder in a different location in the future. This is all in my garage. Anyone know why a garage would require GFCI receptacles? Could it possibly be a code requirement in Texas?
I have no running water there except the water heater,which is elevated 2 feet off the floor with a good pan.
Mike mentioned “stand alone GFCI” receptacle. Do you mean by this a receptacle attached to the breaker with no other receptacles in between? A dedicated circuit? Thanks

Gregg

"Stand Alone" means that this GFCI has no other receptacles fed by it, offering them GFCI protection.
"Generally speaking", most garages built in the last 20 years will have GFCI protected duplex receptacles by code. Whether the garage is attached, or detached, will also impact wiring requirements.
There are "interpretations" and the applications, of BOCA requirements that will cause differences between geographical regions of the US, so yes, I would expect to see GFCI protected duplex receptacles in "new construction" garages in Texas.