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+-- Thread: Bench Grinder vs GFCI (/showthread.php?tid=7342042)
RE: Bench Grinder vs GFCI - Bob10 - 08-28-2018
Unless you buy the commercial units most sold at home centers will go poof if you plug something in that draws a lot at start up or has problems with brushes. I had people re-side part of a building, the worm drive they were using burned up the GFCI in short order. I had the same thing happen with arc fault breakers at $45 a piece. I waited until I was done with the remodel to put in the replacements.
RE: Bench Grinder vs GFCI - Mr_Mike - 08-29-2018
More testing. I have this really cool power strip that has individual switches for each outlet. I use it for my tool battery chargers. It also happens to be a surge suppressor.
When plugged into the circuit with the GFCI and switched on, nothing bad happens. As soon as some additional load is introduced, the GFCI trips. It doesn't matter if the device is on the power strip or not. Weird.
The grinder seems fine. Plug it into the wall and unplug the power strip and all is good.
I really want to use the power strip, so I'll replace the GFCI and see if the behavior repeats. In that case, I might just delete the GFCI from the circuit. I do not know what, other than the shop, is on this circuit. If only the shop, no big deal. If the outdoor outlets are on it, maybe not the best idea.
RE: Bench Grinder vs GFCI - Roly - 08-29-2018
(08-29-2018, 08:22 AM)Mr_Mike Wrote: More testing. I have this really cool power strip that has individual switches for each outlet. I use it for my tool battery chargers. It also happens to be a surge suppressor.
When plugged into the circuit with the GFCI and switched on, nothing bad happens. As soon as some additional load is introduced, the GFCI trips. It doesn't matter if the device is on the power strip or not. Weird.
The grinder seems fine. Plug it into the wall and unplug the power strip and all is good.
I really want to use the power strip, so I'll replace the GFCI and see if the behavior repeats. In that case, I might just delete the GFCI from the circuit. I do not know what, other than the shop, is on this circuit. If only the shop, no big deal. If the outdoor outlets are on it, maybe not the best idea.
You might check the powerstrip and make sure the neutral is not grounded in the powerstrip. Use the ohmmeter to check. Roly
RE: Bench Grinder vs GFCI - TDKPE - 08-29-2018
Makes think even more that it's a tired MOV in the power strip, shunting spikes from motor on or off transients to ground, which will trip a GFCI. If it is, you may be able to replace or remove the MOV, since you like the power strip.
RE: Bench Grinder vs GFCI - Bob10 - 08-29-2018
(08-29-2018, 08:22 AM)Mr_Mike Wrote: More testing. I have this really cool power strip that has individual switches for each outlet. I use it for my tool battery chargers. It also happens to be a surge suppressor.
When plugged into the circuit with the GFCI and switched on, nothing bad happens. As soon as some additional load is introduced, the GFCI trips. It doesn't matter if the device is on the power strip or not. Weird.
The grinder seems fine. Plug it into the wall and unplug the power strip and all is good.
I really want to use the power strip, so I'll replace the GFCI and see if the behavior repeats. In that case, I might just delete the GFCI from the circuit. I do not know what, other than the shop, is on this circuit. If only the shop, no big deal. If the outdoor outlets are on it, maybe not the best idea.
Wow i missed the power strip in the mix. Toss it and carry on, few are built well IME. If you are using the power strip to power down a portion of the shop isolate it with a breaker that can be switched on and off or a shut off switch for the line. I have a switch that shuts down an entire sub panel that supplies the bigger machines that can eat a person and another for the 220 outlet on the exterior of the house
RE: Bench Grinder vs GFCI - Mr_Mike - 08-29-2018
(08-29-2018, 11:00 AM)TDKPE Wrote: Makes think even more that it's a tired MOV in the power strip, shunting spikes from motor on or off transients to ground, which will trip a GFCI. If it is, you may be able to replace or remove the MOV, since you like the power strip.
Well, I'd be clueless troubleshooting. I'm not much into electronics. I'll replace the GFCI and if it doesn't help, I might see if I can bypass all the power strip electronics.
RE: Bench Grinder vs GFCI - TDKPE - 08-29-2018
(08-29-2018, 11:08 AM)Mr_Mike Wrote: Well, I'd be clueless troubleshooting. I'm not much into electronics. I'll replace the GFCI and if it doesn't help, I might see if I can bypass all the power strip electronics.
It probably only has a few MOVs, which looks like this. If there is one between the neutral or hot and the equipment ground, a small amount of leakage can trigger the GFCI circuitry. They're designed to conduct current, but only at a higher threshold voltage than normally seen - but if that threshold sags or is just too low, motor transients may be enough to pass a little current to ground.
Better strips have several MOVs, between the three poles, so there's a good chance it's just a tired or low threshold MOV that isn't actually fried. Better strips may have other electronics in them. Cheapest ones have a single MOV between hot and neutral to clamp voltage spikes, but that shouldn't trigger a GFCI.
[attachment=12601]
RE: Bench Grinder vs GFCI - Mr_Mike - 09-01-2018
Definitely the power strip. I replaced the GFCI with no change in behavior.
So, my choices are to eliminate the GFCI, use a different power strip or gut the power strip. The powerstrip is held together with anti-tamper screws. The ones that cam out in reverse. Hard to remove.
Not sure what I'll do yet.
RE: Bench Grinder vs GFCI - TGW - 09-01-2018
I would still run a Megger test on the windings. Just mo rule out the worst case scenario.
It is fairly common to find old grinders that have been overloaded too many times so the insulation has degraded. The only way of fixing it is to rewind the entire motor...... and it isn't exactly easy. I am struggling with a rewind at the moment. Trying to learn.......... but I cannot afford to pay anyone else for doing it and I cannot afford a new motor....... so I keep struggling.
RE: Bench Grinder vs GFCI - Roly - 09-01-2018
(09-01-2018, 12:52 PM)Mr_Mike Wrote: Definitely the power strip. I replaced the GFCI with no change in behavior.
So, my choices are to eliminate the GFCI, use a different power strip or gut the power strip. The powerstrip is held together with anti-tamper screws. The ones that cam out in reverse. Hard to remove.
Not sure what I'll do yet.
Find the correct screwdriver for those screws or it you can get a Dremel with a cut off wheel to cut a slot in the screw head for a regular flat blade screwdriver. Places like Harbor Freight has kits for the tamper proof screws. Roly