GFI outlet issues

My understanding of a GFIC is that it senses an imbalance between the current on the load line and the neutral line. An imbalance is interpreted and leakage to ground, whether at the ground terminal or through an external path, and it trips the GFIC. It doesn't look at a voltage difference between the ground and neutral lines. Normally, there will be a small difference between the voltage on the neutral line and the ground line because normally, the ground line carries no current but the neutral line does. because it does, there will be a IR voltage difference due to the resistance of the wire.

A high resistance short can occur in a device which can bring a voltage to a point where a person could contact it. An example would be a portable tool left out in cold weather and brought into a warm environment. Condensation would occur and could provide a path for voltage to reach the case of the tool. A GFIC will trip on a few milliamp imbalance, not enough to trip a breaker but but sufficient to prevent a person from a lethal shock.

A three wire circuit, (load neutral, ground) with properly grounded appliances or machines should not need a GFIC as there is no possibility of personal contact with an exposed voltage. Double insulated appliances with two terminal connections can fault to the point where a person is in contact with a dangerous voltage and if also in contact with an external ground. a potentially lethal situation could arise.
 
RJSakowski said:
My understanding of a GFIC is that it senses an imbalance between the current on the load line and the neutral line. An imbalance is interpreted and leakage to ground, whether at the ground terminal or through an external path, and it trips the GFIC. It doesn't look at a voltage difference between the ground and neutral lines. Normally, there will be a small difference between the voltage on the neutral line and the ground line because normally, the ground line carries no current but the neutral line does. because it does, there will be a IR voltage difference due to the resistance of the wire.

A high resistance short can occur in a device which can bring a voltage to a point where a person could contact it. An example would be a portable tool left out in cold weather and brought into a warm environment. Condensation would occur and could provide a path for voltage to reach the case of the tool. A GFIC will trip on a few milliamp imbalance, not enough to trip a breaker but but sufficient to prevent a person from a lethal shock.

A three wire circuit, (load neutral, ground) with properly grounded appliances or machines should not need a GFIC as there is no possibility of personal contact with an exposed voltage. Double insulated appliances with two terminal connections can fault to the point where a person is in contact with a dangerous voltage and if also in contact with an external ground. a potentially lethal situation could arise.
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Very insightful. Thanks for that bit of explanation. Question - what is a double insulated appliance with two terminal connections? Something with 220V or split phase?
 
Yeah, Multi-Wire Branch Circuits would not work with GFCI. The load between the hot and neutral are not the same in those circuits, by design. Since the neutral carries the difference in current between the two hots.

I think the reasoning for GFCI in a garage is that you have the giant door that might well be open for long periods, wet vehicles etc.. So water exposure is more likely. I don't know how reasonable that is. I believe it's specific to garages, so shop buildings might not qualify. And, of course, every area has it's own take on electrical regulations.
 
Portable drills of recent vintage are often double insulated. They have plastic cases rather than the metal case of old. The plastic case is one level of insulation and the normal electrical insulation of the components is the other. Basically, any tool that has a two wire plug can be assumed to be double insulated. It is usually listed as a feature in the description or specification.
 
ttabbal said:
Yeah, Multi-Wire Branch Circuits would not work with GFCI. The load between the hot and neutral are not the same in those circuits, by design. Since the neutral carries the difference in current between the two hots.

I think the reasoning for GFCI in a garage is that you have the giant door that might well be open for long periods, wet vehicles etc.. So water exposure is more likely. I don't know how reasonable that is. I believe it's specific to garages, so shop buildings might not qualify. And, of course, every area has it's own take on electrical regulations.
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The neutral wire from the GFIC socket to the load center can carry different loads but the neutral wire from the GFIC to the appliance will carry the same current as the load wire from the GFIC to the appliance. That is the current the GFIC senses.

In northern climates, salt is commonly used as a road deicer and a vehicle will pile up a goodly amount of slush behind the wheels. When you bring a vehicle into a garage, the slush melts and forms a nice pool of electrolyte on the floor. Since the primary purpose of a gaarge is to house vehicles, the GFIC requirement makes sense.
 
In my area the main Code push for GFCIs is when it’s within 3 or 4 feet to a water source. I think 3 or less feet. So kitchen countertops and the bathroom outlet next to the sink. Washer machine outlet also. So if your washer is in the garage then that would explain it . That’s where you should have GFCIs...close to a water source. All outdoor outlets too.
Mind you, I’m not an expert but I did sleep in a Holiday Inn.

Just kidding but after Katrina electricians were impossible to hire so I rewired my mothers house. Before that I had rewired a commercial building I put up for rent. I had two friends... one a super sharp journeyman Union electrician and another licensed master electrician. Anyway I read up on the codes and then had them to ask when I had a question.
Both buildings were then inspected by the city and fully passed inspection. FWIW, this was before New Orleans adopted a more recent building code. So arc interrupters weren’t even used back then. And as far as the commercial building... since it was brick, I wired it with Grey PVC conduit.( Interesting side note... Romex in conduits are a no no. Because there’s a heat buildup in the wiring)
So, as best as I remember the Codes. GFCIs are when there’s a water source close by or outside outlets. Definitely needed for carports too. But an indoor workshop without a water source has no need for a GFCI as best as I can remember.
But remember that Codes tend to be modified depending on where you live. Down here, we don’t have snow or salted roads.
And it’s not too cold. So plumbing codes and electrical codes and building codes are modified to our climate. But, because we have hurricanes we have the Florida Dade county wind codes. Anyway if you planning on a big job, I’d recommend going to your public library to access your codes. Heck, you can even call the code department and get answers.
 
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@Philzy beat me to the punch already on his thread, but I found a fix for the Delta MS-300 VFD. It actually diverts "electrical interference" to ground, apparently to protect other VFD's on the circuit, but this can trip "Residual Current Detectors". There's a jumper that can be removed to fix this. Worked like a charm for his PM-1130 lathe, and there many be similar features on other VFD's

ES-300 VFD fix for GFCI outlets.jpg
 
MikeWi said:
Some people seem to be having trouble running variable speed controllers off of GFI controlled outlets, and these are becoming required in more and more places. I've seen it discussed here before, and at least one person has said they found certain brands would work where others would not.

Does anyone here run their VS machines on GFI? Do you know the brand that you have? I'd like to try building a list of what works and what doesn't. I have one customer right now who has tried two outlet style, and two cabinet style and none are satisfactory.

I put in an inquiry at the factory to see what they suggest, but I half-expect them to ask me what a GFI is... :)
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I have a LMS lathe with a 1000 Watt (1.34 HP) brushless DC drive at my school job. It throws the GFCI immediately.

I read here that these brushless DC motors (or controllers thereof) throw spikes on the line so I tried using ferrite cores. I was able to get up to about 200 RPM before throwing the GFIC, even with 5 turns of wire around the hollow ferrite core. I tried five cores added to the power cord to no avail. I tried five turns of AWG 10 wrapped around a core for each of the three power cord lines, hot neutral and ground. It didn't improve over just sticking the cores around the power cord. I added a 20 amp RLC power line filter to the ferrite cored power line and it made the situation worse.

I looked at the power line signal with a 200MHz oscilloscope to see if there were spikes on the mains and did not see them. This is consistent with the minimal gains I got from ferrite cores and a filter.

I spoke with the school's electrician about trying a hospital grade GFCI. He had an industrial grade GFCI on the truck. The industrial grade GFCI has a pilot light and one outlet. He installed the industrial grade GFCI and now I can spin my lathe all the way up to top speed! I have yet to try it under load. I'll post the model number of the GFCI in a separate post in case HM doesn't like specific recomendations.
 
jrobert2 said:
I have a LMS lathe with a 1000 Watt (1.34 HP) brushless DC drive at my school job. It throws the GFCI immediately.

I read here that these brushless DC motors (or controllers thereof) throw spikes on the line so I tried using ferrite cores. I was able to get up to about 200 RPM before throwing the GFIC, even with 5 turns of wire around the hollow ferrite core. I tried five cores added to the power cord to no avail. I tried five turns of AWG 10 wrapped around a core for each of the three power cord lines, hot neutral and ground. It didn't improve over just sticking the cores around the power cord. I added a 20 amp RLC power line filter to the ferrite cored power line and it made the situation worse.

I looked at the power line signal with a 200MHz oscilloscope to see if there were spikes on the mains and did not see them. This is consistent with the minimal gains I got from ferrite cores and a filter.

I spoke with the school's electrician about trying a hospital grade GFCI. He had an industrial grade GFCI on the truck. The industrial grade GFCI has a pilot light and one outlet. He installed the industrial grade GFCI and now I can spin my lathe all the way up to top speed! I have yet to try it under load. I'll post the model number of the GFCI in a separate post in case HM doesn't like specific recomendations.
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Leviton GFPL2-PLW 20A-125V​

 
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