# GFI outlet issues



## MikeWi (Feb 17, 2021)

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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## Howard E. (Feb 17, 2021)

Some gfci's just don't like inductive loads.  I've heard that hospital grade units are more robust in this respect.


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## freethink (Feb 17, 2021)

I had this issue with my PM1127, and tried multiple different "hospital grade" GFI plugs with no luck.  Some would run a little longer than others, but they would all eventually pop within 15-30 seconds of starting up.  Ultimately I just gave up and replaced the GFI with a non-GFI heavy duty 20 amp outlet for the circuit the lathe runs on.  I know it's not within code, but I'm not too concerned with water or flooding in my workshop.


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## mksj (Feb 17, 2021)

Just about everybody I know who has tried a VFD on a GFCI circuit has had it trip, in particular 120VAC input type. I do not know if a line RFI/EMI filter would make a difference or exacerbate e tripping as ere are many types with different leakage currents and grounding. NEC code  requires these for for 120VAC receptacles in specific wet locations and as of 2020 now also requires them for receptacles up to 250VAC inclusive of garages at or below grade. One can circumvent the requirement by not using a receptacle and hard wiring the power. 




__





						210.8(A) GFCI Protection. Dwelling Units.
					

Which receptacles in the laundry room require GFCI protection?



					www.electricallicenserenewal.com
				




The issue is the trip current is something like 5 mA, which is very low. There are GFCI's for use with VFD's, but they are very expensive and trip at around 25 mA. Alternative is an isolation transformer which could get expensive.


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## aliva (Feb 17, 2021)

Is a GFCI really necessary? I would think as long as you have good grounding system you should be ok. Where I used to work none of the machinery had GFCI's that I'm aware of. Most of the equipment was 600V 3Phase and up.
I do have a GFCI breaker on my whirlpool tub 20 amps was around $100.00


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## RJSakowski (Feb 17, 2021)

Considering that the function of a GFIC device is to detect an imbalance in the currents in the load and neutral wires, their behavior is surprising.  We have GFIC protected outlets in our kitchen and the Cuisinart can opener routinely trips the GFIC.  We have replaced the can opener, the GFIC with no sucess.  Last week, when I used the can opener, it tripped a GFIC on another circuit.  

The annoying one though is the one in our half bath.The room has no windows so you are totally dependent on the lights which are pulled off the GFIC outlet.  You sitting on the toilet and decide you really have to switch on the exhaust fan and you trip the GFIC.  Now the GFIC is across the room from where you're sitting so there you are, in the dark, wondering how to solve your dilemma. Fortunately, there is a nearby door so you can crack the door to let in some light so you can finish what you were about. The fan motor is a simple synchronous motor with a piddling little current draw.  Yes, I know that I can rewire the outlet so the light circuit is on the line side rather than the load side.  The problem is that I only think about it when the GFIC acts up.

Back to machining, I have seen recommendations not to use machines on GFIC circuits.  This is particularly valid with a CNC machine as a power cut there can have consequences, sometimes serious.


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## MikeWi (Feb 17, 2021)

So far this sounds like it's going to be an increasingly big problem. Great!


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## KevinM (Feb 17, 2021)

Me and some others were having random non-GFI breakers trip instantly on startup on a variable speed lathe before the motor would actually be turned on. The only thing that stopped it for me was a 30A breaker.


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## ttabbal (Feb 17, 2021)

I didn't have a problem with what looks like a standard GFCI on the circuit with my PM1127. It was not plugged into that outlet, it was downstream. I found out the hard way that it does in fact trip, so it's not just broken. Apparently, if you drill through the romex, it does that. Who knew?  

Eventually, I added a bunch of circuits to the garage that don't have GFCI, so it's a non-issue now. I had more trouble with nuisance trips with large inductive loads like power tools. The PM is the only 110V VFD I have available to test with, so I can't say how common issues with them might be.


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## Bi11Hudson (Feb 17, 2021)

I have disputed the use of GFCIs since their inception. They have gotten better over the years, but still cause problems with inductive loads. In particular, any load with a speed controller. Or any device that "deforms" or modifies the symmetrical sine wave of the power company. I have had trouble with such things as remote control devices and "WiFi" computer devices when they overlay the sine wave.

Code requirements protect "sheeple" from themselves and their inherant stupidity. An end user is exempt from any standards of the "code". The local authority cannot shut you down for having code violations in your own property. . . yet. *But*, and this "but" is serious, if a property is not code compliant, insurance is no good, they don't have to pay in the event of a fire or other damage. Including personal injury. Further, most power suppliers will do an overview before restoring power after an outage. If any visible code violations are extant, they can refuse to connect. If any other resident is primary, the exception does not apply.

I cannot offer any real solution to the basic problem, beyond doing an obviously illegal modification and doing away with the GFCI. It can be blamed on an eariler modification before a specific requirement. GFCI should, however, be kept wherever moisture can be contacted, but there are limits to (in)sanity. A bathroom and kitchen can be rewired, the wiring rerouted so that GFCI is still available where needed but the usual inductive loads are not supplied. Quite frankly, and brutally, if you cannot picture what I am espousing, you should stay with the existing installation.

My house was built before electricity was used. I rewired when I acquired it in 1975, not so much to the code but what I knew at the time. As it turns out, I sort of "over built" it, the inspector not only passed it but told me that many things I did were not required. That, of course, was before GFCIs. I tried GFCIs when they became available but have never had any successful use of them. I have SqD "QO" type circuit protection and GFCIs are available to fit my panel. But, they don't work, have never worked, and I quite frankly have scrapped several hundreds of dollars worth of attempts.

End of rant. . .

.


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## RJSakowski (Feb 17, 2021)

KevinM said:


> Me and some others were having random non-GFI breakers trip instantly on startup on a variable speed lathe before the motor would actually be turned on. The only thing that stopped it for me was a 30A breaker.


If by variable speed lathe, you mean one powered by a DC motor, there is a possible cause.  DC motor require rectification of of the ac supply followed by a filter capacitor.  On initial energization, the circuit is subject to a large inrush current due to charging the capacitor.  

This can be dealt with in a number of ways.  The simplest is to add a small resistance to the input to limit the surge current.  This however reduces the efficiency of the supply which can be objectionable for high current devices like a lathe motor.  

Another way is to use a negative resistance device, aka varistor or inrush current limiter.  It has a fairly high resistance when cold, limiting the inrush current but as it heats up, the resistance drops significantly.  This method is often used for switching power supplies.  One that I used was this: https://www.digikey.com/en/products/detail/ametherm/AS32-10015/2614390


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## markba633csi (Feb 17, 2021)

In defense of GFIs:  I have them in my kitchen, but not in the garage.  The ones in my kitchen proved their value once when I plugged in a coffee machine with a shorted heating element; it shut off the power immediately.  In cases like that, they are nice to have.
For the garage,  I never had any GFIs, just standard outlets.  I don't think GFIs in the garage are required in my area, if they are original
I'm not sure what the code says about hard-wired machinery in residential garage settings.  I wonder if hard-wired stuff is given a pass on the GFI requirement?  Sure, you'd have to cut the plug off, but it's a small price to pay
-Mark


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## KevinM (Feb 17, 2021)

RJSakowski said:


> If by variable speed lathe, you mean one powered by a DC motor, there is a possible cause.  DC motor require rectification of of the ac supply followed by a filter capacitor.  On initial energization, the circuit is subject to a large inrush current due to charging the capacitor.
> 
> This can be dealt with in a number of ways.  The simplest is to add a small resistance to the input to limit the surge current.  This however reduces the efficiency of the supply which can be objectionable for high current devices like a lathe motor.
> 
> Another way is to use a negative resistance device, aka varistor or inrush current limiter.  It has a fairly high resistance when cold, limiting the inrush current but as it heats up, the resistance drops significantly.  This method is often used for switching power supplies.  One that I used was this: https://www.digikey.com/en/products/detail/ametherm/AS32-10015/2614390


$5 30A breaker and 5 minutes was pretty simple for me.    My state only requires GFI in kitchens and bathrooms, washing machines and water heaters get a pass.


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## Cooter Brown (Feb 17, 2021)

Take all the GFI outlets out of the shop they are for bathrooms and OSHA job sites only....


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## rwm (Feb 17, 2021)

I am thinking of a new product here. It is a GFI breaker that has been internally re-wired to be a regular breaker. You could only sell it on the dark web with bitcoin payment. Or maybe in the HM sales section!
Robert


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## MikeWi (Feb 19, 2021)

RJSakowski said:


> Another way is to use a negative resistance device, aka varistor or inrush current limiter.  It has a fairly high resistance when cold, limiting the inrush current but as it heats up, the resistance drops significantly.  This method is often used for switching power supplies.  One that I used was this: https://www.digikey.com/en/products/detail/ametherm/AS32-10015/2614390



@RJSakowski How is this used? Is it placed in series with one leg?


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## RJSakowski (Feb 19, 2021)

MikeWi said:


> @RJSakowski How is this used? Is it placed in series with one leg?


Yes, in series with one current carrying leg.  

For the one that I chose, the initial room temperature current was around 10 ohms, limiting the peak current to 15 amps.  As it heats up, the resistance drops to a small fraction, the final value depending on current draw.  When the power is cut, the varistor cools down again.  In a circuit like a switching power supply, this isn't a problem since the supply draws what is needed to provide the proper output voltage and current.  If you are switching a lathe or mill motor off and on, the varistor needs a cool down period to cool.  If you are powering a lathe through a VFD, the main power would remain on continuously with control being performed downstream so it behaves much like a switching power supply.


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## fursphere (Feb 19, 2021)

I've had this issue a couple of times.  Most recently was with a Jet Wood Lathe my wife picked up with a variable speed drive.  The solution for me has always been put a robust power strip in-between the device and the GFI protected circuit.  Simple fix.


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## Todd727 (Feb 20, 2021)

RJSakowski said:


> The annoying one though is the one in our half bath.The room has no windows so you are totally dependent on the lights which are pulled off the GFIC outlet.  You sitting on the toilet and decide you really have to switch on the exhaust fan and you trip the GFIC.  Now the GFIC is across the room from where you're sitting so there you are, in the dark, wondering how to solve your dilemma. Fortunately, there is a nearby door so you can crack the door to let in some light so you can finish what you were about. The fan motor is a simple synchronous motor with a piddling little current draw.  Yes, I know that I can rewire the outlet so the light circuit is on the line side rather than the load side.  The problem is that I only think about it when the GFIC acts up.


As stated, that circuit was wired incorrectly.  Use this thread to remind yourself to get off your butt (when it isn't an issue) and fix that now.


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## Todd727 (Feb 20, 2021)

Also, different localities use different editions of the NEC Code Book and the locality can not adopt everything in the code or conversely, as in my case, be more restrictive.  We can't use 14 gauge wire on 15 amp circuits, everything is minimum of 12 gauge.  You also can make the argument that the circuit you are using is for an "industrial" type setting, which allows you to not have a GFCI on your machine circuits.


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## ttabbal (Feb 20, 2021)

Todd727 said:


> We can't use 14 gauge wire on 15 amp circuits, everything is minimum of 12 gauge.



That's one I support. 14 gauge is too small in my opinion. This happened in my house, partly as a result of smaller wire. Load never tripped the 15A breaker. Measurements never got above 12A. The damaged plug was not in use, the heat came from the back as far as I can tell. I replaced the breaker as well to be on the safe side. A little extra copper costs less than a fire. 

Looking at this again makes me want to swap all the 14 gauge circuits to 10A breakers, if I can find some..


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## tq60 (Feb 21, 2021)

That was NOT the wire size, if it was it would have been melted inside the wall.

That was poor connection at the outlet.

Simple ohm's law...

The heat (watts) is greater where resistance is greater.

E=i*r, p=i*e, p is watts, series circuit has i (amps) equal in all parts, voltage is different in all parts related to resistance.

A poor connection has resistance, current flow across that resistance generates the heat.

Looks like the return side of outlet was not a tight fit on heavy load and that started the chain of events that created the heat that resulted in metals relaxing reducungcontact and generating more heat.

Cheap outlet with heavy load.

Sent from my SAMSUNG-SM-G930A using Tapatalk


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## ttabbal (Feb 21, 2021)

I wondered about the resistance of the connection. It was wired with the spring terminals in the back. I have never really liked those. The replacement is done with the screw terminals and feels much more solid.


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## Logan Novice (Feb 21, 2021)

MikeWi said:


> So far this sounds like it's going to be an increasingly big problem. Great!


I agree, Mike.  This isn't something that should be ignored.  At some point it will peak and the outcome(s) could be costly.  I'm not referring to how it could affect sales, although that is a consideration, but if a user experiences a loss related to a ground fault and the insurance carrier refuses to pay the anguish could be enormous.  Let's hope that the manufacturer can get back with his electronics engineering group and figure out how to fix this.


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## Logan Novice (Feb 21, 2021)

KevinM said:


> $5 30A breaker and 5 minutes was pretty simple for me.    My state only requires GFI in kitchens and bathrooms, washing machines and water heaters get a pass.


But for the 30A breaker the wire size requirement is #10.  If the user stays with 12 gauge wire on 30 amps the wire will fail before he breaker trips; that's a fire hazard.


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## KevinM (Feb 21, 2021)

Logan Novice said:


> But for the 30A breaker the wire size requirement is #10.  If the user stays with 12 gauge wire on 30 amps the wire will fail before he breaker trips; that's a fire hazard.


The circuit uses 12 gauge with a 1' wire length which is adequate.


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## Logan Novice (Feb 21, 2021)

KevinM said:


> The circuit uses 12 gauge with a 1' wire length which is adequate.


Thanks ...  I appreciate knowing that.
Let's not lose sight of the original problem under discussion though.  GFI nuisance tripping isn't going to be eliminated by a breaker with higher amperage rating.


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## KevinM (Feb 21, 2021)

Logan Novice said:


> Thanks ...  I appreciate knowing that.
> Let's not lose sight of the original problem under discussion though.  GFI nuisance tripping isn't going to be eliminated by a breaker with higher amperage rating.


It is a transient spike that trips the breaker, not an extended current consumption.


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## middle.road (Feb 21, 2021)

I've got a 36' enclosed car hauler about 50' from the shop. (Which is now an awful mess of a storage _shed_.)
I ran a 'temporary' 12ga cord to it with a site grade GFI plug at the shop end. (Need to figure out how to run conduit under 24'+ of concrete.)
The trailer is properly wired for AC, with a breaker subpanel and all.
It has two 4' florescent tube fixtures, plus I run the tumblers out there and I have an electric power washer out by the trailer and occasionally I'll run the small compressor to fill up tires.
Only issue is that the pressure washer will sometimes go into a "growling trying to engage" mode when sitting idle, and that trips the 15a breaker way back on the garage subpanel and *not *the GFI plug at the outlet.
Then I've got another 12ga extension cord made up with another GFI plug for use outside of the shop on the driveway or yard. Never has tripped with weed trimmers or drills or the electric chainsaw.


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## RJSakowski (Feb 21, 2021)

ttabbal said:


> I wondered about the resistance of the connection. It was wired with the spring terminals in the back. I have never really liked those. The replacement is done with the screw terminals and feels much more solid.


I never use the spring terminals for electrical connections.  It's just asking for trouble.  They are OK as long as there is no corrosion but if any corrosion develops the resistance will increase resulting in more corrosion and higher resistance.  Things should be designed for worst case scenarios, not best case.  Considering the scorch marks on the neutral on the front, I would suspect a high resistance plug connection may have started the

I only use 14 AWG wire for lighting where I know that the current draw will be on the order of a few amps at most.  Never on outlets. 

Regarding using a 30 amp breaker  with 12 AWG wire,  12AWG copper has a resistance of 1.6 milliohms/ft.  If it were carrying 30 amps, the wire would experience a power dissipation of 1.4 watt/ft per conductor.  By comparison, a heat tape used to keep pipes from freezing has a power dissipation of 7 watt/ft.  I would not expect a catastrophic wire failure due to a 30 amp draw.

However, the point about insurance not covering a loss if the breaker was mismatched with the wire size and a fire was even remotely connected is well made.


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## FOMOGO (Feb 21, 2021)

I have made a habit of never using push in outlet connections on outlets. They just always seemed iffy to me. And like RJ, 14 gauge for lighting only. Mike


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## Tim9 (Feb 21, 2021)

Throw away the GFCI when using a machine tool motor. At least that’s been my experience. Just make sure you lathe or mill is properly grounded. You should be fine.
   Now mind you. Most licensed electricians aren’t going to throw away the GFCI for a customer that they don’t know. Too much liability. Can’t blame them.
12 gauge only for me. I follow code as best as I can. But I’ve been told by a number of electricians that the GFCIs are problematic. I make sure I don’t cut corners with electricity. And try to follow the codes...But, I may be a year or two behind. I’m sure in about 10 years.... maybe GFCIs may be more reliable. But until then...I don’t plug my big stuff into them. They and the arc-fault interrupters are problematic with big motors.
And totally agree. I don’t like the stab in connections.


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## Todd727 (Feb 22, 2021)

ttabbal said:


> That's one I support. 14 gauge is too small in my opinion. This happened in my house, partly as a result of smaller wire. Load never tripped the 15A breaker. Measurements never got above 12A. The damaged plug was not in use, the heat came from the back as far as I can tell. I replaced the breaker as well to be on the safe side. A little extra copper costs less than a fire.
> 
> Looking at this again makes me want to swap all the 14 gauge circuits to 10A breakers, if I can find some..


I was happy to comply also. Best part is, I just put 20A breakers in throughout when I was building the house. The difference in overall cost for wires and breakers was less than $300.


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## Todd727 (Feb 22, 2021)

ARC Fault is even worse from what I've heard.


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## NegativeK (Feb 22, 2021)

fursphere said:


> I've had this issue a couple of times.  Most recently was with a Jet Wood Lathe my wife picked up with a variable speed drive.  The solution for me has always been put a robust power strip in-between the device and the GFI protected circuit.  Simple fix.


Can you elaborate? Is the power strip somehow filtering..?

I'd love to get 220V 50A service in the garage for tools and electric car charging, and I'd really rather not go down the rotary phase converter path (or worse -- an expensive isolation transformer). But we'll burn that bridge when we come to it.


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## fursphere (Feb 22, 2021)

NegativeK said:


> Can you elaborate? Is the power strip somehow filtering..?
> 
> I'd love to get 220V 50A service in the garage for tools and electric car charging, and I'd really rather not go down the rotary phase converter path (or worse -- an expensive isolation transformer). But we'll burn that bridge when we come to it.


Just a simple 110v power strip.  Nothing fancy - has a built in breaker.    For whatever reason it fixes the VFD tripping the GFI.   Give it a try.  

My new PM-30MV-HS has a 110v drive, and appears to get along with the GFIs in my garage.  No issues so far.


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## middle.road (Feb 22, 2021)

fursphere said:


> Just a simple 110v power strip.  Nothing fancy - has a built in breaker.    For whatever reason it fixes the VFD tripping the GFI.   Give it a try.
> 
> My new PM-30MV-HS has a 110v drive, and appears to get along with the GFIs in my garage.  No issues so far.


I would be leery of power strips. The last few I've taken apart used 'stab' in connections.
One 10A fried using a dremel on it.
A web search on '_fail power strip_' will show more than you ever wanted to see.


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## mksj (Feb 22, 2021)

The PM-30MV is a DC motor, at least on the current models, so should play better than VFD's. There are low leakage line filters that may mitigate some of the issues, such as the Shaffner FN3260 series, downside is they cost more than your VFD. I do use line filters on the incoming power to my VFD's and a toroid on the motor leads as well as shielding with star grounding. Problem is that there is no standard fix for grounding and stray current problems with VFDs. If you are running a 230VAC VFD, then until this year (per NEC) it would not require a GFCI, and if required it would compare both hot legs and not to neutral unless there was a 120 circuit. Usually the stray currents are in the neutral. Another misnomer is that GFCI is not an over current device, so it does not mitigate the need for a breaker. There are breakers with GFCI built in, but not sockets. Breakers use current vs. time curves to trip, and house wiring is only rated at 80% of the breaker amperage for continuous use.


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## Tim9 (Feb 23, 2021)

GFCI’s are just very problematic in my opinion. If I remember correctly, the old school method of running two 2 separate circuits using 12/3 or 10/3 wire was to share the common ground in the single Romex cable. Unfortunately with the newer codes in the 2000 years which dictates GFCIs, that method of saving time no longer works. 12/3 and 10/3 Romex is constantly tripping the GFCIS. MKSJ IS CORRECT. THEY SENSE THE GROUND. 
   Now, if you want to run GFCI’s it’s just better to run two separate Romex 12/2 or 10/2 cables. GFCIs do sense through the grounds. They are problematic. Yeah, they are great when using an outlet near a water source. I want them on those kitchen countertop outlets and bathroom outlets. 
  But no way would I waste my time with GFCI outlets in my workshop. I’d be spending my day walking back one forth to the electrical panels.


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## vtcnc (Feb 23, 2021)

I'm not up to speed on NEC codes and the like, but I don't understand why there would be a code requirement for shop or garage outlets. It sounds like the requirement is possibly for outlets that are below grade - i.e. susceptible to flooding hazards. This would make sense to use GFCI but I can certainly understand why one would want to avoid nuisance tripping as well given the surges in current a GFI circuit would realize in your typical shop. With that said, I have my little HF Titanium 125 welder plugged into a 20A GFCI outlet in my garage coming off the subpanel. Zero nuisance tripping on that outlet.

I guess my big question is that a ground fault in a shop (outside of the disaster scenario of a flood) is likely going to trip the breaker regardless. I mean, GFCI as it is conventionally used is for safety around the moist/wet working environments. It seems silly to require GFCI on say a lathe circuit because the load is going to trip a regular breaker without a ground fault. Maybe I'm just not understanding but the GFCI is designed to provide personnel protection not equipment protection.

With that said, back in the day, I was a manufacturing engineer for an injection molding machine manufacturer. Our division built the control panels for the machines. The OSHA officer demanded that we provide ground fault protection for the final test assemblers while doing live, point-to-point testing in the cabinets. I was scratching my head for a few weeks - there wasn't any electrical supply contact in the area that even knew what I was talking about: 480V GFI personnel protection? It doesn't exist - I was told - good luck with your search.

I finally figured it out. The movie industry is required to provide 480V GFI protection for underwater filming. The lighting used in underwater shots - think JAWS - is 480V. Wasn't cheap, about $1500 per station, but we did it and it was the right thing to do. It actually was put to the test a few months later and I'm glad we had it in place.


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## RJSakowski (Feb 23, 2021)

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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## vtcnc (Feb 23, 2021)

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.


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?


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## ttabbal (Feb 23, 2021)

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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## RJSakowski (Feb 23, 2021)

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.


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## RJSakowski (Feb 23, 2021)

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.


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.


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## Tim9 (Feb 23, 2021)

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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## MikeWi (Oct 12, 2021)

@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


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## jrobert2 (Mar 10, 2022)

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...


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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## jrobert2 (Mar 10, 2022)

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.
> 
> ...


Leviton GFPL2-PLW 20A-125V​


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## MikeWi (Mar 10, 2022)

jrobert2 said:


> Leviton GFPL2-PLW 20A-125V​


Thanks, I'll make a note of it. That's the first time I've seen a name for one that works.


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## gunsmither (Mar 10, 2022)

You can use a dedicated non GFI single outlet to run a VS machine tool in a residential shop or garage, and meet code as far as I recall.
That's what I did for my VS Belt Grinder which was tripping the GFI outlet.


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## pontiac428 (Mar 10, 2022)

I wired my entire shop with GFCI, because the code says so.  Anything with an outlet requires it.  The loophole is for hard-wired connections that go to a shutoff switch or breaker.  They are exempt because the purpose of GFCI is to protect a person from being electrocuted for touching ground and a live wire at the same time.  The assumption is that this occurs at the outlet, usually in a bathroom, with wet hands and some handheld appliance like a curling iron.  Pop goes the GFCI.

I have not had a single issue with GFCI in the shop.  I have a few GFCI breakers powering 220v circuits to my RPC, a 5hp Baldor compressor motor, my Mig, Tig, and plasma, and my (ahem!) imported tools and appliances that run on EU 240v.  All of the 110v circuits have GFCI outlets first in the chain, so all outlets are protected.  All of my stuff works just fine.  

The only reason I can think GFCI would cause problems is if one did not have an up-to-date or quality tool.  It's also possibe that the black and white wires are switched...  Bottom line is that ground should never carry current for any reason, at any time except for a fault condition, in which case it should trip immediately.


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