GFI outlet issues

MikeWi

MikeWi

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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... :)
 
Some gfci's just don't like inductive loads. I've heard that hospital grade units are more robust in this respect.
 
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.
 
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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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
 
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.
 
So far this sounds like it's going to be an increasingly big problem. Great!
 
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.
 
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.
 
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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