New GFI 110v outlets blow out TECO VFD

Mark,

The quote below is from the NFPA website, authors of the National Electric Code. Most municipalities that I’m aware of (certainly not all) who even have a code, usually rely on the NEC. Like Blacjjackjacques said, you may not be required to have GFCIs for your new circuits. Has the inspector said that you do? If so, have you asked him to point you at the written code or county requirement?

Tom

https://www.nfpa.org/Public-Educati...re/Electrical/Electrical-circuit-interrupters
“GFCI protection is required by the 2017 NEC for newly installed and replacement 15 and 20 amp receptacles on kitchen countertops, in bathrooms, outdoor areas, unfinished basements and crawl spaces, garages, boathouses, laundry areas, and within 6’ of sinks, bathtubs and shower stalls. GFCI protection is also required for certain appliances that have a history of being a shock hazard. Drinking fountains, vending machines, dishwashers and boat hoists are examples of appliances that require GFCI protection.”

If you take this regulation literally, it only applies to Receptacles. Hard wiring would be the way to go. Glen-have you confirmed that would be acceptable?
Robert
 
An isolation transformer if floated (neutral and 120VAC) would negate the GFI effect, typically they use a faraday shield to ground to cancel out the EMI/RFI generated. But many 120VAC isolation transformers bond the neutral to the primary and secondary coils, so I am not sure if this would remedy the GFI tripp situation, vs. 240VAC where both 120VAC legs are floated (isolated). The cost of a 1800 VA isolation transformer like a Tripp-Lite would be more expensive than the VFD, and would most likely need to be modified to float the secondary neutral line. It would seem that it is a very expensive band-aide vs. other options: bypass the GFI at one receptacle, hard wire the grinder to a non-GFI box, buy a 240VAC VFD.
 
Any type of switching power supply has leakage current due to the magic of how they work so gfi and larger ones do not play together.

Hard wire one option the other is to change outlet to a twist lock type.

Make sure device is properly grounded via the plug and due to the not common interface then likely fine.
 
Please let me take a stab at this: if you use conventional 110V receptacles (15A or 20A) to pass code you have to use GFI, right?

Then how about wiring 4 wire 220V Hubbel plugs as per industrial wiring standards. you then use the 110V legs to power your machine. In my jurisdiction, this passes and we don't have to use arc fault. If we do any new wiring here for 110V 15/20A plugs, they now have to be arc fault. All my 220 4 wire twist locks are conforming to the new wiring code.
 
Please let me take a stab at this: if you use conventional 110V receptacles (15A or 20A) to pass code you have to use GFI, right?

Then how about wiring 4 wire 220V Hubbel plugs as per industrial wiring standards. you then use the 110V legs to power your machine. In my jurisdiction, this passes and we don't have to use arc fault. If we do any new wiring here for 110V 15/20A plugs, they now have to be arc fault. All my 220 4 wire twist locks are conforming to the new wiring code.

That is clever! Just wire the room for 220 but only use half of the receptacle so to speak. I ideally you could balance the loads too.
Robert
 
Please let me take a stab at this: if you use conventional 110V receptacles (15A or 20A) to pass code you have to use GFI, right?

Then how about wiring 4 wire 220V Hubbel plugs as per industrial wiring standards. you then use the 110V legs to power your machine. In my jurisdiction, this passes and we don't have to use arc fault. If we do any new wiring here for 110V 15/20A plugs, they now have to be arc fault. All my 220 4 wire twist locks are conforming to the new wiring code.
That is a similar plan but one needs to be certain they do wire with all 4 conductors so the neutral is there and that the breaker is correct size.

Given the op is using a 120 volt input vfd the 240 volt option may not be available.

Another suggestion is to stop by the building department and discuss the options with them as they are local enforcement and may have easier suggestions as the gfi may only be required if within a given distance to outdoors or some other thing and be sure to get a copy of the rule.
 
An isolation transformer if floated (neutral and 120VAC) would negate the GFI effect, typically they use a faraday shield to ground to cancel out the EMI/RFI generated. But many 120VAC isolation transformers bond the neutral to the primary and secondary coils, so I am not sure if this would remedy the GFI tripp situation, vs. 240VAC where both 120VAC legs are floated (isolated). The cost of a 1800 VA isolation transformer like a Tripp-Lite would be more expensive than the VFD, and would most likely need to be modified to float the secondary neutral line. It would seem that it is a very expensive band-aide vs. other options: bypass the GFI at one receptacle, hard wire the grinder to a non-GFI box, buy a 240VAC VFD.

I agree that the iso transformer would render a downstream GFCI inoperable since there would be no ground reference, but any of the iso xfmr windings would have no connection to either neutral or ground. You may be thinking of how an autoformer is connected. With an ISO xfmr, you should be able to grab any secondary lead in one hand, and place your hand flat on a solid ground surface and experience no current.
 
tq60, with 4-wire plugs, there is both 220V and 110V across the legs.
 
Jacque: there is a slight interwinding capacitance however which might produce enough current to deliver a mild shock.
Mark
 
With an ISO xfmr, you should be able to grab any secondary lead in one hand, and place your hand flat on a solid ground surface and experience no current.
I seriously doubt that. If electrical potential is present, it will drain to ground. And if anyone wants to test this, please use a meter or tester, not your hands.
 
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