480V 30A twistlock receptacle...outside....GFI?

[JacksonburgFarmer]

I have a project on a piece of equipment at a precast concrete plant.....they bought this tilt table (not exactly sure how it works, havent seen it run yet) but it is 480V three phase. It is outside, will always be outside. It will be moved from time to time, in the same area but pipe/sealtight and wire is not a option.

So, SO cord and a plug it is (twistlock).

The service at this plant is a ungrounded 480V three phase, no actual ground (you can get a reading to ground, but if equipment faults to ground, it will energize whatever; conduit, enclosures, etc) so the idea of a 'assured equipment grounding conductor program' seems like it would be worthless here to me....

What do you do in a situation like this?

 

[Jraef]

The need for GFCI doesn’t apply to 480V 3 phase equipment.

 

[LarryFine]

The service at this plant is a ungrounded 480V three phase, no actual ground (you can get a reading to ground, but if equipment faults to ground, it will energize whatever; conduit, enclosures, etc) so the idea of a 'assured equipment grounding conductor program' seems like it would be worthless here to me....

The exposed metallic system parts should be grounded regardless of there being a grounded circuit conductor. A fault should ground that conductor, not energize the conduit and enclosures.

What do you do in a situation like this?

I believe you're looking for an L16-30 plug and receptacle.

 

[Cow]

I have a project on a piece of equipment at a precast concrete plant.....they bought this tilt table (not exactly sure how it works, havent seen it run yet) but it is 480V three phase. It is outside, will always be outside. It will be moved from time to time, in the same area but pipe/sealtight and wire is not a option.

So, SO cord and a plug it is (twistlock).

The service at this plant is a ungrounded 480V three phase, no actual ground (you can get a reading to ground, but if equipment faults to ground, it will energize whatever; conduit, enclosures, etc) so the idea of a 'assured equipment grounding conductor program' seems like it would be worthless here to me....

What do you do in a situation like this?

That's not right then.

They are not the only facility in the US with an ungrounded 480v system. I have not had much experience with them, but I believe you need either ground detectors if they want it to remain truly an ungrounded system. Or you corner ground it.

In either case however, all metal and other non current carrying metal parts should STILL be bonded together properly.

If that is not the case, and you wire this machine up, you are taking on a huge liability if someone were to ever get hurt or killed over this deal.

I would be having a very frank discussion with this company over their safety liabilities operating in a manner such as this, if that's the case.

 

[zbang]

Not a cheap option, but you could install a 480/480 transformer and bond the secondary.

 

[don_resqcapt19]

I have a project on a piece of equipment at a precast concrete plant.....they bought this tilt table (not exactly sure how it works, havent seen it run yet) but it is 480V three phase. It is outside, will always be outside. It will be moved from time to time, in the same area but pipe/sealtight and wire is not a option.

So, SO cord and a plug it is (twistlock).

The service at this plant is a ungrounded 480V three phase, no actual ground (you can get a reading to ground, but if equipment faults to ground, it will energize whatever; conduit, enclosures, etc) so the idea of a 'assured equipment grounding conductor program' seems like it would be worthless here to me....

What do you do in a situation like this?

A ground fault on an ungrounded system does not really energize anything. It just creates a corner grounded system. The grounding and bonding keeps all of the conductive parts that are connected to the electrical system at the same voltage. If there is a second fault to "ground" on an ungrounded system, that is really a line to line fault, and the EGC that connects the points between the two faults must be able to clear the fault.

 

[kwired]

A ground fault on an ungrounded system does not really energize anything. It just creates a corner grounded system. The grounding and bonding keeps all of the conductive parts that are connected to the electrical system at the same voltage. If there is a second fault to "ground" on an ungrounded system, that is really a line to line fault, and the EGC that connects the points between the two faults must be able to clear the fault.

+1

People sometimes don't realize you can ground any point of a system, NEC just happens to specify certain points (usually a neutral conductor) that must be the point that gets grounded, but a three wire delta can be any conductor with basically same result from any of the three. People see a "grounded phase" conductor and think that is impossible and something should go seriously wrong if you ground a phase conductor. they need to realize that you can ground any point of the system and you don't have a ground reference until you do ground a point in the system. Once you do ground a point, even if non intentional, you then have a grounded system and a second fault will result in undesirable current flow.

 

[Barbqranch]

+1
. Once you do ground a point, even if non intentional, you then have a grounded system and a second fault will result in undesirable current flow.

Unless it is the (1 in 3 chance) same phase.

 

[Jraef]

Again, the term "GFI" is an improper non-specific term. If you were thinking that you needed a GFCI because it is outdoors, that is incorrect. The NEC does not require GFCI for 480V equipment.

If however you were thinking of GFP (Ground Fault Protection), at 30A that is only required if the equipment requires it as part of their listing.

If the issue is that you have a 480V ungrounded delta system, you only need Ground Fault Monitoring or as others suggested, corner grounding of the delta.

 

[kwired]

Unless it is the (1 in 3 chance) same phase.

Well you won't have high level fault current but still can have objectionable current on non intended paths.