NEMA configurations

[new_ee]

11-30R for example. There is no ground or neutral. How can this receptacle be used? Isn't it a violation of code?

I have a piece of equipment that is 3 phase, 208V and the spec sheet says 3W connection. I think the spec sheet is wrong. If it was only 3 wires that would be just the 3 phases. No EGC or Neutral?????

for reference:
http://www.leviton.com/sections/techsupp/nema.htm

 

[charlie b]

The absence of a neutral wire is easy to understand ? the machine has no need for 120 volts. The absence of an Equipment Grounding Conductor might be a surprise. But it's not against code, as the code does not apply to the manufacturing of equipment. Also, it is not too uncommon, or else there would be no such receptacle.

Can you tell us anything about the equipment? Perhaps there is a good reason that some member (other than myself) can offer, as to why it does not need an EGC.

 

[steve66]

250.114 Equipment Connected by Cord and Plug.
Under any of the conditions described in 250.114(1) through (4), exposed non?current-carrying metal parts of cord-and-plug-connected equipment likely to become energized shall be grounded.

Exception: Listed tools, listed appliances, and listed equipment covered in 250.114(2) through (4) shall not be required to be grounded where protected by a system of double insulation or its equivalent. Double insulated equipment shall be distinctively marked.

My electric drill, circular saw, and sander all work with ground wires. But it seems less safe with higher voltage, higher current, and industrial equipment.

 

[new_ee]

it's an electro freeze:

http://www.electrofreeze.com/pdf/184873 30T-RMT.pdf

the equipment does not call for 11-30R receptacle specifically. but since it said 3 wire and its 3 phase thats why i assumed the 11-30R (the 3 wires are the three phase wires). then i looked at the 11-30R and realized there was no ground. then i came to the conclusion that the spec sheet probably isnt right, its probably a 4 wire.

w/just three phase wires will there be ground fault/short circuit interruption capability?

 

[charlie b]

Although that spec sheet did not explicitly say so, I would infer that it is intended to be hard wired. I would use a 3 wire plus ground, because the spec sheet does not forbid the use of an EGC.

From what information source did you see a requirement to use a plug and cord?

 

[new_ee]

charlie,

there is no requirement for cord and plug. but i will have to have some sort of disconnect and since its on wheels i figured it would be best to use cord and plug instead of hard wire.

 

[charlie b]

So what prevents you from using a 4-wire cord? The manufacturer only requires 3 wires, but I don't think that forbids you from using 4. Have you asked them that question?

 

[new_ee]

i guess my question wasnt really about this specific equipment since i've already decided to use a 15-30R 3 wire with ground.

i was just questioning where you would use the 11-30R.

 

[ramsy]

spec. for that equip.[/url]]Standard wiring?
208/230 volts A.C., 60 HZ, Single Phase?2 wire
208/230 volts A.C., 60 HZ, Three Phase?3 wire

Its common practice to exclude the grounding wire when specifying circuit conductors or ordering cable.

Whether 3 slashes cross a circuit line on the prints, or we reference cable type (ie) 12-3 or 10-2, the first number is the AWG# and the second number is the total (phases + neutral) only. The grounding wire is always assumed, but never counted.

About that 11-30R, I believe supervised industrial equip. may be bonded to plumbing & building steel, which ties to the main bonding jumper.

Motors on ungrounded Delta systems, and old wiring w/out EGC's come to mind. When an outlet or cord cap w/Grounding prong exists on circuits without grounding wires, test instruments may see an EGC path through equipment bonds to the building, or through illegal and false / bootleg grounds spliced to the neutral.

NEC code prohibits grounding type recepticals / cord caps on circuits with no grounding wire, unless the outlet can be seperately bonded, or fitted with a listed GFCI.