NEC Semi-Temporary Wiring

[powersurge]

Permanent wiring:
I have a 120VAC circuit with 1 pole 30 A breaker feeding a 30A hazardous receptacle. During harzardous operation only it is Class I Div II. When the harzardous comodity is removed, the area is an UNCLASSIFIED area which we perform maintenace.

When the area is UNCLASSIFIED, I need to be able to use the 120VAC with standard 5-20R/P devices for pressure washing and power tools (general maintenance). Plug in for a day and then remove the equipment at the end of day.

One Approach:
I would like to purchase a 20A GFCI portable box (Hubble-GFP20M), cut the standard plug attached and connect a hazardous plug. Does code allow this approach? Or where/how does it explain this issue?

The box and wire probably has 14 AWG wire. The argument is that the box and wire is expendable and replaceable. Assuming only 20A equipment can plug into the GFCI box (5-20R/P).

Reference: NEC 527.6 Temporary Wiring
15, 20 and 30 amp, 125 VAC receptacle.

Second Approach:
I was first going down the path - that the 30A breaker will not protect the 14 AWG wire, so I will need to increase the wire size to 10 AWG-30A. Thinking the 20A GFCI box will be a problem, I would put in a 20A breaker or fuse to protect it. This makes the best sense but is it necessary?

Thanks for the help in advance.

[ July 31, 2004, 12:33 AM: Message edited by: powersurge ]

 

[benaround]

Re: NEC Semi-Temporary Wiring

ALL of the electrical systems in a ClassI Div.II location shall be installed per NEC ClassI Div.II requirements. There is no such thing as TEMP. WIRING in a ClassI Div.II location. The term hazardous receptacle has more than one meaning.

 

[rbalex]

Re: NEC Semi-Temporary Wiring

Obviously maintenance must occasionally be conducted in classified locations and often that maintenance requires the use of equipment not suitable for classified locations - welding, for example.

A relatively new requirement, and commonly overlooked, in Section 500.4(A) is "proper documentation" for classification. This is not a trivial exercise and should be executed by someone genuinely qualified to do so.

My first question however, would be, "Why do you believe the location is classified during operation?" My experience has been that many locations are over-classified (often extremely) and then a great deal of effort is spent attempting to avoid the consequences of installing and operating in a classified location.

Except in Articles 511-517 the Code gives no direct instructions on determining the electrical area classification. In many cases the NEC does not actually require a location to be classified; however, for whatever reason, once an area is classified, operations and installations must be consistent with the classification . The Code does not provide for routinely altering the electrical area classification of a location for convenience.

The answer is the "proper documentation" requirement. Maintenance work may be conducted under a permit similar in concept to the "Energized Electrical Work Permit" in Annex J of NFPA 70E. This is commonly called a "Hot-Work" permit in refineries. Essentially, it provides the "proper documentation" that the area is temporarily unclassified.

With regard to "...cut[ting off] the standard plug attached and connect[ing] a hazardous plug, I would direct you to Section 110.3(B).