Temporary installations

[WesR]

I'm visiting one of my company's facilities for a turnaround; they've disassembled a boiler and are using a fan at the opening of the boiler to cool it down. The fan is plugged into a NEMA 4 receptacle, which is designated for use in Class 1 Division 2 Groups B, C, and D. The receptacle has this rating because the area is Class 1 Division 2. The fan has a general purpose cord, connected to a general purpose extension cord, connected to a 1 foot long cord that fits into the NEMA 4 receptacle. The portion of the 1 foot cord that plugs into the receptacle utilizes a twist lock system, and the other end is an ordinary plug; hence the connection to the general purpose extension cord. I don't think what they've done is permitted (to code), but the plant personnel said there is an exception in the NEC which allows the installation because it is temporary. I recall there being an exception for temporary installations, however not one that applied to Article 500, and upon inspection of 500, I saw no such exception. Some Questions:

Is there an exception for temporary installations in hazardous locations? - Where is it?

Where is the exception for general installations, or are there several exceptions in different places? - Are there actually no exceptions?

Since they're doing maintenance on a potential source that is a C1D2 location under normal conditions, is the area C1D1 while under maintenance?

Given the information provided, is the installation acceptable? If not, why not?


Thank you

 

[hawkeye23]

I could be wrong but i don't think a nema 4 install for a recepticle is compliente with nec. I have seen nema 1 splice boxes in class 1 div 2 . Recepticle will cause sparking , it is awhile since i read the 500 section of the nec .
Some work like the adapter to a twist lock recept. is done with a inhouse hot work permit and maybe a meter to sense the air levels for hazards.
Just an opinun.

 

[don_resqcapt19]

Why is the area classified? Have the products that require the classification been removed from the area for the turnaround?

 

[WesR]

It's classified because of the potential for leakage of H2S, CH4, and liquid sulfur. The H2S has largely been removed, however the CH4 and sulfur are still present. And by present, I mean that they're in pipes that won't have emissions unless there is an abnormal situation.

 

[don_resqcapt19]

In that case I think you can cover this work with a "hot" work permit and continuous monitoring for any flammable gas and shut down the work if you reach 20% of LEL.

 

[WesR]

I agree, however I'm still curious what the NEC says regarding this situation.

 

[don_resqcapt19]

I agree, however I'm still curious what the NEC says regarding this situation.

The NEC does not cover issues like that.

 

[bobgorno]

I've heard it before. It's an argument of convenience, not fact.

Temporary wiring must meet the requirements of permanent wiring. These ain't Christmas lights. 590.2

Also see 501.140. Including (B)(5).

 

[kwired]

I've heard it before. It's an argument of convenience, not fact.

Temporary wiring must meet the requirements of permanent wiring. These ain't Christmas lights. 590.2

Also see 501.140. Including (B)(5).

590.2 All Wiring Installations. (A) Other Articles. Except as specifically modified in this article, all other requirements of this Code for permanent wiring shall apply to temporary wiring installations

Doesn't this qualify what is being done as temporary wiring?:

590.3 Time Constraints. (A) During the Period of Construction. Temporary electric power and lighting installations shall be permitted during the period of construction, remodeling, maintenance, repair, or demolition of buildings, structures, equipment, or similar activities

Christmas lighting is not the only temporary wiring covered in 590.

Whether or not anything in 501 applies depends on if the hazardous environment will still be there during this temporary construction period of time. It is possible the hazard will be removed or made safe somehow, otherwise grinding, welding, and other activities may not be allowed either.

 

[bobgorno]

Whether or not anything in 501 applies depends on if the hazardous environment will still be there during this temporary construction period of time. It is possible the hazard will be removed or made safe somehow, otherwise grinding, welding, and other activities may not be allowed either.

Agreed, if there is no hazardous environment, then there is no issue. If the area is hazardous, Article 501 applies.

Also note 500.3:
500.3 Other Articles. Except as modified in Articles 500
through 504, all other applicable rules contained in this
Code shall apply to electrical equipment and wiring installed
in hazardous (classified) locations.

In other words all aspects of the code apply, except when hazardous, then 500 thru 504 trumps all other Articles.

Bottom line. If it's hazardous. the cord, plugs and receptacles must meet 501.140 amd 145. The "cheater cords" may be considered if a hot work permit is in place....owner's risk here. End of day or shift, they need to be removed. I've walked thru many plants where they are routinely left in place for convenience. I've brought piles of them back to plant control rooms when they have been left plugged in.

BobG