Industrial (NFPA79) Flexible Utility (Electric) Drops 3

[hammey]

I'm looking for a specific reference in NFPA79, NEC, or any OSHA standard that clearly spells out that, in a manufacturing plant environment, allows a 115 VAC power supply drop (through a HUBBELL 3 prong, grounded plug and socket) to a lean piece of equipment (ie. the equipment may be moved for relocation but not on a frequent or regular basis).

My safety department (which is not technically astute, just regulation smart) basically says my power drop is an extension cord and thus not permitted on a "permanent" piece of equipment. Thus far I've been unable to find specific regulations to counter them even though the design is inherently safe.

Specifically, this is what I have. An SJO cable plugged into a lighting circuit, run across rafters to a spring strain relief at the point of drop. The cable drops approx. 20 ft (to a point 10 ft off the floor) where it terminates in a socket (visually, thus far, this is pretty much an extension cord). My machine's power cord (approx. 10 ft long but approx. 6 ft is coiled for flexiblility in future moves) connects to this receptacle. Continuing down, the cord goes into a "chinese finger" type strain relief attached to hard conduit (the strain relief/end of the conduit is approx. 7 ft off the floor). From there the cable goes though the conduit to a lockable disconnect on my control panel.

Thanks for any direction you can give me. I'm all for safety but the safety dept. wants the plug and socket removed; I'm countering that this intrinsically more safe since an electrician could quickly and easily isolate power completely by disconnecting the plug and not rely solely on the lockable disconnect and lockout procedures.

 

[xnuke]

Try NFPA 79 14.4.5. (Make sure you cross-reference with Chapter 5 and 17.2.5.)




xnuke

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MakeItSpin]

This is a great question. Here's how I see your problem, ignoring the fact you're using a lighting circuit. That fact might not be a violation of NEC, I'm not sure, but if your machine faults you take the chance of losing lighting in the area.

The main issue with the NEC that jumps out at me, is that you "do" have an extension cord which by your admission is being used other than for frequent interchange, but rather as a substitute for fixed wiring methods (400.7 & 400.8). Lose the male plug at the receptacle and maybe it becomes a pendant or a vertical riser. There's a couple of ways to do this that might work for you.

You can run a cord drop in an industrial environment if it's fed from a busway (see 368.8), a pretty unlikely scenario for 120v. This also allows you to attach the cable to the building surface until you get to your drop point, so the line end of the cable doesn't have to be directly above the drop.

The more likely method would be to set a box above the drop point, run the circuit to the box in conduit, then use a kellums grip fixed to the box and call it a pendant, (210.50(A)). I've done 3 phase drops this way, used twist-lock caps at the bottom of the cable and not had a problem with AHJ, although your mileage may vary.

Good luck.

 

[jbartos]

Suggestion: Visit

http://www.hubbell-wiring.com/library/SectionT-part1.pdf

for:
1.
Kellems Grips for strain relief help make electrical
systems safer, and save money by minimizing
downtime from costly electrical failure due to cable
pull-out. Kellems Grips also aid in compliance with
the National Electric Code’s terminal tension
protection requirements (see NEC Section 400-10.).

The electrical installation up to a junction box where the Kellem Grip will be applied (either directly attached to the junction box or separately suspended, depending on the application) shall be a permanent type complying with NFPA 70-2002. This needs more information to determine a permitted type of installation for the posted run in the original posting.

 

[afterhrs]

Hammey,
If your machine is powered 230 VAC or 480 VAC, I would
install a 2KVA transformer on the side of the control cabinet and step the voltage down to 110 VAC.
This would eliminate the SJO from the overhead and the additional 110 VAC will always be available, with out regard to location of the machine.
Just make sure you have the additional amperage to supply the transformer.

Regards,
Afterhrs