ECN Forum Forums Code Related Discussion NEC & other Code issues Legality of Shore Power Cable

Are shore power cables legal to use for temporary power connections, like to connect portable generators to a switchboard while the main building generators are undergoing mainenance/upgrade? NEC seems silent on the matter- would it rely completely on the UL listing? They're perfectly suited for this, though- flexible, tough, watertight, weathertight, etc.

By the same token, could other UL listed cable (like welding cable) be used in permanant installations? I've seen it done and been told it was legal, but never pressed the issue.

Steve,
You can't use welding cable unless it has a dual listing as building type wire. Some welding cable is also listed as RHH and you can use that. There is also type W power cable that is very much like welding cable and it can be used per the rules in Article 400.

Speaking of "temporary" installations, what is the time period that temporary is good for? Specifically, when I worked on a movie set, welding cables were used to hook up portable distribution centers to installed building wiring. These cables were left installed for about 9 months. The facility was not a theater but a former manufacturing / warehouse structure.

Larry, the NEC defines temporary as 90 days or less.

Don, I agree with your answer, but not the reasoning.
When an issue comes up, I check the UL "White Book" for a little more clarification as to what the listing means.

In the case of welding cable, UL states that it is only rated for 100 volts, unless marked differently.

Then there is the issue of connectors. Most lugs and connectors are only evaluated for use with "ordinary" stranded wire. Very finely stranded wire ... welding cable, locomotive cable, whatever ... require connectors that are designed for use with them. In 'practical' terms, the approved connectors will have two set screws, bouble length barrels, etc.

[This message has been edited by renosteinke (edited 02-26-2007).]

One other thing about welding cable is it is destroyed by U/V. I found this out on my boat

John I do not understand.

Welding cable is not (generally) listed as building wire.

If it is not listed in article 400 we can not use it.

The portable power cables we can use are listed in 400 and I think it goes without saying that you must use the proper terminals.

As far as I know the proper terminals are compression terminals, I don't think any lug that the set screw contacts the fine strands is listed for that use.

Type W cable is listed in article 400 as going up to 1000kcmil, which is the size shore power cable I'm talking about, not just some #10 extention cord for a portable generator. 400.7 (B) which requires plugs does give an exception, "as permitted in 368.56" which allows direct bus connections for hard-usage.

If welding cable is cross-rated as class W, then 400.7 does appear to permit the uses I've seen it in, which is good news for me!

I believe the shore power cable I have availible is THOF/MIL-915. I've found a couple references to UL 44, RHH & RHW-2 in the catalog entries for these cables, but I don't know if those are universal throughout the industry or just happen to be what those particular manufacturers have done.

Follow-up question: if "Shore Power Cable" is RHW-2, is it exempt from cableway requirements for temporary installations? I don't see RHW-2 listed in Article 400. Where is RHH/RHW discussed? (Curse my non-searchable paper copy of NEC!)

John,
Most of the welding cable used around here is rated for 600 volts, but the UL listing says that the cable is only listed for use on the secondary side of electric welding machines. That being said I think that this is another bogus issue. I looked into using some Type "W" power cable for a temporaty installation a few years ago and found that in the case of one manufacturer the only difference between their Type W power cable and their welding cable, other than the listing and price, was that the welding cable had an insulation that was 25% thicker than the power cable. The stranding, strand count, and insulation type was identical. After finding that information, I went ahead and used the welding cable. Note this may not be true for all brands of cable, but it was true for the brand that I used.

Don

Larry,
I think that would not be an Article 590 installation. It would be covered by 530. In a quick look, I did not see a time limit for the portable wiring on a movie set. However, listed cables and cords are required and welding cable would not be permitted.
Don

[This message has been edited by resqcapt19 (edited 02-27-2007).]

Steve,
RHW is a building wire. See Table 310.13.
Don