welding cable ampacities

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mgb

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In preparation of a possible temporary emergency power installation using a portable generator, from what I've found in NEC tables 4/0 welding cable with insulation rated at 90 C has an ampacity of 405 amps. The cable would be layed on the floor/ground. Am I correct?
 
Re: welding cable ampacities

No, 360 for free air. You have to use table 310.17 for 4/0. You can use the 90 degree table for de-rating purposes, but it cannot be higher than the 75 degree column, which is 360-amps. The cable insulation has to be dual listed for the purpose like DLO and RHH/RHW.

Edited for free-air table.

[ June 02, 2004, 09:50 AM: Message edited by: dereckbc ]
 
Re: welding cable ampacities

Even though they're single conductors and aren't in a conduit? Wouldn't they be considered "free air"?
 
Re: welding cable ampacities

See Article 630, Part IV. Welding Cable

Welding cables are allowed by the NEC for use as described.

Did you find that there was an insulation on the cable that was in Table 310.13?
 
Re: welding cable ampacities

Originally posted by mgb:
Even though they're single conductors and aren't in a conduit? Wouldn't they be considered "free air"?
Click to expand...
They are considered free-air, that is why you can use table 310.17. You can use the 90 degree column for de-rating purposes (temperature), but it cannot be higher than the 75 degree column because or the 75 degree limitations of the equipment you are connecting it to.
 
Re: welding cable ampacities

My apologies, I was looking at Table 310-16. :eek: Thank you very much for your help!
 
Re: welding cable ampacities

No apologies needed. However 405-amps comes from table 310.17 90 degree column @ 4/0.

Curious, your login name is MGB, is that your intials, or are you in the telecom sector?

[ June 02, 2004, 10:17 AM: Message edited by: dereckbc ]
 
Re: welding cable ampacities

mgb,
Welding cable is not permitted to be used for electric power circuits. Its only permitted use is for cables on the secondary side of electric welding equipment. The type "W" cable in Article 400 is not welding cable. It is flexible power cable and is listed for use in electric power circuits.
Don
 
Re: welding cable ampacities

Even if it's temporary? If not I'll make sure they purchase the correct wire. Thanks!
 
Re: welding cable ampacities

Even temporary. That is what I tried to point out earlier that it had to be dual listed. Look for RHH/RHW. Use the same stuff that is on your battery plants.
 
Re: welding cable ampacities

mgb:

See 527.4 and if you have the handbook, read the commentary. The exception MAY apply allowing you to use the welding cable in an emergency. However, if you have time to purchace a cable, why not purchace one of the types of cables allowed and listed in table 400.4? I would assume an "emergency" would only apply when you have to use what you currently have on hand (no other possible way to get power to a piece of critical equipment, for example).

The handbook commentary states "all temporary wiring methods must be approved by the authority having jurisdiction."

STeve
 
Re: welding cable ampacities

Steve,
I don't see how that exception would permit the use of welding cable. The exception only permits the use of single conductors as opposed to the cable or cord assemblies required in 527.4(B). It also does not modify 527.2(A).
Don
 
Re: welding cable ampacities

Originally posted by don_resqcapt19:
Steve,
I don't see how that exception would permit the use of welding cable. The exception only permits the use of single conductors as opposed to the cable or cord assemblies required in 527.4(B). It also does not modify 527.2(A).
Don
Click to expand...
Actually they are single conductors, I shouldn't have called them cables, sorry. But I'll probably go with RHH/RHW like dereckbc suggested. Thanks again, appreciate all the informative feedback!
 
Re: welding cable ampacities

So you are putting the RHH/RHW in a raceway, or its part of a cable assembly?

According to the handbook, Cable assemblies, multiconductor cords, and single conductor cords are permitted for temporary feeders. Cords have to be identified for hard or extra hard usage. Open or individual conductors can be used if part of a cable assembly or used in a raceway system. Open or individual conductor feeders are permitted only during emergencies or tests.

Steve
 
Re: welding cable ampacities

This would only be used for an emergency situation. Conductors would be laying on the floor/ground.
 
Re: welding cable ampacities

mgb:

I hate to beat a dead horse, but it seems like you are going to use the exception to 527.4(B). That seems more restrictive than 527.4(B). Why not buy a cable assembly that doesn't require you to use the exception??

Steve
 
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