DLO/Welding Cable Ampacity

M

MoorePowerSystems

Member
Location
Albany, NY
Occupation
Electrical/Instrumentation Contractor
I've always been told DLO/Welding cable/very fine stranded copper conductors have a higher ampacity than their courser stranded counterparts, but I cant find anything to support that. Customer wants 400amp fuses replaced with a 500 amp fuses, load side is parallel 4/0 super fine stranded conductors that go to a cable tray type cable. (I say cable tray type because its in a cable in a tray, but not tray rated, its part of a skid). According to 310.16 my 4/0 wire is only good for 230 amps. Is there anything I'm missing?
 
DLO (alone) is not a recognized NEC wiring method. The cable would need to be dual rated such as DLO,RHW and would have the ampacity of the NEC accepted conductor ie: RHW

That said, almost if not all NEC recognized conductors sized 500 kcmil would have an ampacity greater than 500m when paralleled.
 
Typically the manufacturer's data sheet will show an ampacity based on free air and 90°C for those conductors. Not too often you can make an installation like that.
 
jim dungar said:
Aah, good old Marketing versus real world application.
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For the things DLO is made for it works pretty well with those ratings.

The insulation is able to take a higher temperature so is not damaged by the higher temperature.

You still get the same voltage drop as a lesser rated insulation.

Two 4/0 copper in parallel is 460 Amps of ampacity. If the load calculation is 460 Amps or less no reason you cannot go to the next size standard Cb/fuse size which just happens to be 500 Amps.
 
petersonra said:
For the things DLO is made for it works pretty well with those ratings.

The insulation is able to take a higher temperature so is not damaged by the higher temperature.

You still get the same voltage drop as a lesser rated insulation.

Two 4/0 copper in parallel is 460 Amps of ampacity. If the load calculation is 460 Amps or less no reason you cannot go to the next size standard Cb/fuse size which just happens to be 500 Amps.
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Not really ... you get those same ampacities when you use 310.17 and the 90°C column. If you look at the typical data for 4/0 DLO you would find almost always find it rated at 405 amps.
 
Southwire gets into it in their DLO cut sheet.

It seems you would be correct in the notion that DLO has a slightly higher rating, but it is a negligible amount IMO (more like 1-5 amps difference but definitely not 100.
 
I guess it depends. I use a lot of Type W (very similar) in temporary power applications. If you are talking single conductors at 90C, 4/0 is good for 405A. Even 3 CCC's is 316A.

Mark
 
The Conclusion I've come to, is the insulation on DLO can handle more heat than your everyday THHN, but that doesnt help you when sizing wire with the NEC. My terminals on my breaker are 75 Deg C, so this higher temperature capability doesnt really help me. Thank you everyone
 
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