Ampacity adjustment factors

[wattup]

I have a customer specifying the use of 535MCM loco cable. The only info I can get from the manufacturer on the load rating of the cable is that it is good for 730 amps in free air.
I will have 4-6 of these in each conduit. My question is how do I derate? I know I have to derate table 310-16 ampacities which already covers (3) current carrying conductors by 80% to cover more than three conductors in the conduit. Since I don't have a conduit rating for the 535 Loco cable is there any additional derating that has to be considered other than normal for temperature compensation?

 

[charlie b]

Re: Ampacity adjustment factors

This is a tough situation. You would do well to derate by 80% for more than three current carrying conductors. But strictly speaking that rule does not apply. You don?t get to Table 310.15(B)(2)(a) without first starting at Article 310.15(B). That is where it tells us to start with the ampacities in Table 310.16, and adjust in accordance with the paragraphs that follow. In other words, nothing tells you to start with a manufacturer?s rating for a cable that is not in Table 310.16, and then derate per Table 310.15(B)(2)(a).

I think that your best option is to bring an engineer into the project. Ampacities can be determined ?under engineering supervision.? If your customer insists on using that particular cable, then they are going to have to pay to have it evaluated.

 

[derf48]

Re: Ampacity adjustment factors

I would also check with your AHJ, even if that is an insurance company. Since it is not a recognized conductor for installation in a chapter 3 wiring method, the manufacurer might not have any info on its installation in a raceway. You probably will need special permission as well as engineering supervision.

Fred Bender

 

[don_resqcapt19]

Re: Ampacity adjustment factors

DLO cable is available with a dual listing as DLO/RHH. As long as it has the RHH rating it is a Chapter 3 wiring method and code compliant. Just use the ampacities for 500kcmil RHH and the appropriate correction and adjustment factors. In most cases the manufactures rated ampacity is equal to the next smaller standard wire size at 90 degrees C. I see in this case they have increased it a bit, maybe because there is a bit more copper. When I have used DLO/RHH the manufacturers ampacities have matched the next smaller code size, but they always specify the 90?C rating, and you cannot use that for most code applications.
What is the cable being used for?
In my case we have used it for large DC motors where the armature votage was 700VDC. You can't use standard building wire over 600 volts. DLO is rated 1000 or 2000 volts. The 1000 volt rating is harder to find, so we used the 2000 volt rating. It is a great product for making up the terminations in the motor junction boxes and drive cabinets because of its flexibility. Note that you may have some trouble finding wire connectors to fit because of the nonstandard sizing. Compression connectors are available but will most likely be "special order". You cannot use standard mechanical wire connectors with DLO.
Don