DLO cable question

[Purr24]

Has anyone used DLO cable to wire a transformer? I have a 225 KVA transformer 208v 3 phase 600amp secondary and it will very difficult to bend these cables to terminate in the transformer, drawings want parallel 500’s X4 per set. I know they are oversized but that’s engineers for you! What chart should I size these DLO cables? these would be much easier to bend and terminate

 

[Shaneyj]

I’ve used DLO and Type P quite extensively on non NEC installs (oilfield). For ampacity I’d use IEEE 1580 and DLO ampacity charts. If I had to drop temp due to termination point I’d interpolate.
But all that is useless if you have an NEC install. I think you’d have to find a cable that’s marked with a chapter 3 approved type.
If it has a RHH/RHW-2 marking then you’d use it at the values found in that column.


Sent from my iPhone using Tapatalk

 

[electrofelon]

Yes many people use DLO for the increased flexibility. Keep in mind the sizes are funky above 4/0 and you will need to round down or possibly extrapolate. The fine stranding may require special terminations. Finally make sure it's type RHH/RHW-2 for NEC use, but most is.

 

[ron]

Yes many people use DLO for the increased flexibility. Keep in mind the sizes are funky above 4/0 and you will need to round down or possibly extrapolate. The fine stranding may require special terminations. Finally make sure it's type RHH/RHW-2 for NEC use, but most is.

Round down to a recognized size in 310.16, do not interpolate.

 

[electrofelon]

Round down to a recognized size in 310.16, do not interpolate.

Linear interpolation would provide a ampacity more conservative than actual. South wire provides interpolated values ( but I didn't check what the interpolation method was). If you don't know your inspector and don't want to risk getting called in it , then don't or ask first. My inspector would be fine with it.

 

[don_resqcapt19]

Round down to a recognized size in 310.16, do not interpolate.

Because of the non-standard sizes and the fact that most manufacturer's published ampacity tables for DLO/RHW are based on 90°C and free air, the following was added to 310.15(A) in the 2020 code.

...Under engineering supervision, ampacities of sizes not shown in ampacity tables for conductors meeting the general wiring requirements shall be permitted to be determined by interpolation of the adjacent conductors based on the conductor’s area. ...

Of course the key is that it requires "engineering supervision", whatever that may be.

 

[busman]

I would use Type W cable instead. Very durable and comes in standard sizes so you can get crimp pads for Finely Stranded.

Mark

 

[electrofelon]

Because of the non-standard sizes and the fact that most manufacturer's published ampacity tables for DLO/RHW are based on 90°C and free air, the following was added to 310.15(A) in the 2020 code.

Of course the key is that it requires "engineering supervision", whatever that may be.

My engineer friend came over and distracted and supervised my cat while I interpolated the value

 

[zbang]

(Omitting the already-stated reasons)
Many people manage to connect transformers with large THHN/THWN, is there anything different about this install?
THHN/THWN is likely to be less expensive than any fine-strand cable and usually easier to get.
Cable benders exist for a reason. (https://rack-a-tiers.ca/product/bend-all/ or https://www.kleintools.com/catalog/cable-benders/cable-bender-14-inch, there are others)

(Starting to think that there should be a DLO FAQ....)

but that’s engineers for you!

Occasionally they have a good reason, have you asked or just assuming they're using a larger size to make your life difficult?

 

[don_resqcapt19]

I would use Type W cable instead. Very durable and comes in standard sizes so you can get crimp pads for Finely Stranded.

Mark

The only issue with that is the rule in 400.12(1), as I see the installation in this thread as being the fixed wiring for the structure.

 

[Todd0x1]

I would use Type W cable instead. Very durable and comes in standard sizes so you can get crimp pads for Finely Stranded.

Mark

Type W is not a chapter 3 wiring type. Its a Article 400 cord product.

 

[Todd0x1]

Check out Cobra X Flex. Comes in 500, is a regular PVC jacket and listed as THW. It's also about 1/4" smaller diameter than 535 DLO.

X-FLEX® UL 1232, UL 1283, UL 1284 | Cobra Wire & Cable, part of the Genuine Cable Group

 

[busman]

Type W is not a chapter 3 wiring type. Its a Article 400 cord product.

I did not have enough information to know whether a Cord would be permitted. I was just saying that if it was appropriate for a Ch. 4 method, then I would use Type W over DLO.

Mark

 

[Tim Davies]

I always use the manufactures charts, see attached for info. Be careful when using DLO in cable trays, as the smaller dia. DLO will require a 9" rung spacing. hope this helps.