DLO (Diesel Locomotive Cable) Ampacity/Derating Question

BEI_PM

Member
Location
N. Calif
Can anyone tell me if it is true that more than single DLO cable in a conduit starts the derating process per 2011 NEC 310.15(B)(3)(a)?
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
The derating is the same as for any other conductors, but if it is only marked DLO, you can't use it for an NEC application. To be used in an NEC application it has to be marked with one of the wire types found in Table 310.104(A) or Table 310.13(A) in older codes.

You can find it with the required markings...usually is it DLO/RHH or something like that.

Note that you cannot normally use the ampacities listed by the manufacturer for an NEC application ...they typically list the free air 90°C ampacities.

The DLO does not come in the typical wire sizes....I normally use the Table 310.15(B)(16) ampacities for the next smaller size conductor. For example, for the 535.3kcmil DLO cable I use the 500kcmil ampacity from the table.
 

ron

Senior Member
The derating is the same as for any other conductors, but if it is only marked DLO, you can't use it for an NEC application. To be used in an NEC application it has to be marked with one of the wire types found in Table 310.104(A) or Table 310.13(A) in older codes.

You can find it with the required markings...usually is it DLO/RHH or something like that.

Note that you cannot normally use the ampacities listed by the manufacturer for an NEC application ...they typically list the free air 90°C ampacities.

The DLO does not come in the typical wire sizes....I normally use the Table 310.15(B)(16) ampacities for the next smaller size conductor. For example, for the 535.3kcmil DLO cable I use the 500kcmil ampacity from the table.
Same
 

topgone

Senior Member
Can anyone tell me if it is true that more than single DLO cable in a conduit starts the derating process per 2011 NEC 310.15(B)(3)(a)?

Nope. I believe NEC doesn't address DLO cables as we don't see it in the NEC table of conductors.
You need to ask the AHJ in your area whether you are allowed to derate if you have more than 3 current-carrying conductor in your tray/conduit as with NEC rules.
 

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Fulthrotl

~Autocorrect is My Worst Enema.~

yup. i've done cable bus, and there was no derating,
but it was racked and ran not touching other stuff in the tray,
so maybe it's allowed to run with free air ampacity. there's
phenolic blocks, and it was in a 2' wide tray, 4 layers, 8 across, iirc.

i think it was 929 MCM or some odd size... a changeover at fox news,
started friday night before superbowl sunday.... we worked 30 hours
nonstop... what a perfect time to change out the transformer that
was going to power satellite feed for the superbowl, 'eh?

one more example of DWP = department of worthless planning.
 

BEI_PM

Member
Location
N. Calif
It's for a PV Line Side Tap Installation

It's for a PV Line Side Tap Installation

Thank you all who have responded to my inquiry.

It is true about a "True" DLO cable isn't listed in NEC for applications. This particular situation is actually RHW/RHW-2 and is listed at 90 degrees C. I am trying to use 444 DLO. The design is pretty much 10 gallons of wire to fit in a 5 gallon bucket. I'm trying to help him out of this mess he designed and all I am getting is flak about derating, and more than a SINGLE conductor in a conduit and he's saying the ampacity drops to 400 amps per conductor and blah, blah, blah. He designed it originally using 1,000 KCMIL AL X 5 runs for a line side tap-in a space 34" wide and 18" tall with minimum buss access to tap it. Imagine a total of 15-1,000 KCMIL AL conductors in that space?

He tried the 75 degree C terminations angle until I showed him that the high press connectors I am using are listed at 90 degrees C and then came back with so much nonsense, it's driving me nuts.

I was trying to help out by "re-designing" the mess that was created and nothing but push back..... :rant:
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
yup. i've done cable bus, and there was no derating,
but it was racked and ran not touching other stuff in the tray,
so maybe it's allowed to run with free air ampacity. there's
phenolic blocks, and it was in a 2' wide tray, 4 layers, 8 across, iirc.

i think it was 929 MCM or some odd size... a changeover at fox news,
started friday night before superbowl sunday.... we worked 30 hours
nonstop... what a perfect time to change out the transformer that
was going to power satellite feed for the superbowl, 'eh?

one more example of DWP = department of worthless planning.

Cable bus is a special application and one of the few in the NEC where you can use the free air ampacities, but even with cable bus, it is a rare application where you can use the 90°C ampacities.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
...
He tried the 75 degree C terminations angle until I showed him that the high press connectors I am using are listed at 90 degrees C and then came back with so much nonsense, it's driving me nuts. ...
It is not just the connectors on the wire, but it is also the rating of what the connectors are landed on. There are some applications where you can use the 90°C rating, but they are rare.
 

Ingenieur

Senior Member
Location
Earth
At least they give you 75°C ampacities and both free air and conduit. Most only give you 90°C in free air.

Not sure if you can use the manufacturer's ampacities for the non-standard sizes. I would check with the AHJ before using those ampacities.

It may be prudent to seek pre-approval by the lahj but I personally don't see an issue as long as:
adjusted for actual cross sectional area per the NEC
insulation is certified to ICEA/UL/CSA specification

a couple of caveats
insulation is not as abrasion resistant re: pulling in conduit
more expensive

I usually see this stuff used in portable power centers where flexibility is required and large quantities are not required

here's another data sheet
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet429
UL listed, etc
can be treated as RHH-RHW
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
One of the problems I've seen with it is what was talked about here, the fact that not all DLO cable bears the right listings. Cable mfrs make straight DLO, no RHH listing, and it sells for less, especially when surplus houses get hold of it and word-of-mouth on a great price spreads. Contractors who don't realize the difference use it, then get tagged on a job. You just need to be careful, as always, when a deal looks too good to be true.

The other problem I see is the lugs issue. That's been getting better not only because of education through forums like this and word of mouth, but because there are more lug and terminal block mfrs addressing the issue by providing listed products. But again, careful attention to details is key.
 

Carultch

Senior Member
Location
Massachusetts
One of the problems I've seen with it is what was talked about here, the fact that not all DLO cable bears the right listings. Cable mfrs make straight DLO, no RHH listing, and it sells for less, especially when surplus houses get hold of it and word-of-mouth on a great price spreads. Contractors who don't realize the difference use it, then get tagged on a job. You just need to be careful, as always, when a deal looks too good to be true.

The other problem I see is the lugs issue. That's been getting better not only because of education through forums like this and word of mouth, but because there are more lug and terminal block mfrs addressing the issue by providing listed products. But again, careful attention to details is key.

Lugs are another issue, not only because of the termination ampacity, but also because of the fine stranding. DLO wire usually has fine strands, and most standard mechanical lugs are only rated for class B/class C stranding.
 

dkidd

Senior Member
Location
here
Occupation
PE
Note that you cannot normally use the ampacities listed by the manufacturer for an NEC application ...they typically list the free air 90°C ampacities.

I had a project where we had to increase the main feeder size by adding additional runs of 500 kcmil. The electrician showed everyone a cut sheet for cable showing the 90 degree free air ampacity, and told them that he could pull out the old 500 and pull in the magic wire without adding any raceways.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
It may be prudent to seek pre-approval by the lahj but I personally don't see an issue as long as:
adjusted for actual cross sectional area per the NEC
insulation is certified to ICEA/UL/CSA specification
The issue is that there is no provision in the NEC that lets you make that adjustment and the increase in capacity is not a linear function of the cross sectional area. As long as your AHJ is fine, you are good to go.
a couple of caveats
insulation is not as abrasion resistant re: pulling in conduit
more expensive
The jacket does have a lot of friction with the conduit if you are pulling it in conduit...make sure that you get 100% coverage of the wire pulling lube on the conductors so there are no high friction dry spots.
I usually see this stuff used in portable power centers where flexibility is required and large quantities are not required ...
I have used it for 1,500 hp DC motors for two reasons....there was very limited room in the DC drive to terminate the cables....they required a total of 16 cables, and more importantly the armature voltage was 750 volts. The DLO/RHH is available in 1,000 and 2,000 volt ratings, with the 2,000 being more common. My conduit runs were 150-250 long and it pulled with no issues.
 

Ingenieur

Senior Member
Location
Earth
The issue is that there is no provision in the NEC that lets you make that adjustment and the increase in capacity is not a linear function of the cross sectional area. As long as your AHJ is fine, you are good to go.

The jacket does have a lot of friction with the conduit if you are pulling it in conduit...make sure that you get 100% coverage of the wire pulling lube on the conductors so there are no high friction dry spots.

I have used it for 1,500 hp DC motors for two reasons....there was very limited room in the DC drive to terminate the cables....they required a total of 16 cables, and more importantly the armature voltage was 750 volts. The DLO/RHH is available in 1,000 and 2,000 volt ratings, with the 2,000 being more common. My conduit runs were 150-250 long and it pulled with no issues.

2011 310.15.(C) Engineering Supervision
that is how the manufacturer calculates the ampacity

not linear
but close to the sqrt (area ratio)

from data sheets:
1
The above ampacities are
based on single conductors in
free air, 30°C (86°F) ambient
air temperature, conductor
temperature as specified, per
Table 310-17 of the 1999 NEC
(adjusted for size on 262.6
MCM and larger.)


looking at the numbers they used 2011 table 310.15(B)(17) and rounded down
examples for 90C
DLO 262 455 A, table 250 455 A

DLO 444 615 A, table 400 615 A
DLO 929 985 A, table 900 980 A (revised from prior edition)
DLO 1111 1055 A, table 1000 1055 A
 
Last edited:

JoeStillman

Senior Member
Location
West Chester, PA
Doesn't it defeat the purpose to put DLO cable in a raceway? I've used the stuff in free air to facilitate a flexible connection, but always with a splice box to connect to THWN-2 in raceway.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Doesn't it defeat the purpose to put DLO cable in a raceway? I've used the stuff in free air to facilitate a flexible connection, but always with a splice box to connect to THWN-2 in raceway.
I have used it for large DC motors because the termination spaces at both the motor and the drive were cramped and because the motors had a 750 volt armature. This was in conduits and the runs were 150-200'. The motors required four 4" conduits with each conduit having four 535.3 kcmil DLO/RHH/RHW conductors.
 
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