Overhead Cable Sizing

[Sparky2791]

Do not do a lot with overhead. I have to feed a 60A sub panel using OH wiring. How is this size per the NEC. Tables, Charts, how to specify correctly so a contractor knows what to purchase. Seems so simple yet have not done it. I assume ACSR is the cable of choice. Overhead from an outdoor dist panel to an outdoor sub panel strung between poles about 75' away.
Thanks for replies!

 

[augie47]

ACSR is commonly used here for that application, however, AFIK, it is not an NEC acceptable wiring method buyt has been routine accepted in this area.

 

[Sparky2791]

ACSR is commonly used here for that application, however, AFIK, it is not an NEC acceptable wiring method buyt has been routine accepted in this area.

Is that specifically shown in the NEC for selecting cable sizes or is it based on 310.15(B)(17) and what type of insulation is used?

 

[augie47]

Is that specifically shown in the NEC for selecting cable sizes or is it based on 310.15(B)(17) and what type of insulation is used?

Most of the ACSR I've seen is XLPE conductors and neither ACSR or XLPE are liste4d in 310.104.
There well may be a NEC compliant cable on the market but the ACSR is widely used in these parts.

 

[don_resqcapt19]

Most of the ACSR I've seen is XLPE conductors and neither ACSR or XLPE are liste4d in 310.104.
There well may be a NEC compliant cable on the market but the ACSR is widely used in these parts.

I accept it using the following from Table 396.10(A)

Other factory-assembled, multiconductor control, signal, or power cables that are identified for the use.

The ampacities are really limited by the requirements in 110.14, so I apply the 75°C ampacities from 310.16.
I am not aware of a code compliant triplex or quadplex cable.

 

[Sparky2791]

The ampacities are really limited by the requirements in 110.14, so I apply the 75°C ampacities from 310.16.
I am not aware of a code compliant triplex or quadplex cable.

I see. I also found the #6 is the smallest they make and according to manufacturers info it is good for 105A. Ill look at the code sections you reference as well. Thanks for the replies!

 

[retirede]

I see. I also found the #6 is the smallest they make and according to manufacturers info it is good for 105A. Ill look at the code sections you reference as well. Thanks for the replies!

105A for #6 seems high. Are you sure that’s not a temp rating? Some XLPE insulation is rated for 105C.

 

[wwhitney]

105A for #6 seems high. Are you sure that’s not a temp rating? Some XLPE insulation is rated for 105C.

Table 310.17 indicates that the 90C rating of #6 copper in free air is 105A. So for an overhead application where the ACSR is spliced at each weatherhead with 90C connectors, you get to use the full 105A ampacity, subject to temperature correction.

Cheers, Wayne

 

[retirede]

Table 310.17 indicates that the 90C rating of #6 copper in free air is 105A. So for an overhead application where the ACSR is spliced at each weatherhead with 90C connectors, you get to use the full 105A ampacity, subject to temperature correction.

Cheers, Wayne

Thanks for the correction. I was shooting from the hip. The 105 being a not uncommon temp rating seem too much of a coincidence.

 

[Little Bill]

I accept it using the following from Table 396.10(A)

The ampacities are really limited by the requirements in 110.14, so I apply the 75°C ampacities from 310.16.
I am not aware of a code compliant triplex or quadplex cable.

With your new hobby, you could submit a rule to allow the overhead cable.