properly sizing LB conduit bodies

[wbwald]

A Contractor has an LB installed on a 4" conduit with (4)-600Kcmil (1)-#2(G).
The opening for the LB is only 14".

Per the 2017 NEC Article 314.28 (3) - I think I understand that unless the LB is marked with the maximum number of conductors and the maximum size then this LB is not of the proper size?
In my history i have never seen an LB that was marked for more then a maximum of 3 conductors?

 

[electrofelon]

A Contractor has an LB installed on a 4" conduit with (4)-600Kcmil (1)-#2(G).
The opening for the LB is only 14".

Per the 2017 NEC Article 314.28 (3) - I think I understand that unless the LB is marked with the maximum number of conductors and the maximum size then this LB is not of the proper size?
In my history i have never seen an LB that was marked for more then a maximum of 3 conductors?

There is a letter out there from someone at Carlon stating that you can calculate other wire combinations from the marked number. But yes, the LB "fill" is always less than the maximum raceway fill as far as i know. Solutions are to use reducers and a larger sized conduit body, or use a mogul.

 

[GoldDigger]

A Contractor has an LB installed on a 4" conduit with (4)-600Kcmil (1)-#2(G).
The opening for the LB is only 14".

Per the 2017 NEC Article 314.28 (3) - I think I understand that unless the LB is marked with the maximum number of conductors and the maximum size then this LB is not of the proper size?
In my history i have never seen an LB that was marked for more then a maximum of 3 conductors?

I believe that the proposed 2020 allows you to extend the manufacturer's markings of, for example, 3 of a large size, with a calculated equivalent of 4 or more of a smaller size.

 

[jumper]

I believe that the proposed 2020 allows you to extend the manufacturer's markings of, for example, 3 of a large size, with a calculated equivalent of 4 or more of a smaller size.

2017

View attachment 18537

 

[don_resqcapt19]

This is probably one of the most violated code sections where dealing with the installation of conductors 4 AWG and larger. The rules in 314.28 have always applied to conduit bodies as well as pull boxes. The provision for the use of boxes or conduit bodies with smaller dimensions, provided that the box or conduit body have been marked with the maximum size and number of conductors has been in the code since at least 1978 (oldest book I have).

There have been published methods of calculations for other wire size combinations and all of the conduit body manufacturers have published tables showing other size combinations. However, prior to the 2017 code there was no provision to do a field calculation of use the manufacturer's table. The 2017 has a specific provision to do a field calculation.

A reasonable inspector would accept the combinations listed in the manufacturer's table.