LB TOO SMALL ?

[hawkeye23]

I came across a installation recently that I know has to be a violation but can't get to read the inside of the lb. There is a 2" Galv. conduit with 3 4/0 thwn and a #4 egc wires inside going to a crouse hinds short LB through a cinder block wall to another LB down into a disconnect. There is way to much bending in these lb's to not cause damage to the wires. Should I look for the cu in or number of conductors ? I also recall a 6x rule , would I use that ? thanks to anyone for the help.

 

[infinity]

The 6X rule applies to the LB. There is an exception for conduit bodies marked by the manufacturer with a specific combination of conductors on the conduit body. If your installation doesn't comply with the 6X or the manufacturers listing then it's not compliant.

 

[don_resqcapt19]

As far as I know none of the conduit bodies are marked for use with more than three conductors, and there is nothing in the code that supports the idea that you can do a calculation for other combinations of conductors. There are manufacturers that have tables showing other combintations of conductors, but the code rule specifically requires the marking to be on the conduit body itself.

 

[infinity]

As far as I know none of the conduit bodies are marked for use with more than three conductors, and there is nothing in the code that supports the idea that you can do a calculation for other combinations of conductors. There are manufacturers that have tables showing other combintations of conductors, but the code rule specifically requires the marking to be on the conduit body itself.

I agree. It would nice to say if the conduit body is listed by the manufacturer for 3-#3/0's that I could safely install 4-#2's but the NEC wording does not support that.

 

[kevin]

As far as I know none of the conduit bodies are marked for use with more than three conductors, and there is nothing in the code that supports the idea that you can do a calculation for other combinations of conductors. There are manufacturers that have tables showing other combintations of conductors, but the code rule specifically requires the marking to be on the conduit body itself.

http://www.ecmag.com/section/codes-standards/box-fill-calculations-part-xi


The above link discusses the issue raised by the OP in a very thorough manner. The author maintains that if either a conduit body or a manufacturer's installation instruction sheet lists the maximum size and number of conductors allowed, the maximum size can never be exceeded, whereas the number of conductors can be exceeded as long as the total volume of (smaller) conductors does not exceed the total volume of the (three) original "marked" conductors.

 

[don_resqcapt19]

http://www.ecmag.com/section/codes-standards/box-fill-calculations-part-xi


The above link discusses the issue raised by the OP in a very thorough manner. The author maintains that if either a conduit body or a manufacturer's installation instruction sheet lists the maximum size and number of conductors allowed, the maximum size can never be exceeded, whereas the number of conductors can be exceeded as long as the total volume of (smaller) conductors does not exceed the total volume of the (three) original "marked" conductors.

There is nothing in the code that supports the idea of using a volume calculation to permit the use of conductors #4 and larger in a conduit body. The code says that if the conduit body does not meet the 6x or 8x rule for 90? or straight pulls, then the maximum number and size of the conductors permitted in that conduit body must be marked on the conduit body. No where in the code does it let us do a calculation for other combinations of conductors. The volume of conductors does not even enter into the sizing of a pull box or conduit body where the conductors are #4 and larger.