PM Question received

[rbalex]

I received the following PM

hi

can you please help me for this question??

according to NEC code the max length of Liquid tight flexible metal conduit(LFMC) in CLASS 1 DIV. 2 is 6ft

But what is the practical problem if I connect 8ft instead of 6 ft??? is this will make explosion in CLASS 1 DIV. 2 location ???(note: I know this is not acceptable for NEC code but I need to understand )


thank you.

The practical problem is you have increased the maximum allowable length 33%. In truth, it has more to do with the limits of the UL test standards; they just don't test lengths longer than 6'.

Your statement, "according to NEC code the max length of Liquid tight flexible metal conduit(LFMC) in CLASS 1 DIV. 2 is 6ft ", isn't entirely correct either. Six feet is the maximum for LFMC with an external bonding jumper. See Section 501.30's cross reference: 250.102, especially 250.102(E).

I honestly don't know the full history, but at one time CMP14 was absolutely paranoid about grounding/bonding in all classified locations. I agree with the bonding level required for Class I, Division 1; Class II, Group E and disallowing locknut and locknut/bushing bonding. My personal opinion is the requirements are a bit overkill otherwise - but they are the requirements.

 

[stev11]

I received the following PMThe practical problem is you have increased the maximum allowable length 33%. In truth, it has more to do with the limits of the UL test standards; they just don't test lengths longer than 6'.

Your statement, "according to NEC code the max length of Liquid tight flexible metal conduit(LFMC) in CLASS 1 DIV. 2 is 6ft ", isn't entirely correct either. Six feet is the maximum for LFMC with an external bonding jumper. See Section 501.30's cross reference: 250.102, especially 250.102(E).

I honestly don't know the full history, but at one time CMP14 was absolutely paranoid about grounding/bonding in all classified locations. I agree with the bonding level required for Class I, Division 1; Class II, Group E and disallowing locknut and locknut/bushing bonding. My personal opinion is the requirements are a bit overkill otherwise - but they are the requirements.

thank you.