NEC 502 - using non-metallic flexible conduit.

[Jonusmc]

Hello,
Our company is building our first Class 2 Division 1 and 2, Group G machine. And in reviewing NEC 502, i have discovered that Liquidtight flexible nonmetallic conduit with listed fittings can be used. What we don't know and want to verify is "do we have to run an outside ground conductor to complete/continue the grounding". This is a spec one of our senior engineers believes to be the case. What we would like to have is verification yes or no - and where that spec might be written [as i have yet to find anything relating to it yet.] I have found fittings that seem to be rated for our machine, Crouse-Hinds - and they do not have an external ground lug.
thanks for any views and suggestions.
and thanks to MHF for all the help.
JLR

 

[Andy Delle]

Hello,
Our company is building our first Class 2 Division 1 and 2, Group G machine. And in reviewing NEC 502, i have discovered that Liquidtight flexible nonmetallic conduit with listed fittings can be used. What we don't know and want to verify is "do we have to run an outside ground conductor to complete/continue the grounding". This is a spec one of our senior engineers believes to be the case. What we would like to have is verification yes or no - and where that spec might be written [as i have yet to find anything relating to it yet.] I have found fittings that seem to be rated for our machine, Crouse-Hinds - and they do not have an external ground lug.
thanks for any views and suggestions.
and thanks to MHF for all the help.
JLR

First, the NEC does not generally deal with manufactured products. That's UL, ETL, or other listed test lab. If the machine is all metal construction and the conduits are just going between boxes or components bolted to the metal frame, then a ground wire in the conduit may be optional as the frame is a solid ground. If this conduit is to connect to an external device, then yes, a separate ground wire is needed.

 

[rbalex]

Hello,
Our company is building our first Class 2 Division 1 and 2, Group G machine. And in reviewing NEC 502, i have discovered that Liquidtight flexible nonmetallic conduit with listed fittings can be used. What we don't know and want to verify is "do we have to run an outside ground conductor to complete/continue the grounding". This is a spec one of our senior engineers believes to be the case. What we would like to have is verification yes or no - and where that spec might be written [as i have yet to find anything relating to it yet.] I have found fittings that seem to be rated for our machine, Crouse-Hinds - and they do not have an external ground lug.
thanks for any views and suggestions.
and thanks to MHF for all the help.
JLR

This is actually a bonding rather than grounding issue. [Section 502.30(A)] See Sections 250.100 and 356.60. There are a ton of cross references and I won’t connect all the dots for you. Ultimately though, your senior engineer is correct and qualified NRTLs will enforce these requirements against the appropriate product standards.