Metal and non-Metal Q

[FionaZuppa]

any issue with using metal liquid tight fitting with non-metal liquid tight conduit? my elctrical house didnt have non-metal for two fittings i needed, and i opted for all pvc conduit for some flex i needed. its all outside above ground.

 

[iwire]

Using the fittings in ways other than listed is one violation. 110.3(B) 350.6 356.6

Another possible issue, and potentially a real safety hazard, would be lack of grounding continuity.

 

[FionaZuppa]

Using the fittings in ways other than listed is one violation. 110.3(B) 350.6 356.6

Another possible issue, and potentially a real safety hazard, would be lack of grounding continuity.

i will check the listing for the fittings (LTB100) . both metal fittings are connected to metal boxes (two boxes bolted to each other), each box has #8 ground tied to it, and one box is bonded to an 8ft ground spike. the purpose of the conduit is to connect disconnect switch to the breaker/distribution box. the Cooper PDF on the fittings only says they are UL listed for various hazardous locations, and does make mention that the Nylon fittings are for use with NM conduit, but does not say the metal fittings cant be used on NM conduit nor does it say say for metal lined conduit only.

doesnt any PVC conduit create lack of grounding continuity if both ends are not tied via ground wire that comes through the conduit??

 

[kwired]

Another possible issue, and potentially a real safety hazard, would be lack of grounding continuity.

doesnt any PVC conduit create lack of grounding continuity if both ends are not tied via ground wire that comes through the conduit??

I think main concern here is that you don't use a metallic fitting on non metallic conduit and terminate into a non metallic box as well - that can leave the metallic fitting ungrounded - though one could use a grounding bushing I guess.

I think many liquidtight metal flex fittings are listed for use with non metallic liquidtight flex also, but you may want to confirm the ones you are using indeed are listed for it.

 

[kwired]

After a little looking there may not be many metal connectors that are also listed for use with non metallic flex.

I will say I have installed many on non metallic flex and have never had an inspector reject one yet, always been installed in a grounded metal box so grounding was never an issue.

 

[iwire]

I think many liquidtight metal flex fittings are listed for use with non metallic liquidtight flex also, but you may want to confirm the ones you are using indeed are listed for it.

After a little looking there may not be many metal connectors that are also listed for use with non metallic flex.

Can you post even one brand that is listed for both LFMC and LFNC?

I will say I have installed many on non metallic flex and have never had an inspector reject one yet, always been installed in a grounded metal box so grounding was never an issue.

.

I have never done this and consider it a violation.

 

[FionaZuppa]

the connectors i posted have the plastic insert to keep the wires off the metal, the the locking nut bites into the box thereby grounding the metal fitting to the box. from a purely electrical/physical standpoint i dont see any safety issue. from NEC verbiage standpoint i am not 100% this flys, etc.

does NEC call for metal conduit & fittings when the box itself is metal? my risers into my box are PVC sched-80.

 

[kwired]

Can you post even one brand that is listed for both LFMC and LFNC?

No, which is why I changed what I originally said.

I can't find one that is listed for both metallic and non metallic conduit, but Arlington's "Snap2IT" zinc connectors are a metal connector listed for non metallic flex, but not listed for metal flex - which may be a little surprising to some people.


I use LFNC often to connect irrigation well pump motors (usually in the 50-100HP range). I prefer non metallic flex because condensation buildup in the flex seems to rust out the metallic flex - and it is fairly unavoidable. I have also seen many broken non metallic connectors where used in this application. Broken conduit fitting in this application means a mouse nest will likely be in the motor, will usually also mean they will degrade winding insulation and motor will need rewound. Not listed - I understand, sometimes you have to do what works best, and hope inspectors will understand when you explain it to them. Most of the inspectors I deal with have done this before and understand the problem very well as they have gone through it themselves.