nec 350

[carlito]

is it acceptable to use a liquid tight flexible conduit in lieu of bends/elbows in a rigid steel conduit run?

 

[carlito]

NEC 350

NEC 350

guys out there... i just needs some clarification for this query. thanks..

 

[infinity]

I don't think that you'll find a prohibition for what you've described in Article 350. But you may find some argument as to whether or not the transitions between LFMC and RMC are permitted.

 

[Volta]

Consider it from a grounding viewpoint too. The RMC is an EGC, so your LFMC size/length has to qualify as an EGC too.

 

[infinity]

Consider it from a grounding viewpoint too. The RMC is an EGC, so your LFMC size/length has to qualify as an EGC too.

Good point. For larger trade sizes of LFMC the raceway cannot be used as an EGC. What about a bonding jumper on the outside of the LFMC? They do make LFMC connectors with integral bonding lugs for this purpose.

 

[Cow]

I have to use bonding jumpers around flex all the time, rigid stubups to motors are one example. I've been using water pipe clamps though, anybody have a link to the connectors with the pre-installed lug on them?

 

[kwired]

The reason for using RMC, such as the mechanical strength of the RMC, may be totally voided by using LT flex for the elbows, or if using it in a hazardous location you may not be able to use it at all. Just something to think about.

 

[Bompa]

Based on a recent thread that I started, the responses to same, and the language (350.30(A) Exception 2) added to the liquidtite flex this year, I'd say you would have to add a separate support in the flex span which would probably negate any advantage that you may have seen in transitioning to flex and then back again. Also, those fittings are going to be WAY more expensive than even an elbow and a couple of nipples. Why would you not want to use a simple bend?

We always require wired bonding conductors for the entire length, so that wouldn't be an issue if that is your case also.

 

[carlito]

the conduit run referenced in this query is for instrumentation, so it is low 24dc volt for control cable/signal cables. the cable has aground wire incorporated and the conduit run is only approximately 20 meters at the instrument side, the rest a cable tray is used to run the cable to marshalling cabinet more than 300 meters away or so.

 

[carlito]

the reason why liquid tight flex conduit was used because position of the RSC pipe on the corner is not aligned. the flex conduit is 2 inch dia and no problem for bonding ground.

guys thanks for the response for this query.

 

[carlito]

re. query, the conduit run is about 7 meter high and conduits are fully supported with conduit hangers not threaded rod hangers.