LFMC in Class I, Div 2 area?

[sirdle]

The installation of Sealtite (liquidtight flexible metal conduit) in a class I, Div 2 area is permitted "...where provision must be made for limited flexibility." [Article 501.4(B)(2)] What is meant by the word "must" in this context?

I often see installations where 3-feet sections of Sealtite, with external bonding jumpers, are used to connect process instruments to RMC conduit systems. Replacement instruments often have different physical dimensions than original equipment and using Sealtite GREATLY facilitates this exchange. Is this permitted? (Assuming the instrument has seals properly installed.)

Corollary: If a full-size equipment ground is installed inside the Sealtite, can a Sealtite connector (non-tapered threads) be attached directly to a threaded conduit coupling? Or does the Sealtite need to connect to a fitting which has tapered threads?

 

[kentirwin]

Re: LFMC in Class I, Div 2 area?

Without bothering to whip out the code book, my only comment is that when the NEC says "must" it means you absolutely have no other choice - it MUST be done. Do you have no other choice? Of course you drop some bucks and install listed flex - OZ Gedney type ECGJH. It's listed up to class 1 div 1. It's pricey but absolutely permissable. I've used that type quite a few times over the years and just recently ordered some more for a c1 d1 project.

Disclaimer: the author is not in and has never has been in the employ of OZ Gedney or EGS Electrical Group. He just happens to have their catalog sitting less than a foot away.

 

[rbalex]

Re: LFMC in Class I, Div 2 area?

I hate referring to 90.1(C).

As are all of Chapter 5, Classified Locations are ?Special Occupancies" and a fairly in-depth level of experience and training are necessary to properly apply Articles 500-516. In this case, I?d probably underscore training. I?ve seen people who have worked under certain ?company? standards so long they don?t truly understand the underlying principles. And everyone, myself included, tends to view unfamiliar installation practices with suspicion. We should until we?ve had the chance to thoroughly think it through.

In this case, must is not an imperative (See 90.5), but rather a judgment call made by an ?experienced? and ?trained? person. For Division 1, 501.4(A)(2) provides an example of such necessity for flexibility, but it is not an exhaustive list.

Vibration and facilitation of replacement of equipment are the primary examples of ?must? for ?limited flexibility;? but they may not be the only reasons, so 501.4(B)(2) leaves it open ended.