LT or LA LFMC ???

[factoryrat]

I’m working in a Class II Div I area. We ran RMC to 24 explosion proof “T” boxes and out of each box ran a short length of LFMC to a sensor. We used type “LT” liquidtight. We ran a ground wire from the electrical panel in the RMC and landed it to the ground screw in each box and ran a ground wire through LFMC to each sensor and landed it to ground screw in sensor. In other words everything is tied to our ground wire. We are now told we have to replace all 24, 2’ to 3’ lengths, of LT LFMC’s with type “LA” type LFMC. The reason we were given was the type “LT” liquidtight was not a proper ground and therefore not approved for this Classification of area. I think the “LT” LFMC was code compliant – what to you think? I was told the “LA” LFMC has a copper wire in it (which I can see) that makes it an acceptable ground. Have you ever heard of this as a reason for running type LA sealtight in this situation?

350.10 (2) Uses Permitted tells me to look at 502.4 (A) (e) which I did and therefore I believe “LT” LFMC is allowed to be used in Class II Div I locations. I hope some of you can tell me if I’m right or wrong.

 

[barbeer]

Art. 502 says the use of LFMC is acceptable with listed fittings, with the given info I agree with you.

 

[don_resqcapt19]

Why would you use "explosionproof" fittings in a Class II area? Standard LBs, Ts, ect. with gasketed covers are suitable for Class II, Divison 1.
Don

 

[factoryrat]

You won't believe but ---

You won't believe but ---

Believe it or not we originally were running standard LBs, Ts, ect. with gasketed covers. Then there were concerns raised by some people that this was a hazardous area and we needed for someone to classify it so we would know we were wiring it correctly. So an insurance agent and our fire-marshal looked at the area and said to mimic the existing wiring methods. Those existing wiring methods happened to be explosion proof boxes, sealoffs, etc. We then tore out all the conduit and fittings we had installed (which was considerable) and replaced LBs, T's, etc with boxes rated Class I / Class II ratings.

I have not seen the documentation for the area but have been told the area is rated Class II Div I.

Don I am trying to get any information on the subject that I can. I believe at this facility we have very little experience with hazardous areas. That is from top management down to the electricians. Most of us are trying to learn.

Thanks.

 

[rbalex]

Neither the NEC nor UL makes a distinction between the Type "LA" or "LT" LFMC constructions. It is a marketing tool. The distinction, if any is necessary, is whether the fittings used are also listed for grounding. See 502.30

 

[rbalex]

... So an insurance agent and our fire-marshal looked at the area and said to mimic the existing wiring methods...

I have not seen the documentation for the area but have been told the area is rated Class II Div I.

...

It surprises me that documentation wasn't the first thing they demanded.(You should be too) [Section 500.4(A)] Since they didn't, it doesn?t surprise me they didn?t really know what to tell you to do either.

 

[factoryrat]

The quest for truth, justice, and the American way goes on.

Thank you for responses.

 

[bobgorno]

I see you are in Michigan. Have you checked the Michigan Electrical Code Rules Part 8? The last job I did in Michigan, the inspector failed us. Apparently Michigan does not (or did not in 1999, 2000 time frame) allow LFMC to be used as a grounding means. A separate bonding jumper is required.

We were in CI, D1 and D2 areas and all of our wiring methods were intrinsically safe. We transitioned shielded PLTC/ITC cable out of cable tray, to RMC, to LFMC with approved grounding connectors, to our process instruments. He said he would allow us to use the shield wire as the ground. When I explained that the process instruments could not be relied upon if our shield was grounded at both ends he didn't care.

I finally convinced him (calmy) that the Michigan Code Rules obviously did not consider their impact on intrinsically safe or other 24VDC process wiring; that I-Safe can be installed using general purpose wiring methods, hence our raceways were just our preference for mechanical protection; that the raceways were continuous and bonded; that the IS barrier limits any fault to < 28VDC and < 110mA; and that the enclosure of the process instrument was bonded to the raceway using the LFMC and approved connectors; and that this was acceptable at every other jurisdiction we had ever worked in.

So, as I learned the NEC is not always the final rule. Learn the local rules.

Happy to say he passed us. Sometimes you have to be willing to teach the AHJ.