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| | The NEC classifies conduits within a slab that is on grade as a wet location. Traditionally we have installed plenum rated cable to work area outlets in floor boxes where the majority of the run is ceiling pathway with conduit running under the slab to the floor box and stubbing to accessible space. Recently I have seen designers designating wet rated cable in wet location requiring a transition point from plenum cable to a dual rated (OSP & CMG). I don't think an OSP cable that is unrated would be suitable for this. If the transition point is in a plenum then it would need to be an enclosure approved by AHJ. I am think a 110 block with the cables interconnected for the transition, although Some of the manufacturers have transition points that were intended for undercarpet applications. I think using a wet rated cable is a good design practice as we all know that floor boxes are usually wet. Any thoughts? P.S. NEC 2008 article 800 does not stipulate that wet locations require wet cable, while Article 300,725, and 760 do. John McNamara, RCDD |
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| I am dealing with a job right now with a similar issue. Please tell me where I am misguided in my logic.
Article 800 is a stand-alone section of code; it does not require adherence to any other Article, unless specifically sited, for compliance.
Argument 1:
Article 310.8 (in the 2005 NEC) addresses locations but is not specifically called out in Article 800. So does this mean it is not a requirement of Communications Cable? I would assume Article 310.8 does not apply. Meaning, the cable does not have to be listed for wet locations.
Argument 2:
Article 800.2 refers to Article 100 for definitions. Article 100 defines “Locations, Wet” and “Listed”. Does Article 800.2 work in conjunction with Article 800.179 or does Article 800.179 trump the Article 100 “Listed” definition ? I would assume Article 100 works with Article 800.179. Meaning the cable must be listed for wet locations.
Any guidance on where the truth lies would be appreciated.
Tim Deely RCDD, RTMP(i)DSU, llc Tim.Deely@DSUllc.us |
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| A few random thoughts:- Article in EC&M magazine discussed this issue in Apr 2004: http://ecmweb.com/news/install/
- Manufacturers have requirements and exclusions in their SCS Warranty. If the Manufacturer's warranty will not cover any issues that arise with CMP cable in floor box, what is the Owner's expectations?
- So far the SCS Manufacturers in the USA do not offer AC6 cable for a wet location.
We typically route floor box conduits directly to TR to avoid the cost of a transition. Sometimes this is not feasible. When that is the case, transitions between cable types are then provided. We have run into situations where floor boxes were flooded during and after construction. In these situations having a cable with a jacket for a wet location has been worthwhile. ben |
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