Plastic Conduit now allowed in Class I Division 2 areas

from
electrician2.com
A new change in the 2008 NEC allows the use of plastic conduit in Class I Division 2 areas. It is at Section 501.10(B)(1)(7). There are some provisions that state PVC and RTRC conduit are only allowed when metallic conduit does not provide enough corrosion protection, the areas have restricted access by the public, and only qualified persons service the installation. I thought plastic coated rigid metal conduit that Robroy and KorKap make provided protection when corrosion is a problem. I inspected an installation where RobRoy was used where a company maintained its vehicles used for pumping acid down oil wells at Prudhoe Bay and it seemed to do the job. However, the plastics people are always trying to expand their domain. In the 1987 or 1990 NEC Metal Clad cable got approved for Class I Division I locations and that was a major blow to the people that sell their labor installing electrical systems in classified areas. Metal Clad cable often called industrial rope reduces the labor bill substantially when wiring in classified areas. But let us not fool ourselves; metal clad cable and plastic conduit are no substitutes for the real McCoy, Rigid Metal Conduit! You can’t climb and walk on metal clad cable like you can rigid conduit and after 20 to 30 years of people working in these industrial facilities the conduit or cable will be walked on, used for climbing, and in some cases for holding ladders and scaffolds . Plastic is worse. Plastic has a problem in cold climates. In 40 to 50 below zero F, plastic becomes very brittle and shatters with a minimum impact. Plastic also expands too much. For a climate with -50 degree F to plus 90 degree F temperatures an expansion joint is required for as little as 10 feet of plastic conduit. Carlon, a manufacturer of plastic conduit, boxes, and fittings said in 1993 that making a plastic product for cold temperatures was not cost effective so in cold climates we are out of luck.