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Illustrated Catastrophes

Aug 1, 2010 12:00 PM, By Brian J. McPartland, NEC Consultant

As usual, never consider the following commentary associated with these photos as a formal interpretation of the National Electrical Code (NEC). Without criticizing anyone or any product, the following scenarios present us with serious safety questions.

Sorry — It’s Just Not Tough Enough

This installation is in bad shape. As you can clearly see, the Schedule 80 PVC used for this sewage pump circuit just wasn’t up to the task of protecting the enclosed circuit conductors. But what raceways would have been? It seems clear that even rigid metal conduit (RMC) would not be able to withstand repeated strikes by automobiles and the like. However, both RMC and PVC conduit are recognized in other sections of the Code as providing protection for these types of enclosed circuit conductors.

For example, in 300.5(D)(4), the Code says, “Where the enclosure or raceway is subject to physical damage, the conductors shall be installed in rigid metal conduit, intermediate metal conduit, Schedule 80 PVC conduit, or equivalent.” It should be noted that even though this rule mandates the use of RMC, IMC, PVC, or equivalent (whatever “equivalent” is), the use of one of these identified raceways does not eliminate the need to satisfy the rule in 110.27(B).

As noted in 110.27(B), “In locations where electrical equipment likely to be exposed to physical damage, enclosures or guards shall be so arranged and of such strength as to prevent such damage.” The term “likely” always poses a problem for me simply because if you decide that something is not likely and something happens, then obviously you were wrong. Whenever I encounter the term “likely,” I take it to mean, “If it is at all possible in your wildest dreams, then assume it’s likely.”

The installer on this job must have been aware of the rule in 110.27(B), as you can see that a bollard (on left) was installed to protect the metallic enclosure on the left. However, he clearly didn’t feel that such additional physical protection was necessary for the raceway. Obviously, he was mistaken.

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