Code Change Summary: Rules have been added pertaining to power distribution blocks installed in metal wireways.

Power distribution blocks are commonly used in gutter boxes or metal wireways for splicing conductors. Some gutter boxes where power distribution blocks are used are service gutters that contain service entrance conductors.

Through the inspection process it has been found that many power distribution blocks are installed on the line side of a service disconnect, inside a metal wireway, without first checking to see if the power distribution blocks are listed for such use.

UL product category QPQS states that “power distribution blocks marked "Suitable for Use on the Line Side of Service Equipment" (or equivalent) have been investigated for use on either the line side or the load side of service equipment”. That being said, if this marking is not present, then the power distribution blocks are not suitable to be used on the line side of the service disconnect.

In the 2014 NEC^® this issue has been addressed in 376.56(B)(1).

As well, according to the new text added in 376.56(B)(2), its time to start keeping things organized in the wireway. The new language states that conductors must be arranged so the power distribution block terminals are unobstructed following installation.

Below is a preview of the NEC^®.  See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).

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