National Electrical Installation Standards

Standards as High as Your Own

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Monday, September 13, 2021

Question:

Hello Code Friends,

I have always understood that a electrical panel ( say a 200 amp home panel ) "can not" be used as a junction box or to make joints or splices in. I was wondering if this is still the case , I can't find it in my old NEC book.

Thanks for a reply.

Tom Retired license electrician.

A

Answer:

Hello Tom,

The definition of panelboard should help clarify the requirements. It says that a panelboard is  a single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or against a wall, partition, or other support; and accessible only from the front. So from the definition, a panelboard is generally installed in a cabinet. Article 312 addresses cabinets and cutout boxes. Section 312.8(A) provides the general restriction you are thinking of, but there are some allowances. Here is what the rule says about slices, taps, and feed-through conductors. The wiring space of enclosures for switches or overcurrent devices shall be permitted for conductors feeding through, spliced, or tapping off to other enclosures, switches, or overcurrent devices where all of the following conditions are met: (1) The total of all conductors installed at any cross section of the wiring space does not exceed 40 percent of the cross sectional area of that space. (2) The total area of all conductors, splices, and taps installed at any cross section of the wiring space does not exceed 75 percent of the cross-sectional area of that space. (3) A warning label complying with 110.21(B) is applied to the enclosure that identifies the closest disconnecting means for any feed-through conductors. Hope this information is useful.

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