Based on the 2017 NEC-

Question: Can an Panelboard enclosure be used as a junction box and/or a raceway?

A) No

B) Yes

C) Only as a junction box

D) Only as a raceway
E) I do not know

Answer:  B

2014/2017 NEC-

312.8 Switch and Overcurrent Device Enclosures with Splices, 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.

From the 2014 Handbook-

Feed-through conductors, splices, and taps are permitted in the wiring space where conditions (1) through (3) are met. The total conductor fill in the enclosure must not exceed 40 percent of the cross section of the enclosure wiring space and no more than 75 percent if splices or taps are necessary.

APPLICATION EXAMPLE:

An enclosure having a wiring space of 4 inch wide by 3 inch deep has a cross-sectional area of 12 inch.2 Thus, the total conductor fill (see Chapter 9, Table 5, for dimensions of conductors) at any cross section cannot exceed 4.8 in.2 (40 percent of 12 in.2), and the maximum space for conductors and splices or taps at any cross section cannot exceed 9 in.2 (75 percent of 12 inch2).

In general, the best way to avoid overcrowding enclosures is to properly plan and lay out work before installation and use properly sized auxiliary gutters (366.22, 366.56, and 366.58) or junction boxes (314.16 and 314.28). For wiring space in enclosures for motor controllers and disconnecting means, see 430.10 and the associated commentary. See also 110.59 for tunnel installations over 600 volts.

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