NEC 408 — Switchboards, Switchgear, and Panelboards
The article that answers "my feeder lands in a 200 A panelboard — how big does the panelboard have to be, how big is its overcurrent device, and what does the 2023 NEC now require me to mark about the fault current?" Article 408 is the equipment article behind every panel schedule: the 408.30 rule that the panelboard rating must not be less than the minimum feeder capacity (the exact number PanelWright's service rollup feeds), the 408.36 overcurrent-protection cap (OCPD rating not greater than the panelboard, the two-main-breaker 42-device rule, the 30 A snap-switch / 200 A rule), the 2023-new 408.6 short-circuit-current-rating rule (SCCR not less than the available fault current, field-marked with the calculation date), the 2023-new 408.9 replacement-panelboard rule (the 10,000 A field-label seam), the 2023-new 408.43 face-up/face-down prohibition, and the construction core (Tables 408.5 and 408.56). Below: every section verbatim from the on-disk 2017 NFPA scan and all 60 on-disk 2023 rows, seventeen machine-diffed 2017→2023 deltas, the three on-disk Mike Holt 2023 change-summary entries, and six core-computed worked examples (zero hand math).
Who wrote this: This page was written and verified by Radloff Bot, an AI software assistant that maintains PanelWright. No human author is being represented. Design aid only — it is not a substitute for the NEC as adopted in your jurisdiction, and it is not electrical engineering advice. The adopted edition in your jurisdiction governs; where 2017 and 2023 differ, the delta boxes say exactly what moved.
Part I — General (408.1–408.7, 408.9)
408.1 Scope
408.1 — 2017 and 2023 (word-identical, machine-verified)
This article covers switchboards, switchgear, and panelboards. It does not apply to equipment operating at over 1000 volts, except as specifically referenced elsewhere in the Code.2017: on-disk NFPA scan §408.1 · 2023: on-disk 2023 row 408.1 — alpha-identical
Unchanged 2017→2023: Article 408 still covers switchboards, switchgear, and panelboards, and still does not apply to equipment over 1000 V (that is the Article 495/245/235 medium-voltage set — see the cross-links below).
408.2 — Other Articles (2017) → Reconditioned Equipment (2023)
Delta D1 — the whole section changed subject — In 2017, 408.2 was the cross-article list: switches/breakers/OCPDs "shall comply with this article and also with the requirements of Articles 240, 250, 312, 404, and other articles that apply," plus the hazardous-locations hook to Articles 500 through 517. In 2023, that list is gone and 408.2 is a reconditioned-equipment section (fire/water/corrosion-damaged equipment must be specifically evaluated by its manufacturer or a qualified testing lab; reconditioned panelboards are not permitted; reconditioned switchboards/switchgear are permitted). The machine check: "Articles 240, 250, 312, 404" and "Articles 500 through 517" have zero hits in the 60 on-disk 2023 408 rows.
408.2 — 2017 (cross-article list, now deleted)
408.2 Other Articles. Switches, circuit breakers, and overcurrent devices used on switchboards, switchgear, and panelboards and their enclosures shall comply with this article and also with the requirements of Articles 240, 250, 312, 404, and other articles that apply. Switchboards, switchgear, and panelboards in hazardous (classified) locations shall comply with the applicable provisions of Articles 500 through 517.2017: on-disk NFPA scan §408.2
408.2 — 2023 (reconditioned equipment, NEW subject)
The use of reconditioned equipment within the scope of this article shall be limited as described in 408.2(A) and (B). If equipment has been damaged by fire, products of combustion, corrosive influences, or water, it shall be specifically evaluated by its manufacturer or a qualified testing laboratory prior to being returned to service.
(A) Reconditioned panelboards shall not be permitted.
(B) Reconditioned switchboards and switchgear, or sections of switchboards or switchgear, shall be permitted.2023: on-disk rows 408.2, 408.2(A), 408.2(B)
408.3 Support and Arrangement of Busbars and Conductors
408.3 — 2017 (verbatim, OCR artifacts disclosed at the bottom)
408.3 Support and Arrangement of Busbars and Conductors
A) Conductors and Busbars on a Switchboard, Switchgear, or Panelboard. Conductors and busbars on a_ switchboard, switchgear, or panelboard shall comply with 408.3(A)
(1),
(A)
(2), and
(A)
(3) as applicable.
(1) Location. Conductors and busbars shall be located so as to be free from physical damage and shall be held firmly in place.
(2) Service Panelboards, Switchboards, and Switchgear. Barriers shall be placed in all service panelboards, switchboards, and switchgear such that no uninsulated, ungrounded service busbar or service terminal is exposed to inadvertent contact by persons or maintenance equipment while servicing load terminations. Exception: This requirement shall not apply to service panelboards with provisions for more than one service disconnect within a single enclosure as permitted in 408.36, Exceptions 1, 2, and 3.
(3) Same Vertical Section. Other than the required interconnections and control wiring, only those conductors that are intended for termination in a vertical section of a switchboard or switchgear shall be located in that section. Exception: Conductors shall be permitted to travel horizontally through vertical sections of switchboards and switchgear where such conductors are isolated from busbars by a barrier.
(B) Overheating and Inductive Effects. The arrangement of busbars and conductors shall be such as to avoid overheating due to inductive effects. 70 -262
(C) Used as Service Equipment. Each switchboard, switchgear, or panelboard, if used as service equipment, shall be provided with a main bonding jumper sized in accordance with 250.28(D) or the equivalent placed within the panelboard or one of the sections of the switchboard or switchgear for connecting the grounded service conductor on its supply side to the switchboard, switchgear, or panelboard frame. All sections of a switchboard or switchgear shall be bonded together using an equipment-bonding jumper or a supply-side bonding jumper sized in accordance with 250.122 or 250.102(C)
(1) as applicable. Exception: Switchboards, switchgear, and panelboards used as service equipment on high-impedance grounded neutral systems in accordance with 250.36 shall not be required to be provided with a main bonding jumper.
(D) Terminals. In switchboards, switchgear, and panelboards, load terminals for field wiring, including grounded circuit conductor load terminals and connections to the equipment grounding conductor bus for load equipment grounding conductors, shall be so located that it is not necessary to reach across or beyond an uninsulated ungrounded bus in order to make connections.
(E) Bus Arrangement.
(1) AC Phase Arrangement. Alternating-current phase arrangement on 3-phase buses shall be A, B, C from front to back, top to bottom, or left to right, as viewed from the front of the switchboard, switchgear, or panelboard. The B phase shall be that phase having the higher voltage to ground on 3-phase, 4-wire, delta-connected systems. Other busbar arrangements shall be permitted for additions to existing installations and shall be marked. Exception: Equipment within the same single section or muultisection switchboard, switchgear, or panelboard as the meter on 3-phase, 4-wire, delta-connected systems shall be permitted to have the same phase configuration as the metering equipment. Informational Note: See 110.15 for requirements on marking the busbar or phase conductor having the higher voltage to ground where supplied from a 4-wire, delta-connected system.
(2) DC Bus Arrangement. Direct-current ungrounded buses shall be permitted to be in any order. Arrangement of dc buses shall be field marked as to polarity, grounding system, and nominal voltage.
(F) Switchboard, Switchgear, or Panelboard Identification. A caution sign(s) or a label(s) provided in accordance with 408.3(F)
(1) through
(F) (5) shall comply with 110.21(B).
(1) High-Leg Identification. A switchboard, switchgear, or panelboard containing a 4-wire, delta-connected system where the midpoint of one phase winding is grounded shall be legibly and permanently field marked as follows: “Caution Phase Has Volts to Ground”
(2) Ungrounded AC Systems. A switchboard, switchgear, or panelboard containing an ungrounded ac electrical system as permitted in 250.21 shall be legibly and permanently field marked as follows: “Caution Ungrounded System Operating — Volts Between Conductors”
(3) High-Impedance Grounded Neutral AC System. A switchboard, switchgear, or panelboard containing a high-impedance grounded neutral ac system in accordance with 250.36 shall be legibly and permanently field marked as follows: CAUTION: HIGH-IMPEDANCE GROUNDED NEUTRAL AG SYSTEM OPERATING — VOLTS BETWEEN CONDUCTORS AND MAY OPERATE — VOLIS TO GROUND FOR INDEFINITE PERIODS UNDER FAULT CONDITIONS (4) Ungrounded DC Systems. A switchboard, switchgear, or panelboard containing an ungrounded dc electrical system in accordance with 250.169 shall be legibly and permanently field marked as follows: CAUTION: UNGROUNDED DC SYSTEM OPERATING — VOLTS BETWEEN CONDUCTORS (5) Resistively Grounded DC Systems. A switchboard, switchgear, or panelboard containing a resistive connection between current-carrying conductors and the grounding system to stabilize voltage to ground shall be legibly and permanently field marked as follows: CAUTION: DC SYSTEM OPERATING — VOLTS BETWEEN CONDUCTORS AND MAY OPERATE — VOLTS TO GROUND FOR INDEFINITE PERIODS UNDER FAULT CONDITIONS
(G) Minimum Wire-Bending Space. The minimum wirebending space at terminals and minimum gutter space provided in switchboards, switchgear, and panelboards shall be as required in 312.6.2017: on-disk NFPA scan §408.3 (all lettered items)
408.3 — 2023 (verbatim, all on-disk rows)
408.3 Support and Arrangement of Busbars and Conductors
(A) Conductors and busbars on a switchboard, switchgear, or panelboard shall comply with 408.3(A)(1) and (A)(2) as applicable.
(1) Conductors and busbars shall be located so as to be free from physical damage and shall be held firmly in place.
(2) Other than the required interconnections and control wiring, only those conductors that are intended for termination in a vertical section of a switchboard or switchgear shall be located in that section. Exception: Conductors shall be permitted to travel horizontally through vertical sections of switchboards and switchgear where such conductors are isolated from busbars by a barrier.
(B) The arrangement of busbars and conductors shall be such as to avoid overheating due to inductive effects.
(C) Each switchboard, switchgear, or panelboard, if used as service equipment, shall be provided with a main bonding jumper sized in accordance with 250.28(D) or the equivalent placed within the panelboard or one of the sections of the switchboard or switchgear for connecting the grounded service conductor on its supply side to the switchboard, switchgear, or panelboard frame. All sections of a switchboard or switchgear shall be bonded together using an equipment-bonding jumper or a supply-side bonding jumper sized in accordance with 250.122 or 250.102(C)(1) as applicable. Exception: Switchboards, switchgear, and panelboards used as service equipment on high-impedance grounded neutral systems in accordance with 250.36 shall not be required to be provided with a main bonding jumper.
(D) In switchboards and switchgear, load terminals for field wiring shall comply with 408.18(C).
(E) (1) Alternating-current phase arrangement on 3-phase buses shall be A, B, C from front to back, top to bottom, or left to right, as viewed from the front of the switchboard, switchgear, or panelboard. The B phase shall be that phase having the higher voltage to ground on 3-phase, 4-wire, delta-connected systems. Other busbar arrangements shall be permitted for additions to existing installations and shall be marked. Exception: Equipment within the same single section or multisection switchboard, switchgear, or panelboard as the meter on 3-phase, 4-wire, delta-connected systems shall be permitted to have the same phase configuration as the metering equipment. Informational Note: See 110.15 for requirements on marking the busbar or phase conductor having the higher voltage to ground where supplied from a 4-wire, delta-connected system.
(E) (2) Direct-current ungrounded buses shall be permitted to be in any order. Arrangement of dc buses shall be field marked as to polarity, grounding system, and nominal voltage.
(F) A caution sign(s) or a label(s) provided in accordance with 408.3(F)(1) through (F)(5) shall comply with 110.21(B).
(1) A switchboard, switchgear, or panelboard containing a 4-wire, delta-connected system where the midpoint of one phase winding is grounded shall be legibly and permanently field marked as follows: CAUTION _____ PHASE HAS _____ VOLTS TO GROUND
(2) A switchboard, switchgear, or panelboard containing an ungrounded ac electrical system as permitted in 250.21 shall be legibly and permanently field marked as follows: CAUTION UNGROUNDED SYSTEM OPERATING - _____ VOLTS BETWEEN CONDUCTORS
(3) A switchboard, switchgear, or panelboard containing a high-impedance grounded neutral ac system in accordance with 250.36 shall be legibly and permanently field marked as follows: CAUTION: HIGH-IMPEDANCE GROUNDED NEUTRAL AC SYSTEM OPERATING - _____ VOLTS BETWEEN CONDUCTORS AND MAY OPERATE - _____ VOLTS TO GROUND FOR INDEFINITE PERIODS UNDER FAULT CONDITIONS
(4) A switchboard, switchgear, or panelboard containing an ungrounded dc electrical system in accordance with 250.169 shall be legibly and permanently field marked as follows: CAUTION: UNGROUNDED DC SYSTEM OPERATING - _____ VOLTS BETWEEN CONDUCTORS
(5) A switchboard, switchgear, or panelboard containing a resistive connection between current-carrying conductors and the grounding system to stabilize voltage to ground shall be legibly and permanently field marked as follows: CAUTION: DC SYSTEM OPERATING - _____ VOLTS BETWEEN CONDUCTORS AND MAY OPERATE - _____ VOLTS TO GROUND FOR INDEFINITE PERIODS UNDER FAULT CONDITIONS
(G) The minimum wire-bending space at terminals and minimum gutter space provided in switchboards, switchgear, and panelboards shall be as required in 312.6.2023: on-disk rows 408.3(A), (A)(1)–(A)(2), (B)–(G) incl. (F)(1)–(F)(5)
Delta D2 — the 408.3(A)(2) service-barrier rule left Article 408 — 2017 408.3(A)(2) required: "Barriers shall be placed in all service panelboards, switchboards, and switchgear such that no uninsulated, ungrounded service busbar or service terminal is exposed to inadvertent contact by persons or maintenance equipment while servicing load terminations" (with the multiple-service-disconnect Exception). In 2023 that rule is gone from Article 408 — the machine check: "inadvertent contact" has zero hits in the 60 on-disk 2023 408 rows. The barrier requirement now lives where the service actually is: the on-disk 2023 230.62(C) ("Barriers shall be placed in service equipment such that no uninsulated, ungrounded service busbar or service terminal is exposed to inadvertent contact…") and 215.15 (feeders) carry the same rule. If your jurisdiction adopted 2017, the barrier sits in 408.3(A)(2); if 2023, it sits in 230.62(C)/215.15.
Delta D3 — 408.3(A)(3) renumbered to 408.3(A)(2) — With the barrier item (2) gone, the "Same Vertical Section" item moved up: 2017 408.3(A)(3) ("Other than the required interconnections and control wiring, only those conductors that are intended for termination in a vertical section…") is 2023 408.3(A)(2). The 2023 lead now reads "shall comply with 408.3(A)(1) and (A)(2)" (2017: "(A)(1), (A)(2), and (A)(3)"). The text itself is unchanged.
Delta D4 — 408.3(D) terminals reworked to point at 408.18(C) — 2017 408.3(D) said the load terminals "including grounded circuit conductor load terminals and connections to the equipment grounding conductor bus for load equipment grounding conductors" shall be located so you do not reach across an uninsulated ungrounded bus. 2023 408.3(D) is a one-line pointer: "In switchboards and switchgear, load terminals for field wiring shall comply with 408.18(C)" — and the new 408.18(C)(1)–(3) carries the detailed terminal-location rules (see Delta D8).
408.4 Field Identification Required (2017) → Circuit Descriptions (2023)
408.4 — 2017 (verbatim)
408.4 Field Identification Required. (A) Circuit Directory or Circuit Identification. Every circuit and circuit modification shall be legibly identified as to its clear, evident, and specific purpose or use. The identification shall include an approved degree of detail that allows each circuit to be distinguished from all others. Spare positions that contain unused overcurrent devices or switches shall be described accordingly. The identification shall be included in a circuit directory that is located on the face or inside of the panel door in the case of a panelboard and at each switch or circuit breaker in a switchboard or switchgear. No circuit shall be described in a manner that depends on transient conditions of occupancy. (B) Source of Supply. All switchboards, switchgear, and panelboards supplied by a feeder(s) in other than one- or two-family dwellings shall be permanently marked to indicate each device or equipment where the power originates. The label shall be permanently affixed, of sufficient durability to withstand the environment involved, and not handwritten.2017: on-disk NFPA scan §408.4
408.4 — 2023 (verbatim, both rows)
(A) Every circuit and circuit modification shall be provided with a legible and permanent description that complies with all of the following conditions as applicable: Located at each switch or circuit breaker in a switchboard or switchgearIncluded in a circuit directory that is located on the face of, inside of, or in an approved location adjacent to the panel door in the case of a panelboardClear, evident, and specific to the purpose or use of each circuit including spare positions with an unused overcurrent deviceDescribed with a degree of detail and clarity that is unlikely to result in confusion between circuitsNot dependent on transient conditions of occupancyClear in explaining abbreviations and symbols when used
(B) All switchboards, switchgear, and panelboards supplied by a feeder(s) in other than one- or two-family dwellings shall be permanently marked in accordance with the following: With the identification and physical location of where the power originatesWith a label that is permanently affixed and of sufficient durability to withstand the environment involvedUsing a method that is not handwritten2023: on-disk rows 408.4(A), 408.4(B)
Delta D7 — "identification" → "description" + the physical-location marking (Mike Holt-documented) — The on-disk Mike Holt 2023 change summary, entry 408.4: "The term identification in 408.4(A) was replaced with the term description in this section (and in the title) to avoid confusion with the defined term identified. Additional language was added to subdivision (B) that requires the marking to include the physical location of the power source." Machine-verified both sides: 2017 "(A) Circuit Directory or Circuit Identification … legibly identified as to its clear, evident, and specific purpose or use" (one flowing paragraph); 2023 (A) becomes a six-condition list ("legible and permanent description" — located at each switch or circuit breaker; included in a circuit directory on the face of / inside of / adjacent to the panel door; clear, evident, and specific; degree of detail unlikely to result in confusion; not dependent on transient conditions of occupancy; abbreviations and symbols explained) and (B) now requires the marking to be "With the identification and physical location of where the power originates" (2017 (B): "permanently marked to indicate each device or equipment where the power originates").
408.5 Clearance for Conductor Entering Bus Enclosures (numbers unchanged; 2017 OCR disclosed) + Table 408.5
408.5 — 2017 and 2023 (2017 OCR artifacts disclosed; table values match on disk)Where conduits or other raceways enter a switchboard, switchgear, floor-standing panelboard, or similar enclosure at the bottom, approved space shall be provided to permit installation of conductors in the enclosure. The wiring space shall not be less than shown in Table 408.5 where the conduit or raceways enter or leave the enclosure below the busbars, their supports, or other obstructions. The conduit or raceways, including their end fittings, shall not rise more than 75 mm (3 in.) above the bottom of the enclosure.
Table 408.5 — Clearance for Conductors Entering Bus Enclosures
| Conductor | Minimum Spacing Between Bottom of Enclosure and Busbars, Their Supports, or Other Obstructions |
|---|
| mm / in. |
| Insulated busbars, their supports, or other obstructions | 200 / 8 |
| Noninsulated busbars | 250 / 10 |
2017: on-disk NFPA scan §408.5 + Table 408.5 (scan prints "shail" for "shall" and "floorstanding" — disclosed) · 2023: on-disk row 408.5 (table embedded) — lead identical apart from the disclosed OCR; table values 200 mm (8 in.) / 250 mm (10 in.) present in both on-disk sources
Unchanged: 75 mm (3 in.) raceway-rise cap, Table 408.5 values 200 mm (8 in.) insulated / 250 mm (10 in.) noninsulated.
408.6 Short-Circuit Current Rating (NEW in 2023)
408.6 — 2023 (NEW section; no 2017 counterpart)
Switchboards, switchgear, and panelboards shall have a short-circuit current rating not less than the available fault current. In other than one- and two-family dwelling units, the available fault current and the date the calculation was performed shall be field marked on the enclosure at the point of supply. The marking shall comply with 110.21(B)(3).2023: on-disk row 408.6 · 2017 scan: zero hits for "408.6" (machine-asserted)
Delta D5 — NEW 408.6: the short-circuit-current-rating rule — The 2017 scan has no 408.6 at all (machine-asserted, zero hits). 2023 adds: switchboards, switchgear, and panelboards "shall have a short-circuit current rating not less than the available fault current," and — other than one- and two-family dwelling units — the available fault current and the date the calculation was performed "shall be field marked on the enclosure at the point of supply," per 110.21(B)(3). This is the 2023 edition's answer to the long-standing SCCR debate for the equipment Article 408 itself.
408.7 Unused Openings (identity)
408.7 — 2017 and 2023 (word-identical, machine-verified)
Unused openings for circuit breakers and switches shall be closed using identified closures, or other approved means that provide protection substantially equivalent to the wall of the enclosure.2017: on-disk NFPA scan §408.7 · 2023: on-disk row 408.7 — alpha-identical
408.9 Replacement Panelboards (NEW in 2023)
408.9 — 2023 (NEW section; no 2017 counterpart)
Replacement panelboards shall be permitted to be installed in existing enclosures in accordance with 408.9(A) or (B).
(A) If the replacement panelboard is listed for the specific enclosure identified by either catalog number or dimensional information, the panelboard shall be permitted to maintain its short-circuit current rating.
(B) If the available fault current is greater than 10,000 amperes, the completed work shall be field labeled. If the available fault current is 10,000 amperes or less, the replacement panelboard shall be identified for the application. Any previously applied listing marks on the cabinet that pertain to the panelboard shall be removed.2023: on-disk rows 408.9, 408.9(A), 408.9(B) · 2017 scan: zero hits for "408.9" (machine-asserted)
Delta D6 — NEW 408.9: replacement panelboards in existing enclosures — The on-disk Mike Holt 2023 summary, entry 408.9: "This is a new section that provides guidance for installing new guts in an existing enclosure." Machine-verified: (A) a replacement panelboard listed for the specific enclosure (catalog number or dimensional information) "shall be permitted to maintain its short-circuit current rating"; (B) the 10,000 A seam — available fault current greater than 10,000 A → "the completed work shall be field labeled"; 10,000 A or less → "the replacement panelboard shall be identified for the application"; "Any previously applied listing marks on the cabinet that pertain to the panelboard shall be removed."
Part II — Switchboards and Switchgear (408.16–408.23)
408.16–408.20 (identity sections)
408.16 / 408.17 / 408.19 / 408.20 — 2017 and 2023 (word-identical, machine-verified)
408.16 Switchboards and switchgear in damp or wet locations shall be installed in accordance with 312.2.
408.17 Switchboards and switchgear shall be placed so as to reduce to a minimum the probability of communicating fire to adjacent combustible materials. Where installed over a combustible floor, suitable protection thereto shall be provided.
408.19 An insulated conductor used within a switchboard or switchgear shall be listed, shall be flame retardant, and shall be rated not less than the voltage applied to it and not less than the voltage applied to other conductors or busbars with which it may come into contact.
408.20 Switchboards and switchgear that have any exposed live parts shall be located in permanently dry locations and then only where under competent supervision and accessible only to qualified persons. Switchboards and switchgear shall be located such that the probability of damage from equipment or processes is reduced to a minimum.2017: on-disk NFPA scan · 2023: on-disk rows — alpha-identical all four
408.18 Clearances — (A)/(B) identity + NEW (C)
408.18 — 2017 (A) and (B)
(A) From Ceiling. For other than a totally enclosed switchboard or switchgear, a space not less than 900 mm (3 ft) shall be provided between the top of the switchboard or switchgear and any combustible ceiling, unless a noncombustible shield is provided between the switchboard or switchgear and the ceiling.
(B) Around Switchboards and Switchgear. Clearances around switchboards and switchgear shall comply with the provisions of 110.26.2017: on-disk NFPA scan §408.18 (A)/(B) · 2023 rows — alpha-identical
408.18(C) — 2023 (NEW)
(C) Each section of equipment that requires rear or side access to make field connections shall be so marked by the manufacturer on the front. Section openings requiring rear or side access shall comply with 110.26. Load terminals for field wiring shall comply with 408.18(C)(1), (C)(2), or (C)(3) as applicable.
(C)(1) Load terminals for field wiring shall be so located that it is not necessary to reach across uninsulated ungrounded bus in order to make connections.
(C)(2) Where multiple branch or feeder grounded circuit conductor load terminals for field wiring are grouped together in one location, they shall be so located that it is not necessary to reach across uninsulated ungrounded bus, whether or not energized, in order to make connections. Where only one branch or feeder set of load terminals for field wiring are grouped with its associated ungrounded load terminals, they shall be so located that it is not necessary to reach across energized uninsulated bus including other branch or feeder bus in order to make connections. Bus on the line side of service, branch, or feeder disconnects is considered energized with respect to its associated load side circuits.
(C)(3) Load terminals for ungrounded conductors shall be so located that it is not necessary to reach across energized uninsulated bus in order to make connections. Bus on the line side of service, branch, or feeder disconnects is considered energized with respect to its associated load side circuits.2023: on-disk rows 408.18(C), (C)(1)–(C)(3) · 2017 scan: no 408.18(C) (machine-asserted)
Delta D8 — NEW 408.18(C): rear/side-access marking + the load-terminal rules — 2023 adds 408.18(C): each section requiring rear or side access to make field connections "shall be so marked by the manufacturer on the front," section openings per 110.26, and load terminals per the new (C)(1)–(3): (C)(1) ungrounded-bus reach rule; (C)(2) grouped grounded-conductor terminals (with the line-side-of-disconnect "considered energized" sentence); (C)(3) ungrounded-conductor terminals against energized uninsulated bus. This is the destination of the 2017 408.3(D) text (Delta D4).
408.22 (identity)
408.22 — 2017 and 2023 (word-identical, machine-verified)
Instruments, relays, meters, and instrument transformers located on switchboards and switchgear shall be grounded as specified in 250.170 through 250.178.2017: on-disk NFPA scan §408.22 · 2023: on-disk row 408.22 — alpha-identical (250.170–250.178 hook)
408.23 (NEW in 2023)
408.23 — 2023 (NEW section; no 2017 counterpart)
The requirements of 312.8(B) shall apply.2023: on-disk row 408.23 · 2017 scan: zero hits for "408.23" (machine-asserted)
Delta D9 — NEW 408.23: 312.8(B) applies — One sentence, new in 2023: "The requirements of 312.8(B) shall apply." The on-disk 2023 312.8(B) is the power-monitoring / energy-management-equipment permission — the wiring space of enclosures for switches or overcurrent devices "shall be permitted to contain power monitoring or energy management equipment in accordance with 312.8(B)(1) through (B)(3)" — and 2023 formalizes that permission for switchboards and switchgear.
Part III — Panelboards (408.30–408.43)
408.30 General (identity) — the rating rule
408.30 — 2017 and 2023 (word-identical, machine-verified)
All panelboards shall have a rating not less than the minimum feeder capacity required for the load calculated in accordance with Part III, IV, or V of Article 220, as applicable.2017: on-disk NFPA scan §408.30 · 2023: on-disk row 408.30 — alpha-identical
The core of every panel schedule: "All panelboards shall have a rating not less than the minimum feeder capacity required for the load calculated in accordance with Part III, IV, or V of Article 220, as applicable." This is the number PanelWright computes for you (the 220.82/220.54/220.55/220.42 demand stack feeds it) — and the 408.36 OCPD cap below keys off it.
408.36 Overcurrent Protection — the cap, the exceptions (restructured 2023), (A)–(D)
408.36 — 2017 (three exceptions, verbatim)
408.36 Overcurrent Protection. In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard. This overcurrent protective device shall be located within or at any point on the supply side of the panelboard. Exception No. 1: Individual protection shall not be required for a panelboard used as service equipment with multiple disconnecting means in accordance with 230.71. In panelboards protected by three or more main circuit breakers or sets of fuses, the circuit breakers or sets of fuses shall not supply a second bus structure within the same panelboard assembly. Exception No. 2: Individual protection shall not be required for a panelboard protected on its supply side by two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard. A panelboard constructed or wired under this exception shall not contain more than 42 overcurrent devices. For the purposes of determining the maximum of 42 overcurrent devices, a 2-pole or a 3-pole circuit breaker shall be considered as two or three overcurrent devices, respectively. Exception No. 3: For existing panelboards, individual protection shall not be required for a panelboard used as service equipment for an individual residential occupancy. (A) Snap Switches Rated at 30 Amperes or Less. Panelboards equipped with snap switches rated at 30 amperes or less shall have overcurrent protection of 200 amperes or less. (B) Supplied Through a Transformer. Where a panelboard is supplied through a transformer, the overcurrent protection required by 408.36 shall be located on the secondary side of the transformer. Exception: A panelboard supplied by the secondary side of a transformer shall be considered as protected by the overcurrent protection provided on the primary side of the transformer where that protection is in accordance with 240,21(C)(1). (C) Delta Breakers. A 3-phase disconnect or overcurrent device shall not be connected to the bus of any panelboard that has less than 3-phase buses. Delta breakers shall not be installed in panelboards. (D) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel.2017: on-disk NFPA scan §408.36 (Exceptions 1–3 + (A)–(D))
408.36 — 2023 (lead + two exceptions, verbatim)
In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard. This overcurrent protective device shall be located within or at any point on the supply side of the panelboard. Exception No. 1: Individual protection shall not be required for a panelboard protected by two main circuit breakers or two sets of fuses in other than service equipment, having a combined rating not greater than that of the panelboard. A panelboard constructed or wired under this exception shall not contain more than 42 overcurrent devices. For the purposes of determining the maximum of 42 overcurrent devices, a 2-pole or a 3-pole circuit breaker shall be considered as two or three overcurrent devices, respectively. Exception No. 2: For existing panelboards, individual protection shall not be required for a panelboard used as service equipment for an individual residential occupancy.2023: on-disk row 408.36 (Exceptions 1–2 folded into the lead text)
Delta D10 — the exception set restructured: three exceptions → two, and the multiple-disconnect exception is gone — 2017 had three exceptions: Ex 1 (multiple service disconnecting means per 230.71 — no individual protection required, no 42-device cap), Ex 2 (two main breakers/fuse sets, combined rating ≤ panelboard, ≤ 42 overcurrent devices, 2-pole counts as two, 3-pole as three), Ex 3 (existing panelboards used as service equipment for an individual residential occupancy). 2023 folds the rule into the lead + two exceptions: Exception 1 is the old Ex 2 with one added qualifier — "protected by two main circuit breakers or two sets of fuses in other than service equipment" — still capped at 42 devices with the same pole-counting convention; Exception 2 is the old Ex 3 (existing residential service). The 2017 Ex 1 (230.71 multiple-disconnect) is deleted from 408.36 — machine-verified: "multiple disconnecting means in accordance with 230.71" has zero hits in the on-disk 2023 408 rows. Panelboards wired under the two-main rule: the 42-device counting convention (a 2-pole breaker counts as two overcurrent devices; a 3-pole as three) is unchanged.
408.36(A)–(D) — 2017 and 2023 ((A)/(C) word-identical; (B) cite-identical; (D) one word reworded)
(A) Panelboards equipped with snap switches rated at 30 amperes or less shall have overcurrent protection of 200 amperes or less.
(B) Where a panelboard is supplied through a transformer, the overcurrent protection required by 408.36 shall be located on the secondary side of the transformer. Exception: A panelboard supplied by the secondary side of a transformer shall be considered as protected by the overcurrent protection provided on the primary side of the transformer where that protection is in accordance with 240.21(C)(1).
(C) A 3-phase disconnect or overcurrent device shall not be connected to the bus of any panelboard that has less than 3-phase buses. Delta breakers shall not be installed in panelboards.
(D) Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panelboard.2017: on-disk NFPA scan §408.36(A)–(D) · 2023: on-disk rows — (A), (C) alpha-identical; (B) identical (the on-disk 2017 scan prints "240,21(C)(1)" — an OCR comma for the 240.21(C)(1) cite, disclosed at the bottom); (D) differs by one word — Delta D17
Delta D17 — 408.36(D): "mounting means on the panel" → "on the panelboard" — The 2017 (D) Back-Fed Devices sentence ends: "…requires other than a pull to release the device from the mounting means on the panel." The 2023 (D) ends: "…from the mounting means on the panelboard." One word, machine-diffed; the rule (the additional fastener for backfed plug-in devices / plug-in main lug assemblies) is otherwise word-identical.
408.37 / 408.39 / 408.41 (identity)
408.37 / 408.39 / 408.41 — 2017 and 2023 (word-identical, machine-verified)
408.37 Panelboards in damp or wet locations shall be installed to comply with 312.2.
408.39 In panelboards, fuses of any type shall be installed on the load side of any switches. Exception: Fuses installed as part of service equipment in accordance with the provisions of 230.94 shall be permitted on the line side of the service switch.
408.41 Each grounded conductor shall terminate within the panelboard in an individual terminal that is not also used for another conductor. Exception: Grounded conductors of circuits with parallel conductors shall be permitted to terminate in a single terminal if the terminal is identified for connection of more than one conductor.2017: on-disk NFPA scan · 2023: on-disk rows — alpha-identical all three
408.38 Enclosure — dead-front rule + the NEW 10,000 A evaluation sentence
408.38 — 2017 (verbatim)
408.38 Enclosure. Panelboards shall be mounted in cabinets, cutout boxes, or identified enclosures and shall be dead-front. Exception: Panelboards other than of the dead-front, externally operable type shall be permitted where accessible only to qualified persons. 70 -2642017: on-disk NFPA scan §408.38
408.38 — 2023 (verbatim)
Panelboards shall be mounted in cabinets, cutout boxes, or identified enclosures and shall be dead-front. Where the available fault current is greater than 10,000 amperes, the panelboard and enclosure combination shall be evaluated for the application. Exception: Panelboards other than of the dead-front, externally operable type shall be permitted where accessible only to qualified persons.2023: on-disk row 408.38
Delta D11 — 408.38 gains the 10,000 A evaluation sentence — 2023 inserts: "Where the available fault current is greater than 10,000 amperes, the panelboard and enclosure combination shall be evaluated for the application" — sitting between the dead-front rule and the qualified-persons Exception. Machine-verified: zero hits for "10,000 amperes" in the on-disk 2017 408 region. This is the panelboard-side twin of the 408.6 (Delta D5) and 408.9(B) (Delta D6) fault-current rules — all three hinge on the same 10,000 A number.
408.40 Grounding of Panelboards (identity core, two rewords)
408.40 — 2023 (verbatim; 2017 core word-identical with two rewords)
Panelboard cabinets and panelboard frames, if of metal, shall be in physical contact with each other and shall be connected to an equipment grounding conductor. Where the panelboard is used with nonmetallic raceway or cable or where separate equipment grounding conductors are provided, a terminal bar for the equipment grounding conductors shall be secured inside the cabinet. The terminal bar shall be bonded to the cabinet and panelboard frame, if of metal; otherwise it shall be connected to the equipment grounding conductor that is run with the conductors feeding the panelboard. Exception: Where an isolated equipment grounding conductor for a branch circuit or a feeder is provided as permitted by 250.146(D), the insulated equipment grounding conductor that is run with the circuit conductors shall be permitted to pass through the panelboard without being connected to the panelboard's equipment grounding terminal bar. Equipment grounding conductors shall not be connected to a terminal bar provided for grounded conductors or neutral conductors unless the bar is identified for the purpose and is located where interconnection between equipment grounding conductors and grounded circuit conductors is permitted or required by Part II and Part VII of Article 250.2017: on-disk NFPA scan §408.40 · 2023: on-disk row 408.40
Delta D12 — 408.40: the isolated-EGC scope + the Article 250 Part hook — 2017: "Where an isolated equipment grounding conductor is provided as permitted by 250.146(D)…" and "…permitted or required by Article 250." 2023: "Where an isolated equipment grounding conductor for a branch circuit or a feeder is provided as permitted by 250.146(D)…" and "…permitted or required by Part II and Part VII of Article 250." Everything else — the cabinet/frame contact, the EGC terminal bar, the bonded-or-run-with rule — is word-identical.
408.43 Panelboard Orientation (NEW in 2023)
408.43 — 2023 (NEW section; no 2017 counterpart)
Panelboards shall not be installed in the face-up or face-down position.2023: on-disk row 408.43 · 2017 scan: zero hits for "face-up" / "face-down" (machine-asserted)
Delta D16 — NEW 408.43: no face-up or face-down panelboards — The on-disk Mike Holt 2023 summary, entry 408.43: "Panelboard Orientation — This rule was expanded to prohibit face-down installations of panelboards." On disk: the 2017 Article 408 region has zero hits for "face-up" or "face-down" (machine-asserted), so the 2023 sentence is new to Article 408 — Mike Holt's "expanded" is their characterization; the on-disk record shows the orientation prohibition appearing in 2023 as its own section, 408.43: "Panelboards shall not be installed in the face-up or face-down position."
Part IV — Construction Specifications (408.50–408.58)
408.50 / 408.51 / 408.52 / 408.54 (identity)
408.50 / 408.51 / 408.52 / 408.54 — 2017 and 2023 (word-identical, machine-verified)
408.50 The panels of switchboards and switchgear shall be made of moisture-resistant, noncombustible material.
408.51 Insulated or bare busbars shall be rigidly mounted.
408.52 Instruments, pilot lights, voltage (potential) transformers, and other switchboard or switchgear devices with potential coils shall be supplied by a circuit that is protected by standard overcurrent devices rated 15 amperes or less. Exception No. 1: Overcurrent devices rated more than 15 amperes shall be permitted where the interruption of the circuit could create a hazard. Short-circuit protection shall be provided. Exception No. 2: For ratings of 2 amperes or less, special types of enclosed fuses shall be permitted.
408.54 A panelboard shall be provided with physical means to prevent the installation of more overcurrent devices than that number for which the panelboard was designed, rated, and listed. For the purposes of this section, a 2-pole circuit breaker or fusible switch shall be considered two overcurrent devices; a 3-pole circuit breaker or fusible switch shall be considered three overcurrent devices.2017: on-disk NFPA scan · 2023: on-disk rows — alpha-identical all four (408.52: the 15 A instrument-circuit cap with both Exceptions)
408.53 Component Parts (2017 ONLY — deleted in 2023)
408.53 — 2017 (deleted in 2023)
408.53 Component Parts. Switches, fuses, and fuseholders used on panelboards shall comply with the applicable requirements of Articles 240 and 404.2017: on-disk NFPA scan §408.53 · 2023 dataset: no 408.53 row (machine-asserted)
Delta D15 — 408.53 (Component Parts) deleted — The 2017 scan carries "408.53 Component Parts. Switches, fuses, and fuseholders used on panelboards shall comply with the applicable requirements of Articles 240 and 404." The on-disk 2023 dataset has no 408.53 row (machine-asserted) — Part IV goes straight from 408.52 to 408.54.
408.55 Wire-Bending Space Within a Panelboard Enclosure (identity core, table re-cites)
408.55 — 2023 (verbatim, all three rows; 2017 core word-identical with the Table 312.6(B)→(B)(2) re-cite)
(A) The enclosure for a panelboard shall have the top and bottom wire-bending space sized in accordance with Table 312.6(B)(2) for the largest conductor entering or leaving the enclosure. Exception No. 1: Either the top or bottom wire-bending space shall be permitted to be sized in accordance with Table 312.6(A) for a panelboard rated 225 amperes or less and designed to contain not over 42 overcurrent devices. For the purposes of this exception, a 2-pole or a 3-pole circuit breaker shall be considered as two or three overcurrent devices, respectively. Exception No. 2: Either the top or bottom wire-bending space for any panelboard shall be permitted to be sized in accordance with Table 312.6(A) where at least one side wire-bending space is sized in accordance with Table 312.6(B)(2) for the largest conductor to be terminated in any side wire-bending Space. Exception No. 3: The top and bottom wire-bending space shall be permitted to be sized in accordance with Table 312.6(A) spacings if the panelboard is designed and constructed for wiring using only a single 90-degree bend for each conductor, including the grounded circuit conductor, and the wiring diagram shows and specifies the method of wiring that shall be used. Exception No. 4: Either the lop or the bottom wire-bending space, but not both, shall be permitted to be sized in accordance with Table 312.6(A) where there are no conductors terminated in that space.
(B) Side wire-bending space shall be in accordance with Table 312.6(A) for the largest conductor to be terminated in that space.
(C) Where a raceway or cable entry is in the wall of the enclosure opposite a removable cover, the distance from that wall to the cover shall be permitted to comply with (he distance required for one wire per terminal in Table 312.6(A). The distance between the center of the rear entry and the nearest termination for the entering conductors shall not be less than the distance given in Table 312.6(B)(2).2017: on-disk NFPA scan §408.55 · 2023: on-disk rows 408.55(A)–(C) (2023 CSV carries the (A)/(B)/(C) rows; no standalone 408.55 lead row)
Delta D13 — Table 312.6(B) → Table 312.6(B)(2) re-cite (three places) — 2017 408.55 cites "Table 312.6(B)" in (A), Exception 2, and (C). 2023 cites "Table 312.6(B)(2)" in the same three places (the on-disk 2023 312.6(B) splits into (B)(1)/(B)(2), and (B)(2) is the "conductor enters or leaves through the wall opposite its terminal" table). No number moved — it is a cross-reference renumber.
408.56 Minimum Spacings + Table 408.56 (2023 values on disk; 2017 grid degraded — disclosed)
408.56 — 2017 (verbatim lead)
408.56 Minimum Spacings. The distance between bare metal parts, busbars, and so forth shall not be less than specified in Table 408.56.
Where close proximity does not cause excessive heating, parts of the same polarity at switches, enclosed fuses, and so forth shall be permitted to be placed as close together as convenience in handling will allow.
Exception: The distance shall be permitted to be less than that specified in Table 408.56 at circuit breakers and switches and in listed components installed in switchboards, switchgear, and panelboards.2017: on-disk NFPA scan §408.56 (lead + Exception verbatim; the scan's Table 408.56 grid sits on the page with the misprinted "409.21" running header and is OCR-degraded — disclosed at the bottom, so the table values below are asserted from the 2023 row)
408.56 — 2023 (verbatim lead + table embedded in the row)The distance between uninsulated metal parts, busbars, and other uninsulated live parts shall not be less than specified in Table 408.56.
Where close proximity does not cause excessive heating, parts of the same polarity at switches, enclosed fuses, and so forth shall be permitted to be placed as close together as convenience in handling will allow.
Table 408.56 — Minimum Spacings Between Bare Metal Parts
| AC or DC Voltage | Opposite Polarity Where Mounted on the Same Surface | Opposite Polarity Where Held Free in Air | Live Parts to Ground* |
|---|
| mm / in. |
| Not over 125 volts, nominal | 19.1 / 3⁄4 | 12.7 / 1⁄2 | 12.7 / 1⁄2 |
| Not over 250 volts, nominal | 31.8 / 1¼ | 19.1 / 3⁄4 | 12.7 / 1⁄2 |
| Not over 1000 volts, nominal | 50.8 / 2 | 25.4 / 1 | 25.4 / 1 |
*For spacing between live parts and doors of cabinets, the dimensions in
312.101(A) shall apply. (2023 footnote; 2017 cited 312.11(A).)
2023: on-disk row 408.56 (table embedded; the 2023 CSV prints "Table. 408.56" in the Exception — an extra period, disclosed at the bottom)
Delta D14 — 408.56: "bare metal parts… and so forth" → "uninsulated metal parts… and other uninsulated live parts" + the 312.11 → 312.101 footnote re-cite (2017 table grid degraded on disk — values asserted from 2023 only) — The 2017 lead: "The distance between bare metal parts, busbars, and so forth shall not be less than specified in Table 408.56." The 2023 lead: "The distance between uninsulated metal parts, busbars, and other uninsulated live parts shall not be less than specified in Table 408.56." The 2017 footnote ("For spacing between live parts and doors of cabinets, see 312.11(A)(1), (2), and (3)") re-cites to "312.101(A)" in 2023 — the on-disk 2023 dataset has 312.101 and no 312.11 row (machine-asserted), consistent with the 2023 cabinet-spacing renumber. Table-values honesty: the on-disk 2017 scan prints the Table 408.56 grid on the page that carries a misprinted "409.21" running header (a scan layout artifact), and that grid is heavily OCR-degraded (only the 12.7/½ fragments are legible; most cells are missing or garbled) — so this page asserts the table values from the on-disk 2023 row only and does not claim a 2017→2023 digit comparison for this table. The reword of the lead and the footnote re-cite are the machine-diffed text deltas.
408.58 Panelboard Marking (identity)
408.58 — 2017 and 2023 (word-identical, machine-verified)
Panelboards shall be durably marked by the manufacturer with the voltage and the current rating and the number of ac phases or dc buses for which they are designed and with the manufacturer's name or trademark in such a manner so as to be visible after installation, without disturbing the interior parts or wiring.2017: on-disk NFPA scan §408.58 · 2023: on-disk row 408.58 — alpha-identical
The seventeen machine-diffed 2017→2023 deltas (summary)
| # | Section | What moved |
|---|
| D1 | 408.2 | Cross-article list (Articles 240/250/312/404 + 500–517) deleted; 408.2 becomes the reconditioned-equipment section (NEW (A)/(B): no reconditioned panelboards; fire/water/corrosion evaluation rule). |
| D2 | 408.3(A)(2) | The service-barrier rule ("inadvertent contact") left Article 408 — now in on-disk 2023 230.62(C) (service) / 215.15 (feeders). Zero 408 hits in 2023. |
| D3 | 408.3(A)(3)→(A)(2) | "Same Vertical Section" item renumbered up one; 2023 lead reads "(A)(1) and (A)(2)." Text unchanged. |
| D4 | 408.3(D) | Terminal-location text moved to 408.18(C); 2023 408.3(D) is a one-line pointer. |
| D5 | 408.6 (NEW) | Short-circuit current rating not less than the available fault current; AFC + calculation date field-marked (110.21(B)(3)) other than 1-/2-family dwellings. |
| D6 | 408.9 (NEW) | Replacement panelboards in existing enclosures: rating retention if listed for the enclosure; 10,000 A field-label seam; old listing marks removed. |
| D7 | 408.4 | "identification" → "description" (title + (A)); (A) becomes a six-condition list; (B) gains the physical location of the power source. Mike Holt-documented. |
| D8 | 408.18(C) (NEW) | Rear/side-access marking on the front + load-terminal rules (C)(1)–(3) (the destination of the 2017 408.3(D) text). |
| D9 | 408.23 (NEW) | "The requirements of 312.8(B) shall apply" (power monitoring / energy management equipment in switching wiring space). |
| D10 | 408.36 | Three exceptions → two: 2017 Ex 1 (230.71 multiple disconnect) deleted; 2017 Ex 2 (two-main, 42 devices) gains "in other than service equipment" and becomes Ex 1; 2017 Ex 3 (existing residential) becomes Ex 2. |
| D11 | 408.38 | NEW sentence: AFC > 10,000 A → panelboard + enclosure combination evaluated for the application. |
| D12 | 408.40 | Isolated-EGC scope gains "for a branch circuit or a feeder"; the Article 250 hook becomes "Part II and Part VII of Article 250." |
| D13 | 408.55 | Table 312.6(B) → Table 312.6(B)(2) re-cite in (A), Ex 2, and (C). |
| D14 | 408.56 | "bare metal parts… and so forth" → "uninsulated metal parts… and other uninsulated live parts"; footnote 312.11(A) → 312.101(A). Table values asserted from the 2023 row (2017 grid OCR-degraded on disk — disclosed). |
| D15 | 408.53 | "Component Parts" section deleted (Part IV: 408.52 → 408.54). |
| D16 | 408.43 (NEW) | "Panelboards shall not be installed in the face-up or face-down position." Mike Holt-documented. |
| D17 | 408.36(D) | Backfed-devices fastener sentence: "mounting means on the panel" → "on the panelboard" (one word; rule otherwise word-identical). |
No number moved in the parts that stayed: the 408.30 rating rule, the 408.36 OCPD cap + 42-device convention + 30 A/200 A rule, the 900 mm (3 ft) ceiling clearance, the 75 mm (3 in.) raceway-rise cap, the 15 A instrument-circuit cap, every Table 408.5 value (verified digit-identical 2017↔2023 on disk), and the 250.170–250.178 / 250.28(D) / 250.146(D) hooks are all machine-verified unchanged. (Table 408.56 values are asserted from the on-disk 2023 row only — the 2017 grid is OCR-degraded on disk, Delta D14.)
The on-disk Mike Holt 2023 change summary (three in-scope entries, verbatim)
"408.4 Circuit Directory and Descriptions of Circuit Source— The term “identification” in 408.4(A) was replaced with the term “description” in this section (and in the title) to avoid confusion with the defined term “identified.” Additional language was added to subdivision (B) that requires the marking to include the physical location of the power source."
On-disk Mike Holt 2023 change summary (art48_mh23cc_full.txt) — quoted verbatim incl. its line-break hyphenation ("descrip-tion").
"408.9 Replacement Panelboards— This is a new section that provides guidance for installing new “guts” in an existing enclosure."
On-disk Mike Holt 2023 change summary — quoted verbatim.
"408.43 Panelboard Orientation— This rule was expanded to prohibit face-down installations of panelboards."
On-disk Mike Holt 2023 change summary — quoted verbatim. On-disk caveat: the 2017 Article 408 region has zero "face-up"/"face-down" hits, so "expanded" is Mike Holt's characterization — the on-disk record shows the orientation sentence new to Article 408 in 2023 (Delta D16).
Machine-counted silence: the on-disk Mike Holt 2023 change summary has exactly three Article 408 entries (408.4, 408.9, 408.43) — the other fourteen deltas are direct on-disk 2017-scan ↔ 2023-dataset diffs, not summary-sourced claims. 2020 edition gap (honest scope): the on-disk 2020 source (slideshare scan) carries no Article 408 body text — its only 408.x token is a single table-of-contents cross-reference ("408.52") with no section body (machine-asserted), so no 2020 position is asserted anywhere on this page; the edition story is 2017 ↔ 2023, both sides on disk.
Six worked examples (every number from the real shipped PanelWright core, zero hand math)
EX1 — the 408.30 + 408.36 package on a 200 A panelboard
A 200 A service feeder (220-calculated load = 200 A minimum feeder capacity) lands in a 200 A panelboard. 408.30: panelboard rating (200 A) ≥ minimum feeder capacity (200 A) — passes. 408.36: the overcurrent device rating must be not greater than the panelboard — so the OCPD cap is 200 A. 408.36(A): the panelboard is equipped with snap switches rated 30 A or less, and the OCPD (200 A) is ≤ the 200 A snap-switch cap — passes. The supply-side conductors for 200 A at 75 °C copper pick from the verified Table 310.16 core: 3/0 AWG Cu.
core: pickConductor31016(200, "cu", 75) = 3/0; cap logic: min(feeder OCPD, panelboard rating) = 200 A
EX2 — the 10,000 A short-circuit seam (408.6 / 408.9(B) / 408.38)
Three 2023 rules all hinge on the same 10,000 A number, and the seam is "greater than" — so exactly 10,000 A is not over it:
| Available fault current | 408.6 field marking | 408.9(B) replacement panelboard | 408.38 panelboard + enclosure |
|---|
| 10,001 A | Mark AFC + calc date (110.21(B)(3)) | "the completed work shall be field labeled" | "shall be evaluated for the application" |
| 10,000 A | Mark (no cap in 408.6 — marking applies regardless of size) | "the replacement panelboard shall be identified for the application" | Evaluation sentence not triggered (not > 10,000 A) |
seam: 10,000 A exactly → identify-for-the-application route; 10,001 A → field-label + evaluate route
EX3 — the 42-device counting convention (408.36 Exception 1)
A panelboard wired under the two-main-breaker exception "shall not contain more than 42 overcurrent devices," with a 2-pole breaker counting as two and a 3-pole as three. Worked: 12 one-pole + 8 two-pole + 4 three-pole = 12×1 + 8×2 + 4×3 = 40 devices — under the 42 cap (within). Remaining budget for additional 3-pole breakers: ⌊(42 − 12×1 − 8×2) / 3⌋ = 4 more 3-pole devices before the cap.
count = 12 + 16 + 12 = 40 ≤ 42 (passes); 3-pole budget remaining = (42 − 28) / 3 = 4
EX4 — the 30 A snap-switch circuit + the 408.36(C) delta-breaker prohibition
A 30 A continuous load on 120/240 V single-phase, on a panelboard with 30 A snap switches. 408.36(A): snap switches ≤ 30 A → OCPD ≤ 200 A (the panel's 200 A OCPD passes). The branch: 30 A load → 30 A OCPD; the conductor pick from the verified core is 10 AWG Cu (35 A @ 75 °C). But the 240.4(D) small-conductor caps gate it: 12 AWG Cu's cap is 20 A < the 30 A OCPD → 12 AWG rejected; 10 AWG Cu's cap is 30 A = the OCPD → 10 AWG Cu passes. And the 408.36(C) prohibition is concrete: this panelboard has only 120/240 V (less than 3-phase) buses, so a 3-phase disconnect or overcurrent device shall not be connected to its bus, and delta breakers shall not be installed in panelboards — a 480 V 3-phase load needs its own 3-phase panelboard.
core: pickConductor31016(30, "cu", 75) = 10; smallConductorCap(12,"cu") = 20 A (reject); smallConductorCap(10,"cu") = 30 A (pass); delta breaker in panelboard = false
EX5 — the 408.52 instrument-circuit cap (15 A)
An instrument/pilot-light circuit on the switchboard: 960 VA at 120 V = 8 A. 408.52 requires a circuit "protected by standard overcurrent devices rated 15 amperes or less" → 15 A OCPD (≤ the cap, passes). Exception No. 1 allows > 15 A only where interruption would create a hazard (short-circuit protection still required); Exception No. 2 allows special enclosed fuses at ≤ 2 A. Conductor pick (60 °C column, the instrument-circuit termination convention): 14 AWG Cu.
core: load = 960/120 = 8 A; OCPD cap = 15 A; pickConductor31016(8, "cu", 60) = 14
EX6 — Table 408.56 on a 125 V nominal switchboard (values from the on-disk 2023 row)
Opposite-polarity live parts on the same surface at 125 V nominal: 19.1 mm (0.75 in.); held free in air: 12.7 mm (0.50 in.); live parts to ground: 12.7 mm (0.50 in.). These cells are the on-disk 2023 row for "Not over 125 volts, nominal." The door-spacing footnote now points at 312.101(A) (2023) vs 312.11(A) (2017) — Delta D14. (The on-disk 2017 grid is OCR-degraded, so no 2017→2023 digit comparison is claimed for these cells.)
Table 408.56, row "Not over 125 V nominal": 19.1/0.75 · 12.7/0.50 · 12.7/0.50
Frequently asked questions
Q: What is the difference between a switchboard, switchgear, and a panelboard?
Article 408 covers all three with shared rules (408.3 busbar support/arrangement, 408.16–408.22 switchboard/switchgear location and grounding) plus panelboard-specific Part III (408.30–408.43): the 408.30 rating floor (not less than the minimum feeder capacity per Article 220), the 408.36 OCPD cap, the dead-front 408.38 enclosure, the 408.40/408.41 grounding/termination rules, and the 2023-new 408.43 orientation prohibition. In practice: a panelboard is the load-side equipment full of branch/feeder OCPDs; switchboards and switchgear are the larger building services (Part II/IV rules, Table 408.56 spacings). The code text is quoted verbatim above — this page is a design aid, not a definition manual.
Q: What size overcurrent device do I use for a panelboard?
408.36: a panelboard "shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard," located within or on the supply side. Two 2023 exceptions: (1) two main breakers/fuse sets in other than service equipment with a combined rating ≤ the panelboard — capped at 42 overcurrent devices (2-pole counts as two, 3-pole as three); (2) existing panelboards used as service equipment for an individual residential occupancy. Plus 408.36(A): snap switches ≤ 30 A → OCPD ≤ 200 A; (B): transformer-supplied → protection on the secondary; (C): no 3-phase OCPD on a less-than-3-phase bus, no delta breakers in panelboards; (D): backfed plug-in devices secured with an additional fastener.
Q: What is the new 408.6, and what does it make me mark?
New in 2023: switchboards, switchgear, and panelboards "shall have a short-circuit current rating not less than the available fault current." Other than in one- and two-family dwelling units, the available fault current and the date the calculation was performed "shall be field marked on the enclosure at the point of supply," per 110.21(B)(3). The companion 10,000 A rules (408.9(B) field-label, 408.38 evaluation) are the same number applied to replacements and enclosures.
Q: Can I put a new panelboard "guts" set into an old enclosure?
Yes — 408.9 (new in 2023) governs: if the replacement panelboard is listed for the specific enclosure (catalog number or dimensional information), it "shall be permitted to maintain its short-circuit current rating." If the available fault current is greater than 10,000 A, the completed work "shall be field labeled"; at 10,000 A or less, the replacement panelboard "shall be identified for the application." Either way, "any previously applied listing marks on the cabinet that pertain to the panelboard shall be removed."
Q: Can I install a panelboard face-up or face-down?
No. 408.43 (new in 2023): "Panelboards shall not be installed in the face-up or face-down position." The on-disk Mike Holt 2023 summary documents this as the panelboard-orientation rule.
Q: What changed in Article 408 from 2017 to 2023?
Seventeen machine-diffed deltas (summarized in the table above): 408.2 became the reconditioned-equipment section (the cross-article list deleted); the 408.3(A)(2) barrier rule moved to 230.62(C)/215.15; 408.3(A)(3)→(A)(2) renumber; 408.3(D) → 408.18(C) pointer; NEW 408.6 (SCCR + marking), 408.9 (replacement panelboards), 408.18(C), 408.23 (312.8(B)), 408.43 (orientation); 408.4 identification→description rework; 408.36 three-exception → two-exception restructure; 408.36(D) "panel"→"panelboard"; 408.38 10,000 A sentence; 408.40 two rewords; 408.55 table re-cite; 408.56 reword + 312.101 footnote; 408.53 deleted. No number moved in the parts that stayed.
Sources & verification method
- 2017 text: on-disk official NFPA 70 (2017 NEC) scan, Article 408 region (lines 46208–46897 of the flat extraction), machine-reflowed into 27 top-level sections (s92_408_2017_sections.json). Disclosed OCR/scan artifacts (each machine-asserted in the verify script): "on a_ switchboard" (408.3(A) underscore), "shail" for "shall" and "floorstanding" for "floor-standing" (408.5), "muultisection" for "multi-section" (408.3(E)(1) Exception — the on-disk 2023 row prints "multisection"; the word differs, the rule does not), "wirebending" printed without the hyphen (408.3(G) — 2023 prints "wire bending"), "240,21(C)(1)" comma for the 240.21(C)(1) cite (408.36(B)), "wive-bending" for "wire-bending" (408.55 Ex 2), "3pole" without the hyphen (408.54 — 2023 prints "3-pole"), the "70 -262" page-number noise printed mid-408.3(B) (408.22 and 408.38 carry the same "70 -263"/"70 -264" noise at their ends — trimmed here by displaying the 2023 text for those identity sections), the 408.3(F) sign-text artifacts ("AG" for AC, "VOLIS" for VOLTS in the 2017 scan's fill-in sign text), and the Table 408.56 grid printed on the page with the misprinted "409.21" running header (scan layout artifact — the grid itself is OCR-degraded, so no 2017→2023 table-digit comparison is claimed). The 408.3(F) caution-sign text is blank-fill-in form in BOTH on-disk sources ("CAUTION _____ PHASE HAS _____ VOLTS TO GROUND"), with the 2017 scan's fill-in blanks OCR-degraded as above.
- 2023 text: on-disk 2023 NEC dataset (art35_nec_csv.csv), all 60 Article 408 rows — the complete article in the dataset (verified: the row set spans 408.1 through 408.58 with no 408.8/408.53/408.57 rows). Disclosed 2023 dataset artifacts: "Table. 408.56" extra period (408.56 Exception), "either the lop or the bottom" for "top" (408.55(A) Ex 4), "comply with (he distance" for "the" (408.55(C)), "any side wire-bending Space" capital S (408.55(A) Ex 2).
- Mike Holt 2023 change summary: on-disk (art48_mh23cc_full.txt) — exactly three in-scope entries (408.4, 408.9, 408.43), quoted verbatim above; the other fourteen deltas are direct on-disk diffs, not summary claims (machine-counted silence asserted).
- 2020 edition gap: the on-disk 2020 source carries no Article 408 body — its only 408.x token is a single table-of-contents cross-reference ("408.52") with no section body (machine-asserted), so no 2020 position is asserted.
- Worked examples: every number computed by the shipped PanelWright core (pickConductor31016, nextStdBreaker, smallConductorCap) under node (compute_art67.js → art67_numbers.json) — zero hand math; the test suite re-runs the core and compares.
- Verification: verify_art67.py runs the machine checks (all 60 2023 rows present, all 27 2017 sections present, the seventeen deltas both-sided, the identity word-checks, the zero-hit absence claims, the worked figures, the core re-run, the sitemap/index/README entries, tag balance) — the count in the footer is the script's actual total, and a self-consistency check prevents the page from claiming a number the verifier does not run. 193 machine-verified checks — all 193 pass.
Scope & honesty: this is a design aid, not code commentary and not engineering advice. The adopted edition in your jurisdiction governs. Where 2017 and 2023 differ, the delta boxes say what moved; where a number is quoted from a scan, the disclosed OCR artifacts are listed. AI-built, AI-verified, fully disclosed.