Panelboards Practice Questions

C. A device rated not greater than the panelboard, located within it or at any point on its supply side

One device, sized against the panelboard rating and nothing else, and the code does not care whether it sits in the can or upstream in the gear. So the first thing to read in one of these items is the two ratings. What fails is a panelboard whose rating is below the device ahead of it.

NEC 2026 408.36

A. Yes, since the device is not greater than the panelboard rating and may sit at any point on the supply side

Both halves of the rule are met, so nothing here is a violation. The device rating has to be not greater than the panelboard rating, which is a ceiling and not a match. Distance between the device and the panel is not part of the rule at all, though the conductors between them are an ordinary conductor problem answered somewhere else.

NEC 2026 408.36

D. Two main circuit breakers or two sets of fuses in other than service equipment, whose combined rating is not greater than the panelboard

The exception is narrow, it says in other than service equipment, and it caps the panelboard at 42 overcurrent devices. The six-handle picture belongs to the service disconnect rules and is not an exception to this section. Older study material carries a deleted exception that used to cover a service panelboard with multiple disconnects, and a candidate reasoning from it will answer confidently and wrongly.

NEC 2026 408.36

B. A two-pole counts as two and a three-pole counts as three

The exception says so in its own words, and the same counting rule appears again in the section on the maximum number of overcurrent devices a panelboard may be built to hold. So a panelboard full of three-pole breakers reaches the limit at fourteen handles. Counting handles rather than poles is the error the sentence exists to prevent.

NEC 2026 408.36, 408.54

A. On the secondary side of the transformer

The subsection puts it on the secondary and then carries one exception, for the case where the primary protection satisfies the transformer secondary conductor tap rule. That exception is the whole reason candidates get this one wrong, since they remember the relief and forget it is the exception rather than the rule. Read the stem for whether the primary protection has been qualified.

NEC 2026 408.36(B)

C. 200 amperes or less

The limit is on the panelboard protection rather than on the individual switches, which is what makes it easy to misread. It exists because a small snap switch is not built to survive the fault current a larger device would let through. This subsection sits immediately under the general protection rule and is easy to miss on the page.

NEC 2026 408.36(A)

B. They shall not be installed in panelboards

The same subsection also bars connecting a three-phase disconnect or overcurrent device to the bus of a panelboard that has fewer than three phase buses. Both halves are about a device reaching for a phase the panel does not have. High leg marking is a real requirement and it lives elsewhere, which makes it an attractive wrong answer here.

NEC 2026 408.36(C)

D. An additional fastener that requires something other than a pull to release the device from its mounting

Three words carry the rule. Additional, so the normal mounting is not it. Other than a pull, so a stiffer clip is not it either, and what the rule wants is a screw or a bracket. Field-installed is the trigger, which is why a factory main in a main breaker panel is a different situation from a breaker you fed backward on site.

NEC 2026 408.36(D)

C. Where the power source operates only in interactive mode, or where a multimode inverter has island mode open-phase protection

Article 705 relaxes the fastener in exactly those two cases, and both of them are about a source that will not keep the breaker stabs energized once it leaves the bus. An interactive-only source stops producing when it loses the grid. A source that can carry an island earns the relief only where the open-phase protection is there.

NEC 2026 705.30(E)

B. Not permitted, since each grounded conductor gets an individual terminal not also used for another conductor

It is a violation whether or not the screw is tight, because two neutrals sharing a lug means lifting one circuit opens the return path of another. The one exception covers the grounded conductors of circuits with parallel conductors, and it needs a terminal identified for connection of more than one conductor. An ordinary bar is not identified for it.

NEC 2026 408.41

A. On a terminal bar for equipment grounding conductors, secured inside the cabinet and bonded to the cabinet and frame

The section calls for a bar of its own and requires it to be bonded to the metal it is protecting. Equipment grounding conductors are not landed on a bar meant for grounded conductors unless that bar is identified for the purpose and Article 250 permits the two to be connected there. In a subpanel Article 250 does not permit it.

NEC 2026 408.40

D. In neither the face-up nor the face-down position

The rule is one sentence with no exceptions and no listing escape. Debris and water collect in an upward-facing enclosure and a downward-facing one cannot be worked on safely. A stem that describes a panel laid into a countertop or a soffit is testing this line.

NEC 2026 408.43

B. A cabinet, cutout box or identified enclosure, and dead-front construction

Dead-front is the operative word and there is one exception for panelboards accessible only to qualified persons. The section also says that where the available fault current is greater than 10,000 amperes, the panelboard and enclosure combination has to be evaluated for the application. Fault current marking is a real requirement and it lives in a different section.

NEC 2026 408.38

A. Fuses of any type are installed on the load side of any switches

Opening the switch first is what lets someone change a fuse without touching a live fuse clip, so the fuse goes downstream of the switch. The one exception covers service fuses installed under the service equipment rules, which are permitted on the line side of the service switch. That exception is the only place the order reverses.

NEC 2026 408.39

C. Not less than the minimum calculated load

One short section, easily read past, and it sends you to the load calculation article for the number. It is a separate question from the protection rule, which compares the panelboard rating against the device ahead of it. An item that gives you a calculated load, a panelboard rating and a breaker size is asking both questions in one stem.

NEC 2026 408.14

D. That they be closed with identified closures or another approved means giving protection substantially equivalent to the enclosure wall

The word identified is doing the work, since a manufactured filler plate is identified for the opening and a piece of sheet metal is not. The alternative the section allows still has to be approved and still has to match the wall of the enclosure for protection. This one shows up on inspection reports more than almost anything else in the article.

NEC 2026 408.7

A. A description of each circuit that is clear, evident and specific to its purpose or use, including spare positions with an unused overcurrent device

The section adds two more conditions worth remembering. The description may not depend on transient conditions of occupancy, so tenant names do not qualify. And it has to be detailed enough that two circuits could not be confused with each other.

NEC 2026 408.4(A)

C. A label giving the identification and physical location of where the power originates, permanently affixed and not handwritten

The requirement reaches switchboards, switchgear and panelboards supplied by a feeder in other than one- and two-family dwellings. The three conditions are the content, the durability and the method, and the last one rules out a marker pen. It exists so that somebody tracing a fault can find the source without opening anything.

NEC 2026 408.4(B)

B. One, unless the two to six arrangement in 230.71(B) is met

The section opens by saying one and then points at the subsection that permits two to six in specific arrangements. Each of the two to six stands in its own enclosure, its own switchboard vertical section with barriers, its own switchgear or transfer switch compartment, its own metering center compartment, or a motor control center under stated limits. A single can with six handles in it is not among the arrangements.

NEC 2026 230.71, 230.71(B)

D. A disconnect installed as part of listed equipment and used solely to disconnect a surge-protective device

The list runs to four items and all of them are accessory functions rather than load service. Power monitoring, a surge-protective device, the control circuit of a ground-fault protection system, and the control circuit for a power-operable service disconnect. An item that shows you seven handles and expects a violation is often showing you six plus one of these.

NEC 2026 230.71(A)

C. In a bathroom, a showering facility, or a locker room with showering facilities, unless it is supplementary protection

The restriction is written to the room and not to the occupancy, so a bathroom in a commercial building is covered on the plain words. Older material saying it applies only in dwelling units, dormitories and guest rooms is describing a narrower rule than the one in the book you will sit with. Supplementary overcurrent protection is carved out by name.

NEC 2026 240.24(E)

D. The vicinity of easily ignitible material such as clothes closets, and over the steps of a stairway

These rules live in Article 240 rather than Article 408, because what the code restricts is the location of overcurrent devices and the panel is only illegal because of what is inside it. Candidates who go looking for a location rule in Article 408 do not find one and lose the item. Learn where to look before you learn the list.

NEC 2026 240.24(D), 240.24(F)

A. 6 feet 7 inches

The measurement is taken from the grade, floor or working platform to the center of the grip with the handle in its highest position. Four listed cases and one exception let equipment out of it, and they are worth reading because that is where items get their exceptions from. Nothing in the section measures to the top of the enclosure.

NEC 2026 240.24(A)

B. Nothing foreign to the electrical installation, from the floor to 6 feet above the equipment or to the structural ceiling, whichever is lower

This is the dedicated equipment space and it is a different rule from the working space in front, though both live in the same section. A suspended ceiling with removable panels is permitted inside the zone by exception, and sprinkler protection is permitted for the room. The area above the dedicated space may hold foreign systems where protection against leaks and condensation is installed.

NEC 2026 110.26(E)(1)(a)

D. Where it is rated 1200 amperes or more and over 6 feet wide

Both conditions have to hold, and the same rule reaches a group of service disconnects whose combined rating is 1200 amperes or more and whose combined width is over 6 feet. Each entrance is at least 24 inches wide and 6 feet 6 inches high. The 800 ampere figure in the wrong answer belongs to the personnel door rule two paragraphs later, which is about panic hardware rather than about a second entrance.

NEC 2026 110.26(C)(2)