Services practice questions

Correct: B — Ground-fault protection of equipment

230.95 requires GFPE for solidly grounded wye services over 150V to ground but not exceeding 1000V phase-to-phase, for disconnects rated 1000A or more. A 277/480V system falls within that range (277V to ground, 480V phase-to-phase), and 1200A meets the threshold, so protection is required. The industrial-process exception only removes the requirement for nonorderly shutdown hazards, and fuses vs. breakers doesn't change applicability.

Correct: B — At a readily accessible location nearest the point of entrance of the service conductors

230.70(A)(1) requires the service disconnect to be readily accessible either outside the building or, if inside, nearest the point of entrance of the service conductors — not just anywhere readily accessible inside. Bathrooms are explicitly prohibited under 230.70(A)(2).

Correct: C — Not higher than the ampacity of the conductor

230.90(A) requires the overcurrent device's rating or setting to be not higher than the ampacity of the ungrounded service conductor it protects. The 125%-of-ampacity option and the 80%-of-ampacity option both invert or misapply continuous-load sizing concepts from other parts of the Code, and tying the rating strictly to the disconnect rating ignores the conductor ampacity limit this section actually sets.

Correct: A — Cable limiters

230.82(1) permits cable limiters on the supply side. General panelboards, branch circuits, and receptacle circuits are downstream loads that must be fed from the load side of the service disconnect, not the supply side.

Correct: A — Capacity requirements exceed 2000 amperes at 1000 volts or less

230.2(C) permits an additional service where capacity requirements exceed 2000 amperes at a supply voltage of 1000 volts or less. Multiple tenants alone falls under the special-occupancy provision in 230.2(B), a lower amperage doesn't trigger this exception, and different voltages are addressed separately under 230.2(D).

Correct: C — 2.6 m (8 ft 6 in.)

230.24(A) sets the base vertical clearance above a roof at 2.6 m (8 ft 6 in.), maintained 900 mm (3 ft) from the roof edge in all directions. The 900 mm (3 ft) and 450 mm (18 in.) figures are reduced clearances that only apply under specific exceptions (steep slope, guarded roof, or short overhang), none of which apply here.

Correct: C — 3.7 m (12 ft)

Per 230.24(B)(2), residential property and driveways at or under 300 volts to ground require 3.7 m (12 ft). The 15 ft option applies only once voltage exceeds 300 volts, the 18 ft option is for streets and truck traffic, and 10 ft only applies to pedestrian-only areas under the messenger-supported, 150-volt condition.

Correct: D — 100 amperes, 3-wire

230.79(C) sets a 100-ampere, 3-wire minimum specifically for one-family dwellings. The 60 A minimum applies to 'all other' installations under 230.79(D), 30 A applies to two 2-wire branch circuits under 230.79(B), and 15 A applies only to single branch circuit installations under 230.79(A) — none of those apply once the installation is a one-family dwelling.

Correct: C — In a readily accessible outdoor location on or within sight of the dwelling unit

230.85(A)(1) requires the emergency disconnect to be in a readily accessible outdoor location on or within sight of the dwelling unit, unless 225.41 is met. An indoor location or an unrestricted anywhere-on-property placement does not satisfy the sight/accessibility requirement.

Correct: C — A plaque or directory adjacent to the emergency disconnect identifying the location of the PV disconnect

230.85(D) requires a plaque or directory adjacent to the emergency disconnect when other energy source isolation equipment (like a PV disconnect per 705.20) isn't located next to it — relocating the equipment isn't required, and the special EMERGENCY DISCONNECT wording in 230.85(E)(1) applies only to service-related disconnects, not other energy sources.

Correct: A — They must be grouped, and each marked to indicate the load served

230.72(A) requires that the two to six permitted disconnects be grouped and that each one be marked to indicate the load it serves. There's no separate-room or spacing requirement, and every disconnect — not just the largest — must be marked.

Correct: B — Four separate enclosures, each with its own main service disconnecting means

230.71(B)(1) permits separate enclosures, each with its own main service disconnecting means, as one of the allowed combinations. A single panelboard enclosure with only one main disconnect doesn't provide four separate disconnecting means as required, and motor control centers are capped at two service disconnects per unit with barriers required — not four with none. A single switchboard vertical section is limited to one service disconnect per section under 230.71(B)(3).

Correct: B — 8 AWG copper

230.23(B) sets the general minimum at 8 AWG copper (or 6 AWG aluminum/copper-clad aluminum). The 12 AWG copper option is only allowed under the narrow exception for a single limited-load branch circuit, and 6 AWG and 10 AWG copper are not the stated general minimum.

Correct: D — 600 mm (24 in.)

230.54(C) permits the service head or gooseneck to be located not farther than 600 mm (24 in.) from the point of attachment when placing it above is impracticable. The 300 mm and 900 mm figures are not the code-specified distance, and an allowance does exist for this exact scenario.

Correct: C — Ampacity not less than 125% of the continuous load plus 100% of the noncontinuous load

230.42(A)(1) requires an ampacity not less than the sum of the noncontinuous loads plus 125 percent of continuous loads. Applying 125% to the entire combined load, or applying no multiplier at all, misstates the rule — the 125% factor applies only to the continuous portion.

Correct: C — No, LFMC is limited to 1.8 m (6 ft) when used this way, and requires a supply-side bonding jumper

230.43(15) permits LFMC as a service-entrance wiring method only when not over 1.8 m (6 ft) long between a raceway, or between a raceway and service equipment, and only with a supply-side bonding jumper routed with it per 250.102(A), (B), (C), and (E). A 10 ft run exceeds that limit, ruling out the no-restriction option. LFMC is listed in 230.43, so it isn't categorically excluded, and the length limit applies regardless of what other raceway type is used elsewhere.

Correct: D — A guest suite in a motel

230.67(A)(3) lists guest rooms and guest suites of hotels and motels as a mandatory SPD occupancy. The warehouse, parking structure, and machine shop are not among the four listed occupancy types in 230.67(A).

Correct: A — When it is part of a cable assembly identified for underground use

Per 230.30(A)(3), bare copper used for direct burial is permitted without regard to soil conditions when it's part of a cable assembly identified for underground use. Bare copper direct-buried outside a cable assembly still requires soil conditions that approve bare copper (230.30(A)(2)), and bare copper in a raceway is a separate allowance under 230.30(A)(1) that doesn't address direct burial.

Correct: C — 230.6

230.6 lists the specific installation methods (concrete encasement thickness, burial depth, vault construction, etc.) that let conductors run through a building yet still be treated as outside it. 230.9 and 230.24 address clearances for conductors already established as outside, and 230.8 covers raceway seals — neither defines what counts as 'outside.'

Correct: D — A performance test using primary current injection, conducted by a qualified person

230.95(C) requires the ground-fault protection system be performance tested on site when first installed, using primary current injection performed by a qualified person, per the equipment instructions. A visual inspection alone or a manufacturer letter does not satisfy this; the section doesn't establish an annual secondary-injection retest requirement.

Correct: A — A permanent plaque or directory at each service disconnect location identifying all other services, feeders, and branch circuits and the area each serves

230.2(E) requires a permanent plaque or directory at EACH service disconnect location, not just one, denoting all other services, feeders, and branch circuits supplying the building and the area served by each. There's no AHJ justification filing requirement in this section, and grounding/bonding compliance doesn't substitute for the identification requirement.

Correct: A — Plaques identifying all service disconnect locations and supply sources, posted at approved readily accessible locations near each point of attachment or entry

230.40 states that once the number of service disconnect locations for a given supply classification exceeds six, plaques describing all disconnect locations and sources must be posted at approved, readily accessible locations near each service drop or lateral attachment/entry point. The six-or-fewer threshold only triggers the simpler 230.2(E) requirement at each location; it doesn't cap or force a redesign of disconnect count.

Correct: D — They must be 1/0 AWG or larger and listed for use in cable tray

230.44(5) permits single conductors 1/0 and larger that are listed for use in cable tray. The 4 AWG and 2/0 AWG thresholds are plausible-sounding but incorrect minimums, and unrestricted sizing ignores the listing and size requirement entirely.

Correct: A — 230.50(B)(2)

230.50(B)(2) sets the 3.0 m (10 ft) grade-level clearance for individual open conductors and cables (other than SE cable). 230.50(B)(1) instead lists the raceway/conduit types approved to shield SE cable from physical damage, and 230.51(C) covers securing/support spacing for open conductors, not clearance from grade.

Correct: C — 230.28(A)

230.28(A) sets the strength requirement for a service mast (adequate strength or braces/guy wires) and requires identified hubs for conduit used as a mast. 230.28(B) instead governs where conductors may be attached relative to the weatherhead and coupling, not the mast's structural adequacy.

Correct: D — 230.74

230.74 requires each service disconnect to simultaneously disconnect all ungrounded conductors it controls. 230.75 covers disconnecting the grounded (neutral) conductor, a different function, and 230.71 only addresses the maximum number of disconnects allowed, not simultaneous operation.

Correct: A — Only if the distribution panel is the next level of distribution equipment downstream toward the load

230.67(B) allows the SPD location requirement to be satisfied at the next level of distribution equipment downstream toward the load, instead of at the service equipment. There's no Type 3 option under 230.67(C) and no 20kA alternate threshold under 230.67(E) — the minimum stays 10kA regardless of location.

Correct: A — A Type 1 surge-protective device installed per 230.82

Per 230.94, surge protection items — including Type 1 SPDs installed as permitted by 230.82 — are permitted on the supply side without the separate-overcurrent-protection condition. Load management circuits, fire pump supply circuits, and power-operable control circuits are all permitted only when given their own overcurrent protection (and, for control circuits, a disconnecting means).

Correct: C — 6 AWG aluminum

230.31(B) sets the general minimum at 6 AWG aluminum or copper-clad aluminum (8 AWG copper). The 10 AWG aluminum size only applies to the limited single branch-circuit exception, not general service conductors, and 8 AWG and 4 AWG aluminum aren't the stated thresholds.

Correct: A — 230.24(C)

230.24(C), Clearance from Building Openings, is the specific overhead-service rule that points to 230.9(C) for openable-window clearances. 230.24(A) covers clearance above roofs and 230.24(B) covers vertical clearance over grade/sidewalks/etc., neither of which addresses building openings; 230.9 is the general 'Clearances on Buildings' article referenced by the pointer, not the service clearance section itself covering openings under Part II (Overhead Service Conductors).

Correct: B — A window designed to be opened

230.9(A) requires 900 mm (3 ft) clearance from windows designed to be opened, along with doors, porches, balconies, ladders, stairs, and fire escapes. A fixed window that cannot be opened isn't covered by this list, since no one can reach through it toward the conductors.

Correct: C — In an upward slant, with a drip loop formed before the conductors enter

230.52 requires individual, noncombustible, nonabsorbent insulating tubes installed in an upward slant, with drip loops formed on the conductors before they enter the tubes. Sloping downward toward the interior would direct water into the building instead of away from it.

Correct: D — 230.2(C)

230.2(C), Capacity Requirements, is the specific list of conditions allowing a second service when more capacity is needed. 230.2(B) instead covers special occupancies like multiple occupancy buildings, and 230.2(A) covers special conditions like fire pumps and emergency systems, not capacity alone.

Correct: B — 230.76

230.76 requires that a power-operated service disconnect be openable by hand if the power supply to the operator fails. 230.77 only addresses the on/off position indicator, not manual-opening capability, and 230.74 covers simultaneous opening of all poles, not power failure operation.