Class II Locations practice questions

Correct: C — Double locknuts used to make the connection

Per 502.30(B)(1)(a), locknut-bushing and double-locknut contacts shall not be depended on for bonding purposes. Bonding jumpers with identified fittings, other approved bonding means, and 250.102-compliant bonding of support struts are all acceptable methods.

Correct: B — Standard (non-liquidtight) flexible metal conduit with ordinary set-screw fittings

502.10(A)(2) permits dusttight flexible connectors, LFMC, LFNC, listed MC cable, and specific cords/cables for flexible connections in Class II, Division 1. Standard, non-liquidtight flexible metal conduit with ordinary fittings isn't on that list.

Correct: D — Threaded intermediate metal conduit (IMC)

Threaded RMC and threaded IMC are permitted in any Class II, Division 1 location per 502.10(A)(1)(1). The MC-HL, ITC-HL, and Type P cable options are all restricted to restricted industrial establishments under 502.10(A)(1)(3), (5), and (7).

Correct: A — A vertical raceway at least 1.5 m (5 ft) long extending upward from the dust-ignitionproof enclosure

502.15(3) requires the vertical raceway to extend downward from the dust-ignitionproof enclosure, not upward — an upward run doesn't block dust migration the same way. The permanent seal, the 10 ft horizontal raceway, and the downward 5 ft vertical raceway are all explicitly permitted under 502.15.

Correct: B — 502.140(B)

502.140(B) is the Installation subsection covering support, tension relief, and cord-connector/seal requirements for flexible cords in Class II locations. 502.140(A) only lists where flexible cords are permitted to be used, not how they must be installed and terminated; 502.145(A) covers receptacles/attachment plugs, not the cord itself.

Correct: C — A cord connector listed for the protection technique of the equipment wiring compartment, with an attachment plug per 502.145

502.140(A)(1) requires the flexible cord to be attached to the utilization equipment with a cord connector listed for the equipment's protection technique, plus an attachment plug meeting 502.145 — a general-purpose or wet-location-only connector doesn't satisfy the listing requirement, and seal-offs and conduit fittings apply to raceway wiring methods, not this cord connection.

Correct: B — It is permitted as long as it does not interconnect the circuit to any other circuit

Per 502.10(B)(3), simple apparatus not shown on the control drawing is permitted in a nonincendive field wiring circuit if it does not interconnect that circuit to any other circuit. Requiring a dusttight enclosure or a Class I, Division 1 rating misapplies unrelated requirements, and revising the control drawing is not the stated condition.

Correct: C — Bracing against lateral displacement is needed within 12 in. of the stem's lower end, or flexibility within 12 in. of the box

Per 502.130(A)(3), rigid stems longer than 300 mm (12 in.) require permanent bracing against lateral displacement not more than 12 in. above the lower end, or flexibility from a listed fitting/connector within 12 in. of the supporting box. Long rigid stems are permitted with this bracing, not banned, and flexible cord can never serve as the supporting means.

Correct: B — It must be identified for the location and marked with maximum lamp wattage

502.130(B)(1) requires portable lighting equipment to be identified for the location and clearly marked with maximum lamp wattage. The dusttight-enclosure-with-temperature-marking requirement applies to fixed lighting under 502.130(B)(2), the conduit-stem suspension rule applies to pendant luminaires under 502.130(B)(4), and the 502.120(B) reference is for electric-discharge lamp control equipment under 502.130(B)(5).

Correct: A — Totally enclosed pipe-ventilated

Per 502.125(A), Class II, Division 1 motors must be identified for the location or totally enclosed pipe-ventilated. Totally enclosed nonventilated, totally enclosed fan-cooled, and standard open-type machines are options for Division 2 under 502.125(B), not Division 1.

Correct: C — The flexible cord does not exceed 900 mm (3 ft) and is of extra-hard usage type, or hard usage type if protected by location

502.150(B)(5)(2) caps the cord at 900 mm (3 ft) and requires extra-hard usage type, or hard usage type only if protected by location. Extra receptacles beyond what's necessary aren't permitted per (B)(5)(3), and the Class II, Division 2 listing is only excused for nonincendive field wiring or specific restricted industrial cases, not universally.

Correct: A — If the contacts are immersed in oil or sealed in a dust-tight chamber

Per 502.150(A)(1)(b), general-purpose enclosures are permitted only where current-breaking contacts are immersed in oil or sealed against dust entry. An enclosure 'identified for the location' is the primary Division 1 requirement under 502.150(A)(1)(a), not the exception. The nonincendive-circuit allowance applies to Division 2 under 502.150(B)(1)(b), not Division 1. There is no current-rating exception in this section.

Correct: B — A general-purpose enclosure

Under 502.150(A)(2), oil immersion (or sealing in a dust-tight chamber) lets Division 1 resistors use a general-purpose enclosure instead of one identified for the location. The identified-enclosure requirement only applies when that oil-immersion or dust-seal exception isn't met. Explosion-proof is a Class I concept, not the Class II standard here, and a NEMA 4X washdown rating isn't what this section calls for.

Correct: D — Self-closing fire doors on both sides of the wall, sealed against dust

502.100(A)(1) requires self-closing fire doors on BOTH sides of the wall, fitted and sealed to minimize dust entry, in addition to the standard vault requirements. A door on only one side doesn't meet this. The 'identified as a complete assembly' path is the alternative allowed for non-liquid transformers under 502.100(A)(2), not the liquid-filled requirement. Explosionproof enclosures aren't the mechanism specified here — the vault-and-door approach is.

Correct: A — All utilization equipment

502.135(A) requires that in Class II, Division 1 locations, all utilization equipment be identified for the location — there's no carve-out by equipment type. The category-by-category breakdown (heaters, motors, switches/breakers/fuses) only applies to Division 2 under 502.135(B).

Correct: A — A welded joint

502.128(A) requires Division 1 ventilating pipe seams and joints to be riveted and soldered, bolted and soldered, welded, or rendered dusttight by an equally effective means. Welded joints meet this directly. Lock seams and slip joints are the Division 2 allowances under 502.128(B), and riveting alone without soldering does not satisfy the Division 1 dusttight standard.