Deicing and Snow-Melting Equipment practice questions

Correct: B — 38 mm (1½ in.)

426.20(C)(1) requires at least 38 mm (1½ in.) of concrete, masonry, or asphalt over the units, panels, or cables when the base itself is at least 50 mm thick. The 90 mm figure is the maximum embedment depth allowed for the alternate 'other identified base' option in 426.20(C)(2), not the minimum cover here, and 25 mm doesn't meet the code minimum.

Correct: C — 426.50(A)

426.50(A) governs fixed outdoor deicing equipment and expressly permits the branch-circuit switch or breaker to serve as the simultaneous-disconnection means when readily accessible, indicating, and lockable in the open position. 426.51(A) instead covers temperature controllers with an off position, which is a control function, not the disconnecting means.

Correct: C — It must be capable of being locked in the open position per 110.25

426.51(A) requires that a temperature controller with an "off" position be capable of being locked in the open position per 110.25 before it can serve as the disconnecting means. Load rating and sight-line rules aren't the qualifying condition in this section, and 426.51(C) actually bars remote controlled devices from serving as the disconnect at all.

Correct: C — The assembly's design must ensure its temperature limitations are not exceeded

Per 426.21(B), when the heating element is not in direct contact with the surface being heated, the heater assembly's design must keep it from exceeding its temperature limitations. Securing method is a separate requirement under 426.21(A), and GFCI or wet-location rating are not what this subsection addresses.

Correct: D — 150 mm (6 in.)

426.23(A) requires not less than 150 mm (6 in.) of nonheating leads within the junction box, regardless of whether the leads are factory preassembled or field-assembled. The 75 mm and 300 mm options are fabricated distances, and the length requirement isn't conditioned on assembly type.

Correct: A — 426.27

426.27 requires grounding means (copper braid, metal sheath, or other approved means) as part of the heated section itself. 426.28 covers ground-fault protection of the circuit (a different safeguard), and 426.26 covers corrosion protection, not grounding of the heated section.

Correct: A — 426.26

426.26 specifically requires ferrous and nonferrous raceways, boxes, fittings, and supports installed in concrete, in direct earth contact, or in severely corrosive areas to be of suitable material or provided with identified corrosion protection. 426.27 instead addresses grounding braid or sheath continuity, and 426.25 covers equipment marking, so neither answers a materials/corrosion question.

Correct: C — 426.10

426.10 is the general requirement that deicing/snow-melting equipment be identified as suitable for the environment and installed per manufacturer instructions. 426.11 only addresses protecting exposed heating equipment from physical damage, not the identification/manufacturer-instructions requirement.

Correct: A — Embedded

Section 426.1(A) lists driveways, walks, and steps as embedded applications — the heating equipment is buried within the surface. Exposed applications, by contrast, are mounted on structures like roofs or bridges per 426.1(B); Article 426 doesn't use "portable" or "interior" as classification terms.

Correct: B — The surface must be guarded, isolated, or thermally insulated to prevent contact

426.12 requires that outdoor deicing/snow-melting equipment surfaces exceeding 60°C (140°F) be physically guarded, isolated, or thermally insulated against contact by people in the area. GFCI protection and circuit derating address shock and overcurrent concerns, not thermal contact hazards, and being listed for outdoor use doesn't exempt equipment from this contact-protection requirement.

Correct: A — 1300 watts/m2 (120 watts/ft2) of heated area

426.20(A) caps panels or units at 1300 watts/m2 (120 watts/ft2) of heated area specifically, not total slab area. The 1500/140 and 1000/100 figures are plausible but incorrect round-number substitutions.

Correct: C — No less than 25 mm (1 in.) and no more than 150 mm (6 in.) from the raceway

426.22(B) sets both a floor and a ceiling: the splice must be no less than 25 mm (1 in.) and no more than 150 mm (6 in.) from the metal raceway. A splice right at the raceway opening, one placed farther than 6 in. away, or one located anywhere convenient in the embedded run would all violate this specific placement window.

Correct: B — 150 mm (6 in.)

426.22(F) sets the minimum at 150 mm (6 in.) of free nonheating lead within the junction box. 300 mm and 75 mm are plausible-sounding but incorrect lengths, and the rule does specify an explicit minimum rather than leaving it unstated.