Industrial Process Heating practice questions

Correct: A — The disconnects must be grouped and identified as multiple disconnecting means

425.19 requires that where heating equipment is supplied by more than one source, feeder, or branch circuit, the disconnecting means shall be grouped and identified as having multiple disconnecting means. The lockable-in-open-position requirement applies to all such disconnects, not just one, and the rating rule is 125% of total load, not 100% of an individual circuit.

Correct: C — The heater is rated 50 kW or more, marked with a minimum conductor size, wired no smaller than that mark, and cyclically controlled by a temperature-actuated device

425.22(E) permits 100% sizing only when all three conditions are met together: the heater is rated 50 kW or more, it's marked with a minimum conductor size, the conductors used are not smaller than that marked size, and a temperature-actuated device controls cyclic operation. Being marked with a minimum size alone, without the 50 kW threshold, is not enough. AHJ inspection and 240.4 protection are separate requirements, not the basis for the 100% allowance.

Correct: D — Within sight and on the supply side of the fuses

425.19(A) requires the disconnect to be within sight from the supplementary overcurrent protective device(s), and on the supply side if fuses are used. The load-side-only and same-room options ignore that specific supply-side requirement, and 'either side' misses that fuses force supply-side placement.

Correct: D — 425.19(C)

425.19(C) specifically permits a unit switch with a marked "off" position that opens all ungrounded conductors to serve as the disconnecting means, so long as the branch-circuit switch or breaker is readily accessible as the other disconnect. 425.19(A) and (B) instead set the disconnect requirements based on whether the heater has supplementary overcurrent protection, not the unit-switch allowance, and 425.21 only addresses marking switches/breakers as indicating, not the unit-switch substitution itself.

Correct: A — 425.59

425.59 requires means (such as turning vanes, pressure plates, or similar devices) to ensure uniform airflow over the face of a duct heater, especially near obstructions like elbows or air-mover outlets. 425.58 only addresses labeling the heater as suitable for duct installation, not airflow distribution, and 425.60 concerns elevated inlet air temperature ratings, not airflow uniformity.

Correct: D — The installation date and inspector's initials

425.86 lists five required markings: manufacturer's name, volt/ampere/kilowatt rating, electrical supply characteristics, the "Electrode-Type Process Heating Boiler" label, and the disconnect-before-servicing warning. An installation date and inspector's initials are not among them.

Correct: A — 425.10(C)

425.10(C) sets the specific working-space width rule for enclosures located above grade, a floor, or a work platform (width of enclosure or 30 in., whichever is greater). 425.10(B) instead points to the general 110.26/110.34 clearances used when the enclosure isn't elevated on a platform.

Correct: A — As a continuous load, regardless of how long it actually runs

425.4(B) states that fixed industrial process heating equipment and motors shall be considered continuous loads — this is a blanket classification, not one conditioned on the general 3-hour continuous-load definition used elsewhere in the Code.

Correct: B — The branch-circuit switch or circuit breaker can serve as the disconnect if it's within sight from the heater and lockable open per 110.25

Under 425.19(B)(1), for a motor not over 18 hp, the branch-circuit switch or circuit breaker can serve as the disconnecting means if it's within sight from the heater and capable of being locked open per 110.25 — it does not need to be within sight of the motor controller. The 'must be within sight of the motor controller regardless of horsepower' option describes the over-18-hp rule in 425.19(B)(2), and the lockable-open requirement applies in both cases.

Correct: D — The elements must be subdivided so no subdivided load exceeds 48 amperes

Under 425.22(B), equipment rated more than 48 A must have its resistance elements subdivided into loads not exceeding 48 A each. The 120 A/150 A allowance only applies when the elements are integral to the process surface, in a listed enclosure, or in an ASME-rated vessel — none of which apply here, so 60 A total without those conditions doesn't qualify for the higher subdivision limit.

Correct: C — Fixed equipment using electric resistance or electrode heating technology

425.1 limits the article to fixed industrial process heating equipment employing electric resistance or electrode heating technology. Portable equipment is outside this scope, gas-fired heating isn't electric heating at all, and the article does not cover cooling equipment.

Correct: A — It must be factory installed in or on the heater, or supplied for that use as a separate assembly by the heater manufacturer

425.22(C)(1) requires the device be factory installed within or on the heater enclosure, or supplied for use with the heater as a separate assembly by the heater manufacturer. It also must be suitable for branch-circuit protection per 240.10, not merely supplementary-rated, and a field-added fuse holder or reliance on service equipment doesn't satisfy the requirement.

Correct: A — A temperature- or pressure-actuated device must control the cyclic operation of the equipment

Per 425.72(F), the 100% sizing exception for heaters rated 50 kW or more requires all three conditions: marked minimum conductor size, conductors not smaller than that marked size, and cyclic operation controlled by a temperature- or pressure-actuated device. Oversizing conductors beyond the marked minimum, de-rating the heater, or adding extra disconnects are not among the listed conditions.

Correct: D — The elements are contained in an ASME-rated and stamped vessel

Per 425.72(A), the higher 150 A ceiling applies specifically because the heating elements are contained in an ASME-rated and stamped vessel. Occupancy type doesn't factor into this rule. Subdividing into 48 A loads is the non-ASME threshold from 425.72(B), not what unlocks the higher ceiling. Being rated more than 120 A actually triggers subdivision, not a higher allowance.

Correct: B — 425.72(C)

425.72(C) is the specific rule requiring the supplementary OCPDs to be factory-installed on/within the boiler enclosure or supplied as a separate manufacturer assembly, and to be accessible but not necessarily readily accessible. 425.72(A) only sets the threshold for when subdivision is required for ASME-rated vessels, not the installation/accessibility rule for the devices themselves.

Correct: B — A temperature-sensitive limiting means

Per 425.73, a boiler with no change in state of the heat transfer medium (stays liquid) must have a temperature-sensitive limiting means. Pressure-sensitive limiting means applies instead to vapor-phase boilers under 425.74, and the limit control must be separate from the normal regulating thermostat, not replaced by it.