150 mm (6 in.) be- tween the transformer cases and any adjacent combustible material
(3) Dry-Type Transformers. Dry-type transformers shall be installed in vaults or shall have their windings and terminal connections enclosed in tight metal housings without ventilating or other openings and shall operate at not over 600 volts, nominal.
502.115 Switches, Circuit Breakers, Motor Controllers, and Fuses.
(A) Class II, Division 1. In Class II, Division 1 locations, switches, circuit breakers, motor controllers, and fuses shall
comply with 502.115(A)(1) and (A)(2).
(1) Type Required. Switches, circuit breakers, motor controllers, and fuses, including pushbuttons, relays, and similar devices, shall be provided with identified dust-ignitionproof enclosures.
(2) Metal Dusts. In locations where dust from magnesium, aluminum, aluminum bronze powders, or other metals of similarly hazardous characteristics may be present, fuses, switches, motor controllers, and circuit breakers shall have enclosures identified for such locations.
(B) Class II, Division 2. In Class II, Division 2 locations, enclosures for fuses, switches, circuit breakers, and motor
controllers, including pushbuttons, relays, and similar
de
vices, shall be dusttight.
502.120 Control Transformers and Resistors.
(A) Class II, Division 1. In Class II, Division 1 locations, control transformers, solenoids, impedance coils, resistors, and any overcurrent devices or switching mechanisms associated with them shall have dust- ignitionproof enclosures identified for Class II locations. No control transformer, impedance coil, or resistor shall be installed in a location where dust from magnesium, aluminum, aluminum bronze powders, or other metals of similarly hazardous characteristics may be present unless provided with an enclosure identified for the specific location.
(B) Class II, Division 2. In Class II, Division 2 locations, transformers and resistors shall comply with
502.120(B)(1) through (B)(3).
(1) Switching Mechanisms. Switching mechanisms (in- cluding overcurrent devices) associated with control transformers, solenoids, impedance coils, and resistors shall be provided with dusttight enclosures.
(2) Coils and Windings. Where not located in the same enclosure with switching mechanisms, control transformers, solenoids, and impedance coils shall be provided with tight metal housings without ventilating openings or shall be installed in dusttight enclosures. Effective January 1, 2011, only dusttight enclosures shall be permitted.
(3) Resistors. Resistors and resistance devices shall have dust-ignitionproof enclosures identified for Class II locations.
Exception: Where the maximum normal operating tem- perature of the resistor will not exceed 120°C (248°F), nonadjustable resistors or resistors that are part of an automatically timed starting sequence shall be permitted to have enclosures complying with
502.120(B)(2).
502.125 Motors and Generators.
(A) Class II, Division 1. In Class II, Division 1 locations, motors, generators, and other rotating electrical
machinery shall be in conformance with either of the following:
(1) Identified for Class II, Division 1 locations
(2) Totally enclosed pipe-ventilated, meeting temperature limitations in 502.5