UL 875-2009 pdf download – Electric Dry-Bath Heaters.
3A.3 A component that is also intended to perform other functions, such as over-current protection, ground-fault circuit-interruption, surge suppression, any other similar functions, or any combination thereof, shall comply additionally with the requirements of the applicable standard(s) that cover devices that provide those functions. 3A.4 A component not anticipated by the requirements of this standard, not specifically covered by the component standards of this standard, and that involves a potential risk of electric shock, fire, or personal injury, shall be additionally investigated in accordance with the applicable standard, and shall comply with 3A.1 b) – d). 3A.5 With regard to a component being additionally investigated, reference to construction and performance requirements in another end product standard is appropriate where that standard anticipates normal and abnormal use conditions consistent with the application of this Standard. 4 Frame and Enclosure 4.1 The frame and enclosure of a heater shall have the strength and rigidity necessary to resist the abuses likely to be encountered during intended service. The degree of resistance inherent in the appliance shall preclude total or partial collapse with the attendant reduction of spacings, loosening or displacement of parts, and other defects that, alone or in combination, constitute an increase in the risk of fire, electric shock, or injury to persons.
4.8 The requirement in 4.4 also necessitates that a switch, transformer, relay, solenoid, or the like be completely enclosed, unless it can be shown that malfunction of the component is not likely to result in a fire, or unless there are no openings in the bottom of the heater enclosure. An unbaffled opening in the bottom of the heater enclosure is not to be used when it is located directly below field- or factory-made splices or overcurrent protective devices. Exception: Terminals of a switch, transformer, relay, solenoid, or the like need not be completely enclosed. 4.9 An opening for ventilation provided in the enclosure of a heater or in an externally-mounted component shall be located so that it will not vent into concealed spaces of a room, such as into false-ceiling space, into hollow spaces in the wall, or the like when the heater is installed as intended. 4.1 0 An opening for ventilation in the enclosure (other than in the bottom) of a heater and an opening associated with the dissipation of heater air from the element shall be provided with one or more baffles that will restrict the emission of flame, molten metal, burning insulation, or the like from the heater. Exception: In a compartment other than one that houses an overcurrent protective device (such as fuses, circuit breakers, and the like), the baffles are not prohibited from being omitted when: a) No ventilation opening in a vertical wall, other than one associated with the dissipation of heated air from the elements during intended operation of the heater, is more than 3/8 inch (9.5 mm) wide or b) The heater is constructed so that it complies with the intent of these requirements, as shown by investigation.