UL 988:2020 pdf download.STANDARD FOR SAFETY-Humidifiers.
1.1 These requirements cover humidifiers rated 600 V or less, and intended to be used in accordance with the National Electrical Code (NEC), ANSI/NFPA 70, and the rules of CSA C22.1, Canadian Electrical Code (CEC), Part I.
1.2 These requirements cover humidifiers intended for residential and commercial use. This includes humidifiers of the centrifugal atomizing type, evaporative-media type, water-injection type, steam type, and the like. The humidifiers are intended for installation in a room, mounted on a wall or a ceiling, or for duct or plenum mounting.
1.3 These requirements apply to equipment that includes an electric heating element to heat air or water, or both.
1.4 These requirements do not apply to evaporative coolers that are also intended to be used for cooling.
1.5 These requirements do not apply to portable, electrode-type products, such as vaporizers, which are covered by UL 499 and CAN/CSA-C22.2 No. 64.
2 Definitions
2.1 The following definitions apply in this Standard.
2.2 CIRCUIT, EXTRA-LOW-VOLTAGE — A circuit that has an ac potential of not more than 30 V (42.4 peak), and power of 100 VA or less; or 30 V dc supplied by a primary battery; or supplied by a Class 2 transformer; or supplied by a combination of a transformer and fixed impedance that, as a unit, complies with all the performance requirements for a Class 2 transformer. A circuit that is derived from a circuit which exceeds 30 V by connecting resistance or impedance, or both, in series with the supply circuit to limit the voltage and current, is not considered to be an extra-low-voltage circuit.
2.3 CIRCUIT, HAZARDOUS VOLTAGE — A circuit having characteristics in excess of those of an extra- low-voltage circuit.
2.4 COMBINATION TEMPERATURE-REGULATING AND TEMPERATURE-LIMITING THERMOSTAT -
A thermostat whose function is to regulate the temperature under normal conditions of use, and that also
serves to prevent a hazard that might result from conditions of abnormal operation of the heater.
2.5 ENCLOSURE — The enclosure that houses the electrical components, live parts, and/or moving parts. It may be an integral part of the component, a separate item, part of the ultimate enclosure, or the ultimate enclosure (e.g., the outer cabinet).
2.6 HEATER ELEMENT — A complete or partial assembly of a heating element, an electrical insulation (e. g., refractory, mica), a metal sheath, a glass or quartz envelope or panel, thermal insulation, and a frame or adaptor for holding the assembly together and fastening it in the heater; and leads or terminal connections, or both, which may or may not include bolts and nuts.
2.7 HEATING ELEMENT — The actual electrical conducting medium that is intended to be heated by an electric current.UL 988 pdf download.