UL 539:2018-05 Single and Multiple Station Heat Alarms.
1.1 These requirements cover heat-actuated, single and multiple station heat alarms intended for indoor
installation in accordance with the National Fire Alarm Code, NFPA 72, Chapter 11.
1.2 These requirements do not cover electrically operated single or multiple station smoke or heat alarms.
2.1 Except as indicated in 2.2, a component of a product covered by this standard shall comply with the requirements for that component.
2.2 A component is not required to comply with a specific requirement that:
a) Involves a feature or characteristic not required in the application of the component in the product covered by this standard, or
b) Is superseded by a requirement in this standard.
2.3 A component shall be used in accordance with its rating established for the intended conditions of use.
2.4 Specific components are incomplete in construction features or restricted in performance capabilities. Such components are intended for use only under limited conditions, such as certain temperatures not exceeding specified limits, and shall be used only under those specific conditions.
3 Units of Measurement
3.1 Values stated without parentheses are the requirement. Values in parentheses are explanatory or approximate information.
3.2 Unless otherwise indicated, all voltage and current values mentioned in this standard are root-mean-square (rms).
4 Undated References
4.1 Any undated reference to a code or standard appearing in the requirements of this standard shall be
interpreted as referring to the latest edition of that code or standard.
5.1 For the purpose of this standard the following definitions apply.
5.2 ALARM SIGNAL — An audible signal intended to indicate an emergency fire condition.
5.3 COMPONENT, LIMITED LIFE — A component that is expected to fail and be periodically replaced and whose failure is supervised. Typical examples of such components include incandescent lamps, electronic tube heaters, functional heating elements, and batteries. See also 43.4.
5.4 COMPONENT, RELIABLE — A component that is not expected to fail or be periodically replaced and is not supervised. A reliable component shall have a predicted failure rate of 2.5 or less failures per million hours.
5.5 HEAT ALARM, SINGLE STATION — A self-contained fire alarm system comprising of a heat alarm, an alarm sounding device, and a stored energy source (wound spring) incorporated in one integral package.
5.6 MECHANICALLY-OPERATED-TYPE — A heat alarm having a temperature sensitive bimetal or
eutectic element and a spring-wound-type mechanism with clapper mounted within a bell housing. The
snap action of the bimetal or melting of the eutectic element releases the spring mechanism resulting in
a bell-type sound.
5.7 RISK OF ELECTRIC SHOCK — A risk of electric shock is determined to exist at any part, when:
a) The potential between the part and earth ground or any other accessible part is more than 42.4 volt peak and
b) The continuous current flow through a 1500 ohm resistor connected across the potential exceeds 0.5 milliampere.UL 539 pdf download.