BS EN ISO 13297:2021+A11:2023 ISO 13297:2020+A1:2022
4.4 Switches and controls shall be marked to indicate their function, unless the purpose of the switch is obvious and its operation cannot, under normal operating conditions, cause a hazardous condition.
5 General requirements, DC systems
5.1 The system type shall be either a fully insulated two-wire DC system or a two-wire DC system with negative ground. Engine-mounted wiring systems can use the engine block as the grounded conductor. For DC systems with a negative ground, the main grounding/earthing point shall be either: a) the engine negative terminal; or b) a main grounding bus of sufficient current carrying capacity.
Systems with multiple battery banks shall have a common negative connection. Exceptions to this are for dedicated power systems isolated from craft systems, e.g. propulsion systems that are clearly identified as part of the isolated system.
5.2 An equipotential bonding conductor, if fitted, shall be connected to the craft's main grounding/earthing point.
5.3 Protective devices such as trip free circuit breakers or fuses shall be provided at the source of power, e.g. the panel board (switchboard), to interrupt any overload current in the circuit conductors before heat can damage conductor insulation, connections or wiring system terminals.
5.3.1 The selection, arrangement and performance characteristics shall allow:
a) maximum continuity of service to healthy circuits when fault conditions exist in other circuits, through selective operation of the various protective devices; and
b) protection of electrical equipment and circuits from damage due to overcurrents, by coordination of the electrical characteristics of the circuit or apparatus and the tripping characteristics of the protective devices.
5.4 All DC equipment shall be capable of function within a voltage range of 75% to 133% of nominal voltage at the battery terminals, e.g.:
— for a 12 V system: 9 V to 16 V; — for a 24 V system: 18 V to 32 V; — for a 48 V system: 36 V to 64 V.
EXCEPTION Where the circuit includes equipment requiring a higher minimum voltage, the specified minimum voltage shall be used in the calculation of the conductor size in accordance with Annex A.
5.5 The length and cross sectional area of conductors in each circuit shall be such that the calculated voltage drop shall not exceed 10 % of the nominal voltage.
5.6 Equipment vital to safety, where the voltage drop is critical, shall be supplied with the proper voltage to achieve the rated performance. NOTE 1 See Annex A for voltage drop calculations. NOTE 2 A 3% voltage drop is acceptable for this equipment. NOTE 3 Examples of circuits that can be dependent on a minimum voltage drop include: a) panel board/switchboard main conductors;
6 © ISO 2022 – All rights reserved
Distributed by the RYA under licence number 2020ET001 © BSI
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