T E C HN I CAL
Circuit-breaker markings O B JE C TIVE
The aim of this article is to explain the meaning of the numbering and lettering used on low-voltage circuitbreakers. By understanding the marking, the correct protective device can be selected for the particular application and environmental conditions. Introduction This is the second of two articles whose aim is to describe the meaning of the numbering and lettering manufacturers place on fuses and circuit-breakers. In the first article, the information written onto fuses was discussed with the emphasis being directed at BS 88 fuse types. Fig 1 Typical marking found on circuit-breakers for AC operation
Manufacturer’s name
B6
230/400VEN 60898
1
x 6000 3
2
I ON 0 OFF
0-OFF
1 BS EN 60898 has two parts. The first part, BS EN 60898-1, covers circuit-breakers for AC operation in household and similar locations. The second part, BS EN 60898-2, covers circuit-breakers for AC and DC operation in household and similar locations. 2 The 0.5 A rating is only available for circuit-breakers having C and D curve characteristics.
This article will focus on decoding the markings on circuit-breakers to BS EN 60898 and BS EN 60947-2. The selectivity and co-ordination between protective devices is outside the scope of this article.
Circuit-breaker markings to BS EN 60898 Clause 6.1 of BS EN 60898-1: 2003 (as amended) gives the complete listing of markings that shall either be found: • placed on each circuit-breaker, either on its front, side or back, or • published in the manufacturer’s documentation. BS EN 608981 devices are for operation at 50 Hz or 60 Hz, having a rated voltage not exceeding 440 V (between phases), and have typical current rating from 0.5 A2 to rated current not exceeding 125 A and a rated shortcircuit capacity not exceeding 25 000 A (Clause 1 of that standard refers). The characteristic curves for BS EN 60898 given in Appendix 3 of BS 7671 include the preferred current ratings starting at 6 A. For characteristic curves for circuit-breakers outside of this range, manufacturer’s data must be consulted. The BS EN 60898 range of circuit-breaker would normally be the final overcurrent protection measure in the electrical system, for example protecting socket-outlet or lighting circuits and other similar applications. The name of the manufacturer or a trade mark by which they may be readily identified must be marked on all circuit-breakers. The rated current (In) is shown without the symbol "A", and is to be preceded by the symbol denoting the instantaneous tripping characteristic (that is Type B, C or D). The device shown in Fig 1 has a rated current of 6 A and the instantaneous tripping characteristic ‘Type B’. The rated current value is always given for an ambient temperature around the device of 30 °C. The voltage indicated shows that it can be used single-phase (line-to-neutral) or three-
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