phase, using 3 single-pole circuit-breakers (3-wire or 4-wire). The rated short-circuit capacity along with the energy limiting class number is shown in the rectangles. The short-circuit capacity of this device is 6 000 A, and its energy limiting class is 3. The range of energy limiting class is between 1 and 3, with 3 being the lowest and 1 the highest. From Table ZA.1 of BS EN 60898-1: 2003, the permissible I2t let-through energy for a B6 circuit-breaker having an energy limiting class 3 is 35 000 A2s. The symbol shown in Fig 2 indicates that this circuit-breaker is fitted with a thermal overload and a magnetic short-circuit trip relay. This symbol will also be found on RCBOs to BS EN 61009-1. All circuit-breakers should be capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time, and automatically breaking currents under specified abnormal circuit conditions such as those of a short-circuit. The CE marking indicates compliance of a product with the appropriate directives of the European Union (EU) and is marked on the product or its immediate packaging.
Fig 2 Circuit-breaker symbol
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voltages release mechanisms for example. The window(s) provide a means for observing their status, such as if they have tripped or an alarm has been activated. The manufacturer’s name or trademark must be clearly visible when mounted in position.
x
Rated current ( 80 A) The 80 A shown on the switch is the value of current that the circuit-breaker can carry continuously without overheating or operating. In BS 7671, this is given the symbol In. This current value is always given for an ambient temperature around the device of 40 °C. If the temperature is higher, which might be the case when mounted in a distribution board with other loaded circuits or due to ambient conditions; it may be necessary to reduce the operating current.
2
Rated operational voltage (Ue) The circuit-breaker shows rated operating voltages (Ue) for currents Icu and Ics. This is the voltage(s) at which the circuit-breaker can be used. The value indicated is usually the maximum rms value.
BS EN 60947 series Part 1 of the BS EN 60947 series refers to general rules relating to low-voltage switchgear and control gear; therefore, when completing certificates or reports for example, it is important that the correct BS EN number is used. Part 2 of BS EN 60947 relates to the product standard for circuit-breakers, the main contacts of which are intended to be connected to circuits, the rated voltage of which does not exceed 1 000 V AC or 1 500 V DC (clause 1.1 of that standard refers).
Markings on circuit breaker to BS EN 60947-2
Lockable screw Window Manufacturer’s Name lcu 415 V ~ = 18 kA lcu 240 V ~ = 25 kA lcs 415 V ~ = 18 kA
OFF
80A
IEC 60947-2 PUSH TO TRIP
Ir (x In) o.8
3 o.6
BS EN 60947-2 circuit-breakers are for use by skilled or instructed persons in industrial and commercial settings. An example of such a circuit-breaker is shown in Fig 3. Clause 5.2 of BS EN 60947-2: 2006 (as amended) gives the complete list of data that should accompany each circuit-breaker. The clause stipulates which details should be visible when the circuit-breaker is mounted in its operating position. It is this data which will be discussed. The lockable screw provides access to allow for additional auxiliary contacts to be added either side of the main switch such as: alarms, earth leakage devices, under-voltage or over-
Fig 3 Example of a circuit-breaker to BS EN 60947-2
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