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IP2.25.6 Other safety devices
© Oxford University Press 2011
Other safety devices
IP2.25.6 Other safety devices
© Oxford University Press 2011
Years ago, electrical systems were also protected by a fuse box. Each different electrical circuit had its own fuse that was rated for that
particular circuit (e.g. the lights, the sockets or the cooker). These fuses were very similar to the fuses in plugs. If too much current was
drawn through the circuit the fuse in the fuse box would melt and break the circuit.
They were fiddly to replace and as technology has advanced they were relatively slow to break the circuit.
IP2.25.6 Other safety devices
© Oxford University Press 2011
Now electrical systems are protected by circuit breakers in the consumer unit.
In a similar way to fuse boxes, each electrical circuit has its own circuit breaker rated for that particular circuit.
Like the fuse, this is connected to the live wire but rather than heat up it detects tiny changes in current.
Despite being more complex than fuses, circuit breakers have a number of advantages. They switch the current off much faster than fuses and they can be easily reset and used again.
IP2.25.6 Other safety devices
© Oxford University Press 2011
There are two main types of circuit breaker: Residual current circuit breakers (RCCBs) detect a difference in the
current between the live and neutral wire. If these values don’t match this means there must be a fault and so the circuit breaker shuts off the current.
Earth leakage circuit breakers (ELCBs) work in a very similar way; however they detect any small current in the earth wire.
