Fuses And Circuit Breakers

A conductor will heat up if an unusually powerful current flows through it. This can damage electrical equipment and create a serious fire risk if it is allowed to continue at any part of the domestic wiring system. As a safeguard, weak links are included in the wiring to break the circuit before the current reaches a dangerously high level.

The most common form of protection is a fuse, a thin wire that’s designed to break the circuit by melting at a specific current. This varies according to the part of the system that the fuse is protecting – an individual appliance, a single power or lighting circuit, or the entire domestic wiring system.

Alternatively, a special switch called a circuit breaker is used that trips and cuts off the current as soon as an overload on the wiring is detected.

A fuse will ‘blow’ in the following circumstances:

1. If too many appliances are operated on a circuit simultaneously, then the excess demand for electricity will blow a fuse in that circuit.
2. If the current reroutes to earth due to a faulty appliance, the floor or power increases in the circuit and blows a fuse. (this is known as an earth fault).

WARNING: The original fault must be dealt with before the fuse is replaced.

Measuring Electricity

Watts measure the amount of power used by appliances when working. The wattage of an electrical appliance is normally marked on its casing.
One thousand watts (1000W) equal one kilowatt 1kW.

Amps measure the flow of current that is necessary to produce the required wattage for an appliance.
Volts measure the ‘pressure’ provided by the generators of the electricity company. This drives the current along the conductors to the various outlets. In this country, 230 Volts (formally 240) is standard.

If you know two of these measurements you can determine the other one:

Watts/Volts = Amps – use this method to determine what kind of fuse or flex is safe.
Amps x Volts = Watts – Indicates how much power is needed to operate an appliance.

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