Fuses and circuit breakers are safety devices. A fuse is designed to burn out extremely rapidly if there is a power overload, while a circuit breaker trips a resettable switch. Both devices stop power coming through your wiring
Your electricity consumer unit or fusebox is used to control and distribute electricity around our homes. It should contain a mains switch, fuses, circuit breakers and a residual current device (RCD).
Mains switch
This allows you to turn off your electricity supply. Some installations have more than one mains switch. For instance, electric storage heaters might have a separate consumer unit. Make sure you know where your mains switch is to turn the electricity off in an emergency, it should be easy to reach.
Fuses
Rewirable fuses have special fuse wire running between two screws. When a fault or overload current flows through it, it gets hot, and melts when the current exceeds an acceptable level. This breaks the circuit, disconnecting the faulty circuit. Fuses must be replaced each time they burn out. A fuse should be the weakest link in a circuit. Replacements must be of the correct rating and type. Never try to use another piece of metal to "jump" a blown fuse – this is very dangerous and could start a fire.
Circuit breakers
Circuit breakers automatically switch off a circuit if there’s a fault. They give more precise protection than fuses. When they trip, you can simply reset the switch.
RCDs
This is a switch that disconnects the electricity supply under certain conditions. If your installation includes one or more RCDs, test them regularly. The instruction label should be near the RCD and should read:
‘This installation, or part of it, is protected by a device which automatically switches off the supply if an earth fault develops. Test quarterly (every three months) by pressing the button marked ‘T’ or ‘Test’.’
Doing this should switch off the supply – switch it back on to restore power. If the RCD doesn’t cut the power when you text it, contact an electrician. Don’t hold the test button down to try to force it to trip.
A blown fuse or tripped circuit breaker
If you experience a power interruption at home, there are some simple steps to follow:
- unplug any appliances that are sensitive to power spikes (eg computers, phones)
- never change fuses or reset circuit breakers in the dark – keep a torch nearby
- switch off the power at the main switch in or near your consumer unit. Never work with electrical wiring unless you have done this. If you don't have a main switch, turn all circuit breakers to "off."
- if you have fuses: a blown fuse will look blackened or discoloured. Replace it with a new one of the correct rating for the circuit (typically 15 amps).
- if you have circuit breakers: flip the one that is "off" back to "on"
- try to determine what caused the problem and correct it. There’s no point replacing a fuse or resetting your circuit breaker if it will blow/trip again
- restore power
Do your fuses blow or circuit breakers trip a lot? This might mean that you’re overloading your circuit with too many appliances or lights. Try unplugging or turning off some appliances or lights, then replace the fuse or reset the breaker. If the problem continues, use the services of a qualified electrician.