Every household meter box contains a series of overload protection devices, designed to cut the power to particular circuits when their amperage has been exceeded.

There are two main devices; Fuses and Circuit Breakers.

Difference between Overload and Overcurrent

Overload protection is protection against overheating of the protected equipment. It operates slower. Its typically operates on an inverse time curve where the tripping time becomes less as the current increases.

Whereas Overcurrent protection is protection against short circuits. It generally operates instantly. With standard breakers, between 500% and 1000% of full-load current is the point where the overcurrent protection over-rides the overload protection and opens the circuit instantly.

Some devices provide both overcurrent and overload protection.

A thermal-magnetic circuit breaker has both thermal (overload) and magnetic (overcurrent) elements. Both elements operate as described above. Likewise the dual element fuse has both instantaneous and inverse time characteristics in the same fuse providing both overcurrent and overload protection.

Frequent Circuit Breaker Tripping

One of the biggest causes of frequent circuit breaker tripping is the overloading of power boards. Most homes and apartments, even newer ones, don’t have enough power points to cater to, for example, a complete home entertainment unit setup. If circuit breakers in your home are tripping frequently, it could be down to circuit overload. Prevent this by:

• Never daisy-chain power boards.
• Remove devices that aren’t in use (for example, phone chargers still draw power even when not connected).
• Spread your electrical needs around. Don’t overburden a single circuit.
• Be mindful of how you connect devices around the home – what’s in use, and what is unnecessary.

Power boards also have built-in overload protection. This is usually in the form of a small circuit breaker which trips when more power is drawn than the board is rated to carry. The board also contains a reset switch to return it to normal use after the circuit breaker has been tripped.

Overload Precautions

The precautions that should be taken to avoid the overloading of domestic circuits are as follows:

• Do not connect too many appliances in a single socket.
• Do not use too many appliances at the same time.
• Use the appliances within the safe limit of electric circuit.
• Fuse should be connected in series in the circuit to protect overloading and short circuiting.

If a fuse or circuit breaker blows or trips in your meter box, it usually means there is a problem in the circuit. You are either running too many high-amp appliances, or there is a fault somewhere in the circuit. Before you replace the fuse or reset the circuit breaker, check for a problem. If you can’t find a reason and it happens again, have an electrician inspect your wiring, because when electricity is involved, small faults left unfortified can turn into large and dangerous problems very quickly.