How do fuses work?

While most of us know that without a fuse, a household plug, and whichever appliance it’s attached to, won’t work. A question frequently asked is “How does a fuse work, what is its purpose, and why it is important to fit the correct one?”

In our world of hi tech appliances, fuses play a very important, but sometimes overlooked role which is frequently misunderstood. This can leave expensive electronic equipment inadequately protected and at risk.

A plug fuse is a safety device which is connected into an electrical circuit to prevent excessive current flow during fault conditions. Upon overload, the wire fuse element heats up and melts, or blows with a resounding bang, interrupting and cutting off the current flow. The plug fuse may be thought of as an electrical safety valve which provides extra protection in addition to the main house fuse box or circuit breaker. By doing so it helps reduce the risk of electric shock and fire.

All electrical appliances in the UK must be marked with the correct plug fuse rating by law. This figure is generally found on the plugs rating plate, or on an affixed label.

• In the UK, most household appliances with a motor and/or heating element, such as a washing machine, fridge/freezer, dishwasher, vacuum cleaner, etc, will usually require a fuse with the maximum rating of 13 Amps.

• Appliances with a small heating element (toaster, clothes iron, electric kettle) will also need a high rating fuse of 7 or 13 Amps.

• Lamps, radios, small TV sets, computers, power drills, video’s, etc. with a rating up to 100 Watts (or 100 VA) need a fuse of 3 Amp rating.

UK household plugs are generally fitted with either a 3A or 13A fuse. For appliances up to 700w you need to use a 3A fuse and for appliances over 700w you need to use a 13A fuse.

Most appliance manufacturers have now standardised plug fuse ratings to either 3A or 13A. But take care; some older equipment may use 5 amps fuses which are still available today.

Having discussed the importance of fuse ratings, the other safety aspect relating to safety and reducing risk in the home is the plug into which the fuse is fitted. Damaged electrical plugs pose a risk of fire and injury making a quick periodic check essential for peace of mind.

Checking the plug and cable from time to time is simple and takes minutes at most. Check the following;

• With the plug removed from the socket, check the cable for signs of wear or damage. Never repair damaged electrical cables with insulating tape or join with connectors

• Check the cable is securely attached to the appliance and plug. Check that the plug cable is securely clamped into the plug with no plug wires showing.

• Check for cracks or damage on the plug casing. When replacing plugs, check it meets British Standard BS 1363.

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