Electrical fuses and what to do with them

What's a fuse?

Fuses can be found in electrical plugs and inside some appliances. They are cylindrical, usually about 2cm long and 5mm in diameter and have metal ends. Inside the cylinder is a wire that is designed to melt if too much electricity passes through it.

What use is that?

Occasionally there can be power surges that 'push' too much electricity into your appliance or a fault in the appliance could also 'suck' too much in. Both of these could seriously damage the appliance and also be dangerous to the person using it. The fuse prevents this from happening by melting when the amount of electricity gets too high and no more electricity can flow through the plug into the appliance.

What do 5A and 13A mean?

The amount of electricity, known as current, is measured in Amps. Americans tend to refer to current as Amperage. 5A simply means that a fuse is rated at 5 Amps. Any more than 5 Amps of current will blow the fuse and stop the electricity from flowing.

The most common ratings for fuses are 3 Amps, 5 Amps and 13 Amps.

The three most common household fuses: 3, 5 and 13 Amps.

I need a 5 Amp fuse but I don't have one, can I just use a 13 Amp one?

No, an appliance that needs a 5 Amp fuse will be damaged by current of more than 5 Amps. A 13 Amp fuse won't protect you or your appliance until the current is over 13 Amps; by which time it might be too late!

My appliance has stopped working, what should I do?

If your appliance stopped working suddenly it might have blown a fuse. Unplug it from the mains and unscrew the back of the plug. Remove the old fuse and replace it with one of the same rating. You can buy fuse testers from most DIY shops which will enable you to check if the fuse is definitely blown, or you can use a multimeter if you have one handy.

If you don't have a fuse tester swapping the fuse for a new one will tell you if it was the fuse that was blown of some other problem. If it works with the new fuse then the old one is blown, if a new fuse doesn't fix the problem the old one might be ok and there is definitely something else causing a problem.

The fuse can be seen on the right hand side marked '13A' for 13 Amps.

I changed the fuse and when I turned on the appliance it started to work and the stopped almost immediately

If there is an internal fault with the appliance, for example a loose wire, it will continue to blow fuses each time you change them. The appliance needs to be repaired before it can be used again.

I have a four socket multiplug, does it matter what I plug into it?

Yes. Sockets in your home are rated at 13 Amps. If you plug 4 appliances that each need 5 Amps into a multiplug then the total will be 20 Amps. This is more than the 13 Amps that the socket can handle. If the multiplug has a fuse then it will blow. If not it will trip the fuse in the fuse box, now known as a consumer unit, which is often located in the cupboard under the stairs. This can be reset by flicking the switch from off back to on.

You said that 3, 5 and 13 Amps are the most common, does that mean there are other types of fuses?

Yes. So far we've been talking about plug fuses but some appliances have internal fuses. These are not usually designed for users to replace and will require a professional to do it for you. The fuses are different sizes and ratings and are only available from more specialist outlets.

What is an RCD or Powerbreaker, is it like a fuse?

An RCD or Residual Current Device is like a fuse that doesn't need to be replaced. If it blows then is can be reset with a button. They are most often used to protect people using power tools and garden equipment such as lawn mowers, hedge trimmers and strimmers where there is a possibility of cutting the cable accidentally whilst working.