PAT Testing AtoZ – F is for Fuse

You may have noticed that we have a lot of old electrical fuses kicking around here at Skybur Testing. As you can see from the picture at the top of this page, we frequently change out fuses which are incorrectly rated for the appliance they are found in, or the standard 13 amp fuses in replacement plugs. We expect each engineer to replace around 2000 electrical fuses each year! But why do we offer this free service?

What is the electrical fuse for?

Most people think the fuse is there to protect the appliance. It isn’t.

Electrical fuses are actually fitted to protect the power lead. They won’t necessarily blow if that lead is overloaded. Fuses have a tolerance of up to 50%, meaning a 13 amp fuse can actually take a load of almost 20 amps before it blows. Additionally, electrical fuses are less likely to blow if the current is increased gradually than if there is a sudden surge.

Counterfeit fuses

Cheap counterfeit electrical components are a growing problem, and fuses are no exception. Counterfeit electrical fuses can, in fact, be highly dangerous. Electrical fuses which comply with British Standard 1362 are filled with silica or sand to prevent them exploding. They also have very securely fitted end caps which cannot be removed by hand.

Although the following (very short) video by Electrical Safety First is obviously staged, it illustrates why counterfeit fuses are so dangerous. A good PAT tester should spot counterfeits easily, but they aren’t always obvious.

Getting it right

Electrical fuse ratings are not always straightforward. A quick search on Google will return many different options for working out which fuse is required. This is often based on the wattage of an appliance or a calculation to work out the current. (Power in watts divided by Voltage equals Current).

Others say:

  • According to BS1362 and the IET Code of Practice we should fit a 3A fuse where the appliance is rated at 700W or less, and a 13A fuse when the appliance is rated at more than 700W. This is the simple method, aimed at the general public.

PAT Testing Expert website, extracted Feb 2015

Since the fuse protects the cable, the most sensible option is to use the lowest appropriate electrical fuse for that cable. Although many manufacturers have standardised their fuse ratings in accordance with BS1362, many others have not.

Add to this the fact that many older appliances were supplied without plugs, and have probably had replacement plugs and fuses fitted. Because of this we check every fuse as part of the PAT testing process and adhere to the following guidelines:

Fuse ratings cheat sheet infographic
By using the lowest appropriate fuse for the lead, we help to reduce the risk of electrical fires and shocks. The price of your PAT testing includes the cost of replacement fuses – no nasty extras or hidden surprises here!

When you’re blowing your fuse

If your appliance is repeatedly either blowing the fuse in the plug or tripping the mains circuit breaker, switch off and unplug immediately, and either have it professionally repaired or replace the item. Repeatedly blowing fuses are an indicator of a short circuit within an appliance. Under no circumstances should you replace the fuse with a substitute such as a nail, screw, or drill bit (we’ve seen all of them and more!) Remember, electricity is highly dangerous and is not something to be taken lightly.

If you’re ever unsure or concerned about your appliances, you can always contact us by email at hello@skyburtesting.co.uk, through social media, or call Emma on 07518 688 233. We’ll get you booked in for your testing and take it from there!

Try not to blow your fuse until next time (cue groans and eye rolls)

Adrian

 

Leave a Reply