A 13A plug does not always need a 13A fuse

13A Plug

13A BS1363 plug showing rating of 13 Amp

Just because it says 13A on the plug doesn’t mean it has to have a 13A fuse in!

The plugs that we use on a day-to-day basis are BS1363 – that is they conform to the British Standard 1363, which first came into being in 1947 and has been updated a few times since. Most people refer to the them as ‘square pin plugs’ or simply ’13A plugs’

Usually, you’ll see 13A stamped onto the plug – because this is maximum current the plug is allowed to carry.

However, this does NOT always mean that a 13A fuse should be fitted, or even that it will be fitted.

The purpose of the plug fuse is to protect the cable. Therefore the fuse in the plug should be rated in such a way that, in the event of a fault, the fuse will blow before the cable melts. Fuse sizes do not always correspond exactly to cable sizes, but as a general rule a 0.5mm2 cable (3A) cable should be protected by a 3A fuse, a 0.75mm2 (6A) cable should be protected by a fuse of 5A or 3A, and a 1.25mm2 (13A) or 1.5mm2 (15A) cable should be protected by a fuse of 13A or less. There are one or two exceptions, but as a general rule the fuse rating should be the same or less than the rating of the cable.

A common mistake made by people starting out in PAT Testing is to read the 13A rating on the plug and assume that means the plug is fitted with a 13A fuse, but in fact the correct procedure would be to open the plug and have a look. You could fit a 13A plug onto a washing machine or tumble dryer, fitted with heavy cable, in which case a 13A would probably be the correct value. But, the same plug could be removed and fitted to a small appliance, such as a table lamp, with thinner cable, in which case a 3A fuse should be fitted. It’s still a 13A plug, but the smaller fuse inside is providing protection to the cable.

For the purposes of being complete I will also mention that some moulded plugs (especially those found on computer leads) might be rated at 5A, 7A or 10A. In this case, obviously, a fuse of that value or less would be required.

Don’t assume that a 13A fuse will be fitted with a 13A cable. Open the plug and have a look!  (moulded plugs can’t be opened but you can, and should, still check the correct fuse is fitted.)


Posted in PAT Testing Information

PAT Testing Network

The PAT Testing Network is a professional association for people engaged in the PAT Testing industry, and is the first such organisations for PAT Testing professionals.

The group is currently planning its first ever meeting in Sheffield, in October 2014, and the group is looking forward to meeting up and chatting about the current state of the industry and looking at ways to improve the reputation and standing of the PAT Testing community.

More information about the work of the PAT Testing Network is given on their site:-



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How to check the Plug Fuse is correct during PAT Testing

It’s easy to get confused when checking the plug fuse during PAT Testing.

One important thing to remember is that the job of the person doing the PAT Testing is expected to look at the plug fuse and make a decision on whether or not it is suitable. Many people simply check the fuse and write down the value, without actually considering whether it is appropriate or not!

A very simple way of checking the fuse is to look at the Power Rating on the rating plate of the appliance. You should always be able to see how much power (in Watts) the appliance will consume when in use. A mark of 150W means that the appliance is ‘rated’ at 150 Watts – or to express it scientifically, it will use 150 Joules of energy every second.

If the appliance is rated at less that 700W then the best fuse to use is a 3A.

If the appliance is rated at more than 700W then it can be fitted with a 13A fuse.

This method is very simple, and quite basic, but works well enough.

The main purpose of the plug fuse is to protect the cable, and you may find appliances with 6A cable fitted with 5A plug fuses. This is quite acceptable. Many power tools (such as electric drills and jigsaws) are like this, as well as many mains leads supplied with computers.

It is not usually necessary to replace a small fuse with a bigger one, – for example if a TV is fitted with a 3A fuse, and is working correctly, it would not be a good idea to fit a larger fuse – even if it is fitted with heavier cable. New appliances (provided they are purchased from a reputable supplier) are required by law to have a suitable plug (with an appropriate fuse inside) fitted when sold. However, very old appliances were probably not supplied with a plug, and the person fitting the plug all those years ago has probably fitted a 13A fuse when a smaller one would have been better. Hence, the older the appliance is, the more likely it is that the fuse will be too big.

Be prepared to replace lots of 13A fuses with smaller ones if you routinely deal with older appliances!


Posted in PAT Testing Information

PAT Testing Leakage Test

Why Does the Leakage Test Sometimes Fail on Computers and Other IT Equipment?

seaward 300x250

Testing a Computer with a Seaward Primetest 250.

The leakage test often causes difficulties for PAT Testing IT equipment, and in many cases, of course, it’s better sometimes to leave out the leakage test as just concentrate on the insulation test value.

However, if you carry out a leakage test on a computer equipment, then you may get a ‘FAIL’ coming up on your machine. It’s not always a correct interpretation, however.

According to the IET Code of Practice for In-Service Inspection and Testing of Electrical Equipment, the pass value for a Class 1 leakage test is a maximum of 0.75 mA for handheld equipment, but 3.5 mA for other Class 1 appliances (including IT equipment.) The problem arises because the PAT Tester has no way of determining whether the appliance is hand-held or not, and so it defaults to the lower setting of 0.75mA.

It is not unusual to find IT appliances which have a small amount of leakage current down the earth wire in normal operation, and in some cases this may be slightly more that 0.75 mA – obviously not enough to cause a problem (and less than the 3.5 mA pass value defined by the IET) but more than the very strict limit set by the PAT Tester.

Therefore, as long as we get a measured value of less than 3.5 mA on the leakage test, we know that the appliance is ok.

Some testers have the Pass Value set at 0.75mA – including the Kewtech KT71 and KT72 and the Seaward Primetest 100.

More advanced testers allow the user to change the Pass setting – the Seaward Primetest 250 allows the user to change the leakage pass value from 0.75 mA to 3.5 mA.

Please note that the leakage test is now referred to ‘touch current test’ on a Class 2 appliance, and the ‘protective conductor current test’ on a Class 1 appliance, although most PAT Testers still refer to the ‘leakage test’ and so I’ve used the latter term in this short article.

There is more information about the leakage test in this article here:-

Leakage Tests in PAT Testing



Posted in PAT Testing Information

SimplyPATS software compatible with Seaward Apollo

Seaward Apollo

Seaward Apollo now compatible with SimplyPats Software

Some Good News for Owners of the Apollo 500 or 600 and SimplyPats software.

If you’ve been tempted by the new Seaward Apollo range of PAT Testing machines, you may have been looking around for suitable software for it. The Apollo is designed to work with Seaward’s own PAT Guard 3 software (which is of course, very good) although some people have been put off by Seaward’s decision to license the software (via a yearly subscription) rather than sell it outright.

Other people have been using SimplyPats software with their previous PAT Testing machines, (or maybe used a selection of different testers) and were disappointed to discover that Seaward had only allowed the Apollo 500 and 600 to work with their own software.

Now, Simply PATs have announced that their latest version of their software (7.0.4) will support the Apollo 500 and 600.

The latest version is due to be released later this year but is available immediately on request to any user wishing to use it with an Apollo PAT Tester.

Carl Mason from SimplyPats writes:-

Version 7.0.4 includes support for the Seaward Apollo 500 and 600, however users will need to make sure that their PAT Tester is running Firmware Version 2.9.1-29 or newer as this includes the optional “Output Data to Other Software” option.
We are only able to import the data that is included in the “Other Software” option, at the present time this includes:
  • All electric test results, including point to point and RCD data.
  • Images (max of 2).
  • Retest dates, but will not include the fields form the electrical risk assessment form used to calculate the retest period.
The firmware will not support upload of data from SimplyPats to the Apollo.

See it in Action here: Seaward Apollo and SimplyPats

The Seaward Apollo range of PAT Testers, as well as the latest editions of SimplyPats are available from Yotari Ltd and other suppliers.

Seaward Apollo and SimplyPats Software

Posted in PAT Testing Equipment

Class 1 and Class 2 appliances

How to tell the difference between Class 1 and Class 2 Appliances

One issue which crops up frequently during PAT Testing is the requirement to tell the difference between a Class 1 and Class 2 appliance. Actually – telling them apart is very simple – a Class 2 appliance will bear this symbol:-


Note the that IET Code of Practice refers to the ‘Class’ of the appliance as the ‘Equipment Construction Type’

In very simple terms, a Class 1 appliance will have an earth connection, and a Class 2 appliance will not. If the appliance plugs into the mains, then it’s either Class 1 or Class 2 – the square box symbol tells you it’s Class 2 – if there’s no symbol then it’s Class 1.

There is NO SYMBOL for Class 1!

Of course, you could look inside the plug – a Class 2 appliance should only have 2 wires (brown and blue) whereas a Class 1 will have 3 wires (brown, blue and green/yellow) – however – it is not unusual to find appliances which have been rewired or modified (bodged) with the wrong cable, so the only way to be sure is look out for the Class 2 symbol.

Note that Class 1 and 2 applies to 110V appliances just as 230V appliances.

makita drill
This picture shows the Class 2 symbol on a 110V drill.
Class 1 toaster rating plate
This picture shows the rating plate from the underside of a toaster. We can see various symbols, but NOT the square box symbol, so we assume the appliance is Class 1.

 Please note this is a slightly simplified document designed to provide guidance to people carrying out PAT Testing. For more advanced guidance, please refer to the appropriate appliance standards, as well as the IET Code of Practice.



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PAT Testing Courses from PAT Testing Expert

Just a quick note to say that PAT Testing courses are available from PAT Testing Expert – courses are held across the UK and give competence in PAT Testing.

For more information see PAT Testing Courses

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PAT Testing

Hi, and welcome to to pattesting.com – the best place on the web to get common sense and practical advice about PAT Testing

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Portable Appliance Testing

A blog post about PAT Testing (portable appliance testing)

Posted in PAT Testing Information