PAT testing extension leads is straightforward: an adapter is required in the form of a short IEC lead (IEC plug one end and a 13A plug on the other). When testing extension leads a visual test takes place, where the 12A plug will be inserted into the 13A socket on the tester. The IEC plug of the short IEC lead is plugged into the IEC socket on the tester.
Following this the 13A plug should be placed on the short IEC lead into the end 13A socket (the one furthest away from the mains lead end). This is to ensure that you are testing the full length of the Buss Bars which connect all of the pins in the sockets together. You now proceed with the lead test which comprises Earth Continuity, Insulation at 500 Volts DC and Polarity which checks that Line and Neutral are not reversed. Some people wrongly think that it doesn’t matter, but in fact it is very important to get them the correct way around. If they are reversed, both the switch and fuse are in the neutral leg, which means that the appliance is live even when switched off and if a fault occurs, the fuse will not blow probably resulting in a fire.
Although it is not a written requirement I like to use a socket tester to prove the remaining sockets. You simply unplug the extension lead after the PAT test and plug it into a mains supply. Plug the tester into the remaining sockets on the extension lead, thus ensuring that all sockets have been tested.
A three pin extension lead is tested as a Class I appliance with the addition of a polarity check. An extension lead which does not have an earth wire should be classified as defective and removed from its operation. The length of an extension lead is to be checked to ensure that it is not so high which will result in the performance being affected by voltage drop.
the length of an extension lead should not excel the following:
• 1.25mm2 12 meters
• 1.5mm2 15 meters
• 2.5mm2 25 meters
2.5mm2 extension leads are too large for standard 13A plugs, although they may be used with BS EN 60309 industrial plugs. Extension leads exceeding the above lengths should be fitted with a 30mA RCD manufactured to BS 7071.
Cable reels must be used within their reeled or unreeled ratings as appropriate.