PAT TESTING POWER CORDS & EXTENSION LEADS


Most modern PAT testers have a handy IEC lead test facility. All one has to do during PAT Testing is to plug in both ends of the lead and test Earth Continuity, Insulation Resistance and Polarity. The Polarity test just checks that the lead is wired correctly. This can only be done if one has access to both sides of a power cord.

When PAT testing long IEC leads one needs to remember to adjust the pass limits as outlined in the IET Code of Practice.

PAT Testing Mains Extension Leads

If a PAT Tester has an IEC lead test facility, then this can be easily adapted to test mains extension leads as well. All one needs is a short IEC lead to connect the socket of the mains lead back into the PAT tester as shown. A similar method can also be used if the PAT Tester has a 2-stage IEC lead test.

When PAT testing mains leads, please note the following:

  • Depending on the length of the extension lead, adjust the Earth Continuity pass limit when carrying out the PAT testing

  • When PAT testing a multi-way mains extension, it is important to check every outlet for good Earth Continuity. If any one socket should fail then the whole extension lead must be failed and discarded

  • During PAT testing if the Insulation Resistance test is carried out at 500 V, then one will get a fail if the extension lead has surge protection. In this case use a 250 V test if one is available on the tester. If this is not available then make a suitable note in the test record and pass the appliance. Some testers such as the BattPAT from First Stop Safety do not have this problem as the Insulation Resistance test is always done at a voltage of 350 V

  • It is important to un-reel any coiled extension leads to inspect for any damage to the cable prior to any PAT testing

  • Long extension leads have a higher power rating when un-coiled compared to when they are coiled. During PAT testing, when carrying out the Earth Continuity test at a current of 25A, care needs to be taken not to do this over a long period as this might lead to over-heating. Normally PAT testers limit this to 5 seconds which should not present a problem

  • Some extension leads may have an RCD built in. If this is the case, please refer to Test Examples 8 when carrying out the PAT testing


Users of extension leads must be made aware of the following:

  • Long extension leads have a higher power rating when un-coiled compared to when they are coiled. If the user intends to use the extension lead to power say a 2 kW heater, then it is very important that it is fully uncoiled. If it is not coiled, then there is a risk of a fire breaking out

  • An extension lead wired with normal 13 A cable should not be longer than 12 meters

  • An extension lead must not be plugged into another extension lead such that their total length exceeds 12 meters

  • If the extension lead is longer than 12 m, then it must be fitted with a Residual Current Device (RCD) with a rated operating current not exceeding 30 mA

  • Care should be taken to route the extension lead away from work areas and not across paths where they might get caught and pulled, or run over and damaged