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Inspector unearths potentially dangerous plug

Posted by Chris Thompson on 30th July 2010

The importance of Portable Appliance Testing (PAT) and its value in identifying potentially dangerous components has been underlined by a recent incident reported by Bob Austen, owner of Pattestingman of Ramsbottom near Bury. 

As his company’s name suggests, Bob specialises in Portable Appliance Testing. He is C&G 2337 (Inspection and Testing of Electrical Equipment) qualified. 

He uses a Seaward Primetest 350 which he bought from Acute Sales.  

The problem came to light when he was working in an institution with about 3,000 items to inspect over all the premises. This included a number of computer suites. Each suite had about 30 personal computers each with associated monitor – meaning 60 power leads needed inspecting in each room. The computers were metal boxed, and require an earth as class-1 equipment. 

The first room passed all the tests with no significant problems but in the second room every lead failed on earth continuity. 

Bob returned to the first suite and repeated the tests on some leads. These passed the tests, as before - proving his Primetest 350 was working. Clearly there was a problem associated with the leads in the second suite. 

The leads were marked as BS 1363 compliant but on closer inspection the earth pin had an insulating sleeve moulded on to it. BS 1363 expects the line and neutral pins to have insulating sleeves. It allows the metal earth pin to be replaced by a similarly dimensioned insulated shutter opening device (ISOD) for class-2 equipment which has double insulation and does not have an earth connection. The plugs with the insulating sleeve on the earth pin do not conform to either of these conditions. They are clearly intended for use with class-1 (earthed) equipment and yet cause a potentially dangerous condition. 

When the plug is inserted into a 13 Amp socket, the earth connection in the socket may grip the insulated part of the pin. 

This is what happened when it was plugged into the Primetest 350 and the tester indicated, correctly, that there was no earth continuity. The user had fitted these leads from new and thought, not unreasonably, that the equipment was properly earthed and safe. In fact, the equipment was not earthed and was potentially dangerous. Over 100 of these faulty leads were found and replaced throughout the establishment. They were not confined to the single computer suite and had migrated to all parts of the site. This case shows the importance of regular Portable Appliance Testing, performed by a qualified person using the right test equipment.

Categories: electrician training