Portable Appliance Testing (PAT's), & Fixed Wiring Test Procedures

For more information please contact Graham Moreton on 01483 270400 .

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All items should be tested in isolation. That is: Any equipment interconnected by means of mains or data cables will first have these interconnections removed (this includes the disconnection of "networked" equipment from the network cabling system). If necessary, operations must be requested to "shutdown" systems prior to testing.

The portable appliance tester must be plugged into a 13A socket outlet and the correct date set by following the prompts on the display panel and using the appropriate keys.

The appliance and site codes should be entered for each test.

NOTE: Hard wired equipment should be disconnected from the associated outlet, having first isolated the mains supply at a suitable point. Testing should take place with a the "SAFE BLOC (type)" wire to plug top adapter.

1) EARTH BOND IMPEDANCE TEST - For CLASS 1 appliances the 8 Amp earth bond terminal on the tester will be utilized for appliances fused up to 3 Amps and the 25 Amp terminal for appliances fused between 5 and 13 Amps.

The earth impedance limit should be set according to the size and length of the connecting flexible cord. Typical nominal resistance's values are given in Appendix 3.

NOTE: The British Standards for most IT. Equipment specify an earth bond impedance of 0.1 Ohms. This figure does NOT include the additional impedance/resistance of a flexible cord and plug top. Generally speaking a reading of 0.25 Ohms or less can be considered within acceptable limits for equipment using a 2 metre length cord with 0.5 square millimetres or greater conductors.

A tests engineer should take sufficient care when connecting the earth clip to CLASS 1 appliances to ensure that proper contact is made and thereby reduce the possibility of incorrectly failing an appliance (earth connections can be looked for with a simple Ohm Meter prior to testing with a PAT). Prior to failing any items as a result of an abnormally high earth impedance, the test engineer should first check that all associated equipment has been disconnected (thus removing potential parallel earth paths) and that the Test clip is securely attached to the item in question. It is recommended that this test be repeated at least three times to eliminate such problems.