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PAT Testing > Types of Test

The types of test you will need to do are grouped together under the title ‘In-Service Testing’. It covers an initial visual check, an earth continuity check, (for class 1 equipment) an insulation test and a functional test. Other tests such as the flash test, operation/load test and earth leakage test are optional.

Visual Inspection

Formal visual inspections must be carried out by a competent operator and records of the inspection must be kept alongside the other electrical tests. The operator must be competent to understand the types of electrical, thermal and physical damage that may be present when viewing equipment. It makes sense that the person doing the visual check has a valid PAT Testing certificate.

The following points must be considered when carrying out a visual inspection:


Is the appliance suitable for the environment in which it is operated? If the appliance is in a particularly harsh environment, you may need to assess the frequency of testing. Is the integrity of the appliance being affected by heavy use? Are you confident the appliance is being used in accordance with the manufacturer’s instructions?

Disconnection of equipment

At all times during normal use, the user must be able to easily disconnect the appliance from the power supply. Is it possible for the user to easily do this? Is the plug reachable?


Users of the equipment should be asked, where possible, to report any faults with the appliance and before you do a visual check, ask if the appliance is in working order. You will need to inspect the mains cable, socket outlet, plug and the appliance for damage, wear and any potential problems.

You may need to check if the correct type of fuse has been fitted to the plug. Check for signs of overheating, check the cable anchoring where practical and check the security of the plug top cover, ensuring it is not loose.

General Use

When the appliance is in general use, users should make sure, where possible that:
  • Use of multiway sockets is limited
  • Appliances are being used with safety locks not being defeated
  • Cables are located sensibly as not to cause accidents
  • Means of disconnection from mains easily achieved
  • No strain on mains cable or appliance housing
  • Mugs, plants and other work related items are located a safe distance away to reduce spillages
  • The appliance has adequate ventilation
Earth Bond Test

The earth bond test is for class I equipment only. Results should always be less than 0.1+R Ohms. (Ω) ‘R’ represents the resistance of the lead. The appliance is tested at a current of 1.5 times the fuse rating, for a period of 5-20s at no greater than 25A. There is also an option of testing at 20mA-200mA, mainly for sensitive IT equipment

Insulation (resistance) Test

The test voltage applied should be 500V and the result limits of which should be as follows:
  • Class I appliances (heating appliances: fires etc <3kW) >1MΩ
  • All other class I appliances 1MΩ
  • Class II appliances 2MΩ
  • Class III appliances 250KΩ
Optional Tests

Flash test

You should be looking out for breakdown of the appliance or sparking

Operation/Load test

Compare results with details on nameplate of appliance.

Earth Leakage test

0.75mA for handheld class I appliances, 3.5mA for all other class I appliances and 0.25mA for class II appliances.