PAT is the abbreviation for Portable Appliance Testing – an electrical device that tests appliances and equipment for electrical safety. There are three stages to PAT testing:
The first test checks the appliance is securely earthed inside the equipment, mains plug and cable – known as earth continuity. If earthed correctly, in the event of a fault (or an accident), electricity will be taken safely away from the equipment, which in turn will trip a safety device (RCD) in the electrical consumer unit. If not, then you (or someone else) may receive an electrical shock as the equipment may become live
The second test sequence checks the electrical insulation of the appliance. A fault can often occur inside equipment (such as vaporisers and appliances like kettles), where the heater element deteriorates and a short can occur between the conductors. This may result in the electrical supply tripping in the electrical consumer unit
The third test sequence measures the load or consumption of the appliance, indicating any possible faults. Faulty equipment may take more or less current than it was designed to do.
There are limitations to PAT testing: it can be compared with a car MOT – the basic safety of the car is checked, but it is not serviced, with parts replaced that are worn or dangerous. So, it is important to have your equipment serviced annually to ensure it runs at its peak performance and any faulty components, leads, circuitry, etc, are replaced.