Fixed Equipment Isolation

The term "Portable Appliance Testing" or "PAT testing" is commonly used to refer to the inspection and testing of electrical equipment. However, this term often creates confusion regarding which equipment requires testing. Many people assume that only portable equipment or appliances with a plug need to be tested. In reality, the inspection and testing process includes all equipment that is connected to the fixed installation, regardless of its size or how it is connected. This means that even a storage heater attached to the wall and wired via a fused spur still needs to undergo inspection and testing.

Before the inspection and testing process can begin, the equipment must be isolated from the mains supply. For equipment connected via a plug, this is a simple process of unplugging it from the socket. However, the isolation of fixed equipment is more complicated, which often leads to it being overlooked and left untested.

Isolating fixed equipment requires a competent person to perform the task, using a test lamp/voltage detector and a lock-off device. The IET Code of Practice outlines the minimum steps required for safe isolation.

  • 1 Locate/positively identify correct isolation point or device.
  • 2 Check condition of voltage-indicating device.
  • 3 Confirm that the voltage-indicating device is functioning correctly.
  • 4 Switch off installation/circuit to be isolated.
  • 5 Verify with voltage-indicating device that no voltage is present.
  • 6 Re-confirm that voltage-indicating device functions correctly on known supply/proving unit.
  • 7 Lock-off or otherwise secure device used to isolate installation/circuit
  • 8 Post warning notice(s).

Further information on safe isolation procedures is covered in the HSE publication HSG85

It is common for individuals who are trained and competent in performing in-house Portable Appliance Testing (PAT testing) to lack the ability to safely isolate the supply to fixed equipment. In such cases, what options are available?

The first step is to determine the frequency of testing required. In many instances, it is possible to test this type of equipment during the Electrical Installation Condition Report (EICR), which involves fixed installation inspection and testing. Although EICR testing typically does not include this type of equipment, it makes sense to combine the two tests as they both require circuit isolation. The EICR is usually conducted every 3-5 years, so a risk assessment should be carried out first to determine whether the test intervals are suitable. The duty holder will need to request that this type of testing be included in addition to the standard EICR. If the risk assessment indicates that more frequent testing is necessary, external electrical contractors may be engaged to perform the testing.