Fixed Equipment Isolation
The in-service inspection and testing of electrical equipment is almost always referred to as ‘portable appliance testing’ or ‘PAT testing’. Unfortunately this often leads to confusion about what equipment needs to be tested. Understandably many people assume it only covers portable equipment, or appliances fitted with a plug. In fact the inspection and testing includes all equipment connected to the fixed installation, regardless of it’s size or how it's connected. So for example, a storage heater attached to the wall and wired via a fused spur still needs to be inspected and tested.
For the inspection and testing to take place, the equipment must be isolated from the mains supply. For equipment connected via a plug this is straightforward, it can simply be unplugging from the socket. The isolation of fixed equipment is not so simple, and for this reason it often gets overlooked and is never tested.
The isolation of fixed equipment must be done by a competent person and requires a test lamp / voltage detector and a lock-off device. The IET Code of Practice describes the minimum stages 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: HSG85.pdf
In practice, many people that are trained and competent to undertake the PAT testing in-house, are not competent to safely isolate the supply to the fixed equipment. So what are the options?
Firstly we should look at the frequency of the testing required. In many cases it's possible to test this type of equipment during the PIR (Periodic Inspection Report, the fixed installation inspection and testing). PIR testing does not normally include this type of equipment, but as the testing requires the isolation of circuits it seems sensible to combine the two together. A PIR is usually carried out every 3 - 5 years, so a risk assessment should be carried out first to determine if the test intervals are appropriate. The duty holder will also need to request that the work is carried out as an addition to the standard PIR.
If the risk assessment process indicates that more frequent testing is required, the testing could be done by an external electrical contractor. Alternatively safe isolation training courses are available. For example the NICEIC run a safe isolation workshop for non-electricians: NICEIC Safe Isolation Workshop
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