management of electrical safety and safe isolation procedures for low voltage installations, produced by Electrical Safety First in association with the Health and Safety Executive (HSE) and a number of other leading industry bodies including NICEIC and ELECSA. This can be downloaded free-of-charge at: www.electricalsafetyfirst.org.uk
Check terminal voltages between: (i) earth and line(s) (ii) neutral and line(s) (as shown) and (iii) earth and neutral.
1 www.sentencingcouncil. org.uk
The minimum required steps for safe isolation are given below, based on NICEIC Pocket Guide 5.
Step 1 Check with the occupier/user that it is safe and acceptable to isolate. If the isolator is an off load device, switch off the load. Open the means of isolation for the circuit(s) to be isolated and secure it in the open position with a lock or other suitable means.
Step 2
2 Section 2(1) of the Health and Safety at Work etc. Act 1974 states: It shall be the duty of every employer to ensure, so far as is reasonably practicable, the health, safety and welfare at work of all his employees. Section 3(1) of the Health and Safety at Work etc. Act 1974 states: It shall be the duty of every employer to conduct his undertaking in such a way as to ensure, so far as is reasonably practicable, that persons not in his employment who may be affected are not thereby exposed to risks to their health or safety.
Step 4 Prove the voltage detection instrument again against the known source, to check that it was functioning correctly when the circuit(s) was tested for the presence of voltage. Notes 1. In practice, the equipment being worked on is likely to be remote from the consumer unit, such as a socket-outlet located remotely from the means of isolation. In this case it is necessary to check that all the socket-outlet contact terminals are dead. 2. When checking for a voltage between an earth terminal and live terminals (including neutral), the test probe should make contact with the earth terminal first, to reduce the risk of the remaining probe becoming live. 3. When isolating the main source of energy, it is also essential to isolate any secondary sources of energy (such as microgeneration).
3 http://press.hse.gov. uk/2016/environmentalservices-firm-fined-overelectrocution-of-worker
Prove the correct operation of a suitable voltage detection instrument against a known voltage source, such as that illustrated. Guidance on voltage detection instruments is given in HSE Guidance Note GS 38 – Electrical test equipment for use by electricians.
How can we help? A DVD explaining the safe isolation procedure and a range of products for use when carrying out safe isolation are available for sale from www.shop.niceic.com NICEIC/ELECSA offer training relating to safe isolation at their training centres and now also offer an online training module. For further details visit: www.niceic.com/training/introduction
Step 3 Using the voltage detection instrument, check that there is no dangerous voltage present on any circuit conductor to be worked on. It is important to confirm that conductors are not energised, due, for example, to a wiring fault.
Fig 1 Guidance on safe isolation
Step 1
Step 4
Step 2
T
T
ON
ON
OFF
OFF
OFF
OFF
Step 3
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