Health & safety bulletin
Safe Isolation
24th October 2005
In order to ensure equipment being worked on is turned off, and that it cannot be turned back on until the work is finished, there is a standard Isolation Procedure that must be adopted:
- Locate the means of isolation - this should be labelled. In most cases it would be the circuit breaker at the distribution board. THE MEANS OF ISOLATION MUST BE ABLE TO BE LOCKED IN THE 'OFF' POSITION.
- Switch off the isolator. Ensure you have permission to do so beforehand.
- Lock the isolator in the 'off' position. Take the keys to the lock with you. If the isolation device is a fuse, take the fuse with you.
- Using a suitable test meter, check the meter on a known supply or proving unit to ensure it is working.
- Test the circuit that has been isolated to ensure it is dead. Check between Live to Earth, Live to Neutral and Neutral to Earth to ensure a wring fault has not occurred.
- Using the same test meter, re-check to ensure the meter is still working.
- The equipment can now be worked on. Ensure the supply is re-energised after working on the equipment.
Note, under some conditions, using poor quality meters or test lamps, it is possible to trip a main RCD when testing Neutral to Earth in step 5 above. This can mean that the power to the whole site is isolated, and therefore it is essential that appropriate meters are in good condition.
IF IN DOUBT, ASK YOUR SUPERVISOR OR MANAGER - DON'T WORK!
ELECTRICAL WORK MUST ONLY BE CARRIED OUT BY QUALIFIED/APPROVED PERSONS.