Q&A By Frank Bertie NAPIT Group Technical Director - Q: When we are working on circuits which are supplied from an existing consumer unit what procedures should we take to work safely?
A: Firstly, it is a legal requirement that employers must ensure that their employees working on electrical equipment are competent to do so.
Employees must be trained and instructed in the implementation of safe systems of work. This may involve the issue of written procedures, work permits and instructions on the use of locking-off devices, warning notices, approved voltage indicating devices and voltage proving unit.
The main purpose of safe isolation is that the point of safe isolation should be under the control of the person who is going to carry out the work on the isolated circuit or equipment. There are several ways of achieving safe isolations which depend on the type of:
Consumer unit/fuse board supplying the circuit
Overcurrent device used to protect the circuit
Local Isolation for equipment
Therefore, when working on existing circuits you have to be in control of the supply of the circuit, you have to have proved the circuit is dead and cannot become live during the process of your work.
Your options are Lock Off the circuit breaker or remove and retain procession of the fuse, place warning signs at the point of isolation and prove with a voltage tester that the circuit is isolated.