Appendix F

Isolation Procedures for Safe Working on Extra-Low and Low Voltages (Up to 1000 V)

The chart on page 19 illustrates a Safe Isolation Procedure for persons concerned with work on electrical systems on extra-low and low voltage (as defined in BS 7671).  Isolation is defined as a function intended for reasons of safety to cut off the supply from all, or a discrete section of, the installation by separating the installation or section from every source of electrical energy.  Isolation means the operation of switches, the removal of fuses or links or physical disconnection of conductors in order to make any system or part of a system DEAD and secure so that it cannot be inadvertently made live.  This will involve cutting off an electrical installation, a circuit or any equivalent item from every source of electrical energy.

In general remember the following rules:-

• Identify the source(s) of supply;
  Isolate;
• Secure Isolation;
• Post notices;
• Test that the equipment/system is DEAD; then
• Apply earths where necessary and applicable.
• Begin work.