Isolation and Switching Explained

Isolation and switching provisions allow parts of an installation to be safely disconnected — for maintenance, in an emergency, or as part of normal operation. BS 7671 sets requirements for the different functions these devices serve.

The functions

• Isolation — cutting off the supply to make a circuit safe to work on, with the means to secure it against being switched back on.
• Switching off for mechanical maintenance — allowing equipment to be worked on safely.
• Emergency switching — rapidly removing danger (for example a machine stop).
• Functional switching — everyday on/off control.

Why it matters on an EICR

Inspectors check that suitable, correctly located and clearly identified means of isolation exist. Problems — such as no accessible isolator, or inadequate labelling that makes safe isolation uncertain — are recorded, often as C2 or C3 depending on risk.

Practical importance

Good isolation arrangements make future testing and maintenance safer and less disruptive — important in occupied commercial premises where circuits must be isolated without shutting down the whole site. See managing electrical shutdowns.