We are often asked how do I know which circuit to turn off without accidently turning off the wrong circuit. Labelling is so important, especially if there are several lighting and socket circuits and even more so if there is more than one distribution board. When carrying out an alteration, or maintenance on an electrical system, it is imperative to know exactly which fuse to isolate. This can save much time and money if the person carrying out the alteration or maintenance knows exactly which fuse or circuit breakers to isolate. This also ensures that vital equipment, or other areas of the premises are not unnecessarily, or accidentally switched off.
In an ideal world, every accessory, be it a switch, socket, light, or other fixed appliance, should be labelled, with the distribution board and fuse way that it is fed from. This is even more critical if the electrical installation has more than one distribution board. For example, a light fitting in the reception area may be labelled as DB2/4 if the distribution board is single phase. Looks complicated to the layperson, but it means that the person carrying out the maintenance will have to look for distribution board 2 and then working from the main switch (be it on the left side or the right), count along to the fourth fuse or circuit breaker and isolate. DB2/4/1 (if the board is three phase), means the circuit is on distribution board 2, the fourth three phase way, and the first phase of that way (10th fuse way).
Correct labelling is so important, it cannot be stressed enough, as it can save lives. Yet it is the one thing that is frequently missing in most electrical installations. So often, we find distribution boards incorrectly labelled or worse, not labelled at all. If the accessories, or the board are not labelled in your case then there are no sure ways of not knocking out the server, or items of equipment that must not be switched off. There are circuit finders on the market, these are units that can be connected to a circuit, which then sends a signal down the conductors which is then detected at the fuse board by running a wand across the circuit breakers. It is not a fool proof solution, but it can help in locating the fuse way that protects the circuit to be switches off.
