I have been thinking a lot about the comments made in the past ... about using overload protection at the main switch in the DB.

6.6 Distribution boards
NOTE This clause describes the minimum safety requirements for the construction
and installation of distribution boards. The symbols to be used in distribution boards are
stipulated in annex N.
6.6.1 General
6.6.1.1 Each distribution board shall be controlled by a switch-disconnector
(see 6.9.4). The switch-disconnector shall:


6.6.1.16 All disconnecting devices in a distribution board
a) shall be protected by a fully rated short-circuit protective device, and
b) when used in combination with a short-circuit protective device (see 6.7.4),
shall have a conditional short-circuit current rating (see 3.21.1) appropriate
to its condition of installation, but of not less than 2,5 kA.


If I recall someone mentioned that overload protection is required in the DB ... at the main switch ... I dont know if it has something to do with the type of supply in different provinces ?

From my experience - for domestic applications.

There is a fuse on the pole or in the CDU ... protecting the cable from the pole/CDU to the meter box.

The meter box has a circuit breaker which offers overload and short circuit protection ... protecting the cable from the meter box to the main DB.

The main DB will has a double pole or triple pole isolator which is the disconnecting device "main switch".

If the geyser for example - an isolator is mounted in the DB then overload and short circuit protection must be installed ... hence in the old days you found a 30 amp double pole isolator and 30 amp circuit breaker next to the isolator.

now we use what is referred to as a geyser combo breaker ... a double pole ... with a green and white lever ... which has also become commonly use for inverters.

When we start talking about commercial and industrial applications ... then the main switch has to be selected according to the fault level etc ... busbars and the DB layout is generally used to reduce the fault level etc ... which is why it is important to label the fault level on that type of DB.

Back in the day my old green book was full of highlights ... bent pages and notes ... going through the new SANS 10142-1(ed3.01) ... most of the stuff is still the same ol same ol ... but it has made me realise that I need to start reading the SANS regs more often ... to keep me up to date and just to refresh my memory other wise you forget.