Sub Panel and MCB wiring

Road-Hog

I need some advice on how to wire up the MCB's does anyone know of any good web site with pictures etc that I can log on to. I've taken a feed from the main house panel and I've run it to a garden building (underground and well protected). I intend to install a sub circuit within the building with 3 MCB, one for sockets, one for internal lights and one for an outside socket and light. I don't intend to use any majorily heavy electric equipment from any of the sockets or have any high wattage spot lights or anything.

2011

There is a drawing or two in the circuit diagrams sticky. It is best not to have sockets and lights on the same circuit. Ensue that the sub board has it's own main isolation switch. The sockets must be protected by an RCD. Why 3 circuits? Why put the outside socket and outside light on the same circuit? What type and size of sub mains cable are you installing? SWA is generally considered best for this type of situation. What is the length of run and expected maximum loading?

Dotsie~tmp

To be honest if we are talking about two internal sockets, 1 external and 1 light the whole thing could be put on one 20A circuit at the main board on the RCD (the light is switch by a fused spur at 3 amps). Or if you require separate RCD protection use one RCBO which could still be located in the main board.

As said if the cable is being buried underground use some SWA. If you are going along a wall use some NYMJ. If the shed is expected to have quite a few sockets and have a potential max load of 32A or so at any one time think about a 10sq SWA supply and a local board.

Here's a basic final 20A circuit for a shed say 10m from main board. Board wiring not included

davelerave

don't like the light spur off sockets if possible in sheds.because of potential for hazard

2011

As said if the cable is being buried underground use some SWA. If you are going along a wall use some NYMJ. If the shed is expected to have quite a few sockets and have a potential max load of 32A or so at any one time think about a 10sq SWA supply and a local board.

Good advice, just remember:
1 NYMJ does not provide the same degree of mechanical protection as SWA. It is much cheaper though.

2 NYMJ must be installed in such a way that it is not left exposed to direct sun light.

3 Work out your maximum load, lenght of run, cable type, method of installation and cable size in that order. Ensure that your cable can safley and infefinitley carry the current that it's protective device is rated at. A 2.5 may be suitable for a small load, but if the cable run is too long the volt drop may be excessive.


Nice drawing Dotsie!

2011

don't like the light spur off sockets if possible in sheds.because of potential for hazard

I think that dave is pointing out that if the RCD were to operate then the lights in the shed would be lost and this may present a risk, which might be the case.

davelerave

ya a sub-board for any outbuilding if possible ,more from experience than reading the rules.
314-arrangement of circuits(re :lights and rcd)
462.3-isolation(main switch for shed)

2011

A sub board would be a better job.

+1 a main switch is a requirement for all boards.

davelerave

462.3 and 462.4 .Outbuildings and distribution boards require isolating switches.seems to be ignored quite a bit.