RCD

[hkbrat]

Some help please.

We live on an small island in Hong Kong and have just fitted an external fusebox with an RCD on to a spur going into the garden for the use of powertools. The circuit already has a MCB in the mainsboard but should we install a further MCB besides the RCD. (i.e. in the same fusebox)

Thanks

 

[ericmark]

The whole idea of RCD, MCB, RCBO or fuse is to automatically disconnect in the event of a fault. The selection of size is in the main dependent on what it feeds and the cable used and in the UK the use of 13A sockets means also we have 13A or lower fuses so there is no need to fit loads of MCB's or fuses in the consumer unit.

However in Hong Kong just before the hand over there was a huge mixture of 13A, 5A, and 15A British with also some German stuff so much depends on what it feeds.

Clearly with your rain fall the RCD is very important but you just don't give enough info to answer the question.

So as a rule of thumb if 13A sockets are used feed from a 32A fuse/MCB/RCBO on a ring with 2.5mm cable then that's OK.

With a radial the amps drops down to 25A max with 2.5mm cable.

With German or old British round pin then further drops to 16A max.

There are other considerations but that should give you some idea.

All Best Eric ex VR2ZEP