"Christian McArdle" wrote
| Can anyone think of any IEE objections to having the following
| The circuit is a 32A B/RCBO ring main. I want to have a three way grid
| switch, each way fed from the ring main. Each module is capable of 20A and
| leads to a single unswitched 13A socket. There are no fuses in the system,
| except in the plug tops. The feeds are to appliances, each likely to have
| 2kW heating elements.
| Basically, overcurrent protection for the 20A switch is provided by the
| top fuse, whilst short circuit is provided by the RCBO. DP Isolation is
| provided by the unswitched socket. Is this allowed?
The problem I can foresee, but may not in reality be problem, is that this
is in effect a very high point load on the ring, and may affect current
distribution around the ring ie one leg more heavily loaded than the other.
Also if these appliances now have 2kw elements, are they likely to be
upgraded at a later stage to higher rated appliances? as there isn't much
spare capacity on the ring unless you can show diversity. Having other
sockets on the ring, to cover the 'not more unfused spurs than sockets
directly on the ring' rule, also adversely affects capacity.