another old fuse box

tawraste · Jul 12, 2011

hi all,
here's another one i saw today which i wondered about. my mate was proudly showing me his new bathroom and i thought i'd have a nose at the electrical arrangements.
he too has another old 1361 fuse box, with a new 13A 30mA RCD FCU installed on the wall above said fuse box providing the whole lighting circuit of upstairs (of which the bathroom is part) with RCD protection. the RCD FCU is downstream (by about 6 inches) from the 6A rewirable.
now i thought (yet again, please excuse my learning status) that this would be a questionable appliciation of diversity, but looking over the forum i have found threads where folks have done a similar thing but put the RCD FCU just outside the bathroom door.
aren't these two situations the same? and are they acceptable from the diversity point of view?
yet again, many thanks.

telectrix · Jul 12, 2011

basically all you are doing is adding a RCD to an existing circuit to comply with current regs. the fusing and loading of the circuit is the same as before ( with the exception of any added loads you may have installed , and allowed for )

johnboy6083 · Jul 12, 2011

i think you mean discrimination mate.
diversity is basically allowing gfor the fract that all loads are not on at once, and you use diversity to reduce the cable size needed.
discrimination in electrical terms, is making sure that only the protective device (such as fuse, circuit breaker ect) trips, and not one further upstream, which would cause much more inconvenience to the consumer.

the reason a RCD FCU would be used, is so that the sparks wouldnt have to replace the fuseboard to provide RCD protection. as long as thers is no other RCD in series with this one, then discrimination will be acheived.