Diversity

[david7]

When installing a consumer unit, would you take diversity into account. Say you had a 100A isolator and 2 ring mains 32A each 2 lighting circuits 6A each a Shower 40A and a cooker 40A. Any clues on getting round this I have been told you cannot exceed the 100A maximum load.

Thanks

[buildersmate]

Its exactly because of diversity that one can do it. The max load on the whole circuit is limited to 100A but individually the components add up to more than 100A because one is very very unlikely to have them all on at the same time. If one did the 100A main breaker would trip. The individual rating of the individual circuits protects the cable in each circuit from overload.
Changing a CU is notifiable work under Building Regulations unless you are a self-certifying electrician - in which case you wouldn't be asking the question.

[david7]

Thanks for that. I am studying Electrical Engineering and was asked the question by a friend. I have only done diversity on a cooker circuit

[Disco Fever]

Diversity on a cooker circuit is 100% and the cooker circuit should be protected by a 32 amp mcb not a 40 amp as the 6mm cable is only rated at 37 amps.....

The 100 amp isolator is just an isolator and would not trip on an overload as buildersmate has said above and yes you are supposed to notify buliding control when you change your consumer unit....

Also if you are going to buy a new CU then get a split load board, say a 5x5 split which is 5 on the RCD and 5 on the non RCD side as your shower really needs to go on the RCD side as well as the ring mains, the cooker does not have to go on the RCD side just like the immersion heater and lighting.

The new 17th edition IEE regulations are out on Jan 1st 2008 and will be implemented by June 1st 2008 and that states that all lighting and anything else in the bathroom has to be on the RCD, hepls being a sparky don't it....