Multiple Circuits from single MCB

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I know its not good practice to have multiple circuits from a MCB but how does this stand with the regs?

Many thanks
 
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[restart the old debate that will never be resolved]On the other hand you take the definition of circuit and see that if 2 cables come from 1 MCB they are in fact 1 circuit not 2 and therefore 314-01-04 is not contravened.[/restart]
 
BTW don't be tempted to join rings end to end, it will in all likelyhood create a ring that is badly unbalanced and the total cable length may become an issue too.
 
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Thanks for the answers

Flameport, thanks for the reg no, I knew I had seen something once

Stargazer, it was a circuit which fed contactors which controlled some emergency lighting, the contactor feed had been fed from a completely different lighting circuit doubled up in the MCB, just wanted to check the regs, so I can slag off the original installer ;)

Many thanks
 
I think the quide to part p book even shows two lighting circuits bunched on one mcb.
Cannot find book at the moment
 
How do you know it`s multiple circuits?
If it`s fed from one opd (fuse/Mcb) then it could be one circuit albeit branched , known as a tree.
It is down to what the designer of the circuit(s) allowed.
Having said all that it is far better to seperate circuits indeed there is a reg that states this (314 - 01 - 01) however it uses the word "minimise" - if you follow that strictly then every point would be on it`s own circuit making it just about impossible.
If you do decide to split into more circuits then you must check there are no cross connections such as a "borrowed neutral" which could be dangerous
 

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