Multiple Circuits from single MCB

[The Dentist]

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

Many thanks

 

[flameport]

Doesn't comply - see 314.4 (or 314-01-04 in the 16th edition)

 

[ban-all-sheds]

[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]

 

[plugwash]

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.

 

[stargazer]

OP, did you have a particular scenario in mind?

 

[The Dentist]

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

 

[ColJack]

you can spur off a curcuit at any point, even at the breaker..

 

[333rocky333]

I think the quide to part p book even shows two lighting circuits bunched on one mcb.
Cannot find book at the moment

 

[ebee]

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