More than one circuit on breaker

[Richard3009]

I have found in my house on the downstairs ring main that three lives are terminated into the 32A circuit breaker, two are for the ring main as you would expect; the third is for a socket below the fuseboard, to all intents and purposes its just a spur and electrically wise its sound.
Just wondered how this stands up with regs having three conductors in the breaker.

 

[Richard3009]

so based on this you cant spur from the breaker itself

 

[Spudnik]

If there was a radial circuit from a 20A MCB then thats fine

If there was a "spur" from a 32A RFC MCB then that is also fine.

It is no different at all to taking a spur off the back of a socket or at any point in the ring via jb.

Pg 362/3

 

[wet string]

the spur should only feed one outletunless fed through 13afcu so max current via 13amp plugs, 26amps.

 

[Richard3009]

If there was a radial circuit from a 20A MCB then thats fine

If there was a "spur" from a 32A RFC MCB then that is also fine.

It is no different at all to taking a spur off the back of a socket or at any point in the ring via jb.

Pg 362/3

Correct

 

[Tiger]

yougot aproblem withyour keyboard

 

[wet string]

its past my bedtimethatsall

 

[wattsup]

If you are spuring a socket, no problem, Nothing can be plugged in greater than 13amps. Assuming a ring main, ring circuit from the board and you wire in 2.5 or above...
But you cannot (or should not) spur off for a 20amp switch or similar, the spur must be a socket or a switch fuse.

Outbuildings are notorious for a 'spur' but some use a 20amp dp switch rather than a switch fuse, thus giving a max of 32amps from origin and still use 2.5 feed.

I have in the past done this but use 6mm, ie use ring main supply breaker at origin, sometimes you need to box clever when on on a budget, I know not ideal but costs sometimes means the job is yours, or not if you insist on a new board. As far as I'm aware there is nothing to stop you doing this, except diiferent size cable should not be used on a breaker/fuse.
However, a small run of cable not more than 300mm to an isolator (attached adjacent the board, wired in 2.5 then outbound in 6mm is ok) as I say not ideal but it is acceptable

 

[wet string]

sorry, maybe its late but i dont get the short run of 2.5 with an isolator? do you mean an fcu or whats protecting the 2.5 cable from carrying 32amps+ for some time.

 

[Richard3009]

17th edition onsite guide 7.2.2

Spurs can be connected from a ring at exsiting socket terminals, junction box or source of circuit in dist board.

 

[flukey]

LOOKS LIKE YOUVE ANSWERED YOUR OWN QUESTION THEN

 

[Richard3009]

Yes just looked at the book this morning, couldnt get my hands on it last night

 

[flukey]

think its down to personal prefernce then.
if it was me running a 2.5 t/e from a cu to a socket below cu then it would be on a correctly rated mcb for the cable thats in the cu.
havent checked the book but does it mention cable size from cu.
from memory diagram shows interconnections in ring but not directly from cu.

 

[Spudnik]

from memory diagram shows interconnections in ring but not directly from cu.

I am not sure why this is turning into a huge debate

You need to read the words and not just look at the pictures

 

[flukey]

WHAT IS A FORUM WITHOUT DEBATE

WHETHER IN PICTURES OR WORDS MY INTERPRETATION IS QUITE CLEAR, RIGHT SIZE CABLE FOR THE MCB

I THINK RICHARD EVEN MANAGED TO ANSWER HIS OWN QUESTION SO ALL IS GOOD ME THINKS

 

[fog]

I agree with Flukey it is a radial circuit and as there is only 1 earth not 2 as in a ring (which has two t& e thus two means of earth) it would be better not compulsary to lower the breaker/mcb put it on a 20A or 16A if possible not the Immersion though