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Richard3009

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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.
 
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wet string

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  • #2
my understanding of the regs, from memory mind, is that a spur can originate from a termination at a socket outlet, a junction box or at the origin of the circuit.
 
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Stixicus

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  • #3
yes, would agree with wetstring - it is acceptable to have a spur on the circuit from the consumer unit in this way.
Never done it on sockets, but it is a good way of adding an outside light on a lighting circuit if there are no spare "ways" in the consumer unit.
 
would agree with the other replies if all the cable calcs work out.

what size cable is supplying the single socket??
 
then i would see that individual socket as more of a radial being served directly from the breaker in this way and i wouldnt have a 32 amp radial on a 2.5 t/e :confused:
 
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Richard3009

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  • #7
why?????? maximum load 26A no different to a spur,
 
if i was designing a circuit being fed from an mcb directly to a socket irrespective of what other cables were in the mcb already i would see that circuit as a radial, not a spur.
26a cable and 32a breaker :confused:.
i see where your coming from spurring from existing socket etc etc but not from board.
just my opinion ;)
 
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Richard3009

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  • #9
the regs permit it, any spur is a single 2.5mm cable protected with 32A breaker
 
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Richard3009

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  • #14
its not a radial, you can't have more than one double 13A on it, a radial you can providing the conductor size is correct for the potential load.
 
didnt mean you tiger, was asking richard. ;)

dont forget Ib has to be equal to or greater than In when selecting a cable richard.

point me to the correct reg and i will stand corrected :confused:
 
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Richard3009

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  • #16
so based on this you cant spur from the breaker itself
 
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Spudnik

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  • #17
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
 
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wet string

  • Thread Starter Thread Starter
  • #18
the spur should only feed one outletunless fed through 13afcu so max current via 13amp plugs, 26amps.
 
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Richard3009

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  • #19
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 :)
 
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wattsup

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  • #22
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
 
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wet string

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  • #23
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.:confused:
 
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Richard3009

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  • #24
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.
 
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Richard3009

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  • #26
Yes just looked at the book this morning, couldnt get my hands on it last night
 
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.:confused:
from memory diagram shows interconnections in ring but not directly from cu.:confused:
 
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Spudnik

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  • #28
from memory diagram shows interconnections in ring but not directly from cu.:confused:
I am not sure why this is turning into a huge debate:D

You need to read the words and not just look at the pictures:D
 
WHAT IS A FORUM WITHOUT DEBATE :confused::confused:

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 :cool:
 
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fog

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  • #30
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
 
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Spudnik

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  • #31
WHAT IS A FORUM WITHOUT DEBATE :confused::confused:

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 :cool:
Calm down.

No point in getting worked up over it:D
 
HAHAHA, ME, WORKED UP :confused:

MUST BE MISSING SOMETHING HERE JASON AS I AM THE MODEL OF A RATIONAL PERSON. ;)

THE WHOLE IDEA OF A FORUM IS TO ENCOURAGE DEBATE AND IF WE ALL THOUGHT THE SAME AND AGREED, WHAT A DULL PLACE IT WOULD BE.
 
P

pb electricals

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  • #33
I would agree with this

Imagine dull!! That is like is watching XXXXXX fottball team :)
 
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Spudnik

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  • #35
HAHAHA, ME, WORKED UP :confused:

MUST BE MISSING SOMETHING HERE JASON AS I AM THE MODEL OF A RATIONAL PERSON. ;)

THE WHOLE IDEA OF A FORUM IS TO ENCOURAGE DEBATE AND IF WE ALL THOUGHT THE SAME AND AGREED, WHAT A DULL PLACE IT WOULD BE.
I think it must be the CAPS then!
 

Had8Lives

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Arms
I just see it as lazy. If the single 2.5mm T&E for the socket below goes back to the board it ought to either be on a separate breaker or have two pieces of 2.5mm T & E and be part of the ring.
 
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wattsup

  • Thread Starter Thread Starter
  • #38
Hey, you can spur off a 1000a busbar if less than 300m, wired in 2.5mm (for alarms etc) so long as fitted adjacent busbar chambre. Many hospitals I have worked on have this arrangement. Point being you cannot run cables outside the area, the spur must be adjoined, hence the 300mm length. By the way I have fitted fire alarms to live 300a busbars, so now can you tell me how I drilled the busbar red...oops brown phase without isolating cos the nat health peeps would not allow isolation, even for a 2 minutes...

All answers please...
 
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