Junction box spurs

[scottmeister71]

I've noticed what seems to be the main circuit cable (2.5 T&E) with a branch feeding a junction box. This then feeds a spur socket. If this is correct does it then mean I can branch off the main cable, then take branches of the branch (hope this makes sense)?

 

[pdcelec]

Is it a ring, radial or feeding an item of fixed equipment?

 

[scottmeister71]

I think it is a radial

 

[andy]

I think it is a radial

on radials, you can take brances and ad to another brance etc. for rings tho, you can only take as many unfused spurs as there are fused spurs and sockets. you can only feed 1 double/single socket from each unfused spur

 

[ban-all-sheds]

I think it is a radial

It is extremely important that you establish this with 100% certainty....

 

[scottmeister71]

I think it is a radial

It is extremely important that you establish this with 100% certainty....

The only reason I wasn't 100% sure is that there are two lives going into the MCB for the kitchen circuit but when I removed a socket it had 3 cables in it, none of which could provide a result on a continuity test so someone suggested the it could be two seperate radials coming from the MCB.

I guess the way to tell is to remove the two lives (with the power off) from the MCB and do a continuity test?

 

[comms]

Yes
Do the same with the earth (cpc) & neutrals.

 

[plugwash]

what rating is the breaker and what size is the cable

my guess is it was originally a ring but has since been broken by kitchen fitters or similar. if this is the case then the breaker will almost certainly be two large for the size of cable in the new radial configuration (a ring allows a larger breaker for the same size of cable thats why it has to have special rules on spurring etc)

 

[scottmeister71]

what rating is the breaker and what size is the cable

my guess is it was originally a ring but has since been broken by kitchen fitters or similar. if this is the case then the breaker will almost certainly be two large for the size of cable in the new radial configuration (a ring allows a larger breaker for the same size of cable thats why it has to have special rules on spurring etc)

The cable is 2.5mm T&E. I know this may seem daft but when I look at the MCB's I can't see where it states the size of them

 

[andy]

what rating is the breaker and what size is the cable

my guess is it was originally a ring but has since been broken by kitchen fitters or similar. if this is the case then the breaker will almost certainly be two large for the size of cable in the new radial configuration (a ring allows a larger breaker for the same size of cable thats why it has to have special rules on spurring etc)

The cable is 2.5mm T&E. I know this may seem daft but when I look at the MCB's I can't see where it states the size of them

most have a letter and number. i.e B20, B32, C6 etc. some older types only have the number

 

[scottmeister71]

what rating is the breaker and what size is the cable

my guess is it was originally a ring but has since been broken by kitchen fitters or similar. if this is the case then the breaker will almost certainly be two large for the size of cable in the new radial configuration (a ring allows a larger breaker for the same size of cable thats why it has to have special rules on spurring etc)

The cable is 2.5mm T&E. I know this may seem daft but when I look at the MCB's I can't see where it states the size of them

most have a letter and number. i.e B20, B32, C6 etc. some older types only have the number

Thanks Andrew, you are right. The MCB for the kitchen sockets is 32A.

 

[plugwash]

i thought so, a 2.5mm radial on a 32A breaker is not an acceptable configuratin.

so you have basically 3 choices.

1: turn it back into a proper ring that follows the ring spur rules. this will require a lot of inspection of the current situation (probablly with the help of a meter) to make sure that everything is correct for a ring configuration.

2: keep it as a radial and reduce the breaker to 20A. depending on the model and age of your CU this may be problematic and you may have issues with the breaker tripping under heavy load.

3: split the cuircuit into 2 seperate 20A radials. this will require an extra space in the CU and like the previous option will require you to obtain 20A breakers suitable for your CU but is less likely to suffer from nusense tripping.