Neither a ring nor radial!

[Smart Sparks]

Hello all,

I did some per inspections at my next job and found that the customer had no cpc at some points in the lighting circui, I then looked further around the other circuits and noticed the upstairs power circuit looked a little strange. At each SO there was only 1 cable so I assume someone has run a JB under the floor and then took various supplies from this point to feed all socket outlets. My question Is can I just reduce mcb to 20amp and class as a radial or is it a re-wire. The circuits with no cpc will be re-wired without question.

Cheers in advance for any advice you can offer.

 

[MDJ]

is it an old system? in the olden days sparks installed "jamaican ringmains" under the floor, basically it was a ring and a JB added everywhere where a socket was needed and a short spur from the JB to the socket, every socket in the house had one wire in it but there was a ring under the floor, before you ask, I have no idea why it is Called a Jamaican ring main.

 

[Sintra]

You could verify by testing r1 r2 & rn at the consumer unit.

 

[loop3]

Conduit?

 

[DNS1]

Stupid question, but how many lines go to the MCB/fuse?

If 1 it's a radial, if 2 it's either 2 radials or a ring so a continuity test will tell the story.

 

[Guest55]

yes , you can de-rate the circuit to 20amps if you feel thats best.
how many legs / feeds at the mcb ?
if theres 2 with end to end continuity , then its still a ring even if wierdly connected at the sockets.

 

[loop3]

I'm jamaican. And I've never heard that, maybe a behind the back comment eh?

 

[MDJ]

eh????

 

[loop3]

Never mind mj, we're obviously from different parts of town.

 

[loop3]

Rewire defo, btw, it's now called the polish ring, don't know why doh???

 

[DNS1]

It's fairly evident that were are going to be JBs under the floor and clearly they won't be MF.

What code would that be getting? 3?

 

[Smart Sparks]

So would you all suggest a re-wire is the right way forward as JB's under the floor dont conform to regs...........however the work I am doing relates to completely different cirrcuits........so assuming that work is correct, how far do you go?.

 

[Sintra]

JB's under the floor dont conform to regs......

Where did you get that info from?

 

[DNS1]

Where did you get that info from?

Hmm, I suppose technically they do, just bad practice...

They're still "accessible" if the house is pulled apart!

 

[telectrix]

So would you all suggest a re-wire is the right way forward as JB's under the floor dont conform to regs...........however the work I am doing relates to completely different cirrcuits........so assuming that work is correct, how far do you go?.

if your readings are OK, then leave as is. this method was used some years ago to save a few quid on cable. ( when a drum of 2.5mm was about a fiver ). considering the current price of cable, it's time it came back.