1 MCB, 2 spurs...?!?!?! How to add sockets.....?

[LONESOMESOUND]

Okay, this is my problem...

I have quite an old flat I'm about to sell. It's been completely redecorated downstairs and I'm just in the process of sorting out upstairs before selling it. The electrics have been sorted out downstairs, but we never quite got round to sorting out upstairs, so the two rooms up there (two bedrooms) are still the same as when we bought the flat which is one socket in each bedroom. Obviously this is insufficient so we have used extension cables to add new socket capability as required. Not ideal. Now, just prior to replastering upstairs, I would like to add a couple more sockets so have been investigating the electrical setup. Basically, this is what I found...

Each single socket in each bedroom is wired (one cable per socket) into the same mcb on the consumer unit (which is modern and up-to-date by the way); the central heating control panel and burglar alarm are also fed from the same MCB (so it has three wires going into it). The cable is 4mm and the MCB is rated at 32 amps.

As I've said, I would like to add more sockets so have the following questions...

1) is what I have described basically 3 radial circuits being fed from the same MCB, and is this acceptable? (Small question... does the fact that each radial has only the one socket on it technically make each a spur directly off the MCB?!?!?)

2) can I add a couple of (double) sockets to each radial circuit and if so, do I use 2.5 or 4mm?

3) can I/should I be changing this to a ring circuit, and if so how (and, while I'm at it, what would be the benefit?)

4) owt else I should know??!!??

Many thanks for any help, cheers!

 

[andy]

for the sockets, you could make them into a ring. the existing 4mm will be OK and the MCB wont need changed. if you do make it into a ring, use 2.5mm

to change to a ring, add the sockets you want and connect them

you have

CU ------- socket
------- socket

make

CU --------socket------socket--------socket------CU

 

[plugwash]

if you keep them as radial branches then you will need to stay in 4mm

if you link them together to make a ring you can use 2.5mm

which is the easier/cheaper option wil depend on exactly where stuff is located.

 

[felix]

Plugwash is technically correct but I'm with Andrew2022 on this one. Starting from one socket, run 2.5mm cable round as many extra sockets as you want and finish at the other existing socket. The resulting ring will be more adaptable in future and the 2.5mm cable will be cheaper and easier to handle. Your MCB should be 30 (or 32) amps.

 

[Damocles]

Well running a 30A/32A radial through 4mm cable is not listed as a conventional circuit in the on site guide. You need 6mm. So continuing as two 32A radials is out.

This should never cause a problem if you only have one socket on the end, for exactly the same reasons a spur to one socket only is allowed from a ring.

You have a choice then of reducing the breaker to 20A or combining the two halves into a ring. Making a ring is probably easiest. But if you reduce the breaker, then there is no need to join the two ends and you can still fit as many sockets as you like.

Another neat solution would be to add a second breaker and make two separately controled circuits. This would allow more current, but in reality 20A is very likely to be quite sufficient for two bedrooms.