Just Pondering a concept... 2.5mm T&E from 32A MCB

[SPECIAL LOCATION]

Whilst adding some extra sockets in a garage the other day...

I was just mulling over in my mind....a bog standard 32A ring with say 10 sockets on the ring plus 4 unfused spurs supplying 4x Double sockets....  This is acceptable to BS7671..

Also one of these unfused spurs could be connected directly to the MCB at the fuse box...

What about if the four unfused spurs were all directly connected to the MCB and there was actually no ring....

so basically 4x Double sockets via 4x 2.5mm T&E direct to 32A MCB at fuse box.....

Should these be from 20A or 25A or are they still good to go via a 32A MCB???

My gut feeling is all good to go electrically...

BUT quite a strong risk Mr Prat-Head customer may come along later and extend further making spur off a spur from 32A MCB which is not good.

 

[Sidney]

If there's only one point on each 2.5 radial then technically there's no risk of overload so electrically it would be sound.

But as you've said, DIY Bob doesn't care about such things...

 

[Evans Electric]

No risk of overload  with  one twin socket , in theory  could be loaded to 23A   cable  clipped direct  is rated at 27A .  A short circuit would trip the 32A  MCB .  

But looking at the 17th ed. ratings  ...in a stud wall with thermal insulation and cable NOT TOUCHING the inner wall   your rating is down to  13.5A    so you'd have to fit just a single socket  or wire it in 35 sq,mm  X 2 core  Pyro  to be on the safe side . :innocent    

 

[kerching]

Yep

4mm wrapped up all cozy in fibreglass is only good for 16A.....I put some on 20s and was remonstrated with

 

[Andy™]

see similar all the time. 32a MCB with a ring and a 2.5 spur going to a socket. all fine, no problems. take away the ring and have just the socket oh no, thats a C1, the house will burn down.

 

[Evans Electric]

Whats the world coming to  ?   We've now got  Specs  "Pondering concepts "   :C  

 

[Sharpend]

Whats the world coming to  ?   We've now got  Specs  "Pondering concepts "   :C  

He’s on a mission to go boldly where no other spark has been before————————

to write a Plain English set of regs!

 

[SPECIAL LOCATION]

Whats the world coming to  ?   We've now got  Specs  "Pondering concepts "   :C  

It was generated from a job I worked on putting some extra power in a garage...

But one existing double socket outlet had three cables in it..

(I assumed initially this was part of a ring as flicking the MCB showed it powered from 32A MCB)

but it turned out as follows:-

cable 1: Supply coming direct from 32A MCB in fuse board  (approx. 8foot away)

cable 2: Up over garage rafters to opposite side of garage, (approx. <20foot away Inc up and over), with fused spur connected into boiler.

So with just cables 1 & 2 although not a method of wiring I would have adopted, it did not ring any major overload possibilities..

But there was also a third cable going off though the wall to supply something in the kitchen behind the garage wall...

This was a Blue-brown ..

Cables 1 & 2 were black red...

The 32A MCB had 2x ring cables going into in..

PLUS the extra third cable supplying the double socket...

Which made me ponder the concept that a competent person could add one or more sockets onto a 32MCB supplied circuit...…

But how much common sense should we as competent persons apply to the probability that "Mr-No-Brain-I-Can-Wire-Electrics-For-You-Love"..

Isn't going to come along and just overload your wiring!?

opcorn

(as wiring in garage was all surface clipped it wasn't too  hard to amend circuit so above socket and my additional sockets were suitably wired and protected.)