Short in socket - baffled

[jay jay]

Hi. I'm in the process of getting my qualifications and am taking on some small jobs for family to try and get some experience in.

Today I was looking at a socket on a final ring circuit. The house was built in the 80s and the socket is almost certainly original to then.

There were 3 cables running through the wall connected to the socket - with all 3 conductors twisted together (ie all 3 lines twisted together and connected to the socket as one).

I presumed 2 would be part of the ring, and wanting to know where the other was spurring to I untwisted everything and with a bit of tugging worked out that one was connected to a socket in an adjacent room.

I then attempted to rewire the socket, but rather than retwisting everything I put the conductors back in individually (it was a bit of a faff as it was tight, and the old cables quite inflexible) but I got there in the end.

However when I re-energised the circuit and plugged the appliances back in there was a crack, a small bang, and a weird (perhaps acidy) smell, which I understand to be a short circuit.

Confusingly nothing tripped.

I'm baffled though as my understanding is that a short would be due to the live conductors touching, however I definitely did not incorrectly rewire it - ie lines and neutrals separate.

I'd be so grateful if someone could shed some light please?

 

[Geoff1946]

Check you haven't caught one of the conductors with a plate screw.

 

[jay jay]

Hi Geoff. Thanks for the reply. I didn't reattach the face plate so am pretty certain it's not that.

 

[kerching]

Tugging may not have helped, may have loosened something

 

[jay jay]

Tugging may not have helped, may have loosened something

More of a wiggle than a tug

 

[kerching]

More of a wiggle than a tug

A wiggle has got me in trouble, serious trouble. Anyway we’ve been married 44 years in September! So be careful

 

[apprentice87]

You need to separate all the wires and work out exactly what is what now. IR testing too.

john..

 

[ProDave]

I did encounter an old metal fronted socket once where if you made the cables entering a terminal too long, they could touch the metal front and short out (demonstrating why the front MUST be earthed) but as this socket is described as "old" it is unlikely to be metal fronted.

 

[SPECIAL LOCATION]

Hi. I'm in the process of getting my qualifications and am taking on some small jobs for family to try and get some experience in.............................................

.............................................Confusingly nothing tripped.

I'm baffled though as my understanding is that a short would be due to the live conductors touching, however I definitely did not incorrectly rewire it - ie lines and neutrals separate.

I'd be so grateful if someone could shed some light please?

Welcome to the forum Jay-Jay.. Great opening post..
giving good background & experience about yourself..
and the question you need help with..

A few of my thoughts are as follows....

(1) When investigating the composition of a circuit and what cables go between the various sockets / accessories etc.. tugging, pulling, wiggling, can often introduce other problems due to loose connections in hidden junctions boxes, tape joints, weak crimps etc.. It is not uncommon to find old DIY junction boxes of various standards hidden in the most obscure places under floors, in stud walls, in lofts etc..

(2) Dead tests ALWAYS come before any live tests.

(3) A decent continuity tester, insulation resistance tester, and a handful of lever Wago connectors, (especially those that can take up to a 6.0mm conductor), e.g. https://www.toolstation.com/wago-221-5-way-compact-lever-connectors/p25142 plus a notepad & pen are your friend in these situations..

(4) If you open up a suspect ring circuit, the first task is to read & note continuity L->L, N->N, E->E. to verify if it is a ring and if ALL legs are continuous AND that all readings are proportional to each other.. i.e. Live & Neutral near equal, Earth proportional to either 1.0mm or 1.5mm, or a mix of both?

(5) Disconnecting ALL the conductors of a ring at the consumer unit... Then join L,N & E of one half of the ring into a Wago, creating a short between all legs of one half of the ring...
Then go round every socket on the circuit noting the continuity reading L->N, L->E & N->E.. will give a basic join-the-dots type map of the circuit arrangements as the laws of physics will give increased continuity readings the further along the circuit that you go.

(6) A reasonable quality continuity tester, that has the function to zero-out the meter leads and probes/clips is essential.. NOT a basic cheap multi-meter!

(7) Comprehensive continuity and insulation resistance tests on any circuit will verify the integrity of that circuit, highlighting potential problems and compliance with BS7671.

(8) NEVER assume anything is correctly connected..............

(9) ALWAYS assume that a circuit you are investigating is faulty, wired wrong, dangerous, and non-complaint with BS7671.. Until you have PROVED otherwise!

(10) Its Friday.... getting later.. ..The 's have now got into multiple numbers..
So I just hope my thoughts are of some help to you?

 

[Murdoch]

What type of fuse / mcb is there protecting this circuit ?