Disaster - maybe

[gee-force]

Hello, after some advice before i rip out all of my hard work, and all of my hair!

- background first -
i have been tinkering with electrics sinse i was a kid, learning as i went, and am now what i would call a professional DIYer. i have taught myself how do install electrics, do central heating installations, plaster, lay brick, the lot, and there isnt much i cant do, or learn quickly. (the latest being fibre optic networking). So, NO i am not trained in electrics, but yes, i know what i am doing (in the practical sense).

The problem:
I have installed a new electricity supply to a building (not a public building, not a dwelling etc. etc.). new meter, CU etc. I have 2 rings for sockets, which are floor recessed. the wires run in the floor void.

The problem is that about half of the sockets do not work at all, on both rings. i have checked the sockets themselves, and they are fine. i have tested the V of the wires (multimeter) at the faulty sockets and there is nothing. tracing the problem back it seems that there must be 2 'breaks' in the wire, again, on both rings.

So my only assumption is that there is a physical break in the wire. the wire ( 2.5m t+e) was a little tricky to lay, but did not put any unusual strain on it. the only problem i can see is the possibility of the wire (still fully sheathed) being bent.

Can this type of wire break easily? i have never come across this before. i have done a test to see if i could recreate this break by bending some fresh wire, squeezing with pliers, hitting with hammer etc, but still works fine.

There is no possibility of others breaks, e.g wayward nails/screws, rodents, etc, and the other half of the sockets give no problems and good readings.

am i missing someting fundamental that they teach you on day 1 of electrician school? the break (in 4 places!) seems so unlikely, but i cant think of anything else.. .. ..

Any help very gratefully recieved.

 

[2scoops0406]

Have you tried a continuity test in order to prove or disprove your theory of a broken wire, seems like the logical place to start if this is what you suspect.

 

[gee-force]

my multimeter does not 'beep' when testing the suspected runs of wire, as it does with the working parts. this is for blue, brown and earth! i am begining to think that there was a problem with the wire (new, from rexel senate) before i laid it, as ALL 3 wires broken on 4 runs of cable????? but this is also seriously unlikely (isnt it?)

how sharply would you have to bend this wire before all 3 conuctors break????? ive tried bending a fresh bent completly over on iteslf, and hammered it flat - still ok, and also bending it sideways - a flat bend - in a very tight u shape - still ok.

 

[comms]

Are you testing for ring conductor continuity at the consumer unit, try testing continuity between all 4 legs.

Possibly mixed the legs of both rings up & one pair of legs are not terminated into the mcb correctly.

Highly unlikely that there are breaks in the new t/e more likely to be the above or poor terminations at a socket.

 

[2scoops0406]

unlikely yes, but then your continuity test isn't showing continuity, so you either have broken cables or you haven't connected all the sockets up. Next step I guess is to test continuity between the sockets? Which ever way you do it you have to determine where the break is.

One thing to bear in mind is that I'm a DIY'er, hopefully an adult will be along soon

 

[Pensdown]

The problem is that about half of the sockets do not work at all, on both rings. i have checked the sockets themselves, and they are fine. i have tested the V of the wires (multimeter) at the faulty sockets and there is nothing. tracing the problem back it seems that there must be 2 'breaks' in the wire, again, on both rings.

If you break one cable on a ring circuit all the sockets on the ring will still work because they are fed from 2 sources so I cant understand what you have done.

You need to look in the last working socket on each ring because whether a supply cable is broken or not there must be a problem there for the next one not to work

 

[gee-force]

thank you for taking the time to reply.

I have taken the sockets out, so no possibility dodgy connections getting in the way now.

i am testing the bare ends of the run of cable (between 2 sockets) and multimeter saying no conductivity at all - on cores or earth.

yes this is a ring so must be 2 breaks!!!!! on both rings!!! HOW???


- Last time i had this feeling (bewilderment) i was attemping my first 2-way light switch - a long time ago - and coudlnt work out why my screwdriver tester kept lighting up even though the wire was disconnected at both ends -

i get the feeling there is something, like pen testers being complete rubbish, that i am completely overlooking.

 

[ban-all-sheds]

i am testing the bare ends of the run of cable (between 2 sockets) and multimeter saying no conductivity at all - on cores or earth.

Can you hoik out that length of cable and replace it?

yes this is a ring so must be 2 breaks!!!!! on both rings!!! HOW???

Interesting.

How much cable is left?

What does a continuity test on it show?


BTW - I don't know what type of building this is, nor for whom and on what basis you're doing this work, but it's a bit alarming that all you have is a multimeter. And it seems as though you energised the circuit without testing it first....

 

[Pensdown]

There a so many permutations on this it's hard to know where to start.

It could be the sockets that are live on both rings are in fact on 1 ring and you may have got your wires crossed somewhere.

It's very unlikely that 4 cables have been broken (unless you were a complete animal when you installed them, your name is gee-force ) and even less likely that the drum was faulty.

Pull the whole thing apart and try to find both ends of every leg in the ring. Don't just assume the next socket is the other end of the leg or where you think it should be, test every end in every socket every time. This may take some time but I cant think of any other way

 

[gee-force]

Please be assured that this work is not on any basis at all. it is not for anybody else - i am not that stupid, and is not in a building used by anyone other than myself. it is also a private electricity supply.

The install is very very simple. i know exactly where the cables run and where they go. i am very thorough and label everything.

i have now found the exact lenghts of cable that are not 'working' and yes - 4 different lenghts!!, put pulling it out not easy, though looks like thats what ill have to do.. ..

rings definatly not crossed, as diferent parts of the building.

didnt check before energising because its so simple, each ring just 7 DSSO in a row, same level all the same room- and i have installed sockets so many times in the past - guess thats what you get for not being professional or following proceedures.

but i still cant understand what has happened, i can only think of 'kinks' in the wire, hidden under the floor, but still cant believe it...

 

[Pensdown]

7 sockets is a small ring. If the loads not going to be to high you could install 1 new cable to link the good bits of each ring together and have 1 ring and not 2.

 

[ban-all-sheds]

It could be the sockets that are live on both rings are in fact on 1 ring and you may have got your wires crossed somewhere.

I thought about that, but with T/E, then mixed up or not, if all 4 lives are connected to MCBs at the CU, then all the sockets would be live. Unless one of the MCBs is faulty.

It's very unlikely that 4 cables have been broken (unless you were a complete animal when you installed them, your name is gee-force ) and even less likely that the drum was faulty.

Suppose it could happen. I always think it's worth the minute or two that it takes to do a quick continuity and IR test on a new drum, JIC...

Pull the whole thing apart and try to find both ends of every leg in the ring. Don't just assume the next socket is the other end of the leg or where you think it should be, test every end in every socket every time. This may take some time but I cant think of any other way

Hasn't he done step 1 and found no continuity between any pairs of cables at the CU?

 

[ban-all-sheds]

7 sockets is a small ring. If the loads not going to be to high you could install 1 new cable to link the good bits of each ring together and have 1 ring and not 2.

 

[Pensdown]

 

[diyunotaclue]

so why was part p etc brought in again......