Bang!

[Delboybully]

So I go to a job a couple of days ago in a small shop. One of the things to do is fix an RCD that isnt working in a dual RCD board (not that neat but ok, no labels), everything works but if you turn the RCD off it doesnt disconnect the supply to the 4 MCBs it covers. Also the test button doesnt work. Take the cover off the board and the RCD isnt bypassed, it looks like it has failed closed.

I do a quick Ze, turn off the MCBs, RCDs and the main switch, test for dead and replace the RCD. I then power up and the replacement RCD trips. So I then start doing combined IR test L+N to E for each circuit to find the offending circuit. MCBs 1,2 and 3 or ok

Which leaves circuit 4, I connect my jump lead to neutral and the live and BANG!!!!! Nice pirotechnics with a few bits of hot metal spraying around!
Luckily my jump leads have a plastic covering on them or I could have got a belt!

I can tell you I wasnt expecting that. Luckily my jump leads have a plastic covering on them or I would have got a belt! My apprentice missed the fireworks as he was getting stuff from the van but he was impressed with the jump lead afterwards with a bit missing and the charring on the live cable

So I do some more investigating and it turns out the cable coming into the MCB was live and coming from the upstairs flat and was feeding the other 3 circuits in the shop through the bus bar. The guy in the flat above (luckily he was in) told me he has been getting electric bills of roughly a grand every 3 months, no wonder he had been paying for half the electric bill for a small cafe.

Now I followed the safe isolation procedure as I always do but this still happened. I phoned the Elecsa technical helpline and the guy said you followed the safe isolation procedure and its just one of those things you occasional see. He suggested waving a volt stick around the board in future. I then needed to phone the technical helpline again today on another matter so I asked the new guy the same thing, he again said that there isnt much you can do about these things.

I am one of the hated 5WWs, been doing this for approx 2.5 years. I am prepared for a slating, however I would be interested to learn how any of you would of approached this problem and would you of ended up in my situation. Obviously I followed the correct isolation procedure but still ended up in an undesirable spot. Any suggestions would be appreciated

Del

 

[shanky887614]

They are good for sticking in your shirt pocket next to the neon screwdriver, Mrs Jones and Mrs Smith down the road like to see a professional electrician turn up at their houses when the RCD trips out, the Volt stick looks the part haha

are you sure we are all talking about the same thing? the volt stick is for when you cant see where the cable comes from or goes to.

 

[MDJ]

are you sure we are all talking about the same thing? the volt stick is for when you cant see where the cable comes from or goes to.

yeah we are, they are totally useless thats my view, you can keep posting about how good you think they are all day, after 33 years in the trade I have learnt I just don't need them and can get by very easily without one. That said I have got 2, taped together in case one fails, I can't remember the last time I needed it, vertually extinct in my kit box.

 

[jaypp]

Back in the day, I wished I had a volt stick, we stripped a house out, everything disconnected from the head, temp supply put on and off we went with our cutters, down in the basement 1 2-5 t & e was live, fed from next door, straight through the basement, god knows who put it in, made me jump though
Also had one last year in a warehouse, a double socket that was fed from next door, presumably the units had been linked at some stage.

of course, when we are 'sure' a premises is isolated, we check every cable before cutting it! i do use a voltstick. latest one about a year old and so far it's cost me £40- a tenner plus £30 to replace my ck cutters! i definately put more faith in insulated tools and 'care' than the stick! however, would be lost without it

 

[jaypp]

They are good for sticking in your shirt pocket next to the neon screwdriver, Mrs Jones and Mrs Smith down the road like to see a professional electrician turn up at their houses when the RCD trips out, the Volt stick looks the part haha

shirt WITH pocket to work eh?! nah, you don't need voltstick to look good!!!