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

 

[telectrix]

do your isolation business, then use you approved voltage tester. 1 end on E and then prod all the MCBs and busbar with the other. many a time i've almost been caught with a missing neutral. you test l-n and get no reading.

 

[Deleted member 72666]

But you didn't follow the safe isolation procedure did you?

 

[guest119]

I suggest you read up on safe isolation proceedures before you hurt yourself or another.
What were you doing working in a commercial environment?
Do you consider yourself suitable to train, and keep safe, an apprentice?

Boydy

 

[Clive P]

Hi,

To be honest, I think most of us will have carried out isolations this way.
Turn off all the MCB'S , RCD's and main switch and test. I can't believe that EVERYBODY checks every single circuit on every isolation. For my part I think the OP was getting a bit of a slating; when it's not really due. Good point is, it has reminded us all that you can't take everything for granted.

Regards.

 

[Meggerman]

You have done what most others on here would do on here to be honest. You don't need slating at all mate. Whoever wired those DB's together like that needs slating big style.

 

[Delboybully]

Obviously it is a lesson learnt for me and I shall be doing as Tel suggested from now on. Thanks to clive P for an honest reply.

 

[sparks1234]

We all get a belt from time to time, it goes with the business, no need for any sort of slagging because you are a Electrical Trainee its just the way it is. Fair play to you though for admitting it.

 

[Badged01]

I'll give you your due and tip my hat, it takes some b*lls to openly admit a 'misteak' and being a "Electrical Trainee" at the same time on this forum. Sure as eggs are eggs you know there will be a bunch of members just queuing up to give you a good shoeing for doing so!

Glad your safe, lesson learnt, move on .....

 

[MDJ]

I'll give you your due and tip my hat, it takes some b*lls to openly admit a 'misteak' and being a "Electrical Trainee" at the same time on this forum. Sure as eggs are eggs you know there will be a bunch of members just queuing up to give you a good shoeing for doing so!

Glad your safe, lesson learnt, move on .....

hellooooooooooooooooooo :smilielol5:

 

[southsea1201]

Well let's hope that people don't slag off the OP. He'd done everything but pull the main fuse and even that wouldn't have negated the outcome. It's a lesson for everyone that putting your voltage tester on the main switch means nothing...and that's something 99% of people do...remember the saying " familiarity breeds contempt"....I would be sceptical of even the most experienced sparky who claimed he'd never had a belt or a mishap in his life.
One thing you don't need to do is put down the OP because it will stop further postings of this nature, and it's by sharing experiences we all learn. Well done the OP for a great post.

 

[Marvo]

I also have some sympathy for the OP with this one. Unless you test every single MCB plus the neutrals and even any disconnected cables there will always be a chance of a nasty surprise. Last time I got one was several years ago, there was a disused cable in a DB I'd just isolated and tested for dead, it was laying in the bottom terminated in a choc connector. It turned out to be a feed from a small UPS that was running back into the DB. I didn't get shocked but it cost me my favorite pair of side cutters.

 

[telectrix]

the much maligned voltstick casn be useful in these situations. if it lights, then further investigation , with caution, is the way forward. we've all been caught out, or nearly caught out. as said in an earlier post. familiarity breeds contempt.

 

[Knobhead]

I’ve deliberately had to back feed LV boards several times. Always down to UG cables being damaged. Each time it was documented and warning notices posted. It’s easy on an MV “open ring” it’s designed for it, LV systems it gets a bit more complicated.

 

[itselectric]

Three positive things have come from this, even though by accident. Firstly you have found a fault which could have resulted anyone following on being electrocuted. Secondly you have saved the tenant a lot of money and, thirdly, you have learned a good lesson for the future. As others have said we have all been there with complacency.

 

[dazza1981]

Well done to the op for sharing this, Im qualified but learning every day and this certainly got me thinking.
I like most sparks have never tested every mcb for dead and not in my AM2 or any other exams during safe isolation was i made to test every circuit for dead once the main switch had been isolated and verified as dead.

 

[guest119]

I think the point is being missed here.
The guy shouldnt have been anywhere near a job like this.
A jib spark is not supposed to be able to work alone nevermind a Electrical Trainee, need to be approved spark for that.
As for the apprentice training, poor lad!

Boydy

 

[dazza1981]

So a jib gold card electrician cant work alone??

 

[MDJ]

So a jib gold card electrician cant work alone??

Hi daz, no idea what the rules are today, but in the early eightees a JIB electrician was classed as someone who could carry out electrical installation work correctly to BS7671 under supervision, only an approved at the time could work alone, that said, today I believe 17 days is the legal requirement lol

 

[southsea1201]

So what you're saying Boydy is that all experienced sparks wouldn't have made the same mistake? I doubt that 100%. Who are you to say his level of competence is not up to this job. Some Electrical Trainee have qualifications that would make your eyes water. Most of them in my city tend to be ex.navy and dealt with far more technical problems than this. Cut the guy some slack...he did what many would have done.

 

[dazza1981]

Hi mate i did not know that, i do have my approved sparkies card but only recently got it.
Saying that i did a full apprenticeship and did the whole college route whilst on the tools but i was working on my own majority of the time as its the only way to gain confidence and experience and learn IMO. ( providing a supervisor has checked your work is ok )

 

[guest119]

So what you're saying Boydy is that all experienced sparks wouldn't have made the same mistake? I doubt that 100%. Who are you to say his level of competence is not up to this job. Some Electrical Trainee have qualifications that would make your eyes water. Most of them in my city tend to be ex.navy and dealt with far more technical problems than this. Cut the guy some slack...he did what many would have done.

And the legal implications are.....?

Boydy

 

[southsea1201]

Clearly if his works doesn't meet the requirements of BS7671 and there's a mishap then the sh&t hits the fan....the same would apply to the most experienced man.

...and I'd also be confident that the OP has resolved the issues on this site

 

[dazza1981]

For roughly 3 years i have been working unsupervised being just a mere jib gold card installation spark up until i got approved status couple of months back.Please dont ring the police on me lol.

 

[HappyHippyDad]

Sorry Delboy, I feel bad about saying this and I never thought I'd speak out against Electrical Trainee (seeing as though I am one), but we are simply not allowed to work outside of the domestic arena. We are 'domestic' installers and should not be undertaking electrical work within a shop.

 

[guest119]

Clearly if his works doesn't meet the requirements of BS7671 and there's a mishap then the sh&t hits the fan....the same would apply to the most experienced man.

...and I'd also be confident that the OP has resolved the issues on this site

Its not about bs7671 for goodness sake man!
Its about being qualified to do the task, experience, risk assess, methodoligy, supervising young persons etc etc.
Yes we all make mistakes but you need to be qualified and suitably experienced to do the task.
Are you familiar with common law? Thou shalt not hurt, endanger, kill another by your actions or inactions/omittions.

Boydy

 

[southsea1201]

Fair play with your comments Boydy, but in this instance I think the OP approached the job professionally and was a victim of something unforeseen that would have caught many out. He was probably aware that each of the properties had its own cutout. He had made an assumption that many of us would...ie that with the main switch of the board in the off position (and tested to boot) that he was ok to IR test.
I don't think it is helpful to attack his ability and competence when he has been the victim of a situation that even the most experienced man could easily fall into. His post is exactly what you want on this forum, it helps the knowledge pool and makes all of us think twice about taking anything for granted.

 

[m top]

Sorry Delboy, I feel bad about saying this and I never thought I'd speak out against Electrical Trainee (seeing as though I am one), but we are simply not allowed to work outside of the domestic arena. We are 'domestic' installers and should not be undertaking electrical work within a shop.

If it's single phase what's the difference as long you understand the cuircuit design why not core principle no different?

 

[Deleted member 9648]

Totally agree with the comments that the OP was pretty much blameless on this one. 100% certain it would have caught me out as well.

 

[ifindoubtdont]

I've been at it for 35yrs and can honestly say "You learn something new every day." That's how you gain experience and you very often say "Oh bugger, I won't do that again."

 

[southsea1201]

I've been at it for 35yrs and can honestly say "You learn something new every day." That's how you gain experience and you very often say "Oh bugger, I won't do that again."

Exactly, by sharing experiences we all learn more each day. I can see the impatience on this forum of the senior posters when others ask what they perceive as daft questions, and perhaps they have forgotten they were once the errand boy or teamaker. Now they have vast accumulated knowledge and at times can be a little condescending on more inexperienced people. Clearly they have forgotten their humble beginnings.
Knowledge takes time, and giving your knowledge is the biggest gift of all. We all love to read the occasional threads which show the fountains of knowledge some guys have...but it also seems they just can't resist giving someone a short kick in the nuts!!!!

 

[scammell man]

I think there's an aspect here that is overlooked. The tests are designed to be carried out in order to safely find faults. They are really designed for new build, ie everything starts dead. The tests don't work so well for fault finding and periodic testing, which is why 2395 is one of the highest qualifications. I am on record elsewhere on this forum for stating if you are Part P only you are not qualified for periodics or for offering a fault finding service.

in my view, the OP has made an early assumption which was wrong, and nearly killed himself. Also his powering down of the CU was at fault.

assumption: rcd faulty and was not. This was replaced and not tested. A functional test of the new one to prove the assumption would have shown the assumption wrong and further investigation was required. However he assumed fault fixed and ploughed into a full test of a system which wasn't dead. Golden rule: change one thing at time to prove cause and effect.

powering down CU. OP States no data. It would be better to identify what was powered down by each MCB as it was switched off. Ie identify the circuit. The false feed would be identified as Unknown which should equal warning. With an apprentice to run round the cafe and see what's happening this form of investigation is easy.
golden rule. Take your time.

If you think this is easy to say sitting on the computer, I had exactly this last week. Unlabelled CU with additional circuits added in. I spent 2 hours finding out what was on each MCB and where other supplies in the installation interacted before even thinking if putting my fingers on the copper.

 

[telectrix]

not a good ideas to put your fingers on a copper. you'd be up before the beak on an assault charge before you could say"only joking, occifer".

 

[m top]

I think there's an aspect here that is overlooked. The tests are designed to be carried out in order to safely find faults. They are really designed for new build, ie everything starts dead. The tests don't work so well for fault finding and periodic testing, which is why 2395 is one of the highest qualifications. I am on record elsewhere on this forum for stating if you are Part P only you are not qualified for periodics or for offering a fault finding service.

in my view, the OP has made an early assumption which was wrong, and nearly killed himself. Also his powering down of the CU was at fault.

assumption: rcd faulty and was not. This was replaced and not tested. A functional test of the new one to prove the assumption would have shown the assumption wrong and further investigation was required. However he assumed fault fixed and ploughed into a full test of a system which wasn't dead. Golden rule: change one thing at time to prove cause and effect.

powering down CU. OP States no data. It would be better to identify what was powered down by each MCB as it was switched off. Ie identify the circuit. The false feed would be identified as Unknown which should equal warning. With an apprentice to run round the cafe and see what's happening this form of investigation is easy.
golden rule. Take your time.

If you think this is easy to say sitting on the computer, I had exactly this last week. Unlabelled CU with additional circuits added in. I spent 2 hours finding out what was on each MCB and where other supplies in the installation interacted before even thinking if putting my fingers on the copper.

The guy made a mistake I don't understand your comment regarding the test don't work so well in fault finding why is that you can not find a fault with the dead test continuity insulation resistance ? Please explain you wouldn't look for a fault on a periodic live would you

 

[scammell man]

M top , I don't understand your question.
try this
what is the first test you do
was this done in this case

then try
how do you do an IR test on an unknown circuit. Have you removed all those nice expensive bits that don't like 500v up 'em?

has the OP killed himself, do you think HSE would say 'oh we'll be was faced with a difficult situation which he could not have foreseen and therefore there was nothing he could do' ? That's like saying your dead As soon as you accept the job and that is not so!

 

[m top]

Ok maybe I misunderstood your explanation what test do you do first on a periodic ,prove there's an earth ze identify cuircuits safe isolation dead tests to find any faults, I was not referring to this case in general just didn't understand what you were saying about the dead tests don't work so well for fault finding.

 

[telectrix]

why else would we spend all that money on vde 100v tested tools? it's not because we work live, is it? LOL.

 

[HappyHippyDad]

If it's single phase what's the difference as long you understand the cuircuit design why not core principle no different?

What you're saying is right in theory Mtop, but thats a bit like saying a competent nurse who has watched the doctor do thousands of operations could do it themselves. They might be competent to do it, but that doesn't make it right. I think its a bit of a slippery slope if we say.."well he's not qualified on paper, but he knows what he's doing". I think we need to work within both the 'legal boundaries' AND within our own competency levels.

That all sounds a bit boring but with 60 odd million people in the country there needs to be certain boundaries otherwise ther'd be chaos!! :dizzy2:

 

[scammell man]

An example: full test IR Line neutral
periodic or fault finding this is normally skipped because you don't know what's out there or you can't be bothered to remove several scores of bulbs.

 

[m top]

What you're saying is right in theory Mtop, but thats a bit like saying a competent nurse who has watched the doctor do thousands of operations could do it themselves. They might be competent to do it, but that doesn't make it right. I think its a bit of a slippery slope if we say.."well he's not qualified on paper, but he knows what he's doing". I think we need to work within both the 'legal boundaries' AND within our own competency levels.

That all sounds a bit boring but with 60 odd million people in the country there needs to be certain boundaries otherwise ther'd be chaos!! :dizzy2:

So your saying you would turn a job in a shop down because it isn't right ? Please don't think I am havin a dig but if you are competent you are competent this was a single phase supply so what's the difference,if it was 3 phase and you have not worked on it before ie in a shop that's different and if you are responsible would draw the line and not attempt the work even if you think you have an idea.