Electrocuted by 32 amp MCB

[iSelfBuild]

Yesterday I was giving my electrician a hand by screwing some back boxes onto my wall and feeding cable through the trunking. As he was wiring and testing the other sockets at the same time he isolated the kitchen socket MCB by turning it in the off position and not isolating all of the power. However it turns out the MCB for the kitchen sockets is faulty and remains live no matter when turned off or on.

 

I found this our the hard way by touching the wires when I pulled it through the trunking. Gave me quite a shock but fortunately no burns or serious damage other than a dull ache in the palm of my hand.

 

I bought the consumer unit new from Screwfix over a year ago but we only just made the kitchen circuit live so we only just found the fault.

 

I have contacted the manufacture about this and awaiting a reply. A bit scary to think if I had brushed against it a few minutes earlier whilst plumbing in the copper pipe for my washing machine.

 

How serious do you think they will take this? I can't believe that can happen with a MCB?

 

[Nickfromwales]

Ouch. ?

Did the RCD trip ?

[ToughButterCup]

Have a look at John Ward's YT Channel . He explains the issue

In haste.

ian

[iSelfBuild]

20 minutes ago, Nickfromwales said:

Ouch. ?

Did the RCD trip ?

Nope I just jumped out of my skin and banged my head

[Onoff]

Was this a BG consumer unit per chance?

[iSelfBuild]

3 minutes ago, Onoff said:

Was this a BG consumer unit per chance?

MK Sentor is the culprit. 

[Onoff]

There was a main switch recall a short while back on MK: 

 

http://www.electricalsafetyfirst.org.uk/product-recalls/2013/04/mk-sentry-switches-and-consumer-units/

 

EDIT: Think that was more to do with the main switches catching fire.

Edited August 13, 2017 by Onoff

[Jeremy Harris]

[pedant mode] Nice to hear that you weren't electrocuted (killed by an electric shock), but just got a survivable electric shock.[/pedant mode]

 

MCBs can stick on, as can RCBOs I've found (I had a DP RCBO fail like this), and I suspect any device like this can fail, given the pressure on manufacturers to reduce cost.

 

Personally, I never trust any switch or circuit breaker, and routinely test to make sure a circuit really is dead.  Having said that, I've taken risks from time to time, by just relying on a single pole switch/breaker to "isolate" a circuit, but, to be frank, I still tend to treat any single pole switched circuit as if it were live, unless I've tested it to be sure it's not.  Maybe I'm just a bit paranoid, but over the years I've developed a healthy respect for electricity, having had a few near misses.

[ToughButterCup]

11 minutes ago, JSHarris said:

[...] Personally, I never trust any switch or circuit breaker, and routinely test to make sure a circuit really is dead.  [...]

 

How? Watch.

[Nickfromwales]

8 minutes ago, recoveringacademic said:

 

How? Watch.

Good idea to ping a comprehensive link ?

 

As a quick fire safety point, one often overlooked, for anyone using a multimeter to check mains / where mains may be present:

 

When you have the red and black leads, dont EVER put the red onto live first! That may back-energise the multimeter at 230v which will then be transmitted down the black lead thus making the black probe end live. You could inadvertently grab the end of the black lead and ZAP ?.  Also, when removing the leads from the test points, always try to remove them both at the same time, unless your using the croc clip type where you remove the live first. Remember never to accidentally touch any metal casing either   

Note : Always assume both / either lead ends could become energised and don't let your guard down. 

Stay safe people . 

[Nickfromwales]

1 hour ago, iSelfBuild said:

Nope I just jumped out of my skin and banged my head

You may have had lesser than 30ma ( milliamperes ) going through you, hence the RCD would not activate / trip. 

Rubber soled shoes, wooden floors etc all add significant resistance to earth, so you had an electric shock, but not enough potential to see you off . 

[iSelfBuild]

Just now, Nickfromwales said:

You may have had lesser than 30ma ( milliamperes ) going through you, hence the RCD would not activate / trip. 

Rubber soled shoes, wooden floors etc all add significant resistance to earth, so you had an electric shock, but not enough potential to see you off . 

 

Aye it's more the potential fatality this could have caused and my head that hurts

[ProDave]

Today's lesson (and for all those reading as well) is TEST FOR DEAD before working on a circuit.

 

In fact when I was an apprentice, the mantra drummed into us, was Test your tester, test circuit for dead, test your tester again. Only then do you touch it.

 

Personally I am a huge fan of the humble neon screwdriver, something which some other electricians think are dangerous things never to be used. I don't use one as my primary means of testing for dead, but I am a fan of "don't touch anything my neon screwdriver has not touched first"

[Onoff]

We were made to chant, en mass at college:

 

"Switch off

Lock off

Signs

Test your tester on proving unit or known source of supply

Test for dead

Re-test your your tester on proving unit or known source of supply"

 

And a load of stuff about GS38...2mm/4mm probe tips, fused leads etc. Apparently "the tester must be YELLOW!" isn't a valid answer!

[dpmiller]

My el cheapo DMM has a built in non-contact detector with a couple of LEDS. Very useful. Even more useful that the LEDS still work with the meter powered off, and also with either probe live.

[Onoff]

Love my Fluke volt stick. 

 

Although a lad at work did get a belt the other day relying on one. 

[Nickfromwales]

Fluke volts-stick for me too, but they should only be used to determine power present, not circuit dead. 

It sends a shiver down my spine thinking about DIY vs electricity. Last couple of kitchens I've done have had flexible 3-core cables 1.5mm2 feeding sockets with the source of power being the incoming side of the 6mm2 cooker feed at the cooker switch. 32amps available down an ~18amp rated cable, with the best ones where that small cable is later extended to feed another socket, found almost always where a kitchen had been DIY upgraded, new appliances added, but no electrical involved "because the FiL can fit a plug so we asked him to do it" . 

Literally, shocking.  

[Jeremy Harris]

27 minutes ago, Nickfromwales said:

Fluke volts-stick for me too, but they should only be used to determine power present, not circuit dead. 

It sends a shiver down my spine thinking about DIY vs electricity. Last couple of kitchens I've done have had flexible 3-core cables 1.5mm2 feeding sockets with the source of power being the incoming side of the 6mm2 cooker feed at the cooker switch. 32amps available down an ~18amp rated cable, with the best ones where that small cable is later extended to feed another socket, found almost always where a kitchen had been DIY upgraded, new appliances added, but no electrical involved "because the FiL can fit a plug so we asked him to do it" . 

Literally, shocking.  

 

 

I always use a meter, and check right at the CU first, checking the live side, then flicking the switch and checking the load side is dead.  Finally, I check the end of the cable I'm working on is dead.

 

Whilst I'd agree that some DIY work can be grim, it is worth remembering that DIY work by someone competent, but who no longer happens to hold a ticket, may well be fine.  I'll hold my hand up to having done loads of DIY electrical work, from complete rewire jobs (before Part P came in) to allowable DIY work since the regs changed (and DIY electrical work is still permitted for some aspects of domestic electrical installations).

 

It all comes down to competence and knowledge, and I think we have reduced the level of knowledge in recent years by changes in legislation.  An example, when I was a small boy my mother (who was the practical person in our house) showed me how to wire a plug.  To this day I still remember her drumming into me the "red on the right" rule, and why the green earth wire should always be left with slightly more slack inside the plug (so it would be the last wire to pull out under strain).  This was long before the harmonisation of cable colours, and before we had BS1363 13A plugs, and still used the old round pin plugs.  Even now, every time I wire a plug the old "red on the right" thing pops into my head.

 

How many people today learn even the basics of something as simple as wiring a plug?  Very few, I suspect, since the law changed to require every appliance in the UK to be sold with an approved plug already fitted.  I'm not saying that this new law wasn't a good idea, it was, but an unintended consequence has been to dumb down the level of understanding of electricity and basic electrical safety knowledge by the population as a whole.

 

Finally, just because I know full well that the above will raise a red flag about my personal views with one or two, I'm not advocating that everyone should DIY electrical work at all.  Having a fear of undertaking electrical work, unless you are confident that you have the knowledge to do it safely is life preserving, and no one should think about even something as straightforward as fitting a plug, or changing a fuse, unless they fully understand what they are doing, and the consequences of them getting it wrong, let alone more complex work.  There are a stack of semi-hidden gotchas waiting to cause a potential risk in even the simplest looking electrical installations, unless you understand everything about the job in hand.

Edited August 14, 2017 by JSHarris
typo

[PeterW]

The one I'm redoing at the moment has had a rewire in the past and the wires are horizontal between the sockets. No issue apart from they didn't chase the walls so these are 2.5mm ring circuits just in plaster and in the internal corners the wires come out from the corner by 20mm.... 

 

Behind the sink base unit was a spur for the boiler that was fed from a double socket which then went back to another single socket on a different spur .... all of it in T&E and not clipped..!

 

Took the sparks longer to take the crap out than it did to do it properly ....!

[Nickfromwales]

We have a saying..."they know enough to be dangerous". 

The 'best' thing I've seen to date, however, is a staff member in B&Q giving a young couple advice on how to connect the gas to their newly purchased kitchen hob. He got a flexible rubber hose, told them to fit that into the bayonet, then screwed a couple of fittings to the end of the hose and told them to connect that to the hob and they're away. . I then proceeded to interject and inform him that what he'd just told them to do was not only downright dangerous, and illegal, but also completely contrary to current regs / legislation. He didn't have much to say after that and I explained to the couple why etc, to which they put the stuff back. Another member of staff there, a good friend, is still Gas Safe registered, and doles out the correct advice....."don't touch it unless your a GSR fitter, simple". 

 

@iSelfBuild

This is a very good thread, fortifying the need for periodic electrical testing / condition report requirements etc. @ProDave, do you think annual domestic testing will ever be legislation ? It seems madness that it isn't already. Funny how an HMO gets more scrutiny than say a domestic dwelling sleeping 5-6 family members   

 

[ProDave]

Domestic testing only seems to be done upon sale of a house at the moment, and then only if the lender asks for it. Private rental properties have to be tested every 2 years or on change of tenancy, but not council or HA properties. PA testing is every 5 years on a rental property.

 

The thing that would change that would be if insurers started demanding it?

 

Funny how people get upset though when you find faults and refuse to give it a satisfactory without remedial work.

 

Totally agree about nobody knowing how to wire a plug now, or change the fuse wire in an old style fuse.

 

Kitchen fitters are the worst for electrical (and probably plumbing / gas) bodges, as bad as anything the worst DIYer does in many cases.

[Nickfromwales]

34 minutes ago, ProDave said:

 

Kitchen fitters are the worst for electrical (and probably plumbing / gas) bodges, as bad as anything the worst DIYer does in many cases.

Yup. 

A very large and well known kitchen supply company, that begins with an M, did a £30k kitchen at a customers house. They connected a new large 5-burner hob where the old range cooker was, so in essence, a like for like swap, downsizing the required volume of gas at that location. Electric ovens fitted in a tower opposite. Less gas being consumed, so the gas fitter ( IF one actually came to the job, which I doubt, ) clearly thought hey-Ho, no need to do any checks, gas rates etc, just for and FO. 

I called my GSR mate out as there was a U6 domestic meter there, and it was feeding :-

1x Baxi 40kw combi boiler ( main house ) 

1x Ariston 28kw combi boiler ( garage / annex flat / beds it )

1x Potterton 28kw combi boiler ( laundry room / annex 2 ) 

1x 1200mm 22kw all gas range cooker 

1x 9kw gas fire. 

Nearly twice what a U6 will allow to be connected to it. The 'gas fitter' also knew that there was a second kitchenette being constructed at the time ( so the new £30k kitchen could stay 'for display purposes only' ! ) and that that was also having a new 5-burner hob, further increasing the gas consumption. 

The house had been added to / extended / converted in every conceivable direction, with just any local idiot being employed to do the various bits of work. Not one of them ever stopped to say there should be a much bigger gas meter installed, and my mate just capped the meter until the rectification / upgrades to the gas were agreed. When this was pointed out, the customer was happy to remove one of the two satellite boilers and fit one big unified system. 

No electricity was involved, but also, truly shocking. 

[Jeremy Harris]

 

 

1 hour ago, Nickfromwales said:

We have a saying..."they know enough to be dangerous". 

The 'best' thing I've seen to date, however, is a staff member in B&Q giving a young couple advice on how to connect the gas to their newly purchased kitchen hob. He got a flexible rubber hose, told them to fit that into the bayonet, then screwed a couple of fittings to the end of the hose and told them to connect that to the hob and they're away. . I then proceeded to interject and inform him that what he'd just told them to do was not only downright dangerous, and illegal, but also completely contrary to current regs / legislation. He didn't have much to say after that and I explained to the couple why etc, to which they put the stuff back. Another member of staff there, a good friend, is still Gas Safe registered, and doles out the correct advice....."don't touch it unless your a GSR fitter, simple". 

 

@iSelfBuild

This is a very good thread, fortifying the need for periodic electrical testing / condition report requirements etc. @ProDave, do you think annual domestic testing will ever be legislation ? It seems madness that it isn't already. Funny how an HMO gets more scrutiny than say a domestic dwelling sleeping 5-6 family members   

 

 

The key thing is to look at where the real risks lie. 

 

There are undoubtedly lots of poor electrical installation around, but the incidence of deaths or injuries from them is pretty low.  There are a lot more things that are likely to kill people than a bad wiring job, so the focus of those looking at enhancing safety regulation will always be on the highest risks.  Gas systems have to be up there as being in that category, primarily because the consequences of a gas installation being faulty are usually a great deal more serious, like the house that blew up a fee days ago.

 

The incidence of death from electrocution in the home UK is tiny, and the major risk is fire caused by an electrical fault.  The majority of electrical fault fires seem to be appliances being misused, or objects too close to appliances that give off heat, rather than the installation.  Electrical appliance faults are more common than installation faults, and although there doesn't seem to be any reliable statistics to separate out fires caused by appliance faults (like Grenfell Tower - caused by a fridge/freezer fire) from installation faults, it does seem that installation related faults only account for around 10% or less of death or injury from fires as a whole.

 

Given that misuse of appliances is far more significant, followed by appliance faults, I can understand why there is not so much focus on purely installation-related accidents.  Arguably, as primary installation standards improve, as they will as houses get rewired to newer standards, with better fault protection, then the potential for problems caused by bad DIY wiring downstream reduces, anyway.

Edited August 14, 2017 by JSHarris

[daiking]

You only have to look at the work carried out by a 'competent' electrician on my lights. I pulled all 5 lights out and all 5 were the same.

 

One of them also revealed a massive gap in the insulation. Doh. But that's not an electrical problem.

[Jeremy Harris]

8 minutes ago, daiking said:

You only have to look at the work carried out by a 'competent' electrician on my lights. I pulled all 5 lights out and all 5 were the same.

 

One of them also revealed a massive gap in the insulation. Doh. But that's not an electrical problem.

 

 

One big problem is that the incompetent people around won't ever read a forum like this, or any other reputable source of information, as I doubt they are interested in doing a better job.  In my experience, the only professional people who do bad work consistently are those who just don't give a damn; all they want is to get a job done, get paid and move on to the next job.

 

Those who care about doing a good job frequent places like this, and other specialist forums, so that they can continue to learn, and share their knowledge with others to help them learn, too.  By the same token, the best people are often those who don't advertise, and remain practically invisible to members of the public who are looking for a trades person, because they get all the work they can handle by recommendation and word of mouth.

Edited August 14, 2017 by JSHarris