Ouch (Important warnings to all working around electricity)

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Good lesson for all you trainees prove prove and prove again or DIE !!!!!!!!!!!!!!!

We have all done it just take care and think guys 

 
Call today from kitchen fitter who was trying to change lv cabinet under lights for mains but had messed up wiring, had no tester so was asking for advice, I managed to point him in the right direction and he said he realised what he had done wrong

Told him lesson no.1 was always use a qualified person......... He texted back two minutes later to say lesson no.2 was always remember to turn power back off before trying to change wiring......ouch!

 
a while back i was working on a massive house round my area, i was having to work on a local board in the garage i was pulling feeds in for the underfloor heating pumps and port heads into the board when i got a proper belt off the neutral bar, wondering why this had happened i got the tester out to test for any faults in the existing circuits, only to find 240 coming from the neutral bar and 0v from the bus bar, bear in mind everything was working all the lights PIR sensors and even the stereo, went to one of the big 3 phase boards to find a previous electrician had wired it upto a 40A rcbo but mixed up the live and neutral conductors, i couldn't believe it, i'v always tested a board once live for polarity no matter what, lets just say i wasn't happy and could of throttled the sparks that left the board like that, i was definitely more aware the rest of the day.

 
ProDave said:
Neon Screwdriver :innocent
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i was pulling the cables into the board hadn't even started terminating yet so hadn't the need to test anything, even so i'v never wanted to trust a neon screwdriver, i'v got high and a low voltate fluke pen testers for quick voltage tests when needed, and they have never let me down.

 
Always an idea to test for polarity. I think I have told this before but was asked to do some work on a showmans (fairground) caravan I got a belt of the neutral bar and this was because they had wired the 16 amp plug reverse polarity. As others have said test test and test again.

 
batty said:
Always an idea to test for polarity. I think I have told this before but was asked to do some work on a showmans (fairground) caravan I got a belt of the neutral bar and this was because they had wired the 16 amp plug reverse polarity. As others have said test test and test again.
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it's surprising the fact there was no signs of anything wrong i.e everything working as it should and had been for a number of months, i even think i had my makita charger charging battery's fine from one of the sockets, but yes i can't deny that test and test again is the best and only way forward, but it's definitely one that can catch you out.

 
You may not like a neon, but you clearly didn't use any of the testers you have.

What's the old saying, "never touch anything your tester has not tested first"

Never pull cables into a "live" CU either. Turn it off at the main switch first.

 
Most things will work reverse polarity. I had one a shop that sells carpets went to replace a light switched circuit of got a belt off that. Dno or contractors had wired meter reverse polarity when they had replaced overhead cables this had been like that for quite a few years with nothing breaking. We all get lapse and that can be the time it catches you out.

 
burnzybubbles said:
it's surprising the fact there was no signs of anything wrong i.e everything working as it should and had been for a number of months, i even think i had my makita charger charging battery's fine from one of the sockets, but yes i can't deny that test and test again is the best and only way forward, but it's definitely one that can catch you out.
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Alternating current is the clue!

They used to teach it at college??????

:shakehead

 
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Im quite aware what alternating current is, but the electrics inside some equipment is converted to dc and uses diodes in one form or another like a battery charger, my fault for assuming they wouldn't work if polarity is reversed.

 
burnzybubbles said:
Im quite aware what alternating current is, but the electrics inside some equipment is converted to dc and uses diodes in one form or another like a battery charger, my fault for assuming they wouldn't work if polarity is reversed.
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If polarity is reversed, just about everything will still "work" but it won't be SAFE.

For instance, you turn off a light, then get on your steps to change a bulb, but the switch will have only disconnected the NEUTRAL (due to the reverse polarity) so you touch the outside thread of an ES light bulb as you screw it in, and you get a shock, because it's still live.

 
I think we have gone off track a little here as I'm aware of what would happen in that situation, I was more suprised that all the other electrics still worked like the PIR's and the stereo and also my battery charger where dc will have been used in its workings.

I feel as if your labelling me as stupid, I do understand that you can never test enough but I don't think I'd of been the only person to miss this fault in this situation.

 
Yes but you get AC from the sockets, which is converted to DC by the equipment.

so AC in polarity doesn't "matter", it will still work.

 
, I was more surprised that all the other electrics still worked like the PIR's and the stereo and also my battery charger where dc will have been used in its workings.
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Welcome to the forum, Irrespective of how the internal components are powered, DC or lower voltage AC. Any item of equipment that can plug into a standard 13amp socket has 230volts that alternate in polarity at 50 cycles per second. So reversing the 'L' & 'N' connections will have no adverse effect on the internal workings of the appliance. But as Dave said, if only single pole isolation switching is used it can can leave unexpected dangerous potentials at terminals that normally would be at zero volts with respect to earth. 

Which is why one or two members may have been surprised that an electrician was not aware of the importance of never assuming something is de energized or wired correctly unless you have verified it yourself. I think the term Safe Isolation was a common phrase used. 

Doc H.

 
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