A Tale of Woe - A Lesson Learnt

[Nick98]

I was going to post the following in DIY disasters but there is a serious point in the following - and a good indicator of why untrained people should not play with electrics!!

Back in 2001 I moved into a chalet bungalow with my wife, it was built in the 1930's as a traditional bungalow but had a large loft conversion added in the mid 1990's. Not long before we moved in the upstairs ensuite was refitted with some fitted units, lighting board above the units, new power shower, new sanitryware etc. The owner did it himself but I have to say quality was excellent.

All was well until a couple of weeks after we moved in - I walked out into the porch where the fuseboard was and noticed one of the breakers had popped. Not being sure of why I popped, or what it powered I reset it and thought no more of it (just assuming that it was a bulb blown somewhere, or other such minor glitch). Anyway 6 months or so passed and I decided that due to lack of storage space I would board out the loft so up into to small loft in the apex of the roof I climbed. You couldn't stand up but it was an OK space for storing cases and the like.

I started to press the insulation down (whilst on my hands and knees) to make sure there were no wires crossing joists etc before I put some flooring chipboard down when I put my hand on a cable.

Unfortunately the cable turned out to be the feed for an old electric shower that used to be in the ensuite before it was refitted and changed to a mixer bar. Even more unfortunately the end of the cable had been pulled up through from the ensuite and left with bare ends - the other end terminating at the breaker that I had reset some 6 months earlier!! All I can say is I don't remember what happened next but my head hit the roof so hard it broke two roofing battens and smashed two tiles on the outside of the roof, I cut my head open, my right arm was dead for a few hours and the fillings in my teeth ached for days!

In the cold light of day it appears that the power had been 'disconnected' by popping the breaker and the wire left coiled up in the loft. The breaker must have been popped when we moved in, but by not noticing I had assumed it had only just popped when I saw it. By resetting it I made the cable live and then months later I uncover the live end with my right hand.

Had I been older, infirm or a child I could be dead now but by luck I seem to be made of stronger stuff.

In some respects amusing and probably worth £250 on a home video show but equally potentially lethal and caused by a homeowner cutting corners/not appreciating what he was doing.

For this reason and this reason alone always get a professional in if you aren't sure what you are doing!

There endeth the lesson

 

[holmslaw]

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[Guitarguy]

very lucky!

I still don't know how i came off so well when i touched the live and neutral wires of a socket i was changing that happened to still be live (upstairs, every socket upstairs is on one ring main- except this one! so i found out!)

I unscrewed the connectors and removed the socket and went to set the wires and touched the live and neutral! All it did was make me swear- alot! and scared my mum half to death! bit of a belt yes but i didn't get thrown across the room or anything!

 

[Alarm]

Lucky man, if the live cable had been in the palm of your hand you would probably be dead. Your hand would have instantly grabbed the cable, your hand and arm muscles then go into tension and it is impossibl to let go. Or you could have been knocked out and fallen onto the live cable.

Unfortunately it takes a hard lesson like yours to wake people up to the fact that electricity can and does kill people, and leaves many others with serious lifechanging injuries.

It bites without warning, it bites instantly and it bites without mercy.

Anyone who doesn't believe me go to google images and type in 'electrical burns', only for those with strong stomachs.

Nick98, Youve got eight lives left. excuse the pun

Sorry but one of the points of AC versus DC is that DC makes you contract, AC has the oposite efffect of throwing you off.

Electricity can LET you let go or hold on to something. I depends weather it's DC (makes you hold on) or AC (tends to give you a chance of letting go because the current is flowing back and to through your body and doesn't lock your muscles as much as DC).

 

[Stoday]

Shows the value of getting a PIR (or whatever they're called nowadays) when moving into a new, but not newly built, house.

.

 

[Stoday]

Sorry but one of the points of AC versus DC is that DC makes you contract, AC has the oposite efffect of throwing you off.

Rubbish and a dangerous untruth.

Electricity makes your muscles contract; they still contract if the current's reversed. The millisecond or so when the current falls to a non-muscle cramping value is not long enough to allow for a let go.

Your contracting muscles throw you off the live contact if you touch it instead of grabbing it.

 

[JohnW2]

Sorry but one of the points of AC versus DC is that DC makes you contract, AC has the oposite efffect of throwing you off.

Electricity can LET you let go or hold on to something. I depends weather it's DC (makes you hold on) or AC (tends to give you a chance of letting go because the current is flowing back and to through your body and doesn't lock your muscles as much as DC).

I'm not sure where that quote comes from, but (albeit we're talking about a serious simplification of a very complicated situation) I'm afraid that it's essentially back-to-front.

50Hz AC is close to the optimal frequency for producing what it known as 'tetany' in muscles, resulting in a sustained strong contraction which can make it difficult to let go. In contrast, DC tends to produce a single, non-sustained, violent muscular contraction, which tends to 'throw people off' the source of the electricity. That's the general situation for voltages in the range 100V-300V, but things are different at other voltages (and other frequencies of AC), and there is a lot of individual variation of response to electric shock - so there can be no hard and fast rules. 50Hz AC is much more potentially hazardous to the heart than DC at most voltages.

Kind Regards, John.

 

[RF Lighting]

It happened to my mate Chris.

He touched a wire which was live between his thumb and fore-finger.

He couldn't let go until he fell to the floor and the wire was wrenched out of his hand.

He was left with nasty burns, and I've been so so careful since seeing what a disused boiler supply can do when it hasn't been made safe.

 

[holmslaw]

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[JohnW2]

He touched a wire which was live between his thumb and fore-finger.
He couldn't let go until he fell to the floor and the wire was wrenched out of his hand.

Indeed - that's what happens with AC, particularly around 50 Hz. The tetany it induces in muscles, which is much the same as what happens (in that case for chemical, not electrical, reasons) with 'cramp', results in contractile forces which are generally much greater and more sustained than can be produced by conscious effort, and the victim is totally unable to do anything about it. The forces generated can be amazingly large, even with muscles from very small animals.

Kind Regards, John.

 

[Alarm]

Then I stand corrected, I was always taught DC was the more dangerous for "grabbing" and not being able to let go.
I have had a few belts from DC but 50vdc, and a couple from 240vac. As mentioned in another thread here. The DC hurt more.
A friend worked for London Transport and said the accidents there were terrible when on the DC side.

 

[holmslaw]

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[JohnW2]

Then I stand corrected, I was always taught DC was the more dangerous for "grabbing" and not being able to let go.
I have had a few belts from DC but 50vdc, and a couple from 240vac. As mentioned in another thread here. The DC hurt more.
A friend worked for London Transport and said the accidents there were terrible when on the DC side.

Don't worry, you just got it the wrong way around - but you did recognise the nature of the difference. 'High voltage' (even if LV) DC shocks do tend to be more painful. The 'tetany' one gets with AC builds up over a short period (usually 0.5-1 second), whereas the single muscle contraction with DC is very sudden, viiolent and very strong - hence throwing people around. It can be sudden and violent enough to tear muscles and tendons, and has even been known to break bones - and all of that is very painful! Seconday injuries due to falls, getting tangled up with machinery etc. are also more common with DC shocks. All of this gets even worse when DC shocks are above LV.

Kind Regards, John.

 

[Alarm]

Thanks, as I always say.
Everyday is a learing curve.
You have to be a fool not to realise that.

 

[securespark]

I took off like a giant frog.

Didn't know they could fly!