Agbus Posted November 12, 2011 Share Posted November 12, 2011 My guess is that the electrician will fit a new switch and check the light fitting for earth. If there is no earth he will fit a new one that is double insulated and does not require an earth in line with current regs. I would prefer a nylon/plastic switch cover as there appears to be no earth wire. Link to comment Share on other sites More sharing options...
Rupert_Baehr Posted November 12, 2011 Share Posted November 12, 2011 If there are no loose wires and the installation meters up Ok, then what happened is this. A bulb blew as you turned the switch on, they go witha flash sometimes. The surge of current tripped the breaker, as they are designed to. You were so suprised by this, you imagined you had had a 'belt' off the switch. If you had a mains 'belt' you would know about it, they are unmistakable. Your entire body is creased by the pain for a millisecond. Any more than that, and you are dead. Your head is remarkably clear, but you do not feel right for sometime. Probably the worst you got was a bit of static. But its best to checked, if only for the fact that the breaker went. You do talk some rubbish, dear boy. There are a large number of factors which determine your body's response to an electric shock. DC Voltages above 42-4V are deemed to be potentially hazardous. AC Voltages above 90v (other than 60Hz US Supply) are deemed to be dangerous. It isn't just the voltage and the current. The Americans use a supply frequency of 60Hz (makes running a clock easy.) Your heart has a sinus frequency of 59.2 Hz. If your heart senses a frequency of 50 Hz, it isn't too bothered ... but 60Hz is too close to the sinus rate for comfort and if your heart tries to adjust itself to cope ... problems. Some people are less affected than others. I tend to have dry skin and my resistance (in Ohms) is fairly high. The highest voltage shock I've had was 45,000 - low current (made me swear.) I had a 7500 volt shock (between my fingers and the middle of my forearm) which hurt like hell, burned a hole in my arm and caused some short-term nerve damage (probably overlaoded them a bit.) As a child (and young person ) I used to check whether things were live by touching them (with the back of my fingers - your fingers will curl when you get a belt, so they curled away) ... touch the wire with the front and they may curl around it. Before I went to university I trained as an electrician. I got a few belts (but very few that I wasn't expecting.) I am now a lot older and rather more careful. Yes it would. The power surge will trip the breaker, if it doesnt then you have a serious fault. I am talking here of incandescent bulbs, which are now not allowed. As the bulb goes toward blowing, the power surges to the breaker trip point. It is simple electrical theory. Horse crap! I'm not sure who is being simple here. In the UK the standard power contactor (at the box) is 30 amps and lighting contactors are 15 amps (AFAIR.) There is no way that a bulb is going to draw more than 15 amps immediately before it blows. An 'Earth Leak Contactor' (Now known as an RCCB, a Residual Current Contact Breaker) compares (in simple terms) the current going in with the current coming out. - If you want to hook yourself between live and neutral it won't help yuu ... but if you hook yourself between live and earth it will trip. And maybe save your life! An arc welder cannot harm you, it is only 80 volts top wak, you might get burnt, but not killed. This is the mistake they made with the electric chair in the old days. They didnt electrocute them, they slow cooked them. 50 volts 30 milliamps is the lethal dose of alternating current. Above that, across your heart and you will die. No questions asked. That is why we use MCB's in everything these days. 50 volts 30mA. So you have a resistance of 16.6 Kilohms? So a 12volt battery across your gonads won't hurt? :hihi: To get back to the OP: If you had a belt from something, get a competent electrician to check it out. Don't use it until it has been checked out. Electricians are expensive, but your life is valuable. - You are worth the money. During the past 50 years (the time I've been mucking about with elecktrickery) building regs and other laws have improved considerably, but there is no shortage of 'cowboy' work done by either lazy (but [supposedly] 'qualified' electricians, incompetent 'qualified' electricians and incompetent amateurs. Case in point: I live in a house in a community which provides 'free' (I pay for it) maintenance. I decided to replace (at my expense) the ceiling fans. The originals were fitted by a licensed, qualified (but lazy) electrician. I turned off the breaker and removed the unit. The unit I removed was 'fan only' and I was fitting a unit with fan and lights. All the cabling (two live wires (one for the fan, one for the lights) a neutral and an earth) was there. The existing fan housing was metal. - Needs an earth. The existing fan had an earth wire (which had been wound out of the way.) The cabling to the unit also had an earth wire (bare copper, which should be sheathed.) It had been painted with emulsion paint (well, they do look prettier that way) and wound out of the way. That was PROFESSIONAL work! If you've had a belt from a switchplate (or anything else) get a qualified electrician to inspect and repair it. It might cost you 50-100 quid. A coffin costs more. Link to comment Share on other sites More sharing options...
Grandad.Malky Posted November 12, 2011 Share Posted November 12, 2011 An arc welder cannot harm you, it is only 80 volts top wak, you might get burnt, but not killed. This is the mistake they made with the electric chair in the old days. They didnt electrocute them, they slow cooked them. 50 volts 30 milliamps is the lethal dose of alternating current. Above that, across your heart and you will die. No questions asked. That is why we use MCB's in everything these days. I thought it was amps that killed not volts, are you a electrician It sounds to me that the route of the problem may have been wet hands on a metal light switch but then again I am not a electrician. It’s not volts that kill it’s the Amps…. you only need 50mA across your heart to kill you, there is enough in a 9v battery to kill you under the right conditions. Voltage just pushes the current through you, the higher the voltage the easier the path through your body, it all depends upon your resistance, if you touch a 9v battery with your dry finger you won’t feel anything, if you wet your finger and try again you will get a current flow and you will feel it tingle. (don’t try this at home) (especially if you have a pace maker) http://bigquestion.wordpress.com/2008/03/11/how-many-volts-of-electricity-would-it-take-to-kill-someone/ Link to comment Share on other sites More sharing options...
Balpin Posted November 12, 2011 Share Posted November 12, 2011 I thought it was amps that killed not volts, are you a electrician It sounds to me that the route of the problem may have been wet hands on a metal light switch but then again I am not a electrician. http://www.sheffieldforum.co.uk/newreply.php?do=newreply&p=8261877 No, I am an Electrical Engineer, not a house basher. Link to comment Share on other sites More sharing options...
Rupert_Baehr Posted November 12, 2011 Share Posted November 12, 2011 No, I am an Electrical Engineer, not a house basher. What is your qualification, please? Link to comment Share on other sites More sharing options...
Agbus Posted November 12, 2011 Share Posted November 12, 2011 I thought it was amps that killed not volts, are you a electrician It sounds to me that the route of the problem may have been wet hands on a metal light switch but then again I am not a electrician. http://bigquestion.wordpress.com/2008/03/11/how-many-volts-of-electricity-would-it-take-to-kill-someone/ It is a little bit complicated Grandad, and it does depend on current flow which in turn is dependent on EMF (volts) and resistance as Rupert said has an effect on current flow. (I=E/R) I have had a few belts of round about 27,000 volts, but due to the low current the voltage drops right down. A lot of the time it depends on the impedance and a CRT anode has a very high input impedance hence the high voltage which can be sustained with very low currents. Power is a product of Volts * amps Link to comment Share on other sites More sharing options...
Balpin Posted November 12, 2011 Share Posted November 12, 2011 What is your qualification, please? Dont be so cheeky, this a chat forum not a job interview. Link to comment Share on other sites More sharing options...
Grandad.Malky Posted November 12, 2011 Share Posted November 12, 2011 It is a little bit complicated Grandad, At work we had a static bar that was 3000 volts but only one amp ………. It gave you a good kick but it never killed anyone. Link to comment Share on other sites More sharing options...
looby1003 Posted November 12, 2011 Author Share Posted November 12, 2011 Thanks for all the great advice. Definately taken on board. Ive actually learnt a thing or two from this thread...and enjoyed watching the "sparks" fly (sorry couldn't resist!) Link to comment Share on other sites More sharing options...
dosxuk Posted November 12, 2011 Share Posted November 12, 2011 Dont be so cheeky, this a chat forum not a job interview. If you're an electrician, you need to go back to school. The number of things you've posted as facts which are untrue is scary. I am talking here of incandescent bulbs, which are now not allowed. For one, tungsten lamps aren't banned. 50 volts 30 milliamps is the lethal dose of alternating current. Above that, across your heart and you will die. No questions asked. Two, 30mA at 50VAC is not lethal, the vast majority of people would shake it off immediately. If it was lethal, then RCDs would be set at much lower levels, and 100mA RCDs would be illegal. Millions of people have survived shocks of far over 30mA. That is why we use MCB's in everything these days. And three, an MCB will not protect you from earth leakage, an MCB only protects against overcurrent. Now, assuming you actually meant RCD or MCCB / RCBO, which do protect you against earth leakage as well as overcurrent, well, we don't use them on everything. In fact most peoples' lighting circuits won't be RCD protected. Also, there's no requirement to have MCB's / RCD's. Thousands of house are perfectly legally using fuseboards. These are basic things, which any electrician would know. Link to comment Share on other sites More sharing options...
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