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  • #61
    These discussions always amuse me, filled with with very factual sounding information from people who haven't the foggiest idea what they are talking about and they are the ones who always debate the hardest lol I have made it a rule to not get involved in these debates cause its alot like putting your head in a vise...
    Here is some info that may add to the discussion.
    120V kills more people world wide than any other voltage, its not enough to throw you but it is enough to keep you hanging on until your dead. I am a 3rd generation electrician who has been on the job for about 25 years now and I have had many shocks, the worst of which was 120V, it pulled all the muscles in my chest (which made breathing very painful) and very nearly killed me, had my body weight not pulled me off the stove I would be dead. But yes, 347/600V hurt's like hell and will typically leave a burn (as I am sure 277/480v does too), however it will also typically throw you off and the injury from banging your head or falling is usually worse then the shock itself...
    A 480V circuit is no safer then a 600V circuit, period, to say otherwise shows ignorance. There is also no difference in size between a 600 or 480v motor and up here many are rated for 220, 480 & 600 right out of the box, as are the control devices like overloads, contactors, control transformers, etc...
    Its unfortunate us Canucks didn't get together with our American brothers in the beginning to set up a standard distribution and rule system but it is too late now and we have to deal with it when cross border shopping, while the rules are getting closer all the time the 2 power systems will always remain different...
    Cheers,
    Jon

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    • #62
      I have to chuckle at some of these posts. Especially the ones warning of deadly car batteries and phone lines.

      I'm not going to bother trying to educate anyone, but I can assure you that millions of workers touch live, bare telephone wires every day with zero danger. I used to solder over 500 live connections per night, holding the wires and solder with bare hands. The phone lines only have 48 volts DC on them. Since it's DC the resistance from hand to hand is what limits the current.

      At the moment the resistance from left hand to right is 3,126,000 ohms. To get current you divide volts by the resistance. The current from touching a 48 volt wire with two hands is thus .000015355 amps. You don't even notice that.

      If it's AC, then it's a different issue. The impedance becomes the limiting factor. According to Wiki, the impedance of most people is around 2500 ohms at 48 volts. Obviously a lot more current will flow with AC.

      The picture changes if you puncture the skin and get into the more conductive tissue underneath. By the time you have live wires embedded in your skin you have other problems.
      Originally posted by wikii
      A domestic power supply voltage (110 or 230 V), 50 or 60 Hz alternating current (AC) through the chest for a fraction of a second may induce ventricular fibrillation at currents as low as 30 mA.[3] With direct current (DC), 300 to 500 mA is required.[4] If the current has a direct pathway to the heart (e.g., via a cardiac catheter or other kind of electrode), a much lower current of less than 1 mA (AC or DC) can cause fibrillation.

      Thanks for the chuckles guys!

      Dan
      Last edited by danlb; 05-24-2013, 04:18 PM.
      At the end of the project, there is a profound difference between spare parts and extra parts.

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      • #63
        Originally posted by danlb View Post
        At the moment the resistance from left hand to right is 3,126,000 ohms. To get current you divide volts by the resistance. The current from touching a 48 volt wire with two hands is thus .000015355 amps. You don't even notice that.

        If it's AC, then it's a different issue. The impedance becomes the limiting factor. According to Wiki, the impedance of most people is around 2500 ohms at 48 volts. Obviously a lot more current will flow with AC.

        The picture changes if you puncture the skin and get into the more conductive tissue underneath. By the time you have live wires embedded in your skin you have other problems.
        Thanks for the chuckles guys!

        Dan
        So wrong...
        First off, thats 'At the moment', Add some sweat and watch it drop to 20kohm or so. 0.0024A (2.4mA) at 48v, Not fatal sure, but trust me, with wet hands you can start to feel 24v DC, 48v is rather unplesent with wet hands, not very noticable with bone dry hands.

        Also, Phone lines *ring* at 90V *AC*, thats DEFINATELY unplesent, reguardless if your hands are wet or not.

        Next, Impedance is *NEVER* lower then DC resistance. It can't be. Impedance is reactance at a given freqency added to DC resistance. Humans are not huge coils of wire and hence they have near 0 reactance at 60hz, Hence our impedance is going to be near the exact same as resistance at 60hz.

        The *internal* resistance of the human body is around 2500ohms (or less) once you puncture the skin, Meaning that if you are stupid enough to stab each hand with a phone line, even 48v, now at 0.019A (19mA), can be fatal (Typically, 15mA across the chest is considered 'fatal' or at least a good chance of being 'fatal')

        Re: Jon Heron:
        I am not even going to touch the '120v is (less/more) safe then (some other high voltage)' issue, But I will say your logic is flawed if you think comparing the number of deaths caused from *BILLIONS* of 120v appliances and connections operated in large by the untrained public, Often repaired and worked on by untrained unlisenced indivuals, to the number of deaths caused from millions of 600v industrial services only operated on by trained electicians, means anything at all. Its like saying cars are less safe then dragsters because more people die in cars every year, dispite the fact cars outnumber dragsters a million to one.
        Last edited by Black_Moons; 05-24-2013, 04:52 PM.
        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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        • #64
          I can commonly feel a slight tingle from car batteries when my hands are sweaty but there is no danger of passing enough current to cause a problem. Try a 9 volt battery on your tongue. I'm sure most people have. Make it 50 vdc to find what it can do in the right (wrong) circumstances. No thank you.

          Also, when a telephone rings the voltage is around 90 to 110 vac at varying low frequencies. That will get your attention.
          Free software for calculating bolt circles and similar: Click Here

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          • #65
            Originally posted by Evan View Post
            Also, when a telephone rings the voltage is around 90 to 110 vac at varying low frequencies. That will get your attention.
            As a telephone company worker I'd get hit by ringing current once or twice a day. The terminals were less than 1/2 inch apart so the shock was localized to that small patch of skin and felt like a bee sting. The pain subsides immediately, leaving only the memory and a sheen of sweat to ensure that you will feel the next one.

            Ringing signal is typically 20 Hz. I don't recall any instance where i experienced any sort of muscle contractions as a result of ringing current.

            Are there any credible accounts of people being seriously harmed by a ringing telephone? I could not find any.

            Dan
            At the end of the project, there is a profound difference between spare parts and extra parts.

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            • #66
              I do not recall ever seeing a motor rated for 208, 480 and 600 volts?

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              • #67
                The first time my dad had me help him install some wiring, we worked it hot. We were adding several outlets to a circuit. Got a couple of tingles doing that. The last time I got a shock, my wedding band got caught on a corner on the inside edge of an old fuse box at the same time as it contacted a live spot. I don't know/remember if it was a wire, screw or what.

                Dad was a power company lineman and was used to working around hot wires.

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                • #68
                  Hey thank you for answering the original question. This thread has turned into QUITE the education regarding electric power and safety.

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                  • #69
                    Originally posted by ulav8r View Post
                    The last time I got a shock, my wedding band got caught on a corner on the inside edge of an old fuse box at the same time as it contacted a live spot. .
                    I worked for a guy who was a body/shop repairman and he got his stuck between the positive 12 volt and ground of the car frame, turned it red hot within seconds - left one hell of a scar says he almost lost the finger...


                    anyone hear the tale of the death row inmate who refused water for days and days before getting the electric chair and survived the first initial shock or two? not saying it's true - just saying I heard about it and I live in a prison town so take it for what it's worth...

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                    • #70
                      Used to inspect on new pipeline construction, and we quite frequently cut someones phone line. I always carried the stuff to splice them back. One day I was down in a pretty damp bell hole, and had one end of the line in each hand just when someone called, I got a dose of that 90 volts or better AC and it hurt like the dickens. Tingles don't bother me, I just grab on to the plug wire on lawn equipment to check for fire.
                      James

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                      • #71
                        Originally posted by danlb View Post
                        Are there any credible accounts of people being seriously harmed by a ringing telephone?
                        Back in my days in the Finnish Defence Forces, we tied up the rigged up phone line to the big toes of a sleeping private who should have been awake monitoring for calls. When the phone call came in, he surely was awake.

                        Though, it wasn't him who was hurt badly but the guys who attached the wires after he found out
                        Amount of experience is in direct proportion to the value of broken equipment.

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                        • #72
                          Originally posted by GNM109 View Post
                          When we take over and make Canada our 52nd state (right after Puerto Rico)
                          That's a joke right?

                          When your debt finally cause the total collapse of the US we will buy up the northern states for fractions of a penny on the dollar, Mexico can have the southern states back.
                          The shortest distance between two points is a circle of infinite diameter.

                          Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

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                          • #73
                            Re: Jon Heron:
                            I am not even going to touch the '120v is (less/more) safe then (some other high voltage)' issue, But I will say your logic is flawed if you think comparing the number of deaths caused from *BILLIONS* of 120v appliances and connections operated in large by the untrained public, Often repaired and worked on by untrained unlisenced indivuals, to the number of deaths caused from millions of 600v industrial services only operated on by trained electicians, means anything at all. Its like saying cars are less safe then dragsters because more people die in cars every year, dispite the fact cars outnumber dragsters a million to one.
                            I gave none of my logic for you to consider flawed Black moons, I gave you some statistical information and a personal experience, as well as the problem with 120V being nasty for getting hung up on... You can make your own conclusions with your logic, flawed or not...
                            I do not recall ever seeing a motor rated for 208, 480 and 600 volts?
                            Quasi, I have seen many, they make them every day. Not 208 but 220 - 600, you can likely special order one for 208 but they would not be so common, 120/208 3 phase systems are used more in commercial applications then for industrial...
                            Cheers,
                            Jon

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                            • #74
                              120/208V is (or was) used with aircraft.

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                              • #75
                                Originally posted by The Artful Bodger View Post
                                120/208V is (or was) used with aircraft.
                                Also at 400Hz?
                                Max.

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