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Old 02-15-2013, 01:37 AM   #101
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http://engineering.dartmouth.edu/saf...alCurrent.html

It is the intensity of current that kills. Read for yourself.
Yes, it's current through the body that kills. That is not the same as current through a circuit.

Everything that whoaru99 said is correct.

The reason tasers and shocks aren't lethal is because either the source impedance is high (tasers) and limit the amount of current, or the total energy is low enough to dissipate before anything really happens (getting shocked by a doorknob)

It doesn't matter if you touch a hot lead how many amps are flowing through the conductor....you aren't going to trip the breaker, and the voltage isn't going to droop because the source impedance is so low.

The only time a loaded circuit makes a difference is when you are talking about the neutral or return path. If it is poorly connected or loose, a "high load" allows for a low impedance path to the power source and you get fried. If the load is disconnected, or say powering a LED (at a couple milliamps) you just get a tingly feeling even if it reads 220v.

A lot of the time when you have a short to case, you won't see the full voltage because depending on how well the return or case ground is connected, or where the short to power develops, you get a resistor divider and some intermediate voltage...but it's almost always a low enough resistance to power to still give a quite thorough shock.

On the other extreme, one of our suppliers builds current shunts for measure the current in circuits (essential a calibrated low resistance)

To make them, the connect the shunt to a 1000amp supply and use a bench top manual mill to remove material while the circuit is live until the proper resistance is met. Even though there is 1000amps flowing through the circuit, it's safe to touch the bare metal because at most the power supply will only deliver 4v.


In order to be dangerous, the voltage must be high enough to overcome the resistance of a human to a different voltage potential. It also must come from a source with a low enough impedance to not restrict the flow of current.

Unfortunately for the human body...those two requirements are not difficult to meet.
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Old 02-15-2013, 02:13 AM   #102
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Damn, I'm pretty sure if I took a pic of my panel half the guys here would flip **** with how I've wired it. And I'm always in it hot. One of these days I'll tie over to a secondary 100 amp from my 200, just gotta decide when if doubled up too many wires into my breakers.

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Old 02-15-2013, 03:24 PM   #103
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Yes, it's current through the body that kills. That is not the same as current through a circuit.

Everything that whoaru99 said is correct.

The reason tasers and shocks aren't lethal is because either the source impedance is high (tasers) and limit the amount of current, or the total energy is low enough to dissipate before anything really happens (getting shocked by a doorknob)

It doesn't matter if you touch a hot lead how many amps are flowing through the conductor....you aren't going to trip the breaker, and the voltage isn't going to droop because the source impedance is so low.

The only time a loaded circuit makes a difference is when you are talking about the neutral or return path. If it is poorly connected or loose, a "high load" allows for a low impedance path to the power source and you get fried. If the load is disconnected, or say powering a LED (at a couple milliamps) you just get a tingly feeling even if it reads 220v.

A lot of the time when you have a short to case, you won't see the full voltage because depending on how well the return or case ground is connected, or where the short to power develops, you get a resistor divider and some intermediate voltage...but it's almost always a low enough resistance to power to still give a quite thorough shock.

On the other extreme, one of our suppliers builds current shunts for measure the current in circuits (essential a calibrated low resistance)

To make them, the connect the shunt to a 1000amp supply and use a bench top manual mill to remove material while the circuit is live until the proper resistance is met. Even though there is 1000amps flowing through the circuit, it's safe to touch the bare metal because at most the power supply will only deliver 4v.


In order to be dangerous, the voltage must be high enough to overcome the resistance of a human to a different voltage potential. It also must come from a source with a low enough impedance to not restrict the flow of current.

Unfortunately for the human body...those two requirements are not difficult to meet.
And working around 240v meets that requirement. My load on or off debate refers to working with the bus bar. You can touch a hot wire all day, touch two bus bars you get hurt. I'm not debating that. What I am debating is, if you touch a hot leg, and then touch say another hot leg or neutral. You will get hurt worse if there is amperage on the run vs no amperage.
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Old 02-15-2013, 03:39 PM   #104
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And working around 240v meets that requirement. My load on or off debate refers to working with the bus bar. You can touch a hot wire all day, touch two bus bars you get hurt. I'm not debating that. What I am debating is, if you touch a hot leg, and then touch say another hot leg or neutral. You will get hurt worse if there is amperage on the run vs no amperage.
Danny, please don't take this as a personal attack, I promise it's not, but I don't think you understand ohms law.

Everyone here agrees with your statement that current kills.

But, the current is a direct result of the voltage and your body's resistance. Current is not controlled by the circuit in any way except when it might be limited by a breaker.
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Old 02-15-2013, 03:42 PM   #105
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And working around 240v meets that requirement. My load on or off debate refers to working with the bus bar. You can touch a hot wire all day, touch two bus bars you get hurt. I'm not debating that. What I am debating is, if you touch a hot leg, and then touch say another hot leg or neutral. You will get hurt worse if there is amperage on the run vs no amperage.
except, no, you don't. If the neutral is well bonded (and it should be if it's working) then it doesn't matter what the current through it is. it matters what the voltage potential between the two points is. In a household panel there are three potentials. ground, +120v, -120v (+/- are simplified for this discussion)

Current through those buses will shift the voltage slightly (loss in the conductors) but won't affect the current through the body.

By your logic, a 10w light bulb would shine brighter (more current through it) if I plug in a 300w light bulb next to it. (there's more current so it's more intense) that's simply not how electricity works.

Again, the only way a load will affect how you get shocked is if you are touching a ground or neutral with a lot of current through it. the current through the ground will tend to raise the potential (voltage) of the circuit segment relative to ground, allowing you to get shocked. The higher the resistance of the neutral or ground, the less current required to elevate the voltage to dangerous levels.
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Old 02-15-2013, 03:44 PM   #106
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Danny, please don't take this as a personal attack, I promise it's not, but I don't think you understand ohms law.

Everyone here agrees with your statement that current kills.

But, the current is a direct result of the voltage and your body's resistance. Current is not controlled by the circuit in any way except when it might be limited by a breaker.
exactly, it's absolutely true that it's current that kills - current through the body.

That's different than the current in a circuit.
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Old 02-16-2013, 06:22 AM   #107
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exactly, it's absolutely true that it's current that kills - current through the body.

That's different than the current in a circuit.
No it is not, because if there is no current through the circuit, there is no current through the body. If you become one with the circuit, guess what, those ampers are now running through your body. The intensity of the current is now significantly higher, which rocks your world!

If you tie into an unloaded 120v circuit and you somehow complete the circuit but there is no draw or pull on the circuit because nothing is on it, it'll hurt but your chances of being killed are less than say if your dishwasher and fridge were pulling something. You can dispute this all you want, I tie in all the time with stuff pulling all day, but if I have the opportunity to have less appliances, lights, etc pulling on the circuit I'll make sure they are shut off. You have to understand that in my world, the distribution boxes are outside. In movies we pull from a 1200A generator or 1.5 megawatt generator and our bus bars are outside in the elements on the ground. We cover them in rubber matts and place them on wooden boxes but they get rained on. They are exposed to the elements, your chances of being fried are exponentially higher. When it is raining and we are shooting a movie, guess what, all the electricians on set are wet. Guess what, our resistance makes us prime targets for being great conductors, union linesmen working on powerlines also work in the rain. You may not even know if you are upstream or down stream from the current either.

You have to understand that when I am at work, we have several 18,000w lights on the circuit and much more. It may even be raining. I'm gonna make sure those are off when I tie in because there may be 400+amps on the line when my hands are hooking up camlocks in the rain. If they must stay on, I'll make sure the circuit at my point of the rig is terminated at my point of the rig by breakering down before I tie into my section up stream of the source. If not and I must tie in live, I'm very careful to have my hand only on the one connection, I don't have a knee on the ground, and my other hand is not touching anything else that could ground me. I also make sure that nothing upstream from me is turned on. If my feet are wet I stand on a wooden box. My point being, if you were to make a mistake, which most DIY people who have no experience in the electrical world will ultimately do. They will totally add a breaker or wire with a hand planted on the edge of the box, or the mini fridge next to it, or a hand in a bucket of water, or a knee on the ground. Hell, on a home brew forum they'll probably be three or four deep before they even attempt it.

If some of these guys who have never worked as an electrician but are ****ing around with their breaker boxes in their homes to make cheap beer, shouldn't they take the extra precautions and not get killed? If you can tell me seriously that amperage vs no amperage on a circuit makes no difference, you have no idea what you are talking about.

I understand fully that the principle that "current kills" is essentially correct. It is electric current that burns tissue, freezes muscles, and fibrillates hearts. However, electric current doesn't just occur on its own: there must be voltage available to motivate electrons to flow through a victim. A person's body also presents resistance to current, which must be taken into account. Amperage cannot exist without voltage, and electric shock cannot exist without resistance met.

Taking Ohm's Law for voltage, current, and resistance, and expressing it in terms of current for a given voltage and resistance, we have this equation:

I=E/R

That is elementary. You can't have current without the other. But if you have an accident, which happens, amperage is a factor that can be easily avoided by simply shutting a breaker off. Remove it from the equation. It's one less factor that could result in your premature death. Which is one less thing to worry about regarding SAFETY. SAFETY always trumps everything in the union world of being an electrician. Screw that cowboy ****! I'd much rather be hit with 220v with no amps than 220v with 100amps. Just saying as, I've actually been hit by a 220 run before with a significant amount of amperage. Enough to blow me back 10 feet, make my life flash before my eyes, burn a hole through my left hand, and left foot, and almost made me piss my pants. The final result was 3 days in the hospital and a skin graft. What sucks even more, it was out of my hands. The 4/ot gauge cable had frayed and bad shielding which resulted in my my very near premature death. I've also been hit with a 220v neon light(it was an open ballast that acquired some moisture) which shook me up but I continued work. It didn't burn me and I didn't almost pee my pants, it didn't throw me 10 feet against a wall knocking me unconscious.

You can take chances all you want, but you don't know who hooked up your breaker box. You don't know if there is a frayed wire, a pipe leaking somewhere in the house on the circuit, a moist piece of rotten wood that is grounding out a hot frayed wire, or any other messed up variable that is out of your control. There are so many variables to the situation that my life isn't worth not tripping a breaker off before I tie in. If you feel like trusting an equation that is your business. As a journeyman Electrician in the film business, I'll advise otherwise.

If they trust me to hang 18,000w lights over Daniel Day Lewis's head, I'd trust that I know what I'm talking about. Yes that is right, I worked on Spielberg's Lincoln last year, it is nominated for 12 academy awards. I hate no name drop but you've left me with no choice. I doubt that they'd trust me to do my job if I did not know what I was talking about.

Here is my online resume if you don't believe me.
http://www.imdb.com/name/nm3016550/?ref_=fn_al_nm_1

In the meantime people, be safe, think smart, don't make yourself one with power. If you are scared, hire a professional. I've wasted enough time on this thread, trying to prevent people from getting unnecessarily hurt. If you want to be a cowboy and take a risk, go ahead. But there is more than enough power in your main breakerbox in your home to kill you. If your life isn't that important to you and you have no idea what you are doing, trust the guys advice above me who have yet to say what their credentials are, go ahead! **** the ampers on you circuit, it'll make no difference according to these knuckle heads.

I for one would much rather be shocked at 220v with no load than 220v with significant ampers. I've been hit with both. One resulted in a slight sensation and the other blew me back 10 feet. You be the judge, it's your life.
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Old 02-16-2013, 06:54 AM   #108
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Well, this thread has taught me 2 valuable things, one of which I already knew. 1. I know nothing about electricity(but now I am more aware of that) and 2. I will not be electric brewing anytime soon. This is a fascinating thread though. I need to hang out in this part of the forum more.

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Old 02-16-2013, 12:28 PM   #109
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If you tie into an unloaded 120v circuit and you somehow complete the circuit but there is no draw or pull on the circuit because nothing is on it, it'll hurt but your chances of being killed are less than say if your dishwasher and fridge were pulling something. You can dispute this all you want, I tie in all the time with stuff pulling all day, but if I have the opportunity to have less appliances, lights, etc pulling on the circuit I'll make sure they are shut off. You have to understand that in my world, the distribution boxes are outside. In movies we pull from a 1200A generator or 1.5 megawatt generator and our bus bars are outside in the elements on the ground.
As you posted, ohms law.... If you have a live 120V circuit for example, with nothing plugged in to it, current you will recieve (lets say your resistance is 1000 ohms) I=V/R = 120/1000 = 120mA. Now lets assume this circuit is drawing 10amps, I=120/1000 = 120mA.... No difference....

I think what your confusing is when you make/break a connection that is live, if the load is an inductive one (motors/transformers, etc) the blowback voltage/arc you will get can be quite dramatic and dangerous. This is for making/breaking circuits, your body making contact with a live loaded or unloaded circuit will make no difference. Have you ever seen the power company open up on of their substation disconnect switches, and the giant arc that typically occurs (due to the load)? If there was no load on the circuit you wouldn't likely get this dramatic arc, but touch one of those leads and you will get the same shock, because YOU are the load.

I also have seen people blown back when connecting/disconnecting 500-1000A power connections if the load is connected, due to the amount of surge that can happen when this is done. It is NOT for the reasons your stating, your arguing against one of the most fundamental concepts in electrical engineering.

You keep saying you know this, and we're all wrong but you haven't offered any explanation thats not based on your anecdotal experiences, the amount of shock you received from one day to the next is more likely to do with your resistance at the time and how you touched it then the load of the circuit.
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Old 02-16-2013, 02:22 PM   #110
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No it is not, because if there is no current through the circuit, there is no current through the body. If you become one with the circuit, guess what, those ampers are now running through your body. The intensity of the current is now significantly higher, which rocks your world!

If you tie into an unloaded 120v circuit and you somehow complete the circuit but there is no draw or pull on the circuit because nothing is on it, it'll hurt but your chances of being killed are less than say if your dishwasher and fridge were pulling something. You can dispute this all you want, I tie in all the time with stuff pulling all day, but if I have the opportunity to have less appliances, lights, etc pulling on the circuit I'll make sure they are shut off. You have to understand that in my world, the distribution boxes are outside. In movies we pull from a 1200A generator or 1.5 megawatt generator and our bus bars are outside in the elements on the ground. We cover them in rubber matts and place them on wooden boxes but they get rained on. They are exposed to the elements, your chances of being fried are exponentially higher. When it is raining and we are shooting a movie, guess what, all the electricians on set are wet. Guess what, our resistance makes us prime targets for being great conductors, union linesmen working on powerlines also work in the rain. You may not even know if you are upstream or down stream from the current either.

You have to understand that when I am at work, we have several 18,000w lights on the circuit and much more. It may even be raining. I'm gonna make sure those are off when I tie in because there may be 400+amps on the line when my hands are hooking up camlocks in the rain. If they must stay on, I'll make sure the circuit at my point of the rig is terminated at my point of the rig by breakering down before I tie into my section up stream of the source. If not and I must tie in live, I'm very careful to have my hand only on the one connection, I don't have a knee on the ground, and my other hand is not touching anything else that could ground me. I also make sure that nothing upstream from me is turned on. If my feet are wet I stand on a wooden box. My point being, if you were to make a mistake, which most DIY people who have no experience in the electrical world will ultimately do. They will totally add a breaker or wire with a hand planted on the edge of the box, or the mini fridge next to it, or a hand in a bucket of water, or a knee on the ground. Hell, on a home brew forum they'll probably be three or four deep before they even attempt it.

If some of these guys who have never worked as an electrician but are ****ing around with their breaker boxes in their homes to make cheap beer, shouldn't they take the extra precautions and not get killed? If you can tell me seriously that amperage vs no amperage on a circuit makes no difference, you have no idea what you are talking about.

I understand fully that the principle that "current kills" is essentially correct. It is electric current that burns tissue, freezes muscles, and fibrillates hearts. However, electric current doesn't just occur on its own: there must be voltage available to motivate electrons to flow through a victim. A person's body also presents resistance to current, which must be taken into account. Amperage cannot exist without voltage, and electric shock cannot exist without resistance met.

Taking Ohm's Law for voltage, current, and resistance, and expressing it in terms of current for a given voltage and resistance, we have this equation:

I=E/R

That is elementary. You can't have current without the other. But if you have an accident, which happens, amperage is a factor that can be easily avoided by simply shutting a breaker off. Remove it from the equation. It's one less factor that could result in your premature death. Which is one less thing to worry about regarding SAFETY. SAFETY always trumps everything in the union world of being an electrician. Screw that cowboy ****! I'd much rather be hit with 220v with no amps than 220v with 100amps. Just saying as, I've actually been hit by a 220 run before with a significant amount of amperage. Enough to blow me back 10 feet, make my life flash before my eyes, burn a hole through my left hand, and left foot, and almost made me piss my pants. The final result was 3 days in the hospital and a skin graft. What sucks even more, it was out of my hands. The 4/ot gauge cable had frayed and bad shielding which resulted in my my very near premature death. I've also been hit with a 220v neon light(it was an open ballast that acquired some moisture) which shook me up but I continued work. It didn't burn me and I didn't almost pee my pants, it didn't throw me 10 feet against a wall knocking me unconscious.

You can take chances all you want, but you don't know who hooked up your breaker box. You don't know if there is a frayed wire, a pipe leaking somewhere in the house on the circuit, a moist piece of rotten wood that is grounding out a hot frayed wire, or any other messed up variable that is out of your control. There are so many variables to the situation that my life isn't worth not tripping a breaker off before I tie in. If you feel like trusting an equation that is your business. As a journeyman Electrician in the film business, I'll advise otherwise.

If they trust me to hang 18,000w lights over Daniel Day Lewis's head, I'd trust that I know what I'm talking about. Yes that is right, I worked on Spielberg's Lincoln last year, it is nominated for 12 academy awards. I hate no name drop but you've left me with no choice. I doubt that they'd trust me to do my job if I did not know what I was talking about.

Here is my online resume if you don't believe me.
http://www.imdb.com/name/nm3016550/?ref_=fn_al_nm_1

In the meantime people, be safe, think smart, don't make yourself one with power. If you are scared, hire a professional. I've wasted enough time on this thread, trying to prevent people from getting unnecessarily hurt. If you want to be a cowboy and take a risk, go ahead. But there is more than enough power in your main breakerbox in your home to kill you. If your life isn't that important to you and you have no idea what you are doing, trust the guys advice above me who have yet to say what their credentials are, go ahead! **** the ampers on you circuit, it'll make no difference according to these knuckle heads.

I for one would much rather be shocked at 220v with no load than 220v with significant ampers. I've been hit with both. One resulted in a slight sensation and the other blew me back 10 feet. You be the judge, it's your life.
With all due respect, appeals to credentialism do not a convincing argument make.
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