Electrician Talk banner

1 - 20 of 71 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter #1
Hi There
Im new the for form and new to the electrical field. I started working as an apprentice about 2 months ago and today had a run in like i never want to have again.

I was working on putting a emt conduit into a 18x18 junction box that had many different circuits running through it. I had my channel lock pliers on the EMT and my had my hand near some live wires. (thee were all joined properly and had marettes on them) In moving around I knocked one of the marettes off a joint and the wire connected with my hand. My hands both clamped down on the pliers and refused to let go. I only let go because I lost my balance on the short step I was on and fell that pulled my hands from the pliers and I would guess saved my life.

Please do not make comments on how I should have known better or how my journeymen should have known better. Both of us had been over each joint in that box to make sure the marettes were tight and that every live wire was covered. It was a fluke accident. Needless to say I was rather frightened.

Now I have looked up what amperage it takes to harm a person and how much the body and withstand. From what I can find what I experienced was between 5 and 15 milliamps. I know the circuit was only 120 and I also know that voltage plays a role but I am confused with the labeling of the breakers we use. I am assuming that it was a 15 amp breaker, it could have been more but I'll go with that. According to what I have found over 2,000 milliamps would kill me, well a 15 amp breaker would be 15,000 milliamps.

Whats the deal? Do we just call a 15 amp breaker that because it is easier to say that 15 milliamps, or am I really off base here?
 

·
Banned
Joined
·
7,230 Posts
Skin is pretty high resistance. So is the plastic/rubber on tools.

It's a crappy circuit you made, but apparently good enough to give you a good scare.

Consider yourself lucky.

Also, in Canada we have 347V which is a real nasty one.. it's a killer for sure.
 

·
Registered
Joined
·
200 Posts
Rarely, if ever, will you find an ordinary overcurrent protection device with a trip rating less than a single ampere. "Overcurrent protection device" or OCPD is the generic name for fuses or breakers.

If you ever do find a fuse or breaker that small, it will be for a very specialized purpose. 10 or 15 Amps is usually the smallest found in most panelboards and other standard distribution eqpt.

The way that the 15 Amps would be selected, is the current that is expected to flow through it must be less than this rating. Likely up to 12A, as the max continuous current, for a 15A breaker. The breaker is larger, to avoid a nuisance trip, i.e. a false trip occurring when all would otherwise be good.

More than 15A would occur, if there is an unintentional path back to the source, in parallel with the circuit. Aka, a fault. We'd like as much of this fault current to go through the ground wiring as quickly as possible, so that the breaker trips, and turns off the circuit before the fault does damage to you.

It is a myth that "it is current that harms you". It does, but that isn't all there is to the story. Usually, this statement is said to explain a "bird on the wire" touching only one voltage is unharmed. It is actually energy that harms you. The cumulative effect of the power absorbed in you. The cumulative of both current-thru and voltage-across together.

You can reduce this by reducing the current thru you, the voltage across you, or by reducing the time you spend absorbing this current. And that is what an OCPD will do, is reduce the time.
 

·
Registered
Joined
·
6,960 Posts
Whiskey tango foxtrot are you talking about? panel breakers, excluding GFCi breakers, are to protect the wire, not devices or people.

There are several ways electricity can kill you. Burns, which you seem focused on, fibrillation and coagulation (blood clots), or falls.

Please explain how a person "absorbs" current?

Rarely, if ever, will you find an ordinary overcurrent protection device with a trip rating less than a single ampere. "Overcurrent protection device" or OCPD is the generic name for fuses or breakers.

If you ever do find a fuse or breaker that small, it will be for a very specialized purpose. 10 or 15 Amps is usually the smallest found in most panelboards and other standard distribution eqpt.

The way that the 15 Amps would be selected, is the current that is expected to flow through it must be less than this rating. Likely up to 12A, as the max continuous current, for a 15A breaker. The breaker is larger, to avoid a nuisance trip, i.e. a false trip occurring when all would otherwise be good.

More than 15A would occur, if there is an unintentional path back to the source, in parallel with the circuit. Aka, a fault. We'd like as much of this fault current to go through the ground wiring as quickly as possible, so that the breaker trips, and turns off the circuit before the fault does damage to you.

It is a myth that "it is current that harms you". It does, but that isn't all there is to the story. Usually, this statement is said to explain a "bird on the wire" touching only one voltage is unharmed. It is actually energy that harms you. The cumulative effect of the power absorbed in you. The cumulative of both current-thru and voltage-across together.

You can reduce this by reducing the current thru you, the voltage across you, or by reducing the time you spend absorbing this current. And that is what an OCPD will do, is reduce the time.
 

·
Senior Lurker
Joined
·
1,310 Posts
A gfci detects the slightest leaks regardless of cause rapidly. Normally but with exception tuned to kick above an annoyance trip point and below the potentially fatal level. 5-25 mA I think. This is first and foremost an attempt to save lives not equipment or code would require them in the office, and living area where most high tech expensive equipment would be used rather than kitchen and baths. :blink: Now if you are talking overload and or fire that's a different story, but once again the purpose is to protect you. :thumbsup:
 

·
Senior Lurker
Joined
·
1,310 Posts
Look up tetanic contraction related to shock. Very interesting phenomenon. I experienced it once when I was 15 or 16. Luckily I survived somehow. Know a guy that death gripped a ladder when he grounded through it and had to jump from 20 feet. Bad deal either way.
 

·
Ambassador of Amps
Joined
·
9,518 Posts
Whiskey tango foxtrot are you talking about? panel breakers, excluding GFCi breakers, are to protect the wire, not devices or people.

There are several ways electricity can kill you. Burns, which you seem focused on, fibrillation and coagulation (blood clots), or falls.

Please explain how a person "absorbs" current?
A GFCI breaker is not personnel protection, only a gfci receptacle. They have different mA ratings.
 

·
Registered
Joined
·
1,053 Posts
Now I have looked up what amperage it takes to harm a person and how much the body and withstand. From what I can find what I experienced was between 5 and 15 milliamps. I know the circuit was only 120 and I also know that voltage plays a role but I am confused with the labeling of the breakers we use. I am assuming that it was a 15 amp breaker, it could have been more but I'll go with that. According to what I have found over 2,000 milliamps would kill me, well a 15 amp breaker would be 15,000 milliamps.

Whats the deal? Do we just call a 15 amp breaker that because it is easier to say that 15 milliamps, or am I really off base here?
It was likely a 15 or 20 amp breaker, and you are correct 15 amps = 15,000 milliamps.

However, that doesn’t mean 15 amps flowed through you when you were shocked; fortunately you are not as good of a conductor as a copper wire. Current is inversely proportional resistance (more resistance = less current).

Ohm’s Law: Voltage / Resistance = Current
120 V / 500 Ω = 0.24 A (240 ma)
120 V / 1000 Ω = 0.12 A (120 ma)
120 V / 2,000 Ω = 0.06 A (60 ma)

Your resistance can vary dramatically depending on many factors such as, path of current flow through the body, condition of the skin (dry, wet, cut), amount of force applied to the contact area, size of the contact area, and even differences in muscle and fat content.

The table below shows the effect a certain amount of current may have the human body. At 5 ma the average individual can let go, however strong involuntary reactions can lead to other potentially fatal injuries, such as falling off a ladder…

You should read the NIOSH Electrical Safety Manual which is where the below table came from.

And for anyone who's ever wondered how they come up with those values, here is an interesting read on human subject testing.
 

Attachments

·
IBEW L.U. 1852
Joined
·
5,261 Posts
It is a myth that "it is current that harms you". It does, but that isn't all there is to the story. Usually, this statement is said to explain a "bird on the wire" touching only one voltage is unharmed. It is actually energy that harms you. The cumulative effect of the power absorbed in you. The cumulative of both current-thru and voltage-across together.

You can reduce this by reducing the current thru you, the voltage across you, or by reducing the time you spend absorbing this current. And that is what an OCPD will do, is reduce the time.

:blink::blink:
 

·
Registered
Joined
·
1,626 Posts
i will probably face quite a rebuttal, but the circuit breaker has nothing to do with it. i dont know anyone who has tripped a circuit breaker getting shocked unless they arced out one of their tools. what year apprentice are you? and arc flash is totally different than a guy getting bit. be careful. i hope your journeyman will teach you respect for the trade. we have some jerkwads that are about gettingerdone. go home to your friends or family every day after work.
 

·
Registered
Joined
·
7,790 Posts
I'm glad you are OK but, it wasn't a fluke. You were careless. This was 100% preventable. Be WAY more careful in the future. Look at the wires as deadly. If you have to touch them, don't be grounded, especially with a grip.

If you have a good grip on something like the conduit, it makes you super grounded. You shouldn't even be touching live wires if you are seriously grounded like that.

As you know (now), your muscles contract and you can't let go (your heart is a big ass muscle BTW)

I have heard more than one tale where the fall or jump was the only think that broke the connection.

Live, learn and pass it on. Be more careful. :thumbsup:
 

·
Registered
Joined
·
20 Posts
Hi There
Im new the for form and new to the electrical field. I started working as an apprentice about 2 months ago and today had a run in like i never want to have again.

I was working on putting a emt conduit into a 18x18 junction box that had many different circuits running through it. I had my channel lock pliers on the EMT and my had my hand near some live wires. (thee were all joined properly and had marettes on them) In moving around I knocked one of the marettes off a joint and the wire connected with my hand. My hands both clamped down on the pliers and refused to let go. I only let go because I lost my balance on the short step I was on and fell that pulled my hands from the pliers and I would guess saved my life.

Please do not make comments on how I should have known better or how my journeymen should have known better. Both of us had been over each joint in that box to make sure the marettes were tight and that every live wire was covered. It was a fluke accident. Needless to say I was rather frightened.

Now I have looked up what amperage it takes to harm a person and how much the body and withstand. From what I can find what I experienced was between 5 and 15 milliamps. I know the circuit was only 120 and I also know that voltage plays a role but I am confused with the labeling of the breakers we use. I am assuming that it was a 15 amp breaker, it could have been more but I'll go with that. According to what I have found over 2,000 milliamps would kill me, well a 15 amp breaker would be 15,000 milliamps.

Whats the deal? Do we just call a 15 amp breaker that because it is easier to say that 15 milliamps, or am I really off base here?


Thankfully, you are o.k. Sounds like you need to get a better pair of insulated pliers. Also, always venture on the safe side, and lead with your backhand when wading through a bunch of live wires like that. Never clear them palm first.
 

·
Registered
Joined
·
1,053 Posts
Shock current path - bird on a wire explanation.

As long as you are at the same voltage potential, there is no current path. This is why people say it's the current that gets you.

Edit: not sure what's up with my youtube link, so here it is again:
 

·
Registered
Joined
·
1,437 Posts
Rarely, if ever, will you find an ordinary overcurrent protection device with a trip rating less than a single ampere. "Overcurrent protection device" or OCPD is the generic name for fuses or breakers.

If you ever do find a fuse or breaker that small, it will be for a very specialized purpose. 10 or 15 Amps is usually the smallest found in most panelboards and other standard distribution eqpt.

The way that the 15 Amps would be selected, is the current that is expected to flow through it must be less than this rating. Likely up to 12A, as the max continuous current, for a 15A breaker. The breaker is larger, to avoid a nuisance trip, i.e. a false trip occurring when all would otherwise be good.

More than 15A would occur, if there is an unintentional path back to the source, in parallel with the circuit. Aka, a fault. We'd like as much of this fault current to go through the ground wiring as quickly as possible, so that the breaker trips, and turns off the circuit before the fault does damage to you.

It is a myth that "it is current that harms you". It does, but that isn't all there is to the story. Usually, this statement is said to explain a "bird on the wire" touching only one voltage is unharmed. It is actually energy that harms you. The cumulative effect of the power absorbed in you. The cumulative of both current-thru and voltage-across together.

You can reduce this by reducing the current thru you, the voltage across you, or by reducing the time you spend absorbing this current. And that is what an OCPD will do, is reduce the time.
Pardon me. I re read what you wrote.
 

·
Registered
Joined
·
1,437 Posts
Whiskey tango foxtrot are you talking about? panel breakers, excluding GFCi breakers, are to protect the wire, not devices or people.

There are several ways electricity can kill you. Burns, which you seem focused on, fibrillation and coagulation (blood clots), or falls.

Please explain how a person "absorbs" current?
Really! Are you an electrician. Your telling me that when you install a breaker your main concern is the conductor and that that's what they're designed for? HEY EVERYBODY! SAVE THE WIRE, NOT MY LIFE!
 

·
Registered
Joined
·
1,437 Posts
I'm glad you are OK but, it wasn't a fluke. You were careless. This was 100% preventable. Be WAY more careful in the future. Look at the wires as deadly. If you have to touch them, don't be grounded, especially with a grip.

If you have a good grip on something like the conduit, it makes you super grounded. You shouldn't even be touching live wires if you are seriously grounded like that.

As you know (now), your muscles contract and you can't let go (your heart is a big ass muscle BTW)

I have heard more than one tale where the fall or jump was the only think that broke the connection.

Live, learn and pass it on. Be more careful. :thumbsup:
Super grounded huh!??!?!?! Not just grounded everybody. But super grounded. That's like my new super hero name. I like that. SUPER GROUNDED!!!!
 
1 - 20 of 71 Posts
Top