Code related Theory question
- Thread starter crossman
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crossman
Senior Member
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- Southeast Texas
Re: Code related Theory question
DISCLAIMER: never touch an energized circuit, never work on an energized circuit, and always use lock-out tag-out procedures. This thread is a discussion of electrical theory, not a how-to manual for on-the-job experimentation. Thank you.
DISCLAIMER: never touch an energized circuit, never work on an energized circuit, and always use lock-out tag-out procedures. This thread is a discussion of electrical theory, not a how-to manual for on-the-job experimentation. Thank you.
crossman
Senior Member
- Location
- Southeast Texas
Re: Code related Theory question
Thank you. I want to tell all of you that I am thrilled to have found this place. I have always wanted to have intelligent electrical conversation with smart people, and now I can. I have already learned something in the subpanel thread, and hope to continue learning.
I am thinking that i am 100% on this one. The guy would not get shocked in any of the above drawings.
Related story: I was working for a contractor, was doing some construction at a plant. The plant maintenance department would have me help out their electrician with troubleshooting when he was in a jam. A 120/208 panel fed by fuses had lost a leg. We knew the load on this panel was about 120 amps under normal circumstances.
I was about to use my Wiggy to check across the fuses to see which one was blown. The plant maintenance man jumped back and is hollering "don't do it, don't do it!" I stepped back and asked him "why?" He said "because the 120 amps of the load is going to go through your Wiggy and it will blow up in your face!" Next 15 minutes was spent on an electrical lesson.
Thank you. I want to tell all of you that I am thrilled to have found this place. I have always wanted to have intelligent electrical conversation with smart people, and now I can. I have already learned something in the subpanel thread, and hope to continue learning.
I am thinking that i am 100% on this one. The guy would not get shocked in any of the above drawings.
Related story: I was working for a contractor, was doing some construction at a plant. The plant maintenance department would have me help out their electrician with troubleshooting when he was in a jam. A 120/208 panel fed by fuses had lost a leg. We knew the load on this panel was about 120 amps under normal circumstances.
I was about to use my Wiggy to check across the fuses to see which one was blown. The plant maintenance man jumped back and is hollering "don't do it, don't do it!" I stepped back and asked him "why?" He said "because the 120 amps of the load is going to go through your Wiggy and it will blow up in your face!" Next 15 minutes was spent on an electrical lesson.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Code related Theory question
Just what I envisioned from your original question.
Ok do I graduate LOL
Just what I envisioned from your original question.
Ok do I graduate LOL
crossman
Senior Member
- Location
- Southeast Texas
Re: Code related Theory question
Graduate? This thread is just an appetizer for the next discussion that is coming.
But so far, IN MY OPINION, you have an A+! But I'm not sure everyone else is agreeing on this yet. And heck, we may be wrong, but it is going to take some convincing for me to change my mind on this one.
Graduate? This thread is just an appetizer for the next discussion that is coming.
But so far, IN MY OPINION, you have an A+! But I'm not sure everyone else is agreeing on this yet. And heck, we may be wrong, but it is going to take some convincing for me to change my mind on this one.
Re: Code related Theory question
Crossman, you are right, and your diagram tells the story very simply, and that is the best way.
The story about the Wiggy reminds me of a time when a guy tested a fuse with a penlight continuity tester. Fuse open, penlight zapped! Took me 30 minutes to get him to replace the fuse!
Crossman, you are right, and your diagram tells the story very simply, and that is the best way.
The story about the Wiggy reminds me of a time when a guy tested a fuse with a penlight continuity tester. Fuse open, penlight zapped! Took me 30 minutes to get him to replace the fuse!
jwelectric
Senior Member
- Location
- North Carolina
Re: Code related Theory question
Crossman?s disclaimer still stands.
One of the first lab assignments that is done in most basic wiring classes.
Switch paralleled with a light. turn on switch the light goes out.
This is the same principal as the question asked.
Yes, Crossman I like your illustration looks like you spent some time on it.
After looking at my first post the numbers didn?t look right so I ran this on simulator again using a switch to energize the 150k resistor after the circuit was running. I used resistors and inductors as the 200 amp load and there wasn?t a noticeable difference between them. The highest amperage over the 150k resistor when run with the switch was .013. I never did get the numbers I had the first time, might have entered the wrong values somewhere last night. There is one thing that might need mentioning here, (not every one reading this is a qualified person) these numbers are contingent on everything being perfect. A loose wire nut, terminal screw, split bolt or a damaged conductor WILL have a great effect on the amount of amperage the person would conduct in this illustration so PLEASE DON?T TRY THIS EVEN WITH A LOWER VOLTAGE. Let your meter be that person --- not you.
[ January 06, 2005, 10:52 AM: Message edited by: jwelectric ]
Crossman?s disclaimer still stands.
One of the first lab assignments that is done in most basic wiring classes.
Switch paralleled with a light. turn on switch the light goes out.
This is the same principal as the question asked.
Yes, Crossman I like your illustration looks like you spent some time on it.
After looking at my first post the numbers didn?t look right so I ran this on simulator again using a switch to energize the 150k resistor after the circuit was running. I used resistors and inductors as the 200 amp load and there wasn?t a noticeable difference between them. The highest amperage over the 150k resistor when run with the switch was .013. I never did get the numbers I had the first time, might have entered the wrong values somewhere last night. There is one thing that might need mentioning here, (not every one reading this is a qualified person) these numbers are contingent on everything being perfect. A loose wire nut, terminal screw, split bolt or a damaged conductor WILL have a great effect on the amount of amperage the person would conduct in this illustration so PLEASE DON?T TRY THIS EVEN WITH A LOWER VOLTAGE. Let your meter be that person --- not you.
[ January 06, 2005, 10:52 AM: Message edited by: jwelectric ]
Re: Code related Theory question
just thinking, and I think you guys have missed the big point, if I'm wrong, let me have both barrels.
Parallel conductors, there is an EMF of 480 volts driving 200 amps. Cut out a two foot section of copper and insert a man to complete the circuit. You now have a parallel path with diferent resistances in each path.
The amount of current flow in each path is determined by ohms law.
If memory is correct, it only takes 2 milliamps across the chest to kill. good luck
just thinking, and I think you guys have missed the big point, if I'm wrong, let me have both barrels.
Parallel conductors, there is an EMF of 480 volts driving 200 amps. Cut out a two foot section of copper and insert a man to complete the circuit. You now have a parallel path with diferent resistances in each path.
The amount of current flow in each path is determined by ohms law.
If memory is correct, it only takes 2 milliamps across the chest to kill. good luck
jwelectric
Senior Member
- Location
- North Carolina
Re: Code related Theory question
karlwayne
Sometimes electricians in the field soon lose sight of reality due to what the see with their eyes per say. If I am checking a fuse with a voltage tester with the power on I can use my tester and check across (from top to bottom) the fuse. If a voltage is present the fuse is bad if not the fuse is good.
In the case of this thread as I see it we have tried to use the resistance of the conductor to find the VOLTAGE DROP across the cut conductor and applying this finding we say that the voltage across the cut conductor is between two and three volts.
The one factor that has not been applied to this equation is the resistance of the person touching both ends of the conductor. As stated here the person had a resistance of 150k ohm. This man was completely dry.
The guide to electrocution printed by OSHA based on data collected by Kouwenhoven and Milnor states that the human body will have a resistance between 200 ohms wet to 40,000 ohms dry.
There are two facts that apply to a parallel circuit as follows:
1) the total current flow in a parallel circuit is equal to the sum of all the branches
2) the voltage drop across any branch of a parallel circuit is the same as the applied voltages
Do the math including the person and see what you come up with. My math equals dead
karlwayne
Sometimes electricians in the field soon lose sight of reality due to what the see with their eyes per say. If I am checking a fuse with a voltage tester with the power on I can use my tester and check across (from top to bottom) the fuse. If a voltage is present the fuse is bad if not the fuse is good.
In the case of this thread as I see it we have tried to use the resistance of the conductor to find the VOLTAGE DROP across the cut conductor and applying this finding we say that the voltage across the cut conductor is between two and three volts.
The one factor that has not been applied to this equation is the resistance of the person touching both ends of the conductor. As stated here the person had a resistance of 150k ohm. This man was completely dry.
The guide to electrocution printed by OSHA based on data collected by Kouwenhoven and Milnor states that the human body will have a resistance between 200 ohms wet to 40,000 ohms dry.
There are two facts that apply to a parallel circuit as follows:
1) the total current flow in a parallel circuit is equal to the sum of all the branches
2) the voltage drop across any branch of a parallel circuit is the same as the applied voltages
Do the math including the person and see what you come up with. My math equals dead
Ed MacLaren
Senior Member
Re: Code related Theory question
3) the total resistance of a parallel circuit is less than that of the branch with the least resistance.
Ed
There is one more -
3) the total resistance of a parallel circuit is less than that of the branch with the least resistance.
Ed
Re: Code related Theory question
jw, the guy is not dead! The line voltage is 480V, but he has on his rubber shoes, so he might get a faint tingle from that, but no more!
The line voltage does NOT appear across the cut. Only 2.7V appears there, so an insignificant amount of current flows through his bod.
If he cuts both cables and grabs the loose ends, then if not dead, he is in a heap on the floor crying for his mama!
jw, the guy is not dead! The line voltage is 480V, but he has on his rubber shoes, so he might get a faint tingle from that, but no more!
The line voltage does NOT appear across the cut. Only 2.7V appears there, so an insignificant amount of current flows through his bod.
If he cuts both cables and grabs the loose ends, then if not dead, he is in a heap on the floor crying for his mama!
physis
Senior Member
Re: Code related Theory question
Edit: Rattus, you're saying "bod" again.
[ January 14, 2005, 08:12 PM: Message edited by: physis ]
That has to be using 50% of the bodies surface area for each connection. Those values look to me to be just plain rediculous. They must also be considering precise planetary alignments with that.
Edit: Rattus, you're saying "bod" again.
[ January 14, 2005, 08:12 PM: Message edited by: physis ]
Re: Code related Theory question
Sam, if one has a good looking bod, one should flaunt it!
Just where in the Bay Area are you located? I made many a trip to Palo Alto and Cupertino when I was gainfully employed.
Now, in medical electronics, I understand that much care must be taken with instruments that poke around inside the bod. A few volts can create enough current to kill.
Sam, if one has a good looking bod, one should flaunt it!
Just where in the Bay Area are you located? I made many a trip to Palo Alto and Cupertino when I was gainfully employed.
Now, in medical electronics, I understand that much care must be taken with instruments that poke around inside the bod. A few volts can create enough current to kill.
jwelectric
Senior Member
- Location
- North Carolina
Re: Code related Theory question
This is very true there are three facts about a parallel circuit. I stand corrected.
E = I x R is a law a proven law. I can have one opinion and every one else in the world can have their own different opinion but Ohm?s law is still law.
Effects of Electric Shock by Charles F. Dalziel.
Example 1: I = 480 / 1000 = 480mA
Heart fibrillation; might clamp tight @ 100 to 200mA
I do not dispute the ?voltage drop? across the conductor. But this is the voltage drop and not the applied voltage which is 480 volts
To apply the theory that is being pushed in this thread would be to say that each and every circuit through out this building would have a different voltage dependant on the resistance of the circuit conductor. We know this is not true.
Using this theory should we reconnect the conductor then 480 volts would not be the applied voltage on that conductor?????
The voltage drop across the cut conductor in this thread is based solely on the resistance of the conductor. Do the voltage drop with the person in series with the conductor to find the true voltage drop. If he is holding both cut ends of the conductor he becomes part of the conductor. Why is this so hard to see?
All these numbers came from page sixteen of Cooper Bussmann Safety Basics
This is very true there are three facts about a parallel circuit. I stand corrected.
E = I x R is a law a proven law. I can have one opinion and every one else in the world can have their own different opinion but Ohm?s law is still law.
Effects of Electric Shock by Charles F. Dalziel.
Example 1: I = 480 / 1000 = 480mA
Heart fibrillation; might clamp tight @ 100 to 200mA
I do not dispute the ?voltage drop? across the conductor. But this is the voltage drop and not the applied voltage which is 480 volts
To apply the theory that is being pushed in this thread would be to say that each and every circuit through out this building would have a different voltage dependant on the resistance of the circuit conductor. We know this is not true.
Using this theory should we reconnect the conductor then 480 volts would not be the applied voltage on that conductor?????
The voltage drop across the cut conductor in this thread is based solely on the resistance of the conductor. Do the voltage drop with the person in series with the conductor to find the true voltage drop. If he is holding both cut ends of the conductor he becomes part of the conductor. Why is this so hard to see?
All these numbers came from page sixteen of Cooper Bussmann Safety Basics
jwelectric
Senior Member
- Location
- North Carolina
Re: Code related Theory question
Yes - Spring, Summer and Fall semester
Yes - Spring, Summer and Fall semester
Ed MacLaren
Senior Member
Re: Code related Theory question
As some of the others have already stated, our "victim" will likely be OK.
Assuming the voltage drop in each conductor is 2.7 volts, that is all he is exposed to, minus a few microvolts in the cut ends.
Perhaps when it is laid out this way, it is easier to see.
Ed
As some of the others have already stated, our "victim" will likely be OK.
Assuming the voltage drop in each conductor is 2.7 volts, that is all he is exposed to, minus a few microvolts in the cut ends.
Perhaps when it is laid out this way, it is easier to see.
Ed
jwelectric
Senior Member
- Location
- North Carolina
Re: Code related Theory question
Three men rented a room for thirty dollars, ten dollars each.
The next morning the manger sent his little boy to give the men five dollars back. The little boy couldn?t divide the five three ways so he gave each man back one dollar and kept two for himself.
This left each man paying nine dollars each for the room.
Nine times three is twenty seven and the two the little boy kept equals twenty nine.
Moral of the story---if the equation ain?t right the numbers ain?t right neither.
You left the man out again unless he has no resistance.
Three men rented a room for thirty dollars, ten dollars each.
The next morning the manger sent his little boy to give the men five dollars back. The little boy couldn?t divide the five three ways so he gave each man back one dollar and kept two for himself.
This left each man paying nine dollars each for the room.
Nine times three is twenty seven and the two the little boy kept equals twenty nine.
Moral of the story---if the equation ain?t right the numbers ain?t right neither.
You left the man out again unless he has no resistance.
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