Polarized AC plug revisited

A few days ago a gent asked a great question about why Polarized 120 VAC plugs/receptacles are used. (Forces one side to be the Hot, the other the Grounded Neutral) There were good answers and information posted but I dont think this one was??

A typical 120 VAC tool typically has an On Off switch which leads to a motor that has a ton of insulated (insulation can fail ya know) windings and then connections and splices etc before it wires back to where the cord enters the tool. When a short occurs, somewhere in all that maze of windings and splices etc., a live hot conductor could come in contact with the case (unless plastic and double insulated etc which many now are is less a hazard) that you hold in your hands and the hot wire is 120 VAC above Neutral which is tied to mother earth back at the main panel. And you may well be standing on mother earth or something else that is near that same potential, i.e. 120 volts between you hands and feet or other hand etc OUCHHHHHHHHHHHHHHHHHH.

If a polarized plug is used and alls wired correct, when the cord first enters that tool the very first thing is the On Off switch (on the HOT lead) and when off/open all else in the tool (windings n splices etc which may short out to case) is dead and de energized. HOWEVER if the polarized plug isnt used and its not plugged in or wired the correct way even with the switch off (assuming it then switches the Neutral not the Hot) ALL THOSE HOT LIVE WIRES WHICH COULD SHORT TO THE CASE ARE STILL ENERGIZED AT 120 VOLTS EVEN WHEN THE TOOL IS TURNED OFF.

So you can see why its safer if the first thing inside (the switch) i.e. the HOT WIRE is whats de energized so all the rest is dead. If the Neutral was whats broken by the switch opening, then all the rest of all those wires n windings n splices which could short to case n kill you WOULD STILL BE HOT...

Bottom line the UL and NEC are experts on all this electrical and fire safety and if a person follows their guidelines and uses tools they approve, theres a darn good chance their lives may be saved versus doing just the opposite cuz Billy Bob and his know it all Brother in Law Bubba (wired their own homes over a case of beer n all works fine) say they know better... IE I'll take my life chances with NEC and UL instead of Billy Bob, you do as yall please..

In the hopes yall keep SAFE

Ol John T

John T;
Sounds like I ain't the only one that don't miss getting lit up by the old power tools that didn't have a wide spade for the neutral. When you consider just how little tricity it takes across the heart to stop it it's a wonder we ain't all dead. Can't remember if it's .4 amps or .4 volts but either way it ain't much. I'll take the polarized plug any day.

Hey John T - excellent observation and comments as always(!)

You last point about miss-wired outlets particularly important. I've encountered so many "wired by Billy Bob" outlets over the years (i.e. with the hot 'n neutral reversed or an open ground) I always carry a polarity tester and portable GFCI in my toolbox. Now before plugging a power tool into an unknown outlet I first check it with the polarity tester. If the tester says the outlet is OK I'll plug in the GFCI, then plug my extension cord/tool(s) into the GFCI. Otherwise nothing gets until the outlet polarity has been corrected.

SAFETY FIRST!

It is about 15 MILIAMPS that will stop cardiac function. GFI"s are designed to trip at 5ma. Like others here I always carried my own GFCI protection that I knew worked. double insullated tools are a better idea.

Many years ago I (VFD-EMT) was called to a house under construction where the plumber was in the crawl space using a defective sawmill plugged in to a standard outlet. He was grounded by lying on the damp pea gravel and did not go home.

It is hard to be too safe with electrical power.

"double insullated tools are a better idea"

use a drill with an internal short, holding on to a piece of metal that is being drilled or screw run into it.
when you pull the trigger you will light up if you are grounded,
DO NOT trust double insulated tools to save you
BTDT
good luck
Ron

Thanks yall, in response to M Man and Bob, heres the data I have (cant guarantee its accuracy) as to the effect of current on the human body: Its taken from an article published by Jim Biesterveld and Mike Holt. A milliamp is one thousandth of an amp i.e. 100 MA = 0.1 amps

5 milliamps GFCI trips
10 milliamps Cant let go
20 milliamps Muscles contract
30 milliamps Possible suffocation
100 milliamps Heart stops
300 milliamps Breathing stops

John T

I served to provide expert electrical testimony in a lawsuit some years back that was similar. A guy was using a roto rooter tool in a damp basement and was injured because the outer metal case became energized by a short......

Polarized outlets,,,,,,,third wire safety grounded outer cases,,,,,,,and GFCI can save your life

John T

Or to put it another way When dealing with electricity just because it works doesn't mean it's safe. Unfortunately with the way electricians are managed and regulated, the NEC being what it is and what is costs to see the golden word and the fact electrical work is often looked at by the consumer much like health care- I'm entitled to it and I shouldn't have to pay for it we will continue to have problems. Here in the Socialist republic of Wisconsin you have to be a licensed electrician to do anything more than change a light bulb or plug in a cord. Certified and licensed seems to equate to paying Union dues. As much as the NEC seems to be a device to separate us from our out money and not much more they are trying to make electricity safer for us to use.

and I'll repeat it here, gfci doesn't need a ground wire on the tool to work not sure why people think that. Its just watching for imbalance on the hot and neutral.

As much as I hate them for kicking out all the time using large single phase motors on them don't skip out on using them in construction. With all the wet conditions and damaged cords/equipment its pretty darned important.

I agree with the money issue to a point. For example I just took my Masters test in the state of Iowa. First it is $60 to take the test, if I pass(which I did) then it is $375 for a 3 year license, then I need a contracters license which is another $375 for 3 years. Now I have spent over $800 before I have even pulled a job, not to mention maybe getting stiffed on the bill. I am starting to learn how come a business has to charge the rates they do to stay going. But yes the rules are there for a reason. Like the code rule that you cannot have an electrical panel in a bathroom, kinda makes you wonder who thought THAT was a good idea!

Of course, you can still get a nasty short if you are drilling thru a stud and happen to drill into some Romex. Probably the worst part of that experience was that I was wiring my shop, standing on a ladder. The serrations on the Jacobs chuck chewed thru the insulation on the wiring to the lights. No windows and door was closed, so now I'm standing on a ladder in pitch dark, don't recall what all was on the floor, but I knew I had exposed hot wires around my head and hands. Managed to find the door and get some light before I kilt myself.

"and I'll repeat it here, gfci doesn't need a ground wire on the tool to work not sure why people think that. Its just watching for imbalance on the hot and neutral."

Ken, YOURE EXACTLY RIGHT and Ive had licensed union electricians say thats incorrect???

Theres a Torroidal Coil that encircles the Hot and Neutral (NOOOOO Ground involved whatsoever) so as long as the current being returned in the Neutral is the same as that going out the Hot THERES NO NET CURRENT AND NO VOLTAGE IS INDUCED INTO THE CORE. HOWEVER if theres a leakage of 5 milliamps (like to frame or ground or anywhere but the Hot) that current difference yields a voltage induced into the coil which triggers the trip.

John T Long retired EE but still remember the basics

John, thank you, one thing I appreciate and I'll bet many others do also, is the extra mile you go every time these kinds of questions come up, to help explain details, in laymans terms but with sufficient detail as well as "indemnifying" or "holding harmless" yourself,like you do with the legal questions. You provide good generic info, but advise to seek a qualified electrician, or attorney. Your posts are lengthy and thorough, I'm sure it takes up valuable time, I thought it prudent to just state, that I for one highly appreciate it, and if you recall the back up gen set discussion we had a few years back, one thing is for sure I have not forgot what was said about grounding, also helped a novice understand electrical theory a little better, between these and welding posts, I find them very informative.

Really wanted to ask you relative to this post, effects of current on the human body. I've always been told that amperage (current?) is what kills.

That understood, when I was a kid, I had a real bad experience with 220 VAC. Tractor related too, I was in our Ford Tractor dealership building and a mechanic needed a welding lense, I said I'll get one, (helpful kid) was on a shelf on a steel column, below it was a hardwired, (not low control voltage) thermostat to bar joist hung unit heaters. Some jerk left the cover off, and my right wrist, (underside) contacted 3 bare copper wire splices, burned 3 small holes, and I was locked to the column helpless, which seemed like an eternity, 2 men pulled me off, just seemed to take forever, had I been in there alone, I'd have fried, I don't recall being able to yell, it just seemed like I was burning and locked to that column forever, pulsing and you know how weird electrical current feels if you ever had the doctor use that device on your back.

Given the above, 220 VAC, steel column, not sure if both arms were contacting, still have the scars on my right, how the heck did I survive this ordeal, they got nailed taking me off. I never saw a doctor, went to ER, parents were real jerks about things like this, thats what you get for doing what you did, (helping someone). I think someone was watching over me, just seems like a person should not be able to survive this, given the above, them old unit heaters had to draw some amperage, good thing they were not on, likely I would not be here today writing this.

Whats your opinion on something like that, I tell people thats the reason "I am the way I am" LOL !!!!!

I carry a $2 outlet polarity tester when I use power tools at a new site. It's found some mis-wired outlets before they caused me any problems.

I was working for a guy building a house many years ago- strictly cash. He had me cutting lumber with an old, ungrounded skilsaw, in the rain- I kept getting lit up. When I told him about it, he fired me! Said something like "Well, if you can't use the tools I have, I guess I can't use you."

Suited me fine- I didn't much care for the guy anyhow. But can you imagine the ramifications of that now? By the time OSHA and Labor and Industries got done with him, I'D have owned the house.

He ended up with a little comeuppance, though- my dad, a professional carpenter, would help the guy when he was in a spot and didn't know what to do. The guy called dad a couple weeks later and asked him to come help, and dad said "I'd better not- might have to use your skilsaw, and I don't want to chance it."

Thanks for the kind words, for years when I was a wet behind the ears pup many older gents helped me out and nowadays I figure its payback time and I'm glad to help when I can, and since my semi retired law practice keeps me on the computer a lot, its not too hard to chat on here.

On your "shocking" experience its pretty hard to get across 240 volts since its line to line only while 120 is line to many nearby items such as iron bars or a kitchen sink etc. But I cant say sittin here if you were exposed to 240 or 120 butttttttttt if it was 240 you can obviously get killed much easier.

The chart I posted above tells what current it takes to cause muscle contractions and makes it hard to "let go" if youre across a hot voltage source. Yes its current NOT Voltage thru the body and especially the old ticker that messes you up but since I = V/R the more voltage the more current and thats why if you actually got across 240 you may have been killed. The worse path is if the current flows past or in your heart which is why electricians are taught to NEVER have both hands in an electrical panel as if they get across voltage the current path is right near the heart.

I gotta run and thanks again for your kind words I appreciate that

John T

5 milliamps GFCI trips
10 milliamps Cant let go
20 milliamps Muscles contract
30 milliamps Possible suffocation
100 milliamps Heart stops
300 milliamps Breathing stops

John T

As per what is taught in the Navy electronics school it takes 1 milliamp to kill period. It takes under normal conditions 32 volts to get past the resistance of dry human skin but things like being wet or sweat lowers that 32 volts. It was also taught that if done right you can kill a person with a common D cell battery but it has to be just right to do so

A GFCI dont trip until 5 MA so if only 1 kills, just as well toss out the GFCI you done "bought the farm"

Keep safe Rich n behave down there

John T

One thing I learned a long time ago. NEVER depend on GFCIs or any other such thing they will only work to save you if all is just right. Of course the big thing about getting shocked and killing it is where it goes in and where it comes back out. If in one finger on your left hand and out another finger on your left hand it hurts but not likely to kill but if in one finger on your left hand and out another finger on your right hand that could be a deadly shock.
As for being safe I am always safe I just take a chance now and then and am very careful if I do take a chance

Like shot out of a pipe with a cherry bomb ? lol

D cell with 2 line pins hook to each end and then push that into a guys chest he is dead if you can hit his heart with the two pins and you don't even have to get to his heart you just need to hit two major artery's as least in theory that is

(quoted from post at 20:29:32 09/19/12) Like shot out of a pipe with a cherry bomb ? lol

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hat would probably work, too, but he is talking about surgically implanting wires in just the right part of brain or heart & connecting the d-cell. Hard to sneak up on the enemy & do that.

if i make no mistake they claim it's 10 milliamps now, BUT it can take less than that if it interrupts your heart rhythm at the right time

(quoted from post at 20:36:40 09/19/12)

(quoted from post at 20:29:32 09/19/12) Like shot out of a pipe with a cherry bomb ? lol

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hat would probably work, too, but he is talking about surgically implanting wires in just the right part of brain or heart & connecting the d-cell. Hard to sneak up on the enemy & do that.

Click to expand...

Those regular Navy guys.....always thinking they need a weapon! :lol:

I go by the rule "If I can't see it or smell it I don't F!@K WITH IT" . I pay the money they want. I understand the concept of it but it scares the poop out of me. The local power company use to put on a demonstration on what power does when a machine hits it. Boy that will cure your thoughts of I can fix that.

and

Looks like I should be dead long ago. I have been zapped by welders for over 50 years. Sure is more than milliamps involved.

(quoted from post at 23:01:12 09/19/12) Looks like I should be dead long ago. I have been zapped by welders for over 50 years. Sure is more than milliamps involved.

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rong! Just because a source is capable of supplying X amps, does NOT mean that amount of current went through your body! Not at all!!

I spent 30+ years running Magnaflux machines that would put up to 6000 amps between 2 contact plates.

I could put my hands on those plates & not feel a thing.

I think it takes more than just amps to do damage.

Vern

JohnT,

Your numbers look correct. Doesn't the current has to go across your chest to kill? If it goes down your leg it may cook you. When messing with the big stuff you may want to put your left hand in your pocket to prevent it from going across your chest.

Using dc to experiment with, you can't even feel 1 ma, 10 ma is painful and add one more zero and you are dead. Now put this in terms of electrons per second. 1 amp is about 6.25 billion billion electrons per seconds, 1 a = 6.25 E 18. 100 ma = 6.25 E 17, Kills. 10 ma = 6.25 E 16, painful and 1 ma = 6.25 E 14, you can't feel.

1 ma = 625,000,000,000,000 e/s. Add 2 more zeros and you are dead. A little scary don't you think?

George

I spent 30+ years running a Magnaflux machine that would put 6000 Amps between 2 contact plates.

I could put my hands on those plates & not feel a thing. I think it takes more than just Amps to do you harm.

Vern

It's a combination of the right amps and volts that will kill you. When I learned to weld, the teacher had us hold the stinger and ground clamp to show a welder wouldn't kill you. Over 100 amps and around 70 volts. Sometimes you can get zapped pretty good though. I've heard that a car battery can kill you under water though.

Well that just means that machine ran low volts but high amps. Again and I said it in a post here already in theory it takes 32 volts to get past the resistance of the human skin so that means that machine ran with less then that voltage or you have a higher resistance then most. Amp kill volts need to be there to push the amps into you