Can you be fatally electrocuted by contact with an appliance in a properly grounded 20 amp circuit if a load carrying conductor shorts to the metal casing? I have been told that the breaker would trip preventing electrocution even if you were standing in water.
If a hot wire shorts to the case in a properly grounded circuit, that will trip the breaker almost immediately.
If a neutral wire shorts to the case (which isn’t what you asked about, but technically the neutral is a load carrying conductor), then the breaker will only trip if it’s a GFCI breaker. But the case will still basically be at earth ground potential, so no big risk of shock there either.
In a modern electrical system with a separate safety ground, there really isn’t any single fault that can put you at risk. Short the hot to the case, the breaker trips. Short the neutral to the case, the breaker only trips if it’s a GFCI, but no real shock risk. Short the hot and neutral to each other, and the breaker trips. Break the hot wire, and the device just stops working. No shock risk. Break the neutral, same thing. Break the safety ground, and as long as you don’t have any other fault, there’s still no shock risk.
To get a shock risk, you need to have multiple faults, like a broken safety ground combined with a shorted hot wire to the case.
In older 2 wire systems where the neutral acted as the safety ground, a broken neutral could cause the case to float up to the hot voltage, posing a significant shock hazard with just a single fault. That’s why we have a separate safety ground now.
(for what it’s worth, I’m an electrical engineer with about 30 years of experience)
Excellent response. Much appreciated.
I think that in most cases of accidental electrocution, the victim was doing something foolish or downright stupid, like poking a screwdriver in to see what happens.
Exposed conductor on power cord. Device keeps working, but it’s very easy to grab and receive a shock. This is very common (almost too common) on vacuum cleaner cords since they get run over from time to time, and even though the hot conductor can become exposed it doesn’t create a short that trips the breaker to let the user know that there’s a problem. Further more, most people, while using a vacuum, are holding the power cord, specifically to avoid running over it which makes them that more more prone to getting a shock a shock.
To add to that, IIRC, my vacuum may have** even said to replace the entire vacuum when that happens. Many people don’t know enough about electricity to A)identify the shiny copper as a threat B)If they do, know that some electrical tape can do a good job of making the problem much safer and C)have any interest in replacing a perfectly good vacuum because the cord is frayed, to the point that they’re almost going to use it in spite of that just to give a middle finger to the manual. It would be nice if the cord was plugged into the vacuum end as well, not only so the user could replace it every few years, but also so when they tried to get that just a few more feet it would unplug itself instead of bending the prongs and creating a dangerous situation at that end as well.*
Perhaps, and I’ve never given this idea any thought whatsoever until just this second, the cord could shielded in some kind of grounded foil. That way if the user runs over it enough times that they wear through the outer insulation, the shield and the conductor insulation, it shorts itself out and that’s the end of that, the cord is garbage. No more using it, but no one gets a shock either.
Speaking of plugs/outlets the way they’re set up in the US (vs the UK), the prongs are energized before they’re fully inserted and I KNOW I’m not the only person that’s used my hand to find the outlet in a place I can’t see and then slid the plug down my finger and been bitten. You only make that mistake once, well twice.
**To be fair, I’m going from memory on this, but looking at the bissell website, the power cord is listed as a ‘service center part’, not something they’ll send out. I’m sure that’s just be it’s hardwired, but if they gave it a molded end and had it plugged in, ISTM that would solve a few things.
(disclaimer: please excuse any typos or misinformation, it’s early and i’m still tired)
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Pure water does not conduct electricity.
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Electricity follows the path of least resistance.
Let me know the next time you’re standing in distilled water.
No, it takes ALL the paths, it just sends more currents through the paths with less resistance. So, you can have a power cord, plug in, running an electrical appliance in your house, humming along just fine. One day, you reach behind a cabinet/shelf/drawer for something and touch a section of the wire that happens to have some bare copper. Now, the path from the breaker box, to the device and back to the neutral bus bar offers far less resistance then the path through you, through your clothes, through whatever (grounded) surface your touching and back to earth. Yet, you still managed to get shocked, most of us have. Further more, the device didn’t turn off during that fraction of a second which means it was still getting current during that time.
TLDR, if electricity only followed the path of least resistance, you could touch a live wire without getting shocked since copper offers considerably less resistance than human flesh. But we all know that’s not true and most of us are alive because ohms law limits the amount of current that does travel through us to a less than lethal amount.
True but completely irrelevant, because you’re unlikely to ever encounter water that pure outside of a laboratory, and it only takes a very small amount of impurities to make water a good enough conductor to be dangerous.
Untrue. Electricity follows all paths, in inverse proportion to the amount of resistance on each. So, for instance, if the path of second-least resistance has four times the resistance as the path of least resistance, then that second-least path will have a fourth the current of the least-resistance path… but a fifth of the total current might still be enough to kill you.
Minor nitpick:
Pure water does conduct electricity. Some of the water molecules will dissociate into H+ and OH- ions, which will allow current to flow.
That said, I wouldn’t exactly call it a good conductor of electricity. Water with impurities in it definitely conducts better, but even then, something like saltwater is nowhere near as good of a conductor as a hunk of copper.
so what you want is what many power tools already do with the detachable power cords.
Put a small non replaceable fuse inside the molded plug. Otherwise people know exactly where to put the tape.
Whether you trip the breaker or not will depend on how your body is completing the circuit … if your body offers enough resistance, then the current may not be enough to trip the breaker …
I’m assuming this is typical household 110 VAC … and alternating current tends to spasm your muscles … literally knocking you on your ass, thus breaking the circuit … direct current tends to freeze your muscles, locking you into the circuit … and if anyone ties to pull you off by touching you, they too will be electrocuted … my shop in the military had a ten foot length of rope on-hand for such emergencies … the idea was to loop the rope around the victim and pull them off the source that way, without actually touching them … we called that circuit the widow-maker … 230 VDC for the filaments in the vacuum tubes …
ETA: Your heart is a muscle … and AC will spasm that … very very bad for you … don’t try this at home …
Remember that a lot of accidents are a chain of mistakes/failures. No one thing caused it.
Hypotheticals about “What if this one thing went wrong?” don’t accurately reflect a lot of incidents, esp. when electricity is concerned.
Be very careful and don’t assume that there is at most one wrong thing going on with a circuit/appliance.
Eventually, pure vacuum will conduct electricity. Nothing made out of normal matter is an absolute insulator; it’s just a matter of finding the breakdown voltage, at which point charged particles will be forced to move, thereby conducting a current.
Back in the day, I worked for a couple of summers as an electrician’s assistant, and I saw some houses that had all sorts of things wrong with the wiring. Most of them managed to still work… usually… until you did something like open the refrigerator wide enough that the door came close to the oven, or something.
(Yes, that was a real example: One customer called us because every time she opened the fridge door, she saw it arc to the oven. Needless to say, the wiring in that house was a terrible mess.)
I’m going to go out on a limb here and say it’s impossible for your body to trip a 15 A circuit breaker, let alone a 20 A circuit breaker. Even if your skin is pierced.
Slight hijack, but how common is electrocution nowadays, anyway? I’ve read that the most “deadly” aspect of wiring is its ability to start a fire via arcing at contacts, specifically where wires terminate on receptacles.
Genuinely curious about what Crafter_Man said. I just had a post where I was so worried about that if the prongs were exposed, it inevitably means fire, apparently not the case, shock hazard sure. I suppose I shouldn’t be worried there since I was bitten by a line from a transformer and i’m still here. somehow.
I’m also curious about Crafter Man’s question. I’ve been shocked a few times. I’ve seen other people get shocked. Haven’t most people touched a live wire at least once in their life? I’ve never seen anyone actually be injured by it in any significant way. Everyone just cusses and shakes their hand and gets on with whatever they were doing. How badly do you have to get electrocuted for it to really injure you, assuming you don’t have a pacemaker or something?
All good information, but a minor nitpick. If you’re electrocuted, you’re dead. A shock is not electrocution if you’re left alive to talk about it.
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Ah, linguistic pedantry and spam. There’s a Monty Python sketch in here, somewhere, but I’ll confine myself to stating that usage makes correctness as far as language goes, and you cannot out-pedant the rest of the world, because you have no source of authority higher than the language itself.