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Thread ID: 83272	2007-09-26 00:57:00	Electric shocks	FoxyMX (5)	PC World Chat

Post ID	Timestamp	Content	User
595081	2007-09-27 00:11:00	sockets could be dangerous if the house earth is broken. what often gets people is "negative switched" applianices. some appliances have the switch on the other side of the load, so even with it turned off the guts of the applaince is still live. mains will kill, don't play with it. even in the workshop we had rubber shoes and stood on rubber mats and still we would get nasty shocks. the worse thing with AC is it makes you musles twitch so you can't let go. you have to throw your whole bosy away to break the conection. the worse i had was when i got 1400 volts up the arm. ouchy :(	tweak'e (69)
595082	2007-09-27 01:06:00	I've worked on everything including up to 480V and 25KVA . . . . . but I feel 480 is the most dangerous voltage and one that kills more electricians than any other . Every leg of 480 is HOT and can kill . This is single phase too! (Ø) When you work with 12 . 5KVA or 25 . 0KVA, you KNOW what you are up against . . . but 480 sounds kinda wimpy . . and that's the problem . There is no ground or common in 480! Every leg can and will happily kill you . I have heard people here waxing eloquently about their "adult" voltages of 240 at the walls and appliances . . . . . but maybe that's because many kids won't get to adult with a visit with Mr . Kilowatt . At this point, I think 117/128 or so is MORE than enough for many things in the home . . . perhaps ACs and larger motors should run on 240, but they are the exception . We get 200 Amp, 240 Volt service into out distribution panels in the houses, but it's then split to two legs of 120 each . We balance the needs and equal-out the current on both sides of the house . . . but really now . . . it's just a lot safer to have the 120 volts in the home . At least if you get bit by it, you have a MUCH better chance of surviving the experience . :D	SurferJoe46 (51)
595083	2007-09-27 07:45:00	I did not claim to have made up the phrase - it was I thought quite common. And the rest is also true. What was you point? I was replying to FoxyMX's original posting - the web-site she read was probably American.	decibel (11645)
595084	2007-09-27 08:46:00	N.B. Electrocuted means you where killed. You can't be half electrocuted. You were either killed or got an electric shock. It's the same as "drowned". You can either be dead(drowned) or "nearly drowned"	joemac (9739)
595085	2007-09-27 10:53:00	Fingers in a light socket is usually just painful, because the current is flowing between the fingers touching the two pins, and so your heart, brain etc are not in the path of the current. On the other hand, if you were to grab, say, a live wire with one hand while being grounded with the other (resting on a sink perhaps) the current would flow straight through your heart (one arm to another) and probably screw your heartbeat up, killing you if nobody is around to do CPR. So a toaster could be VERY particularly dangerous if there was a path through your body to, say, the sink. So unplug that toaster before sticking knives in it :) Been thinking a bit more... How does dropping a hairdrier into a basin of water kill you if you grabbed it? Assuming it wasn't plugged into an RCD socket and only your hair and then your hands were wet when you picked it up, and you weren't standing in water, where does the current flow? Why would it go through your heart and kill you?	FoxyMX (5)
595086	2007-09-27 12:06:00	Been thinking a bit more... How does dropping a hairdrier into a basin of water kill you if you grabbed it? Assuming it wasn't plugged into an RCD socket and only your hair and then your hands were wet when you picked it up, and you weren't standing in water, where does the current flow? Why would it go through your heart and kill you? I don't quite understand the question (I might, I'm not sure). The traditional one is when you're in a bathtub and someone drops a hairdryer/toaster etc in. In that case, the current can flow from the appliance through the water to the plughole, which is probably grounded. You're right in the way of that. If you dropped a hairdryer in a sink, and then tried to grab it out, all sorts of things could happen. 6mA is all that's needed to kill, and it's a tiny amount of current. 240V AC is a peak of about 340V, and for 6mA to flow, there can be as much as 40k ohms of resistance in the way. If there was water on the floor, your feet could easily be grounded, causing current to flow through your whole body. If you grabbed it with both hands, there is a chance for it to flow from one hand to another. If one hand was grounded - touching a metal tap, or water that was touching metal, current would flow from the hairdryer through from one hand to the other, to ground. There are dozens of scenarios, and it only takes ONE current path to kill you. Oh, and don't take anything I say as irrefutable fact (not that you would anyway). Everything I know about electricity I have picked up myself. Someone will correct me if I've made a mistake I'm sure...	george12 (7)
595087	2007-09-27 12:45:00	A toaster element would snap (so it kills the current), if you put something metallic in it . I would say this is how toasters are made, which is why you dont / wont get an electric shock . :groan:kills the current untill your body completes the circut again, assuming it "snaps", which i doubt it would at that heat (glowing hot metals are very ductile) That is totally false and in fact a dangerous or misleading statement to even make . Even if the element "snapped" one side of that element is still alive . exactly - always unplug at the wall before probing inside your toaster: better safe than sorry Actually . . that's not entirely true . The "common" side is supposed to be also grounded . . . at least here it is and I cannot fathom any electrical engineer letting it be any different in NZ . :eek: asfaik, from what my mate(electrician, almost finished apprenticeship) tells me, it doesn't really matter what way many things are wired up thanks to good ol' AC power . i'm sure he was talking about wall sockets, but if any NZers know better he may have been referring to soley light fittings etc . . . Over here in NZ we have 3 "holes" in our wall sockets, the two live ones and one ground . in the states you guys only have the two holes correct?	motorbyclist (188)
595088	2007-09-27 13:46:00	Been thinking a bit more... How does dropping a hairdrier into a basin of water kill you if you grabbed it? Assuming it wasn't plugged into an RCD socket and only your hair and then your hands were wet when you picked it up, and you weren't standing in water, where does the current flow? Why would it go through your heart and kill you? you don't really want to test it to find out do you? wouldn't the device simply ground via your arm/chest/feet/floor or something? unless your body provides infinite resistance and/or there is no potential difference between your contact with device and anything else you'll get a shock. It's like grabbing a live wire	motorbyclist (188)
595089	2007-09-27 18:20:00	Over here in NZ we have 3 "holes" in our wall sockets, the two live ones and one ground . in the states you guys only have the two holes correct? No . . we have three prong receptacles and here's a drawing: . phy-astr . gsu . edu/hbase/electric/hsehld . html" target="_blank">hyperphysics . phy-astr . gsu . edu Now . . . at the pole drop into the house we have two hot legs and a single "common" or currently called "ground" side that has to be capable of handling the current return on both legs at full current capacity/draw . Then that supply is split into two 120volt LEGS at the panel, and are sent to the various circuits in the home, trying to balance the load on each leg to keep things Kosher . We usually refer to the LEGS as BUS "A" and BUS "B" for clarity . Most of our in the wall wiring consists of: BLACK = HOT (120 volt) leg off either of the 120v leads from the distribution panel . Both LEGS can be BLACK, but a different color CAN be used on one leg if they contractor wants to or if purple wire was available that day . WHITE = ALWAYS COMMON!, and now with the newest transformers on our individual power poles, it is also the GROUND . GREEN = ALWAYS GROUND or Earth to youse guys . This is physically attached to the WHITE and some sort of in-the-ground copper rod or water pipe that must be copper and at least 6 feet in the ground and at least 20 feet long . BARE = the only bare wire that makes connection between the metallic boxes . if they are used, or to the case of an appliance to render it totally neutral . This is NOT intended to carry current of any sort, but is only a back up for the ground, should it become defective or "open" . It is usually the same gauge wire as the HOT wire . The EMT (Electrical Metallic Tubing, or conduit) that carries the wires through hazardous or wet or exterior areas can be considered the same as this bare wire as long as circuit integrity and continuity remains in value . We also have BX, or coiled metallic sheathed wires where the outer flexible case IS also the BARE and GROUND too . So now . . we have three-prong outlets that also have different lengths and sizes of prongs . The GROUND is usually a "U"-shaped prong that is totally capable of carrying the full rated capacity of the HOT wire, to GROUND, and safely away from a person/animal . The wire attached to this is ALWAYS GREEN . . . there are NO exceptions . The COMMON prong is slightly longer and a little WIDER than the HOT prong so it makes contact first upon insertion into the receptical, removing any transient spikes or possibility of static spark that may occur . It has to be heavier gauge to carry any/all possible return loads imposed on it by the HOT side . The wire attached to this is ALWAYS WHITE . . . there are NO exceptions! The HOT prong is usually smaller and/or shorter to maintain polarity . It can have any color wire attached to it as long as it is not BARE, WHITE or GREEN . Our metallic electrical boxes (for receptacles, switches, junctions) are either grounded with the GREEN and the BARE wire, thru the conduit or BX or if they are plastic in newer construction, those BARE and GROUND wires must be separately and singularly connected with crimp-on connections to establish and carry the full capacity of the wires . Twist connectors are NOT allowed on the GROUND or BARE drain wires . So . . . there is no way that you can get a HOT condition on a NEUTRAL or GROUND side of the plug unless there's some serious damage to the system . The NEUTRAL is also attached to the earth's physical ground and would carry away any eddy or transient voltages instantly and continually . All appliances, unless they are UL rated as totally isolated, insulated and incapable of "case-hots" or the enclosure becoming part of a HOT side, will always be grounded via that third, U-shaped prong and totally NEUTRAL to humans/animal even if they stand in a tub of water and lick the toaster or coffee pot housing with their tongues . Most of this style exterior of a device of this sort is plastic or a non-conductive composition anyway . Just looking at that drawing again (cited above) I see it is very clear and quite intuitive . We have some POLORIZED, older appliances and those that are truly current isolated and are considered "Shock-Proof", in that they only have two prongs . They will only go into the receptacle in one direction, the ground lug in that case is wider and thicker and it won't fit into the HOT leg . § As there's AC involved, we know it's not for the sake of phasing or polarity, but for a real GROUND or COMMON return for the HOT side of the appliance . By law, all outlets and lights and circuits in a wet environment (showers, bathrooms, kitchens, laundry rooms, etc) are required to have GFCIs in line . They can either be at the terminal or back at the breaker panel (customer accessed, usually in the home) to keep the hair drier in the tub as a murder or suicide device from being usable . A GFCI is a Ground Fault Circuit Interrupt device that will switch off the HOT side in a millisecond if the ground is opened, fed back with power or loses connection to the appliance . As a security and safety consideration, I usually run four (4) wires through EMT or conduit even if there's no need for the BARE wire under those circumstances . I never trust mechanical connections of the boxes with the conduit, as they might be pulled apart or corrode and lose capacity . Running a HOT, a GROUND, a COMMON and a BARE inside of metal conduit is not required, but I feel better with it anyway .	SurferJoe46 (51)
595090	2007-09-27 21:32:00	Re hairdryer in water... yup you'll be dead. Refer Mythbusters. Toasters can kill? Yep too, but you have a slightly better chance. Dan goes into it a bit in The wonderful world of toasters (www.dansdata.com).	Greg (193)
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