Question for those who know about electricity

Ozarks Tom · #61 09/12/11, 10:21 PM

YH, thanks for asking. I've wondered the same thing for years. Finally I know.

rambler · #62 09/12/11, 11:08 PM

Quote:

Originally Posted by Yvonne's hubby

closer, now please describe to me what sort of circuit the power is taking just because there is water on the floor? We can get to that wood conductivity thing later.

You've never worked at wiring up a dairy barn, have you?

After the millions of dollars of lawsuits on the stray voltage issue, the ground wire is the most important of the 4 wires. Everything, including the rebar in the concrete, needs to be bonded to ground.

Something you assume along the way is that the nuetral wire is always working perfectly. With a lose arching screw, or a wrong connector between a copper/aluminum connection, over tie the nuetral wire can build up enough resistance to have some extra electricity sitting around waiting for somewhere to go.

Be just happy to go through you as anything else conductive.

--->Paul

Energy Rebel · #63 09/13/11, 02:22 AM

Quote:

Originally Posted by Yvonne's hubby

Not according to theory... electricity will seek the path of least resistance. so if we fastened the neutral to the machine... like it was done for many many years... the returning current will be carried back to the box, the dead short blows the fuse and no one is harmed.

Quote:

Originally Posted by Yvonne's hubby

I am curious here... how did I complete a circuit between the white wire and the sink? I tend not to stick a finger into the socket when plugging in my razor! (which oddly enough does NOT have the third wire plug) I also find it amazing that for a hundred years people did not electrocute themselves in this manner when all of those homes and bathrooms were wired just exactly as your scenario describes.

Quote:

Originally Posted by Yvonne's hubby

Yes, I have been given several scenarios.... of which none demonstrate the need for the third wire in the real world. The neutral can serve the same purpose..... and did for a great many years.

The thing of it is, it wouldn't take many incidents until a lawsuit was filed.
I haven't researched it, but I have a feeling that was how this came about.
Remember me telling you the NEC was written by insurance companies, not electricians?
In any case, it's a small thing to do to prevent a very tragic event. When the guy wins that lottery, it ain't no fun.

salmonslayer · #64 09/13/11, 11:01 AM

Quote:

Originally Posted by HermitJohn

That old wiring with the rotting cloth insulation scares me lot more than no ground wire when I'm working in older buildings. If it was mine it would be replaced, or at least disconnected.

And I've had couple old metal casing power tools WITH 3pt plug used in a house with ground circuit and still got a shock. Shock me once, shame on you, shock me twice shame on me for not throwing the blasted thing away.

It scares me too John as I have found pieces where the outer wrapping was completely worn or rotten through and we are indeed replacing it all with Romex, luckily we have a full basement so its relatively easy to get to. The guy that owned this house before us was an odd duck and when he would wire something he never used junction boxes, he had a penchant for duct tape to wrap connections and he left live bare wires dangling in the basement and in the kitchen where he had removed a surface light fixture. It was interesting when we first moved in to say the least.

I see that some of these questions have been exasperating to the electrical savvy but though I am wiring to NEC code as I redo my house I have often ran up to some of the "why is it this way" questions myself. You read about how a circuit is formed and how electricity flows and yet some of the things just dont seem to jive and most of the time the answer to your question just seems to be "because its in the code and its for your safety" even though they cant really explain how it supposedly is safer.

I just follow the code myself because I dont know enough to deviate and figure smarter folks than me figured it out but I have found this thread interesting.

farminghandyman · #65 09/13/11, 08:57 PM

Quote:

Originally Posted by Energy Rebel

Now, the black is SUPPOSED to carry 110v and the white 0 volts.

both wires are carrying voltage, (say 110) the white wire is in common with the ground, that is the difference, thus since you are measuring to ground, you get 0 volts, but the system is charge with 110 volts and is carring amprage as well, (it is like a bird landing on a power line, it is not hurt as it is in common with the wire),

actually you have two hots that are 240 and the center is taped and put in common with the ground, and from hot to ground is 110 and from hot to hot it is 220,

your ground wire is there to make the frame of the tool or appliance at the same potential as the ground just like the neutral,

say one is bare foot in the wet grass, and some thing goes wrong, the hot is in contact with the frame of the tool it will then pass through the tool via the ground not not through you,

farminghandyman · #66 09/13/11, 09:04 PM

Quote:

Originally Posted by Zephaniah

Electrical Code is supposed to cover all scenarios. Today the GFCI uses the ground wire as a reference point for the neutral.

the GFCI compares the power going out and the power coming back and if there not the same it trips,

a GFCI does not need the ground to work,

Quote:

http://www.mikeholt.com/mojonewsarch...s~20050510.php
Q2. Under what condition can a two-wire receptacle be replaced with a three-wire receptacle, when no ground is available in the box?

A. Where no equipment bonding means exists in the outlet box, nongrounding-type receptacles can be replaced with [406.3(D)(3)]:

Another nongrounding-type receptacle.
A GFCI grounding-type receptacle marked "No Equipment Ground."
A grounding-type receptacle, if GFCI protected and marked "GFCI Protected" and "No Equipment Ground."
Note: GFCI protection functions properly on a 2-wire circuit without an equipment grounding (bonding) conductor, because the equipment grounding (bonding) conductor serves no role in the operation of the GFCI-protection device.

CAUTION: The permission to replace nongrounding-type receptacles with GFCI-protected grounding-type receptacles doesn't apply to new receptacle outlets that extend from an existing ungrounded outlet box. Once you add a receptacle outlet (branch-circuit extension), the receptacle must be of the grounding (bonding) type and it must have its grounding terminal grounded (bonded) to an effective ground-fault current path in accordance with 250.130(C).

CarolT · #67 09/14/11, 01:42 AM

Rofl YH, I wasn't exactly talking coming to "fix" what you didn't have up to code, I was talking about _removing_ the 3rd ground to "teach" you why it was needed :-) And before someone says anything, it was a joke! I would never actually let anyone get shocked for a lesson. It hurts at the very least!

Rick · #68 09/14/11, 07:39 AM

Quote:

Originally Posted by Yvonne's hubby

Thanks for all the imput, I now understand how an open in the neutral side of the circuit can possibly create an issue if other conditions happen to be met at the same time without the presence of the third backup ground wire.

When it comes to dying, I get extremely proactive. Cances are you DO SO have a ground in that bathroom circuit! 3wire romex type
electric cable must have come around before the ground was added to the outlets as our circa 1955 house was built with 2 hole outlets, but the 3rd wire was wrapped around the bulk end of all 3 wires, and the clamp was tightened over the bare ground wire to make the ground path available. The bare wire could be unravelled (not real fun laying on the floor) to hook to a new 3 prong outlet.

Waiting Falcon · #69 09/14/11, 10:28 AM

I bought a house that had been "rewired with new wire". At night I could smell hot wire.
I got an electrician to check things out and there were two single wires. The wires (two black copper) had gotten so hot that the insulation had melted.
There but for the grace of God that house did not catch on fire.