the grounding wire should be at zero volts and carry no current under normal situations. it only carries current when it is performing a protecting function.
the neutral is at or near zero volts and carries current anytime you are using electricity.
a ‘ground fault’ is anytime where the hot and neutral wires aren’t carrying an equal amount of current, there is no regard as to where the current is flowing to cause that situation.
I am not an electrician, nor do I play one on TV. Putting aside the question of what’s the difference between neutral and ground… are we all agreed that if a hypothetical person touches just one wire and feels a shock then the truth is that the person was indirectly touching a second wire? For example, the person is touching the floor and the floor is touching the pipes and the pipes are touching another wire.
It sounds to me like we should clarify the answer to the OP thusly: Theoretically, if you touched only one wire, you would not get shocked, but in reality there’s a strong possibility that you’ll actually be touching two wires (indirectly) despite the fact that you think you’re only touching one, so you may get shocked after all. And this is true of both AC and DC.
Are we all agreed on that?
By the way, here is the actual way a house is wired.
In the U.S., most homes are fed from what is called a split phase transformer. This is a transformer connected to a single phase of the distribution line, with a center tap on the transformer coil (hence, split phase). This gives you three connections to the transformer. The wire connected to the center tap is called the neutral. The lines connected to each end of the transformer coil are called the lines (or the “hot” wires). All three wires come into your breaker box. You have 240 volts between the two hot lines, and since the center tap is exactly halfway between these, you get 120 volts between the center tap and either hot line.
Fairly rare in the U.S. (for residential service) but still in use in some areas, you get two out of three phases of a three phase system. I won’t go into details of a three phase system here, but you end up with 120 volts from either line to neutral, but only 208 volts from line to line. Many large business and industrial facilities use three phase. There are some residential areas still using it, but not many.
The neutral is connected to earth ground, fairly close to the breaker box. In older homes, the ground was required to be through the cold water pipe, since this was a common piece of metal that pretty much every home had. When folks started using PVC pipe, the requirements changed. Newer homes are required to use a grounding rod (literally, a rod of copper driven into the ground) for the earth ground connection. However, you don’t want your water pipes to be floating, electrically, because then if a hot wire shorts to a water pipe then your entire water system becomes an electrical hazard. So, water pipes are required to be connected to the earth ground connection as well. So even in a newer home, you still end up with the water pipe connection to earth ground, just for a different reason.
In your breaker box, the connections alternate between the two hot lines. A 120 volt circuit breaker connects to only one of the two hot lines, and those are generally split so that about half of them will be attached to line one and the other half will be attached to line two. 240 volt circuit breakers connect to both lines.
The hot wires run out to all of the circuits, and the neutrals are all connected together inside the breaker box. All of the protective grounds will also be connected together, and are required to be connected to the neutral, which is also connected to the actual earth ground connection, and all of these connections must be close to the breaker box.
That’s essentially what’s happening in the great article linked by Machine Elf in post 5 of this thread. Yes, you can float yourself at any arbitrary number of volts so long as you don’t make a complete circuit. It’s not recommended because it’s easy to make a complete circuit.
See post #12.
If the electrical system in question is not isolated from earth ground, then yes, touching the non-grounded wire while touching anything else that connects you electrically to earth ground results in a shock hazard.
It’s not so rare in New York City; most large apartment buildings are set up that way. This is why it takes me 15% longer than normal to microwave a burrito.
who knows what your specific situation was.
things that were wired like that should have no chassis metal that could be touched. it would have a wood or plastic cabinet, plastic or wood knobs/controls, if the rear was open for ventilation there there would be a wood panel.
that’s not to say that age (of the device) or misuse wouldn’t defeat those more primitive safety features. it was intended to protect a sensible adult.
Rare for single family homes is what I meant. Large apartment buildings, hotels, businesses, and industrial buildings are often wired up for three phase, and all three phase lines enter the building. There are single family homes in New York City and Chicago and a few other places (mostly old rural systems that are slowly being replaced) that are fed by two lines from a three phase system. Which two lines they get alternates from house to house so that they balance out the three phases.
It shouldn’t affect your microwave (unless you have a 240 volt microwave) but it will affect the time it takes for an electrical oven to reach its operating temperature and it will take clothes longer to dry in an electric clothes dryer.
Clothes dryers for apartment use often have different 208 volt heating coils available for when they are installed with buildings that have three phase.
You can be shocked by any of the three.
Besides being shocked by touching hot and ground you can be shocked by touching neutral and ground.
If the house is wired with shared neutrals you might get shocked.
Picture this. Two circuits a and b. Each has their own hot wire. You are changing an outlet on circuit a. Circuit a is turned off at the breaker.
Circuit b is energized and on. The neutral return for circuit b goes through the outlet on circuit a on its way back to the electrical panel. You are changing the outlet on circuit a
If you body is grounded like mine was by leaning my sweaty back against the gas stove I was working behind, your body is at ground potential as the gas stove is hooked to the buried gas pipes by a metal flex hose.
The unattached neutral is at 110V looking for a ground.
Then touching the neutral from circuit b creates a ground path up my arm around my chest to my back to the stove.
The light in the ceiling lights up as well as my arm.
:eek:
Bottom line is either turn everything off or treat every wire as hot. Turning off just one circuit may not ensure full safety.
I do - it’s a very schmancy built-in. 
I believe there are some very remote areas in the US that still use true earth-return systems, as well.
If you can find one still in use, let me know. I thought all of those were gone.
Apparently the only one left is in Alaska, but it’s being decommissioned, according to a report (PDF) on power distribution in Alaska:
Apparently there are still a few left in Australia, though.
Interesting.
Earth return systems were fairly common in the early days of electricity, as it does save you half the cost of your wiring in a simple single phase type setup. What they found though was that these types of systems ended up having a lot of losses and weren’t very reliable.
So, many years later, they try again in Alaska, and find that they have a lot of losses and aren’t very reliable.
Heh.
Those who don’t study history are doomed to repeat it, as they say.
Strictly speaking, it’s also possible to get a brief shock from touching even a single conductor, due to the capacitance of the human body. But the body’s capacitance is pretty low, so it’d be a very small shock.
In the mid 1990’s they were still putting in two phase + earth 38KV transmission systems. The stuff I know about was retro-fitting HV transmission towers to use the protective shield wires as lower voltage transmission systems, where they didn’t have a thrid wire available.
From the helicopter article posted by Machine Elf:
From Musicats common experience:
And Zerc:
That’s not true. You will get “a shock”, which may be only interesting or may be very interesting.
It’s unlikely to kill you. as indicated by the fact that many more people are not killed by it than are killed by it. And if you are killed by it, it’s probably becaue you fell off the ladder and hit your head.
Fortunately, the shock that you get by touching a live 120V power line with one hand while standing on the ground, is not normally enough to fry a large dry man, and mostly does not go through your heart.
Do we have enough conflicting data in this thread yet?
I have owned 2 houses.
The first was re-wired in the early 60’s when the utility lines on the street were buried.
This one was built in 1979 and has original service.
In both cases, the houses are wired as neutral-to-ground. There are no ground rods or stakes.
For those wondering: it means that the ground conductor is wired to the neutral.
The bare wire is electrically identical to the white wire.
Unless you see a ground wire going to a clamp on a copper-coated rod, assume your house is wired ground-to-neutral.
p.s. - in 1984, I bought a high-end Thermidor cook range (240vac). It came with the ground clamped to the neutral. It did have a note that such wiring may not meet local code.
I understand that with a “one wire” shock the reason that you are getting shocked is that the electricity is finding a way to ground through a virtual wire made up of your body, the table you are leaning against, through the tiles the table is standing on and finally to ground.
What confuses me is that the resistance of most of these items is quite high so not much of a current should pass through them so why do I feel a shock?
Is this because even though the current is very small it is enough to feel even though it would actually be nowhere near enough to stop my heart? Sort of like how a static shock can be quite painful because it is thousands of volts but the current is tiny and this tiny current is still enough for my nerves to sense.
Grounding via the neutral conductor in a 240v appliance used to be allowed because the neutral normally carries little to no current. (You’ve got two 120v hot phases opposite each other, so they cancel out.) This is no longer allowed in new construction; you have to use a four-wire circuit with separate neutral and ground.
I’m not sure what you mean by “wired as neutral-to-ground.” All houses in North America have the neutral bonded to ground at the service panel or meter. From there the neutral will be connected to either a ground rod or a water pipe or both. It’s definitely there.
Other than sbunny8’s posts, I think everyone else agrees. What other conflicts are there?
Houses built earlier than 1960 or so will be 2 wire system and will not generally have the third protective ground wire in place. The transition from 2 wire to 3 wire occurred in most places during the 1960s. All homes built after 1970 or so should have the 3 wire configuration.
All homes with 3 wire systems (hot, neutral, and protective ground) have ALWAYS had the protective ground tied to the neutral.
The neutral has also always been grounded. The only difference is exactly how the neutral was grounded.
I don’t recall exactly when the change in grounding occurred, but I would expect a house built in the 1960s to ground through the cold water pipe. You should have a connection from the neutral and safety grounds to the cold water pipe. PVC pipe started getting popular in the 1960s and 1970s, and areas where it was more popular required the grounding change before areas where PVC pipe wasn’t used. By 1979 I would expect your house to have a separate ground rod, but like I said I don’t recall exactly when the grounding change went into the NEC.