neutral vs ground

[xformer]

what is the difference of neutral and ground?

[Th3_uN1Qu3]

Re: neutral vs ground

Ground is there in case neutral fails, so you don't get electrocuted by the appliance you are using. For all intents and purposes they (should) have equal potential so the ground lead could as well be connected to neutral, but in case that fails then the case of the equipment would be at line potential. Also the EU for example doesn't use polarized plugs - so if case ground were tied to line neutral you could well end up with a live case if you plugged it in the other way round.

Ground and neutral are actually tied together at the distribution panel of the building. The reason why they come thru separate wires in your house i have explained above. http://www.electro-tech-online.com/g...vs-ground.html

[Hondaman]

Re: neutral vs ground

Electricity comes from the "hot" side of the outlet, goes through the load and then goes back to the "neutral" side of the outlet (and back to the fuse box).

What if the thing you are using is metal and has a problem -- and it only has a 2-prong plug? You could get a shock, because the electricity will go through you to get back to the outlet (or the fuse box).

If the electrical item has a 3-prong plug and breaks, electricity will go through the third wire with nearly zero ohms of resistance to get back to the fuse box.

Electricity takes the easiest path, so it prefers the third ("ground") wire to going through your body, because you have more resistance.

If you are outdoors, the path THROUGH YOU back to the fuse box can be easier if you are standing in a puddle or something. So outdoors you really must use a 3-wire plug. That third wire always offers a path back to the fuse box that has practically NO resistance, so electricity will choose that path.

And keep in mind -- in the US, 220-240 volts AC have two wires, but BOTH act as "hot", so safety is even more important. This is probably true in other countries but I do not know.

[tom66]

Re: neutral vs ground

No, neutral and ground are NOT interchangeable. Neutral wire carries current. Wire has resistance. So neutral is at a potential, sometimes 10's of volts, relative to ground. At the substation or pole, neutral and ground are connected. If you interchange neutral and ground, you will most likely trip the RCD/GFCI.

[Hondaman]

Re: neutral vs ground

Let me change one paragraph to read as follows:

What if the thing you are using is metal and has a problem -- and it only has a 2-prong plug? You could get a shock, because the electricity will go through you to get back to the fuse box (not the outlet -- because the third wire is not there in this example).

[ratdude747]

Re: neutral vs ground

Let me change one paragraph to read as follows:

What if the thing you are using is metal and has a problem -- and it only has a 2-prong plug? You could get a shock, because the electricity will go through you to get back to the fuse box (not the outlet -- because the third wire is not there in this example).

let me re-word that:

What if the thing you are using is metal and has a problem -- and it only has a 2-prong plug? You could get a shock, because the electricity will go through you to get back to earth (thats where the ground spike/water ground ultimately ends up) (not the outlet -- because the third wire is not there in this example).

[tom66]

Re: neutral vs ground

What if the thing you are using is metal and has a problem -- and it only has a 2-prong plug? You could get a shock, because the electricity will go through you to get back to earth (thats where the ground spike/water ground ultimately ends up) (not the outlet -- because the third wire is not there in this example).

1. Appliances with exposed metal cases must be earthed when there is a possibility of a wire touching the case.

2. An RCD should protect you against a live/earth or neutral/earth shock, but not always.

[PCBONEZ]

Re: neutral vs ground

So neutral is at a potential, sometimes 10's of volts, relative to ground.

Not unless you have a fault.

At the substation or pole, neutral and ground are connected.

In the US neutral and ground are also connected together in the breaker box on the building.
In large buildings that will also be the case in the major sub panels.
If you have volts on neutral then you have an open or high resistance somewhere in neutral.
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The difference is current.
Neutral has it.
The ground shouldn't have any.
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[delaware74b]

Re: neutral vs ground

In the US neutral and ground are also connected together in the breaker box on the building.
In large buildings that will also be the case in the major sub panels.
.

Actually, in the US, the neutrals and grounds are tied together in first panel with overcurrent protection (fuses or breakers). All subpanels beyond the first the neutral busbars are separated and isolated from the grounds per NEC.

In steel buildings, the frame is also bonded to ground along with any gas lines (propane or natural gas) and water lines (copper).

[ratdude747]

Re: neutral vs ground

water ground is a dying term... a lot of new builds use PEX instead of copper for the water pipes... so water grounds are generally unreliable, as many repairs are also being done in PEX. Even if the whole run is copper now, in 5 years there may be a pex repair downstream...

[Agent24]

Re: neutral vs ground

And keep in mind -- in the US, 220-240 volts AC have two wires, but BOTH act as "hot", so safety is even more important. This is probably true in other countries but I do not know.

American 220V electricity consists of 2-phase 110V while, European electricity is single phase 220V.

(http://buyersguide.bargainoffers.com...ge_guide.shtml)

[jamesbo]

Re: neutral vs ground

Actually US 220V is single phase with the neutral center-tapped to create 2-110V feeds.

[PCBONEZ]

Re: neutral vs ground

Actually US 220V is single phase with the neutral center-tapped to create 2-110V feeds.

In older documentation it's referred to as 2-phase.
Never was technically correct but that was still the common name for a very long time.
.

[PCBONEZ]

Re: neutral vs ground

All subpanels beyond the first the neutral busbars are separated and isolated from the grounds per NEC.

That's not the way I read it.
What I see is 'not required' which is fundamentally different than 'not allowed'.
-- If you see something different in the NEC then please give me the article number because I don't want to search the entire 800 or 900 pages to find it.
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It's also not how I've seen industrial buildings wired.
- Talking buildings with load centers up into the MW range and sometimes the size of a 2-car garage.
- The load centers contain 'the first' neutral busbars in that configuration because they start counting after ownership changes from the utility company to the site's ownership.
- There, the sub-panels feed by the load centers have their own grounding rods driven in below the floor slab and the sub-panels are wired as if they were residential Service Entrances in that inside the sub-panel they have isolation breakers on the input to the panel [not just on OP branch circuits]. The input breakers often break both line and neutral and such panels do have the neutral tied to ground via the busbar and the ground rod sticking out of the floor underneath them.
- In other words those sub-panels are electrically identical to a residential or office building Service Entrance configuration in every way - but they are fully inside the building. The input side to them is not owned or maintained by the utility company so they are not classified as the service entrance [the load center is] and thus they are not 'the first' neutral busbars after the Service Entrance.
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See, even the NEC is full of politics.
'Service Entrance' is an ownership thing, not a physical hardware thing.
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[severach]

Re: neutral vs ground

Subpanel neutral and ground must be separated and you don't need the code book to know why. Connecting ground and neutral in a subpanel causes the supply ground to take half the neutral current. Ground becomes a current carrying wire making any ground supplied by that subpanel unsafe. Panels with ground rods are the only ones where neutral and ground can be safely interconnected.

Subpanels are also not allowed to be grounded. Multiple grounds creates ground loops. Only one ground per service entrance though this turns out to be impossible because many things act as grounds like water pumps and equipment set on concrete floors.

Once ground loops are ignored then grounding every panel mostly eliminates the problem of the ground sharing the current.

[PCBONEZ]

Re: neutral vs ground

Panels with ground rods are the only ones where neutral and ground can be safely interconnected.

That's what I said.
And contrary to popular belief Service Panels aren't the only panels that can have their own Ground Rods.
Sub-Panels with their own Ground Rods are in fact very common in large and industrial buildings.
Anyone that thinks not should look around the next time they're in one.
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