What is the difference between earth and neutral?

Answer 1

For USA, Canada and countries running a 60 Hertz supply service.The ground or "earth" wire is a circuit's safety protective wire that normally carries no current.

It is there to force a fuse to blow or a circuit breaker or GFCI to trip if a fault condition occurs in any appliances, their flexible cords or plugs that are connected into the circuit.

By carrying away the excess current in a fault condition - which should cause the protecting fuse to blow or circuit breaker to trip - the "ground" or "earth" wire protects the building and its occupants because the power should be cut off before anyone gets electrocuted or any overloaded circuit wiring or appliances catch on fire.

The neutral is the normal "return" wire: in systems where the load is supplied from only one hot (or "live") wire, the neutral completes the circuit and carries current back from the load to the power station.

All the neutral and ground (or "earth") wires in a building are tied or linked together at the incoming service main breaker panel. This is the only place they should ever be tied togetherbecause it is "upstream" of all the fuses and/or circuit breakers protecting the hot (or "live") wires for the various circuits installed in the building.

Warning: we must never assume that a neutral is safe to touch: it has to be checked with a voltmeter or a voltage indicator to be sure it is not "live". This is because a neutral wire is designed to carry current under normal circumstances.

So, if a neutral wire going back to the incoming main breaker panel has not been properly connected - or suffers a deliberate disconnection or some accidental damage which causes it to break - then it and any neutral wires connected to it further downstream will go live up to the break because of being connected to the downstream loads which still have hot feeds coming into them!

That is why we should never use a neutral as a substitute for a proper, separate, ground or "earth" wire.

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If some external accidental damage or electrical breakdown of the wiring's insulation occurred anywhere to the house wiring, to a socket outlet or to an appliance, these things could be very dangerous if there was no such protective wire.

For example, if there was no protective ground or earth wire, a fault could happen that is of a kind which did NOT draw enough extra current to blow a fuse or make the main circuit breakers on the incoming supply panel "trip" to cut the current off - but the wiring could still catch on fire and/or someone could be electrocuted!

Neutral wires are the return paths to the power generation station for current it supplies to the house or building via single live or "hot" wires in the branch circuits.

For more information please click on the Related Questions below.

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Earth (also called protective ground or ground) and Neutral are normally both near 0 volts to ground potential. The neutral service wire is designed to carry current and the "ground" or "earth" wire is designed so that it should carry no current unless there is a fault.

In North American 120 volt single-phase services, earth and neutral are connected together at each service entry and connected to the earth by a stake in the ground or other reliable grounding means. They are not connected at any other point inside the building. The neutral wire ends at the transformer near the building and does not connect back - via the distribution lines - to the power utility company's generating station(s).

In North American Electrical Engineering and code, the terms "neutral" and "ground" are not officially used. The formal term for neutral is the "grounded" conductor and the term for the earth or ground connection is the "grounding" conductor. Since these are easily confused, it is more common to use the terms neutral and ground.

In North America a 240/120 volt so-called "split single-phase service" from a center-tapped 240/120 volt utility service transformer is often used for major home appliances - such as ovens, ranges, water heaters, clothes washing machines and driers, air conditioning units, etc. - which take a high power draw.

They work as follows: the main heaters and/or motors run on 240 volts single-phase delivered from two "hot" wires. (Usually one hot is colored red and the other hot is colored black.)

If they include some low-power devices - such as time clocks, wash-cycle programmers, etc. - that only need 120 volts, the current for them is delivered from one of the above-mentioned red or black "hot" wires. A separate wire called a "neutral", which is normally colored white, is used to send the current from those small 120 volt devices back to the center-tap on the 240/120 volt service transformer.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.

Answer 2

Some three phase circuits use a neutral connection because they connect the phase loads from phase to neutral, with neutral being a common return. Some three phase circuits do not use a neutral connection because they connect the phase loads from phase to phase. The former is called a wye connection (you can have a three phase load connected to a wye system without using the neutral), while the latter is called a delta connection.

Do not confuse neutral with earth. They are not the same thing. Yes, neutral is tied to earth at the distribution panel, but neutral is a grounded current carrying conductor, while earth is a grounding protective conductor intended only to protect from a ground fault. There is not supposed to be any current on earth. The electrical code requires all electrical equipment be grounded to the system ground grid. In a balanced three phase system, there won't be any current on neutral either, but that's a different situation - if there were some imbalance, perhaps from a single phase load or control circuit, there could well be current on neutral.