No Current in Neutral Wire

I'm not sure I understand your question.

In the US there has to be return current in the neutral wire in a single phase circuit.

The only way that there would be an exception to this is for a fault or miswiring condition to exist, then the ground wire will have the return current.

In the US, for single phase wiring, the (safety) ground and the neutral wires are tied together at the breaker box. Then a earth ground is connected at that point.

The split phase 220 VAC coming into the breaker box has a neutral line that attaches to the neutral/ground terminal strip in the breaker box.

The receptacle in the wall has three connections, ground, hot, and neutral. The neutral and ground are not connected together at the receptacle (that would cause a ground loop).

The ground wiring in a US wired house is a safety ground. It is required to act as a return path in the event that the neutral wire is faulty.

there is voltage not current on the neutral unless the load is unbalanced.

The neutral will be bonded to earth at the substation. This bonding effectively holds the neutral to the same potential as the ground. This is commonly accepted as being at zero volts....

Due to the length of cable runs and the resistance inherent in a long cable run, the neutral can "float" to a voltage above zero WHILE CURRENT IS FLOWING THROUGH THE NEUTRAL. But if NO CURRENT then NO VOLTAGE with respect to ground. Beause they are bonded together!!

In a well ordered system there is usually a legal limit set to just how many volts can appear on the neutral at a house/workshop/factory.....I would guess this is probably slightly variable between countries.....

The resistance to ground from neutral is also set (usually) by the country codes.....this also plays a significant role....

Check local codes for exact values for where you live.

To answer your (incorrect) statement that you made, there would be no voltage on the neutral point on a perfectly balanced system, the name is the help/clue here, it's "NEUTRAL".....

I looked it up in an online dictionary for you as well, I have marked in bold certain elements for you:-

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neu·tral (ntrl, ny-)

adj.1. Not aligned with, supporting, or favoring either side in a war, dispute, or contest.2. Belonging to neither side in a controversy: on neutral ground.3. Belonging to neither kind; not one thing or the other.4. Sexless; neuter.5. Chemistry a. Of or relating to a solution or compound that is neither acidic nor alkaline.b. Of or relating to a compound that does not ionize in solution.6. Physics a. Of or relating to a particle, an object, or a system that has neither positive nor negative electric charge.b. Of or relating to a particle, object, or system that has a net electric charge of zero.7. Of or indicating a color, such as gray, black, or white, that lacks hue; achromatic.

8. Linguistics Pronounced with the tongue in a middle position, neither high nor low, as the a in around.

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I feel that this states clearly enough EXACTLY what is implied with the name "Neutral"......no voltage!!

Having a small voltage on the neutral implies an unbalanced system and inherent resistance in cables, particularly the neutral cable, a normal condition in an imperfect world and unbalanced loads.

As Anonymous Hero has stated, the neutral is for the single phase loads. If you ever try to use the earthing as a return for single phase loads in a plant system with ground fault protection, you will soon learn why not to use this conductor.

I do not know what you are connecting to, but it is apparently a 3 phase only load. Searching for an answer in lieu of sufficient information, I can surmise some possibilities. I have built control panels for equipment that use a 5 wire system, but only have 3 phase loads. Besides providing 25% spare capacity (extra breakers), I also provide a neutral bus and terminals for connection to neutral in the panel should a single phase load be added in future revisions or add ons.

If this is a set application where fututre modifications are not likely, then perhaps there is a second model of the equipment you are connecting that has a single phase load. Companies often write a "one set covers all" manual.

What you are referring to as earthing is what we call the grounded conductor. The Neutral and Ground are bonded at the panel and therefore have the same potential. The Neutral completes the circuit and serves to carry the unbalanced portion of the load.

If you are in a single phase, the neutral must provide the return current.

If it is not providing (no current is neutral) that means the electrician (obviously must be sacked) has used the ground for the return current.

And that further means that in your installation (I assume it is home) the ELCB is not installed. It is potentially dangerous situation.

Get a proper electrician and get the line rectified immediately.

I will try and put it simply for you:-

Firstly, in a single phase system with no neutral current, you have a serious and very dangerous situation that a "good" electrician will find and correct easily and quickly.

Secondly, the reason that earth and neutral are ONLY connected together at the substation is to provide a fault path for any time a phase is accidentally connected to the frame of something. The overcurrent should trip the CB (provided the current exceeds the trip setting, which is not always true!)......

So:-

For proper safety an ELCB is also needed (sometimes they also have over current sensing as well) to sense if a human or pet has accidentally contacted the phase. The fault current (only a few milliamps) to ground will allow the ELCB to remove all voltage from the phase within a very short time (Milliseconds), hopefully saving their life.....

Not having the neutral correctly connected/working will mean that the ELCB will not reset (thankfully!)....it will constantly trip out....which is really good!!

Several other posters have posted technically correctly, but I wanted to be certain that you fully understood the adverse implications of your present installation in a simple and easy way.....

Please ask if you still do not fully understand all the reasons for having a correctly installed/working neutral line....

Also there are small plugs that you can buy in most countries, you simply plug them into each wall socket and some indicators (LEDs, Neons or similar) show if the socket is correctly wired and connected or not....I paid about €10 for mine about 10 years or so ago.....you don't need to understand why they work, you only need to decode the information shown on the indicators....really simple.

Good answer.

In a perfectly balanced 3-phase 4-wire star connected load there would be no neutral current. The neutral is required to carry the current of single phase loads and unbalanced 3-phase loads.

If by chance you have connected random single phase loads that exactly balance, there would be no neutral current and you would not need a neutral wire.

But without a neutral wire all sorts of things could go wrong with the remaining two phases when you disconnect one phase.

Your post is mixing theory (in which it is correct) and practise (where it is not correct).

You will see it yourself if you draw the devices and the wiring out on a piece of paper....The neutral wire in each supply line from the switchboard to the device (including the mains lead of the device) MUST also carry the current for that device.....(in a properly working/connected system of course!)..

If the current is flowing via the earth lead, it is still eventually flowing via the Earth/neutral connection point at the substation ntransformer.....

The possibility that the single phase loads are so exactly matched (assuming no earth leakage) that this happens, even when only observing at the switchboard is as good as never......

I love theory as well, but you must always remember to add the salt of reality, or you can really get lead up the wrong path (pun intended!).....

I stand by what I say.

Off course you need a neutral. That is why my there is a 4 wire supply. But even so , in a perfectly balance star connected load there would be no current in the neutral if the earth leakage was also exactly balanced. So you could disconnect the neutral.

I agree that in practice a perfectly balance load is highly unlikely; so there would be some neutral current most of the time - probably all the time. Except in the case of many 3-phase star-connected motors that do not have neutrals.

I recall from school days that one of the most difficult theoretical problems was to calculate the star-point voltage and current and phase angle, with respect to the unconnected neutral, of an asymmetrical 3-phase load.

Bearing in mind that all we had in those days were slide rules, log tables and trig tables.

Then, after wiring up resistors and chokes and condensers (that dates me) of the theoretical values to measure the voltage and current etc.

Then having to explain why the measured results were different from the calculated ones.

Yes, you definitely need a neutral wire.

Does your house have 3 phases coming into it?

This isn't done by chance it is why we calculate the load for every installation.

As others have posted the neutral is a return path for 2 unbalanced loads
If the loads are equal there's no neutral load
But if the loads are unbalanced the difference returns on the neutral

I am reminded of a time when an open neutral at the meter loop almost set a house on
fire in the USA
The home owner complained of no power and a 115v plug in air freshener
had caught on fire while plugged into the recepticle
I checked the voltage there and found it at 190 volts which is why it burned up
The neutral had opened behind the meter and several large appliances were plugged
in on the other phase on the transformer but could not return on the neutral
so it attempted to supply 220v to the little 120v heater in the air freshener
and a small TV and created as the say a maximum smoke condition

Neutrals are very important and should not be ignored just because they show
no potential voltage when things are normal

An open neutral can set fires and an overloaded neutral can be just a deadly
because the neutral has no fuses or overload protection

The only time that a neutral will carry a load is if the load is unballanced; then the neutral carries the unbalanced portion of the load.

ex. A-Phase 15A B-Phase 15A C-Phase 20A in this instance the neutral load will be 5A

SAFETY ALERT!

The circuit is wired across phase and earth, instead of phase and neutral! In the event of the earth connection at the source of energy becoming disconnected, the casing of all class 1 metal equipment enclosures will become live at the phase voltage!

De-energise the system immediately on safety grounds and consult a qualified electrician! Correct the problem before re-energising!

GA for that....

I thought that I had also said basically the same in my original post......

Much before that refer #3

Prove that you wrote it!!

I wrote that as well "accidently".......

Your question lacks all the information required to provide a definitive answer.

If your load has these connections L1, N, GND and there is current in L1 and no current in N, your have a big safety problem and as previously recommended, disconnect it immediately.

If your load has these connections L1, L2, N, GND and there is no current in the neutral, your may have a perfectly balanced load and everything is just fine. To verify a perfectly balanced load, clip your amp meter around L1 & L2 together and verify that the meter reads zero and also measure L1 & L2 separately and verify that the readings are equal.

If you are referring to a circuit in North America then this holds true.

On a single phase circuit, all of the current travelling to a device will normally return through the Identified Conductor. The Identified Conductor is ussually white or grey in colour and is connected in the panel box to ground via a ground wire from the panel to the ground rod or plate. This wire is not to be confused with a true nuetral wire.

A nuetral wire on a single phase circuit in North America carries only the unballaced load to ground potential. If the loads are ballance there will be no current on the nuetral wire.

If your circuit is in Europe I would heed Andy's advice.

Is it still true in the USA that few houses have a 3 phase supply?

If true, then most of them will have ALL the current going down the neutral!!!! All the time!!

The UK is (or at least was) the same....I was properly chuffed to find 3 phase when I moved into my first house in Germany!!!

Hi Andy

In North America almost all houses are supplied with combination 240vac 2 phase and 120vac single phase service. It will be somewhere between 60 amps (on older houses) to 400 amps on large homes. Most homes are in the 100 to 200 amp range, with 200 amps suplied to homes with electric heat.

The identified conductor is the return wire from the load to the center tap of the 240vac 2 phase system. So you end up with 240vac from one hot phase to the other hot phase and 120 vac from either hot phase to the center tie point (the identified conductor), which is grounded right at the breaker panel. These phases are 180 degrees out of phase with one another.

On any single phase load all of the current will travel from one hot phase to the center tie point via the identified conductor. It is called this because it must be identified by means of colouring, (white or gray) or as in the case of a flat black coloured lamp cord, by means of a raised ridge running the length of the conductor.

Any large load such as an oven or electric heater is connected phase to phase, 240vac and does not use the identified conductor. The suplied identified conductor on an oven will carry only 120vac loads on the oven such as timers, lighting, and convenience receptacles.

How is the system in Germany work?

Super Post Elroy, well written and easily understood. Many thanks. I will give you a GA when I close this....

It explains why some US citizens believe that they have a 2 phase motor!! They don't really, but they do have a single phase motor that runs at 240 volts, eg. almost a European motor except for the frequency!!

We have 3 phase AC coming into the house with a neutral wire and a ground or earth wire from the substation.230 volts phase to neutral or 380V phase to phase.

The phases are each fused by the electric company where they come into the house, the neutral and earth are not fused.

Most loads in a house here are 230 volt Phase to neutral, even some of the modern ovens (I recently got my first oven like this, better insulated) are single phase 230VAC, whereas 5 years ago or longer, the ovens used 3 phases and neutral and earth.

The only time I actually use(d) 3 phase was when I heated with wood, the circular saw needed 3 phases.

At this time I do not have anything that requires 3 phases (we have gone to pellets!), but I have a big three phase socket in the garage and another in the basement (the machines used to do the outside of houses need 3 phase as well and I had my house insulated fully in 2008 and re plastered (is that the right word in English?) or rendered (whatever!!).

In the socket are also the neutral and earth, but only acually used if you want to run some remote single phase sockets, which does happen from time to time. The earth connection is required on all portable equipment by law. A three phase motor does not need the neutral at all....

We also have in the main house switchboard (we have two, one in the basement and one upstairs) an ELCB on each phase to detect "earth leakages" that might be going through a person. It also detects when an element in a kettle or similar goes porous, even before heavy currents start to run that might get dangerous, the ELCB pops for that phase..........

So we have protection from over currents via each CB for each seperate circuit and earth leakages on each phase. Up to now nobody has been killed, though the shock of touching live even with the ELCBs functioning perfectly, is heavy.

I know, I was that "tester" some years ago.....it still HURT!!! 230AC hurts me far more than 220DC......but I can recommend either as a habit!!

Hi Andy

Plastered is the correct word.

The British System does sound like it is safer than ours. We don't have sheathed pins or shutters on our receptacles. We also only have ground fault receptacles near sinks or tubs and on our outdoor receptacles.

We do not have fuses in any of our plugs and we usually have an on off switch on our devices rather than a wired in switch to control a receptacle.

The usual reason we put a switch on a receptacle here is to control table lamps in a living room.

Have a good one.

Your posts are always interesting and informative, thanks.

The best place to install a fuse in a grounded power system is on the ungrounded conductor path to the load.That way when the fuse blows due to an overcurrent, there will only be grounded/safe conductor still connected to the load, making it safer for the people around.. It should be taken care that voltage between either side of the load and ground should not exist when the fuse blows out... :)

Which is exactly why I personally find the British 13 amp (BS 1363) system so good.

1) The same pin is always the phase in a plug. (as are the pins for earth and neutral.)

2) The phase has a fuse in the plug of the device, so provided that the owner has placed the correct size fuse in the plug it will blow on an overload, removing the phase only. Stopping the blowing of fuses in the fusebox.....

3) All pins are sheathed so that before the pin makes contact in the socket, there is no metal of the pin to be seen or touched.

4) The sockets have shutters that are only removed when the erath pin is partly inserted, which is why the earth pin is slightly longer....

5) The sockets are generally (I would say at least 95% in my experience) switched, so you do not need to plug and unplug to remove and restore power, operating the switch removes the phase to the plug.

The biggest problem of the britsih system is that the plugs are bigger than most plugs used in other systems, thats all. The system can be found in many other countries South Africa for example....

I am not saying its perfect as it was originally designed in WW2, but I have yet to see a better system anywhere else.....I would be interested to read about any system thought to be better....

The European system (what is legally required, my system at home exceeds the legal requirements considerably!) is downright dangerous to children and the like......

Anyone needing to learn more can look here:-

http://en.wikipedia.org/wiki/BS_1363

Andy,

I believe that the British system provides another safety advantage that other systems do not. Above a certain rating there is a mechanical interlock which prevents the switch on a receptacle from being able to move to the ON position unless the plug is fully inserted. And the same mechanical interlock prevents a plug from being removed from the receptacle unless the switch is OFF.

I have read the specifications and seen these in catalogs, but have no experience or have seen them. Can you provide some insight on how well these work in practice and are they used in the home, commercial, or at all?

Also, do the higher current plugs (30A+) have fuses in them just as the lower current ones do?

Sadly I cannot help directly in this case as I have lived in Germany for the last 29 years, but many CR4 people live in the UK, I am sure a few can chime in and help.

It sounds like a good thing, but as far as I remember, that was not a feature in my time in the UK.....Also I could not see this in a quick read of the British Standard 1363 , shown here:-

http://en.wikipedia.org/wiki/BS_1363#Other_safety_features

If you are checking an outlet with a multimeter, you'll see a voltage on the hot wire, but no voltage on the neutral (return) because there is nothing connected to it while you are checking the outlet. And of course, there will be no voltage on the ground wire.

This is a dangerous thing to do, but if you opened-up a lamp cord and cut the return wire then plugged the lamp plug into the outlet you would see a voltage between the lamp side of the return wire and the outlet side of the return wire. This is a good way to get electrocuted, so don't try it.