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In most power systems that I know of, the neutral bus bar is bonded to the ground bus bar in the distribution panel, so any current returning to neutral will go out to the service entrance (street power) along the ground conductor. This is the only time that current is permitted on ground, i.e. upstream of the distribution panel.
However, in a properly balanced split phase or three phase system, all of the various hot legs will balance each other out, resulting in very little actual current on neutral/ground. In this case, the ground connection is simply providing a tie point, so that hot leg voltage does not rise inappropriately high. If you were to explore, for instance, with a clamp on ammeter, you might discover that neutral current for one branch circuit is counterbalanced with neutral current for an opposite hot leg branch circuit, and that the net neutral/ground current going to the service entrance is very low. In this case, the neutral bus bar is simply a common tie point.
Wiki User
∙ 13y ago
Wiki User
∙ 12y agoThe current flowing in the neutral wire is offset by the current flowing in the hot wire. That is Kirchoff's Current law - the signed sum of the currents flowing around a series circuit always add up to zero. This means that the neutral current is opposite and equal to the hot current.
However, neutral is not the only return path. In a typical split phase 120/240 circuit, the two hots can oppose each other, with the neutral current being zero, or close to zero. Also, in a 240 circuit, there may be no neutral. It depends on the system design.
In a typical neutral configuration with multiple hots, be it simple split phase, or three phase wye (or star), the ideal configuration is that all of the hots balance one another. This means that neutral current, relative to earth ground beyond the distribution panel, is close to zero.
There is a second interpretation of this question... Neutral is, by definition, grounded, so it can be said that the current flowing in neutral goes to ground. However, it must be clearly understood that, downstream of the distribution panel, no current is allowed to flow on ground in normal operating conditions - it must all flow from hot to hot or from hot to neutral. The only allowed current flow on ground, besides as a protective connection, is upstream of the distribution panel, and into the service transformer, where neutral and ground are connected together.
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What is the neutral in a electrical circuit for?
Good question! In US residential wiring, you have 3 wires feeding your home off the transformer: two hots and neutral. The transformer is a 240V center tapped transformer. The neutral is the center tap. Well, that's all fine and good, but your probably asking "what does that mean?" right about now. Well, since the transformer is 240V, you have 240V in between the two hots. The center tap divides the transformer winding in the middle. So between either hot and neutral you get 120V. Neutral is kind of a return wire for 120V circuits. (I say "kind of" because this is AC, current is flowing in both directons.) Well, why is it called neutral, then? At your main service panel a fourth wire comes into play: ground. Ground is simply a heavy safety wire that goes to a 8ft long copper rod driven into the ground. This ground wire is connected to all metal surfaces you touch (panels, screws, metal junction boxes, metal cases on appliances, etc.) In the main panel (and only the main panel) neutral is bonded to ground. So, while neutral is not ground, when everything is correct it should be "neutral," i.e. it has no potential on it. You cannot assume neutral is grounded or safe to touch, however. By the very nature of wire, if there is a current in a wire there is a potential across it. This potential is usually very small, but is still there. The bigger problem is if the neutral connection becomes very resistive or open. Then the neutral will be live as it cannot "return" the energy to the transformer. (Again, not a totally correct analogy, but it gets the point across.) This is why you shouldn't just bond ground to neutral when you don't have a ground wire at a fixture. When a hot wire goes open, fixtures simply fail to operate. When a neutral goes open, the fixture and the neutral between the fixture and the break go live. The fixture will not work, however, giving people a false sence of security. (No the light is not on, yes it can knock you on your butt.) This is why you want to keep your neutrals in good shape. With the neutral you have two hot wires both capable of producing 120V to neutral. Because the hots have 240V across them (and not 0), one hot goes positive while the other hot goes negative. So, let's say you take two loads with a resistance of 60 ohms. You hook the neutrals of the loads up to neutral, one load to one hot, and the other load to the other hot. How much energy flows through the neutral conductor? 0W. This is because the load is "balanced." The amount of energy flowing through load one is equal to the energy flowing through load two. Let's do a testcase for a specific point in time. Let's say hot 1 for load one is at +60V, and hot two for load two is -60V. Ignoring load two, load one has a current of 1A (60V/60ohms=1A) flowing from hot one through the load and back to the transformer through the neutral. We will call current into the transformer on the neutral positive, and current out of the transformer on the neutral negative. So our neutral has a current of 1A on it for load one. Load two has a current of 1A flowing out of the neutral, through load two, and back into the transformer on hot 2. So, by our signing above, load 2 has a current of -1A on the neutral. To calculate the actual current on the neutral, we add the currents for the two bulbs: 1A + -1A = 0A. Current is flowing out hot one, through bulb one, through bulb two, and back to the transformer on hot 2. Make sense? Now, let's say you have the same setup as above, only load 1 is 30ohms. Well, now the neutral has to carry the extra amp of current. The loads are no longer balanced, so the neutral has to carry the difference. At our 60V test case, the current of load one is now 2A. The neutral current is 2A + -1A = 1A. So, this means that the neutral only carries the difference in power between the two hots. This is also why your neutral doesn't need to be twice as heavy as your hots. Let's say you have 200A service. While you can have 400A of current flowing to 120V appliances all over your home, it is actually +200A to half and -200A to the rest. Your neutral carries 0A, not 400A. Let's go back to our last example, with the 60ohm and 30ohm light bulbs. Let's say some unscroupulous DIYer used the conduit the feed is in for a neutral instead of a dedicated neutral wire. Let's say a clamp to the pipe came off and now we have no neutral connection. Now, we had +60 on hot 1 and -60 on hot 2. So our loads have 120V across them. Now, in this ideal test case, our loads appear as a single 90ohm load to the supply. This means that there is 1.334A flowing through our circuit (120V/90ohms = 1.334A). This also means that load 1 us underpowered by 2/3 of an an amp, while load two is overpowered by one third of an amp. If loads one and two were lightbulbs, bulb one would be dim while bulb two would be brilliant. As both loads have 1.334A flowing through them, load one has 40V across it, while load 2 has 80V across it. Remember, at this point they are both supposed to have 60V across them. Our little set up above is how 240/120V applances work. In, say, your dryer, you would have a third load that is directly across the two hots. Load 3 would be your heater, load 1 would be your timer, and load two could be the light in the drum. If your neutral comes open you could toast your timer or bulb. Most appliance manufacturers actually avoid using both hots for 120V, if possible, for this very reason. You can never be sure, though. Now, the other thing to keep in mind is your whole home functions as a 240V/120V appliance. Load 3 is your heavy appliances, the heaters in your dryer, oven, waterheater, etc.. Loads one and two are all your 120V appliances, light fixtures, etc. So while an open neutral doesn't cause too much of a headache on your dryer, it does cause a big headache in your home. Let's say your service neutral comes open, and you have 1500W of appliances on for load 1, and a 100W porch light on for load 2. That porch light is going to burn out very quick. Now it is impossible to garuantee that load 1 will equal load 2 without being obsessive-compulsive. What you can do is when you plan your load and circuits, try to balance them. This will keep current in the neutral low, which will prevent bad connections from burning open. Also, in the event neutral does fail, if the loads are close to balanced you may only see 90V/150V instead of 10V/230V across your 120V loads. Your appliances my be able to tolerate the former until you notice, they can't tolerate the latter. A resistive neutral is a nasty little problem. It has ultimately the same effects as an open neutral, but is much more subtle. With a resisive neutral, there is a connection, but it is bad. When no current is flowing through the neutral, it appears OK. The more current flows through the neutral, the more potential develops across it by ohms law. This means that if your neutral has 25A flowing through it, and has 2 ohms of resistance, the neutral wire has 50V across it. This also means that your neutral bus in your panel is not at 0V (with respect to the transformer), but is at 50V favoring whichever load (1 or 2, as above) is heavier. This means that the lighter load will be overvoltaged. Also note that resistive neutrals get worse with time. Since our example neutral has 25A at 50V on it, it is dissipating 1250W at some point in the wire. This point is the resistive connection, and will get hot as it dissipates all this power. As it gets hot, it will burn a little further open, and the circle continues. NOTE: This procedure involves probing your service panel or heavy outlet while live. This is dangerous. If you are not comfterable with this, call an electrician. They can check for this quickly and tell you exactly what you need to do to fix it. The easiest way is with a AC voltmeter. Leaving everything on as you normally would. Check the voltage from one hot to neutral, then from the other hot to neutral. This can be done at your panel, at a dryer outlet, at an oven outlet, or at any other 240/120V outlet. If the voltages differ by more than a volt or two, you may have a problem. Call an electrician, as work on your main service must be done by someone licenced, and they have lots of experience with this.
How does a ground fault circuit interrupter shuts down a circuit?
A ground fault circuit breaker detects leakage current between the hot wire coming off the breaker and the neutral/ground since the neutral is bonded to the ground in the panel, if it senses a current of 6 milliamps or more it will trip. Note: no sharing of the neutral for a circuit on a ground fault breaker If a few milliamps from the hot (black) wire do not return on the neutral (white) wire, then a GFCI assumes that current it traveling harmfully elsewhere through your body. So it disconnects. A GFCI can monitor 15,000 milliamps. But if only 5 go missing, then a GFCI trips.
What is the difference between a neutral wire and a ground wire?
They basically act as a return path for the current to zero voltage. But there is a difference. Examples of the two are:A single wire circuit used on automobiles: they have a positive feed wire to each load or group of loads (circuits) and do away with the return wire back to the source (negative terminal). Instead the return is to the chassis which acts as a ground, because the negative terminal on the battery is attached to the chassis.Homes use a double wire circuit: a feed wire supplies voltage to one, or several, circuits and the current flows back to the neutral bus bar in the main distributor box, also known as the "breaker panel". A grounding wire (bare copper wire) goes to all boxes, motors, fixtures, etc. in the system and connects to a separate ground terminal in the main line-box. IF a pos. or neg wire in a circuit shorts in a box, the grounding wire is there to force the circuit's breaker or fuse to shut off the flow of current, thus helping to prevent a possible fire. The first part of circuit will work but not the rest of it.Thus earth ground, and neutral are NOT the same.....
What is the difference between neutral and ground in a three phase system?
No matter whether we're describing a three-phase service or a a single phase service, the bare copper "earth" or "ground" wire normally carries no current. Its purpose is to provide an emergency path for current if ever there is any accidental contact between a hot wire and the external (or internal) metal parts of any electrical device which a user may be able to touch. The electrical device can be a motor, a water heater, an air conditioner unit or any other kind of appliance.By carrying away the excess current in a fault condition - which should cause the protecting fuse to blow or the 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. In "Y-" or "star-connected" three-phase circuits the neutral doesn't normally carry any current if all three phases are properly balanced.If the three phases actually have unbalanced loads - which can easily happen if each phase is being used to provide power to different single-phase circuits, each with their different loads - then some current will flow in the neutral wire and will result in unbalanced 3-phase currents flowing back 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 together because 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.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.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 JOBSAFELY AND COMPETENTLYREFER THIS WORK TO QUALIFIED PROFESSIONALS.
What happens to an electric current when the wire is made smaller?
Electric current as we usually describe it is the flow of electrons. Current is caused to flow by voltage, which can be looked at as "electrical pressure" that forces electrons to move. Currents can be made smaller or larger by decreasing the voltage across a fixed amount of resistance. As resistance is the quality of "resisting" or "limiting" current flow, we can change resistance to change current. For a give voltage, if we increase the resistance, we can make the current smaller, and if we decrease it, we can make current larger. In electronics, voltage equals current times resistance. E = I x R Also true is that current is equal to voltage divided by resistance. I = E/R As current equals volts divided by resistance, if we change one of them without changing the other, current will change. And in increase in voltage (with no change to resistance) will cause current to go up. The opposite is also true. Also, if we increase resistance (with no change in voltage), current will go down. And the opposite is true here, too.
May you use earth wire as neutral wire?
1. SafetyWhen there are separate wires for neutral and ground it is much less likely that a problem in electrical wiring causes a dangerous situation which will cause electrical shock or fire.If the ground and neutral were the same conductor, the cutting only the neutral wire (for example by accident) would cause the grounded metal case of the equipment to be on mains potential just because there is only live connected to equipment and that voltage can go through the equipment to the cut neutral cable and from there to equipment case.When ground and neutral are separate, then cut neutral causes only the equipment to stop working and no dangerous situation. If ground gets cut by accident, there is no danger caused before some equipment gets damaged. So when there is separate wires for neutral and ground, a singe wire fault (cut or short circuit to other wire) on any wire going to outlet does not cause immediate danger to the user of the equipment:2. Minimizing the ground potential differences between outlet groundsIn an ideal separate grounding wire system there is no current flowing in ground wire network, so there is no voltage difference between grounds on different outlets. Unfortunately in real life systems there is always some current leaking to ground, but that current is very small (only probably milli amperes) compared to the current flowing on line and neutral wires (usually amperes).If the neutral and ground were shared on same wire, the current flowing on neutral wire would easily cause a large voltage difference (up to many volts) on different outlets grounds. The ground potential on any outlet will then depend on the load current, neutral wire resistance and the mains phase it is connected to.
Explain why a light switch makes a light go on and off?
A light bulb is wired up to have a current run through it to produce light light. when you disconnect the wire to one end of the light bulb there is no longer a current flowing through it and the light go's out. A switch is a device that is able to disconnect or connect the wire. or otherwise put cause a break in the wire so that power will not run through it.
When a GFCI senses a fault the ground-fault current can originate from what either the hot or neutral wire on the line side of the GFCI either the hot or neutral wire on the load side of the GFCI?
In a very real sense, a "ground fault" cannot come from the neutral side, since, if your wiring is performing as designed, there should be little potential between the neutral and ground. A ground fault is said to occur when the current OUT, through the "hot" side is not equal to the current BACK, through the neutral, meaning that current is leaking to somewhere else... such as through your body. Having said all that, it is certainly possible that you could cause a GFCI to trip by introducing current to the neutral from a circuit that does not go through the GFCI breaker; but that would involve non-standard wiring practices.
What particles are moving from atom to atom in a wire?
In a metal wire electrons go and go and go! when conducting electric current.
Can a burnt out wire cause you to lose a neutral connection?
Not usually. When a wire burns and grounds out the breaker will trip. Wire burns are usually centered around terminal connections points. If a connection becomes loose heat will be produced and this heating action is what burn the insulation on the wire. The neutral wire on the other hand is not switched so it is less likely to have terminal connection points that can become loose. In a circuit the neutral wire is connected under a wire nut with other neutral extensions in the circuit and then connected to the neutral buss in the distribution panel. There is very little to go wrong on the neutral return side of the load wire.
Does the electricity that goes into your house go back out again?
Yes it does, via the neutral wire.
Does the neutral wire go on the silver screw when wiring switches or outlets?
No, the switch just breaks the hot side of the circuit. The incoming hot wire should be connected to the top screw and the load side of the switch should be connected to the bottom screw. The neutral wire is usually connected together with a wire nut and pushed to the back of the switch box.
How and where do you connect the white wire from the shunt breake to the electrical panel?
The white wire would go to the neutral bar. Just be sure of the shunt trip voltage required for the breaker and land the white wire on the appropriate neutral bar in the correct panel.
When a person touches the water on the ground with the current flowing through it from a broken wire will it affect him?
It's not the current flowing through the water that the person has to worry about . . .it's the current flowing through the person. So we have to ask whether there's acomplete circuit through him. Where are his feet ? When he touches the water, ifthere's a voltage difference between the tip of his finger and his feet, then somecurrent will flow through him, which may be a surprise or even a shock to him.Remember . . . a bird can sit on a bare high-voltage wire with no problem, and alineman in the extended bucket of an insulated cherry-picker can handle a bareenergized primary line with no problem. They just have to be careful that currentwould have no place to go if it entered them.
Where does the neutral wire go on a single pole switch?
Unless the switch has a light to indicate the switch is turned on, there is no neutral connection to a single pole switch.
How do you wire a 15 amp 120V breaker in a 240v 30 amp breaker panel?
Look to see if the 30 amp panel is fed with a two wire or a three wire. If it is a two wire then you are out of luck. If the panel is fed with a three wire then the panel should have the neutral terminated in the panel. It is this neutral that you need for 120 volt connections. You didn't state how many panel slots there are in the panel. If you are able install a 15 amp breaker into the panel and connect the wires going to the load. The black wire will go to the breaker and the white wire will go to the neutral bar in the panel.
When you look at diagrams for wiring fluorescent lights you do not see clearly a neutral wire All electrical components need it Where is it in fluorescent lights?
Actually, many components do not have or need a neutral. 3-phase equipment such as motors, heaters and the like do not use a neutral. Some older 240V electric clothes dryers (in the US) did not have a neutral. The 2.5 ton, 240V airconditioner on my roof doesn't use a neutral either. Fluorescent fixtures do however, as you note, need a neutral. The two power wires coming out of the ballast are usually a black and a white wire in the US, the white wire is the neutral. On older fixtures with a separate starter, the white wire (neutral) may not go to the ballast. Instead it goes to the tube socket. It's still white, though. Note that many of the current rapid-start fixtures also need a grounded reflector to reliably start. These fixtures will require a hot, neutral AND ground conductor, properly connected, to work.
