Many of us have never encountered the search for a phase, others do it all the time, and others need it from time to time. For what? There are all sorts of situations. Here are at least some of them:
- You need to hang a chandelier that has two, three or more shades.
- You bought an electrical appliance that requires polarity, and our sockets are not designed for this (and this happens, although rarely).
- You are repairing the wiring in an apartment or doing wiring in a house, but your wires are still Soviet, all the same color. You don’t seem to need much - just find out how to find phase and zero with the indicator screwdriver that you have.
- You need to find a bare wire, which is a source of danger (this situation occurs when dismantling buildings, repairs in unfamiliar premises, and it is not possible to turn off all this).
But before we begin our search, let's figure out what we are looking for.
We all know from our school physics course that alternating current flows in our electrical networks. Some even know how variable it is - 50Hz. That is, in one second the charge carriers jerk back and forth fifty times. The graph of voltage and current in the network graphically looks like a sine wave.
The amplitude of the voltage fluctuation is about 310 V. If we pass this current through and rectify it, we get the effective voltage in the network - 220 V. In fact, this is the average value over the entire sine wave, it is obtained by dividing the amplitude by the square root of two.
But then it gets more interesting. Few ordinary people know that Russia has a three-phase power supply. It clearly looks like this: not one power wire comes out of the transformer booth in your neighborhood, but three, and one more, called neutral or zero. The difference between the first three is that the current and voltage sinusoids in them are shifted relative to each other by 2π/3. This means that if in one wire the cycle is in one third, then the second has just begun, and the third has not yet caught up. It is hard to imagine? You can give this picture:
This phenomenon is called phase shift.
One such wire and a neutral are supplied to each apartment, connecting you to the ends of all three windings of your yard transformer and to the ground. However, you must also have a separate land to remove static from the housings of household appliances.
From this figure you can understand that the statement “there is no voltage at zero” is not entirely true. It won’t be there when everyone in their apartments has electrical appliances operating on three phases - then the load on them will be symmetrical. But few people would think of installing electric motors from industrial units in an apartment, and the load is rarely symmetrical. Therefore, there is always some voltage in the neutral wire.
Phase search
Currently, we can easily determine the phase wire using special devices. This simple operation can be done by anyone. We will do this in two ways - using an indicator screwdriver and a multimeter. And in the end we’ll talk about whether it’s possible to find phase and zero without instruments and how to do it.
How to determine with an indicator screwdriver
An indicator screwdriver is a device with a transparent handle, inside of which there is a capacitor bulb, and the end of the handle is a conductor. It looks like this:
The operating principle of this indicator is simple. You insert a screwdriver into the socket, and if you hit the phase and press the contact plate on the handle, you increase the capacitance of the capacitor at the expense of your body - the neon light comes on. You will find the phase easily. But zero, even if there is voltage in it, is not. It never exceeds 60 V, and below this threshold the indicator screwdriver will not show anything. This is not necessary: when the light bulb lights up only when it comes into contact with a phase, such a screwdriver is the best phase determiner.
More advanced versions of indicators (with LED, sound signal and battery-powered) are not helpful here: they will also show lower voltage. If you show it, then it will be with size. And to determine this value, we’d better use a multimeter. But it is best to use such indicators to find hidden wiring. There are also more advanced devices for this purpose. Some of them react to the field created by alternating current, others - to the metal in the wall. But all these devices have another area of application, which is beyond the scope of this topic.
Looking with a multimeter
It is not difficult. To begin with, let's set the switch of your tester to a function (either this sector will be called ACV, or it will be V~) with a limit above 220 V. For some it will be 500, for others 800. Testers are different. We insert the black probe into the common socket (COM is written next to it), and the red one into the socket for measuring current, voltage and resistance. You don’t need to put it in a socket for working with a ten-amp current; you most likely don’t have it there. Then we insert both second ends of the probes into the holes of the socket. If it is working, the display will show your voltage value - from 220 to 230 V.
It remains to find out where the phase is. We insert the red probe into one of the holes in the socket, and either hold the black one with our fingers or connect it to the ground, for example, to the central heating radiator (find the place where the paint has fallen off, or clean it off a little). If you hit the phase, then the display will show an effective voltage of about 220 V. And if you hit zero, then you will not see more than 60 V (more often - no more than 30 V).
Determining phase and neutral wires for installing a three-phase socket
This situation can happen in the house with Soviet-made electric stoves. You have five wires, they are the same color, the socket will be asymmetrical, and we need to know exactly where the three phases are, where the zero is, and where the ground is. And this is important - all types of three-phase sockets are asymmetrical.
Here you need a little help. If we have 220 V between one phase and the neutral, then between two phases with a shift of 120 degrees (2π/3) 220 will need to be multiplied by the square root of three, and we will get an effective voltage of 380 V.
So we stock up on colored markers, paper and pen, and start solving the puzzle. We mark the insulation with markers of different colors, look for phases in the same way as in a regular outlet, and write down the results on a piece of paper. It will be relatively simple to distinguish three phases. And then you need to find zero and ground. If the grounding is done correctly, the voltage in it will be zero, and in the neutral there will be several tens of volts.
To control, we measure the voltage between phases. It should be 380 V, and between zero and each phase there should be 220 V.
Another interesting use of a multimeter
The tester can be used to search for hidden wiring in an apartment if it is energized. Usually this can be done without it, if the wiring is carried out according to the rules. In this case, you can navigate by distribution boxes. It’s worse if you got the apartment after a home-grown European-quality renovation, 
when everything unnecessary was simply covered with plaster.
To detect wiring you will need a tester and a KP303 transistor (another field effect one is also possible).
Set the switch to somewhere around 200 kOhm. Insert the probes into the standard position (COM and universal socket) and connect their ends to the source and drain of the transistor. A wire antenna can be wound around the gate. If there is a live wire in the wall, it will create an electromagnetic field, albeit a small one, which will change the internal resistance of the transistor.
If there are no devices
What to do if you have neither a tester nor an indicator screwdriver? How to determine phase and zero without instruments? It turns out that this is possible.
True, before you do this, look at your shield: maybe you won’t have to do anything. If the house is new and the wiring in it is done according to the rules, then the wires can be identified by color. So, zero is made blue, phase is any other color, and grounding is yellow-green. Please also note for circuit breakers(like small switches): they must be in phase. If you unscrew the socket and see the ground in its place, then, most likely, the electrician has not confused the zero with the phase either.
In general, there are household methods for diagnosing wiring, here are some of them:
- using a probe;
- using potatoes;
- using old fuses and pliers;
- "with bare hands.
For obvious reasons, we will not discuss the last three.
Using a probe
A probe is an incandescent lamp in a socket with two wires connected. It is not entirely ethical to recommend this method of verification: the instructions prohibit this method. You should not use it in situations where you do not know how many phases are carried into the room and where everything is turned on and off.
But sometimes you have to use a probe. For example, to distinguish zero from grounding in the absence of sockets (we are considering a situation where sockets are not installed, and three wires stick out from the wall).
Recently, three-wire wiring has been installed in residential premises. If electricians have neglected the color rules, you can distinguish where the zero is and where the ground is using a probe. To do this, you need to turn off one of the zeros in the panel, if you don’t know which one is real, and check the functionality of the future outlet. If you disconnect the zero, then the sockets will not work and the light bulb will not light up - the apartment grounding is not connected to the circuit. And when the ground is disconnected, the light bulb will work.
What not to do
In fact, you already know the basic rules of working with wiring., but I would like to repeat some.
- Do not grab the multimeter probes by their exposed parts. I hope there is no need to explain why.
- Some citizens have a habit of looking for hidden wiring with their bare hands. If you are one of these people, there is no point in dissuading you. But I can give you some advice: do this with the back of your hand. If you get an electric shock, you will bounce off the wall, otherwise you risk not letting go of the exposed wire due to a cramp.
- Sometimes it is possible to measure resistance rather than voltage to indicate zero and phase. Be careful: when operating the tester in this mode, do not short-circuit the phase to ground, as a short circuit may occur.
Installation of internal electrical wiring, independent installation of switches and sockets is often associated with the need to determine the phase and neutral wires. This process is not complicated if you have an idea of the possible methods and rules for working safely with electricity. We have devoted today's article to solving these issues.
First, we should remember a little theory. Everyone knows that for the operation of household electrical appliances, only a little is required - the presence of a voltage of 220 volts in the electrical network. To supply electricity directly to it, two (in modern houses - three) wires are used. The first of them is phase, the second is neutral, and the third is grounding, which protects the user from electric shock in the event of a malfunction of the device’s insulation. Why does an ordinary resident of a high-rise building or a country house need to be able to determine zero and phase?
This knowledge may be needed, for example, when replacing a switch yourself, which is recommended to be installed on a phase wire. This makes it possible to repair the lighting fixture without turning off power to the entire apartment. In addition, installation of sockets for connecting various household appliances, especially those whose operation involves the use of running water, as well as those with metal cases. To connect them, in addition to the traditional phase and zero, you also need to use a third wire - grounding.
Phase search with indicator
These days, there are several ways to determine the phase without involving a professional electrician. The first of them involves the use of a so-called probe, or phase indicator. It is a narrow flat-head screwdriver with a plastic handle, which contains a light indicator - a semiconductor or neon light bulb.
The technology for determining the phase with this device is simple. It is enough just to touch the tip of a screwdriver to the bare wire being examined or immerse it in one of the plug holes of the socket.
If there is voltage on the wire or in the socket, the phase screwdriver indicator will respond with a slight glow. But this will only happen if the device is used correctly - one of the fingers of the hand in which you are holding the device should be pressed against the metal end of the handle. In this case, you close the circuit between the wire and the ground, but you should not be afraid of this, since the voltage is sharply reduced by the screwdriver and will not cause any harm to the user.
Phase determination by tester
The second option for determining a phase wire involves the use of a more advanced device - a tester or multimeter. It allows you to measure various electrical quantities of direct or alternating current. Using the rotary switch, set the device to measure alternating current potential difference. Hold one of the probes of the device tightly in your hand, and with the other, touch the wire under test or push it into the hole in the socket. If the neutral wire is hit, the multimeter display will show a set of zeros or a small voltage, usually not exceeding two volts. When in contact with the phase conductor, the numbers on the device display will be higher.
There is a third option, which can be considered the most unreliable. The fact is that currently, according to the rules for installing intra-house and industrial electrical networks, all wires have a certain color marking depending on their purpose. So, to connect to the phase, a black or brown conductor should be used, to zero - blue or cyan, and the grounding conductor is painted partly yellow and partly green.
Unfortunately, the peculiarities of our country and many irresponsible electricians often lead to ignoring established rules, which can lead to unpleasant consequences. You should not completely rely on the professionalism and skill of the workers who installed electrical networks in your home. It is better to use the above methods. In addition, until 2011, the marking of wires was different from the current one. So, a wire painted black was used for grounding.
Having identified the phase wire and carefully bending it, we move on to determining the neutral wire and ground wire. The peculiarity of connecting them to the indoor panel does not involve inserting the grounding conductor directly into the housing of the input device. If you have access to the shield, you can clarify the color of the conductor passing by the machines installed in it and determine its color.
In the event that access to the panel is not possible or if you want to play it safe, you can use the simplest device that any electrician always has - a light bulb with a socket and wires connected to it. By connecting or simply touching one of the wires extending from the light bulb to the phase wire, connect the second wire in turn to the remaining two intended for detection. When in contact with zero, the light should light up. Contact with a ground wire usually does not have this effect.
As a counterbalance to the simplest device, you can use the multimeter already described. Measure the potential difference (voltage) between the known phase and other wires one by one. The value of the zero-phase pair should significantly exceed the value of the phase-ground pair.
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Very few people understand the essence of electricity. Concepts such as “electric current”, “voltage”, “phase” and “zero” are a dark forest for most, although we encounter them every day. Let's get a grain of useful knowledge and figure out what phase and zero are in electricity. To teach electricity from scratch, we need to understand the fundamental concepts. We are primarily interested in electric current and electric charge.
Electric current and electric charge
Electric charge is a physical scalar quantity that determines the ability of bodies to be a source of electromagnetic fields. The carrier of the smallest or elementary electric charge is the electron. Its charge is approximately -1.6 to 10 to the minus nineteenth power of Coulomb.
Electron charge is the minimum electrical charge (quantum, portion of charge) that occurs in nature in free, long-lived particles.
Charges are conventionally divided into positive and negative. For example, if we rub an ebonite stick on wool, it will acquire a negative electrical charge (excess electrons that were captured by the atoms of the stick upon contact with the wool).
Static electricity on the hair has the same nature, only in this case the charge is positive (the hair loses electrons).
The main type of alternating current is sinusoidal current . This is a current that first increases in one direction, reaches a maximum (amplitude), begins to decrease, at some point becomes equal to zero and increases again, but in a different direction.
Directly about the mysterious phase and zero
We have all heard about phase, three phases, zero and grounding.
The simplest case of an electrical circuit is single phase circuit . It only has three wires. Through one of the wires the current flows to the consumer (let it be an iron or hair dryer), and through the other it returns back. The third wire in a single-phase network is earth (or grounding).
The ground wire does not carry a load, but serves as a fuse. In case something gets out of control, grounding helps prevent electric shock. This wire carries excess electricity or “drains” into the ground.
The wire through which current flows to the device is called phase , and the wire through which the current returns is zero.
So, why do we need zero in electricity? Yes, for the same thing as the phase! The current flows through the phase wire to the consumer, and through the neutral wire it is discharged in the opposite direction. The network through which alternating current is distributed is three-phase. It consists of three phase wires and one return.
It is through this network that the current flows to our apartments. Approaching directly to the consumer (apartments), the current is divided into phases, and each phase is given a zero. The frequency of changing the direction of current in the CIS countries is 50 Hz.
Different countries have different network voltage and frequency standards. For example, a typical household outlet in the United States supplies alternating current with a voltage of 100-127 Volts and a frequency of 60 Hertz.
The phase and neutral wires should not be confused. Otherwise, you can cause a short circuit in the circuit. To prevent this from happening and to prevent you from confusing anything, the wires have acquired different colors.
What color are phase and zero indicated in electricity? Zero is usually blue or cyan, and phase is white, black or brown. The ground wire also has its own color - yellow-green.
So, today we learned what the concepts of “phase” and “zero” mean in electricity. We will be simply happy if this information was new and interesting for someone. Now, when you hear something about electricity, phase, zero and ground, you will already know what we are talking about. Finally, we remind you that if you suddenly need to calculate a three-phase AC circuit, you can safely contact student service. With the help of our specialists, even the wildest and most difficult task will be up to you.
Older houses still have two-terminal sockets. In this case, you can simply check the device using a phase tester. You need to take a tester (indicator screwdriver) and insert it into any socket of the socket. Place your finger on the metal cap on the handle. When the neon light comes on, it will show the “phase”. The second terminal should be zero. But this doesn't always happen.
Coloring, indicator screwdriver or multimeter
The easiest way to check grounding is to pay attention to the color of the insulation.
The ground wire should be yellow with green stripes, and the neutral wire should be light blue. But this requirement is not always met.
In some older houses, electrical wiring is done with separate conductors. If the owner had to make changes to the distribution box, then it is quite possible that only two phase or neutral conductors come to the outlet. Therefore, it is necessary to check both sockets. When you touch zero, the neon light on the voltage indicator should not light up.
Modern buildings use three-terminal sockets. It receives phase, neutral and grounding conductors. Contacts must correspond to their functional purpose.
Otherwise, accidents may occur when using the washing machine or boiler. Therefore, questions arise about how to check the grounding in an outlet in order to avoid installation errors and use your appliances calmly and without fear.
The indicator screwdriver is guaranteed to determine only the phase. She cannot distinguish zero from ground. A small amount of interference is not enough to light up a neon light bulb. Then we will find the phase and zero with a multimeter or voltmeter.
Multimeter reading options
Any device, indicator screwdriver or tester, must be checked for functionality and only then used. The insulation must be intact, without cracks or tears. The tip of the probe should be separated from the holder by a dielectric washer to protect it from accidental touches.
The body of the measuring device must be intact. Before measurement, the plugs are inserted into the sockets of the device, which correspond to the measurement of alternating voltage. After making sure that the device is working properly, you need to switch it to the AC voltage measurement mode with a scale of 750 V. This is necessary in case of measuring line voltage when two phases were connected to the socket by mistake.
This method of testing an outlet is suitable if the tester is confident that the ground contact is indeed ground. Then the task is to find zero. One probe touches the ground contact, and the second is inserted into any socket of the socket. The following options may be available:
- the device shows 220 V, which means the contact is phase;
- if 0 or a few volts, then this is the neutral wire.
If the multimeter relative to the ground shows 0 volts at the socket contacts, then they are all shorted to each other somewhere.
A reading of a few volts says it's zero. But how to determine zero when the house is supplied with electricity through a TN - C power supply system and re-grounded next to the building? After all, in this case, the device readings will be zero.
To make sure that this conductor is neutral, you need to disconnect the grounding in the entrance electrical panel. Then measure the voltage between the socket contacts of the socket. The device shows 220 V - the zero of the socket has been found. The multimeter does not show anything - grounding has been detected.
If the device reads 220 V on each contact relative to the grounding one, you need to make an additional measurement between the two sockets of the socket. The device shows 0, which means one phase is connected to both sockets. Otherwise, the device will show 380 V, which means there are two phases on the outlet.
Determining the purpose of conductors
When working with electrical wiring, be sure to double-check the assignment of the outlet conductors. There is no guarantee that the electrician or the previous owner of the premises did not mix up the wires. Therefore, if the tester shows a voltage of 220 V relative to a terminal that appears to be grounding, this does not mean that it is such.
This means that one of the contacts is a phase, and the second is a zero or ground. If the tester shows 0, then there is a neutral and ground conductor. It is impossible to understand exactly what is what.
If you are not 100% sure of the purpose of the grounding terminal, the sockets operate differently. First you need to exclude the presence of two phases. Check the voltage between all contacts. If the device does not show 380 V anywhere, but only 220, it means that one phase conductor is connected to the socket. Now you need to start looking for grounding.
First you need to disconnect the grounding conductor in the floor panel. It is connected through a bolted connection to a special bus welded to the body of the electrical panel.
After this, the voltage between the socket connectors is measured.
If the device shows 220 V, then the socket contacts are the phase and neutral wires, and the ground terminal really is. Now knowing exactly where the ground is, you can determine the remaining connectors, but first you need to reconnect the “ground” to the ground bus.
We measure the voltage relative to the ground terminal. One socket shows 220 V - this is a phase, the second - 0, then this is a zero contact.
If the multimeter shows 0, then the ground has been connected to one of the socket contacts, and the second is neutral or phase. Now we take measurements between the socket and ground contact of the socket. If there is no voltage, then this socket is the real ground.
The readings at 220 V speak for themselves.
Checking the electrical wiring
Checking the grounding of electrical wiring occurs in much the same way as with a socket. To measure network parameters, you will need a three-phase or single-phase multimeter, as well as an indicator screwdriver.
When repairing electrical wiring and connecting a washing machine, electric heater, stove, oven and other appliances, it is necessary to change cables and connections in junction boxes. In this case, you need to find out the purpose of each conductor, you need to check the presence of grounding in the right places.
First you need to turn off the input circuit breaker on the floor switchboard. Then open the junction box. Separate the wires in different directions so that they do not touch each other, and remove the insulation at the connection points.
After this, the input machine is turned on. Use an indicator screwdriver to locate the phase wires. They can belong to one, two or three phases.
If you have a three-phase multimeter, you can immediately check the status of the network. Using a single-phase multimeter, determining the number of phases takes longer. For example, if the voltage between three wires is 0 volts, then these are phase wires from one phase.
If the device shows a voltage between two wires of 380 V, and between the other two wires 0, then there are two phases. At a voltage of 380 V between all conductors, we can talk about the presence of three phases.
Determination of grounding occurs as in the case of a socket, only here there will be more wires. First, the grounding wire in the floor panel is disconnected. Then one probe of the multimeter clings to the phase wire, and the second to a conductor of an as yet unknown purpose.
If the device shows a voltage of 220 V, this wire is zero; if it is zero, then this is ground.
Next, the input machine is turned off. The ground wire is connected. When the check is completed, all elements of the electrical network are correctly connected, the connections are isolated, and the box is closed. The circuit breaker turns on.
The need to solve such a problem may arise when installing a socket, when unmarked conductors approach it. In this case, before installing the outlet, it must be determined which wire is responsible for what. Let's look at how to determine phase, zero and ground using an indicator screwdriver, a multimeter, and also improvised means.
Using an indicator screwdriver
The sequence of actions depends on what kind of wiring system is installed in the room. Let's consider the rules for determining the phase and neutral wires in different cases.
Two-wire network
This wiring option is found in old houses. According to modern terminology, this system is designated TN-C. Its essence lies in the fact that the neutral working wire, grounded at the supply substation, combines the role of a protective grounding wire (PEN). The IT system also contains only a phase and working neutral conductor, but it is not used in ordinary residential and industrial premises. In a two-wire network, there is simply no separate ground wire, that is, there is only phase and neutral. It is very simple to identify them: we touch the indicator sequentially to each of the current-carrying wires, the phase causes the indicator lamp to light up, as shown in the photo below:
The system is outdated. The plug of any modern electrical appliance has three terminals. The wiring must be three-wire, with the exception of the lighting group.
Three-wire network
In this option, three wires enter the house or apartment. There are several types of such networks. In the system, the working zero and protective grounding come separately from the supply substation, where both are connected to the working ground. With this type of wiring, determining the purpose of the wires can be done as follows:
- in the panel or in the distribution box, use an indicator to determine the wire on which the phase is present;
- the remaining two are the working and protective zero (ground), we disconnect one wire from them on the panel;
- If you disconnect the working zero, all electrical equipment in the apartment will stop working, which means that the remaining conductor is the ground, or protective grounding.
Now it remains to determine in the socket among the three wires which of them has phase, zero and ground. If you cannot find the insulation by color, determining their functions can be done using improvised means, without instruments. To do this, you need to take a socket with a screwed-in lamp and wires brought out. We carry out the definition as follows. With one conductor from the socket we touch the phase wire (the phase has already been found using the indicator), with the second we touch the remaining two in turn. If the operating zero is turned off on the panel, the lamp will light up only when connected to protective grounding, and vice versa.
The video below clearly shows how to determine phase, zero and ground using an indicator screwdriver:
Another variation of the TN system is wiring. In this case, the neutral wire is split into a working zero and protective grounding at the entrance to the house. Here, to determine the purpose of the conductors, you can apply the sequence of actions described for the TN-S system. An additional opportunity is added, by examining the place of separation of the PEN, to determine where the working and protective zero (ground) are along the cross-section of the core in the wire.
If the grounding is carried out according to the system, the object (private house) has its own grounding device, from which protective grounding is routed. Under these conditions, as a rule, phase, neutral and ground can be determined by tracking the grounding conductor along the route of its installation.
Determination with a multimeter or tester
Let's start with the fact that it is best to determine the phase using a screwdriver combined with an indicator. We will proceed from the fact that if the household has a multimeter, there will certainly be an indicator. As a last resort, you can do the following. In some cases, determining the voltage between the wire and the heating or water supply pipe using a multimeter can help. Unfortunately, the result here is not always predictable. Most often, the voltage between the phase and the heating system is close to 220 V, in any case, it should be higher than between the same heating and zero. The picture may change, for example, if a thieving neighbor uses heating pipes as a working ground.
In three-wire circuits, the multimeter will show the operating voltage between the conductor to which the phase is applied and either of the other two. Determining which zero is working and which is ground can be done using the method outlined above, that is, by disconnecting one of the incoming zeros on the panel and using a test lamp.
What else is important to know?
Sometimes determining the purpose of current-carrying conductors can be facilitated by knowing their generally accepted color markings:
- Zero can be marked with the Latin letter N. The generally accepted color of insulation is blue or blue. Another option for insulation coloring is a white stripe on a blue background.
- The land is marked with the Latin letter PE. In a grounding system that combines the functions of protective and working zero, it is designated PEN. The color of the insulation used is yellow, with one or two stripes of a bright green tint.
- The phase can be designated by the Latin letter L or marked as a phase of a three-phase electrical network, that is, A, B or C. The color of the insulation can be arbitrary, but not the same as those that indicate earth (protective grounding) or neutral conductor. In most cases, it is red, brown or black.
It is also useful to know the rules for installing electrical wiring. This can also help determine where phase, neutral and ground are. The phase must always come to the distribution panel or fuse. The neutral core can be mounted on a specially designed busbar that has several terminals. In metal shields and terminal boxes of the old type, the neutral or ground was fastened under the nut with a bolt welded to the box body. These rules can make it easier to determine the functions of visiting guides. You can find out more about this in our separate article.
Now you know how to determine phase, zero and ground with a multimeter or an indicator screwdriver. We hope the recommendations provided helped you resolve the issue yourself!
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