How to determine phase and zero - step-by-step instructions for determining and choosing the optimal tool. How to determine phase and zero with an indicator screwdriver or multimeter How to find the phase in a junction box

In most modern cables, the conductors have insulation of different colors. These colors have a certain meaning and are chosen for a reason. What is color marking of wires and how to use it to determine where the zero and ground are, and where the phase is, and we will talk further.

In electrical engineering, it is customary to distinguish wires by color. This makes the work much easier and faster: you see a set of wires of different colors and, based on the color, you can guess which one is intended for what. But, if the wiring is not factory-made and you did not do it, before starting work you should definitely check whether the colors correspond to the intended purpose.

To do this, take a multimeter or tester, check the presence of voltage on each conductor, its magnitude and polarity (this is when checking the power supply network) or simply call where and where the wires come from and whether the color changes “along the way.” So knowing the color coding of wires is one of the essential skills of a home craftsman.

Ground wire color coding

According to the latest rules, wiring in a house or apartment must be grounded. In recent years, all household and construction equipment have been produced with a grounding wire. Moreover, the factory warranty is maintained only if the power supply is supplied with a working grounding.

To avoid confusion, it is customary to use a yellow-green color for the ground wire. The hard solid wire has a green base color with a yellow stripe, while the soft stranded wire has a yellow base color with a green longitudinal stripe. Occasionally there may be specimens with horizontal stripes or just green, but this is not standard.

Ground wire color - single-core and stranded

Sometimes the cable only has a bright green or yellow wire. In this case, they are used as “earthen”. On diagrams, “ground” is usually drawn in green. On the equipment, the corresponding contacts are signed in Latin letters PE or in the Russian version they write “earth”. A graphic image is often added to the inscriptions (in the figure below).

In some cases, in the diagrams, the ground bus and the connection to it are indicated in green

Neutral color

Another conductor that is highlighted in a certain color is neutral or “zero”. The color blue is allocated for it (bright blue or dark blue, occasionally blue). On color diagrams, this circuit is also drawn in blue and signed with the Latin letter N. The contacts to which the neutral must be connected are also signed.

Neutral color - blue or light blue

Cables with flexible stranded conductors tend to use lighter shades, while solid solid conductors have a sheath of darker, richer tones.

Coloring phase

With phase conductors it is somewhat more complicated. They are painted in different colors. Already used ones - green, yellow and blue - are excluded, and all others can be present. When working with these wires, you need to be especially careful and attentive, because they are the ones where voltage is present.

Color marking of wires: what color is the phase - possible options

So, the most common color markings for phase wires are red, white and black. There may also be brown, turquoise orange, pink, purple, gray.

On diagrams and terminals, phase wires are signed with the Latin letter L; in multiphase networks, the phase number is next to it (L1, L2, L3). On cables with several phases, they have different colors. This makes wiring easier.

How to determine if the wires are connected correctly

When trying to install an additional outlet, connect a chandelier, or household appliances, you need to know which wire is phase, which is neutral, and which is ground. If the connection is incorrect, the equipment will fail, and careless touching of live wires can end sadly.

You need to make sure that the colors of the wires - ground, phase, zero - match their wiring

The easiest way to navigate is by color coding of the wires. But things are not always simple. Firstly, in old houses the wiring is usually monochromatic - two or three white or black wires stick out. In this case, you need to understand it specifically, and then hang tags or leave colored marks. Secondly, even if the conductors in the cable are painted in different colors, and you can visually find the neutral and ground, you need to check the correctness of your assumptions. It happens that during installation the colors are mixed up. Therefore, first we double-check the correctness of the assumptions, then we begin work.

To check, you will need special tools or measuring instruments:

• indicator screwdriver;
• multimeter or tester.

You can find the phase wire using an indicator screwdriver; to determine zero and neutral, you will need a tester or multimeter.

Checking with indicator

Indicator screwdrivers come in several types. There are models on which the LED lights up when a metal part touches live parts. In other models, checking requires an additional button press. In any case, when voltage is present, the LED lights up.

Using an indicator screwdriver you can find the phases. We touch the exposed conductor with the metal part (press the button if necessary) and see if the LED lights up. Lit - this is a phase. Does not light - neutral or ground.

We work carefully, with one hand. Second, we don’t touch walls or metal objects (pipes, for example). If the wires in the cable you are testing are long and flexible, you can hold the insulation with your other hand (stay away from bare ends).

Checking with a multimeter or tester

We set the scale on the device, which is slightly higher than the expected voltage in the network, and connect the probes. If we call a household single-phase 220V network, set the switch to the 250V position. With one probe we touch the exposed part of the phase wire, with the second - to the supposed neutral (blue). If at the same time the arrow on the device deviates (remember its position) or a number close to 220 V lights up on the indicator. We perform the same operation with the second conductor - which is identified by its color as “ground”. If everything is correct, the readings of the device should be lower - less than those that were before.

If there is no color marking of the wires, you will have to go through all the pairs, determining the purpose of the conductors according to the indications. We use the same rule: when testing a phase-ground pair, the readings are lower than when testing a phase-zero pair.

When installing electrical wiring of premises, connecting sockets, switches and light sources, the question of correctly determining the purpose of the wires always arises. The apartments have single-phase wiring, the wires in it are assigned as phase and neutral. Therefore, the question of how to determine the phase and zero of the electrical wiring of premises is a priority for both minor and major repairs.

Principles of electrical networks in an apartment

Electrical wiring entering an apartment building is most often three-phase. This means that she has three line voltages, shifted relative to each other by 120 degrees, and the neutral wire, relative to which voltage is applied to each of the phases. The voltage between the neutral wire and the phase wire (phase voltage) is 220 V. The potential difference between the two phase wires (linear) is √3 times greater and equals 380 V.

Each apartment has one phase wire and one neutral wire. In houses with old electrical wiring this was limited. The new standards also require a grounding line. Therefore, there is a difference between two-wire and three-wire residential electrical networks.

The most difficult and dangerous place in the electrical wiring of premises is the panel at the entrance to the house. It distributes phase wires to apartments and installs automatic circuit breakers that cut off the power supply when the current is exceeded (possible short circuit). The machines are distributed into groups corresponding to the power consumption of electrical appliances.

When repairing or installing wiring at home, you need to know the rules for connecting sockets and switches. The power wires are connected to the socket in any order, and the grounding conductor is connected to the brass busbar. The switch is installed in a phase line break, and zero comes directly to the lighting equipment through the distribution box.

This system ensures safety when working with electricity. Electrical household appliances must be connected in accordance with their installation instructions and wire markings, as this will ensure safety of use.

Tools for work

For safe and proper work, you need to select a set of devices and tools. It is used to search and prepare wiring.

1. Multimeter (analog or digital);
2. Indicator screwdriver;
3. Pliers;
4. Stationery knife (any sharp);
5. Insulating tape.

A knife is used to strip contacts, a multimeter and a screwdriver are used to determine the phase, and electrical tape is used to insulate and indicate contacts. For safety, you should also use rubber insulation on the handles of the pliers and non-conductive shoes.

How to distinguish by appearance

You can find out which wires run in a particular apartment by their appearance. You need to know how to determine phase and zero without instruments if both of the indicating instruments are missing. You can distinguish wires by the color of their insulation. But this method is only applicable when electrical wiring is carried out in compliance with all rules for its installation. The yellow-green color of the insulation indicates that this conductor is a grounding conductor. Light blue or dark blue indicates that the wire is neutral, while brown, white or black indicates the phase line.

But even if you are sure of the color of the wiring, it is better to double-check it with an indicator screwdriver or a multimeter, since incorrect connection can result in electrical injury.

Determination of zero and phase

In order not to confuse zero and phase on the switch, or when carrying out other electrical work, you need to use special phase-indicating tools or probes. The easiest way is to use an indicator screwdriver.

Indicator screwdriver

To know how to determine phase and zero with an indicator screwdriver, you need to understand the principle of its operation. It is configured in such a way that the internal neon lamp lights up when a potential difference occurs between the working contact of the screwdriver and the metal terminal at the end of its handle. To correctly indicate the phase with a screwdriver, you need to follow simple steps:

1. Turn off the power supply automatically;
2. Strip the ends of the tested conductors and separate them to a safe distance;
3. Apply power to the electrical network;
4. Touch the tip of the probe to the end of the conductor being tested;
5. Press the metal terminal at the end of the screwdriver handle with your finger; touching the screwdriver tip during operation is prohibited;
6. If the phase is being tested, the light inside the probe should light up.

In addition to the usual indicator, there is a screwdriver for dialing. It differs in that it contains batteries and indicates the phase without touching its opposite metal end with your finger. Also there is an indicator screwdriver with hidden wiring detection function. It can determine where the apartment's electrical network runs inside the wall. It uses a non-contact method of detection by the electromagnetic field arising around the conductor.

To use a screwdriver, you need to remove the cap from it, which will bring it into working condition and place it in the place where the electrical wiring is supposed to be located. When a wire is present in the screwdriver handle, the indicator lamp will light up.

Warning lamp

Another way to determine phase and zero without instruments is to make a test lamp. Such an indicator is created simply: you need to solder wires of sufficient length to the terminals of the socket and screw an incandescent or neon lamp into it. One of the terminals of such a phase detector is connected to the battery, and the second you can check the presence of supply voltage in the network. To do this, touch the test conductor with the stripped end of the wire. If this is a phase, the lamp should flash. This method is very dangerous, so it should be used only in exceptional cases, moreover, it is prohibited by the Rules for the Safe Operation of Electrical Installations.

Multimeter measurement

In the absence of an indicator screwdriver and for more accurate measurements of the network supply voltage, a multimeter is used, also called a tester. With it you can identify phase, neutral and grounding conductors in a three-wire network. The fact is that an indicator screwdriver can only show large differences in potentials, that is, it only shows the phase. The multimeter works with different signals: high and low levels, positive and negative. Its task is to show the parameters of the electrical circuit.

To find out how to find phase and zero with a multimeter, as well as the ground wire, you need to properly configure and connect this measuring device. This is done like this:

1. Install the black probe of the multimeter into the socket marked COM, and the red probe into the socket marked U, Ω, Hz;
2. Use the knob on the front panel to select the AC current measurement mode, the measurement limit is greater than 220 V.

After setting, you need to simultaneously touch the two ends of the probes to the two terminals being tested. Value on the multimeter screen:

• More than 100 V - phase and zero are found;
• More than 160 V - phase and ground line found;
• Less than 70 V is zero and ground.

By testing all three lines in this way, you can confidently determine where the desired potential is present.

An easier way to determine the phase with a multimeter is to use a probe installed in the U, Ω, Hz hole to touch all ends of the electrical network one by one. In case of contact with phase conductor, the multimeter will show a voltage of 8 -15 V. In other cases, the readings will be at the level of 0 - 3 volts. Use the multimeter with caution, using insulated shoes and never touch the ends of the probes without insulation with your hands.

When doing any work with electrical wiring, you must follow safety precautions, that is, de-energize the room when installing and repairing electrical equipment, and during the performance test with the machine turned on, provide yourself with reliable insulation protection.

Very often, when performing repair or installation work related to electricity in an apartment, house, garage or country house, it becomes necessary to find zero and phase. This is necessary for the correct connection of sockets, switches, and lighting fixtures. Most people, even if they do not have special technical education, imagine that there are special indicators for this. We will briefly look at this method, and also tell you about another device that no professional electrician can do without. Let's talk about how to determine phase and zero with a multimeter.

Concepts of zero and phase

Before determining phase zero, it would be good to remember a little physics and figure out what these concepts are and why they are found in a socket.

All electrical networks (both domestic and industrial) are divided into two types - with direct and alternating current. From school we remember that current is the movement of electrons in a certain order. With constant current, electrons move in one direction. With alternating current, this direction is constantly changing.

We are more interested in the variable network, which consists of two parts:

• The working phase (as a rule, it is simply called the “phase”). Operating voltage is supplied to it.
• An empty phase, called “zero” in electricity. It is necessary to create a closed network for connecting and operating electrical appliances, and also serves to ground the network.

When we connect devices to a single-phase network, it is not particularly important where exactly the empty or working phase is. But when we install electrical wiring in an apartment and connect it to the general house network, it is necessary to know this.

The difference between zero and phase in the video:

The simplest ways

There are several ways to find phase and zero. Let's look at them briefly.

According to the color of the cores

The simplest, but at the same time the most unreliable way, is to determine the phase and zero by the colors of the insulating shells of the conductors. As a rule, the phase conductor is black, brown, gray or white, and the neutral is made blue or blue. To keep you informed, there are also green or yellow-green conductors, which is how protective grounding conductors are designated.

In this case, no instruments are needed; you looked at the color of the wire and determined whether it was phase or zero.

But why is this method the most unreliable? And there is no guarantee that during installation the electricians followed the color coding of the cores and did not mix up anything.

Color coding of wires in the following video:

Indicator screwdriver

A more accurate method is to use an indicator screwdriver. It consists of a non-conductive housing and a built-in resistor with an indicator, which is an ordinary neon light bulb.

For example, when connecting a switch, the main thing is not to confuse zero with phase, since this switching device only works to break the phase. Checking with an indicator screwdriver is as follows:

1. Turn off the common entrance machine for the apartment.
2. Using a knife, strip the cores being tested from the insulating layer by 1 cm. Place them apart at a safe distance to completely eliminate the possibility of contact.
3. Apply voltage by turning on the input circuit breaker.
4. Use the tip of the screwdriver to touch the exposed conductors. If the indicator window lights up, it means the wire corresponds to the phase wire. The absence of a glow indicates that the wire found is zero.
5. Mark the required core with a marker or a piece of electrical tape, then turn off the general circuit breaker again and connect the switching device.

More complex and accurate tests are performed using a multimeter.

Finding the phase using an indicator screwdriver and a multimeter in the video:

Multimeter. What kind of device is this?

A multimeter (electricians also call it a tester) is a combined device for electrical measurements that combines many functions, the main ones of which are ohmmeter, ammeter, and voltmeter.

These devices are different:

• analog;
• digital;
• portable lungs for some basic measurements;
• complex stationary with a large number of possibilities.

Using a multimeter, you can not only determine ground, zero or phase, but also measure current, voltage, resistance in a section of the circuit, and check the electrical circuit for integrity.

The device consists of a display (or screen) and a switch that can be set to different positions (there are eight sectors around it). At the very top (in the center) there is an “OFF” sector; when the switch is set to this position, it means the device is turned off. To perform voltage measurements, you will need to set the switch to the “ACV” (for alternating voltage) and “DCV” (for direct voltage) sectors.

The multimeter kit includes two more test leads - black and red. The black probe is connected to the lower socket marked “COM”; this connection is permanent and is used when carrying out any measurements. Depending on the measurements, the red probe is inserted into the middle or upper socket.

How to use the device?

Above, we looked at how to find a phase wire using an indicator screwdriver, but it will not be possible to distinguish between zero and ground using such a tool. Then let's learn how to test the wires with a multimeter.

The preparatory stage looks exactly the same as for working with an indicator screwdriver. When the voltage is turned off, strip the ends of the wires and be sure to separate them so as not to provoke accidental contact and a short circuit. Apply voltage, now all further work will be with a multimeter:

• Select on the device the measuring limit of alternating voltage above 220 V. As a rule, there is a mark with a value of 750 V in the “ACV” mode, set the switch to this position.
• The device has three sockets into which test leads are inserted. Let's find among them the one marked with the letter “V” (that is, for measuring voltage). Insert the dipstick into it.

• Touch the probe to the stripped conductors and look at the device screen. If you see a small voltage value (up to 20 V), it means you are touching a phase wire. In the case where there is no reading on the screen, you found zero with a multimeter.

To determine the “ground”, clean a small area on any metal element of home communications (this could be water or heating pipes, radiators).

In this case, we will use two sockets “COM” and “V”, insert the measuring probes into them. Set the device to “ACV” mode, at a value of 200 V.

We have three wires, among them we need to find phase, zero and ground. Touch the stripped area on the pipe or battery with one probe, and touch the conductor with the other. If the screen displays a reading of about 150-220 V, it means you have found a phase wire. For the neutral wire, with similar measurements, the reading fluctuates between 5-10 V; when you touch the ground, nothing will be displayed on the screen.

Mark each core with a marker or electrical tape, and to make sure the measurements taken are correct, now take measurements relative to each other.

Touch the phase and neutral conductors with two probes, a figure within 220 V should appear on the screen. The phase and ground will give a slightly lower reading. And if you touch zero and ground, the screen will show a value from 1 to 10 V.

A few rules for using a multimeter

Before determining phase and zero with a multimeter, familiarize yourself with several rules that must be followed when working with the device:

• Never use the multimeter in a damp environment.
• Do not use faulty test leads.
• While taking measurements, do not change the measuring limits and do not rearrange the switch position.
• Do not measure parameters whose value is higher than the upper measuring limit of the device.

How to measure voltage with a multimeter - in the following video:

Pay attention to an important nuance in using a multimeter. The rotary switch should always be initially set to the maximum position to avoid damage to the electronic device. And in the future, if the readings are lower, the switch is moved to lower levels to obtain the most accurate measurements.

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!

You probably don't know:

I am an electrician with extensive experience. I have been working with electricity for thirty years. It happens that people ask me how to distinguish phase from zero in the absence of instruments. The question is not simple. Now I will try to tell everything I know about it.

Phase and zero. What is the difference?

Strictly speaking, the phase and neutral conductors do not differ much. In alternating current circuits, the current changes direction fifty times in one second. How can you tell what function this or that wire performs? The only difference between the phase and neutral conductors is that the “zero” (zero conductor) is connected to the Earth. Exactly. An electrical circuit is buried in the ground and at the substation one of the transformer terminals is connected to this circuit. Such an electrical circuit is called a network with a solidly grounded neutral. In such a circuit, the neutral wire is at ground potential. You and I also have the potential of the earth. Therefore, when we touch a grounded conductor, we do not receive an electric shock.

Now that you have an idea of ​​“zero” let’s move on to “phase”. The voltage of the phase conductor changes its polarity relative to “zero” 50 times per second. In a phase-zero circuit, the current also changes its direction 50 times per second. If current flows through a person's body, it will end very badly. Therefore, exercise extreme caution.

In fact, there is not a single device that “feels” the “phase”. All instruments record whether current flows from a given wire to ground or not. Even a single-pole probe, which is often used to detect phase wires, works on this principle. Now we will not go into details of the operation of such probes.

Looking for a “phase”

If we need to distinguish phase from zero, then we must create an electrical circuit with the help of which we will unambiguously know whether current flows from the wire we have chosen to ground or not. Several devices come to mind that can help us:

• bulb,
• one more light bulb, neon,
• Light-emitting diode.

There is another way, which is very unreliable. Recently, wires began to be marked according to the color of the insulation. The neutral wire is blue, the ground wire insulation is yellow-green. But who can guarantee that the electrician made the connection according to the rules or that he was not colorblind?

"Grandfather's" way

For decades, electricians have used the light bulb as a measuring device. Incandescent lamp, socket and two wires. This device was called a “control”. To determine the “phase”, one terminal of the control touched a wire, the other a metal object, which is obviously connected to the ground. This could be the housing of a lighting panel or other distribution device. According to the rules, they are all grounded. Unfortunately, finding a grounded object is not always possible. I have come across advice when it was suggested to use heating or water pipes as land. I absolutely do not recommend it! You can give an electric shock to an unsuspecting person. Take my word for it. If you are in your own home or at the dacha, the role of “earth” can be played by a metal pin driven into the ground, or other metal objects that have a reliable connection to the ground.

The control is prohibited from being used because it can be connected to two phase wires. In this case, the voltage on it will be 1.7 times higher than the mains voltage, the light bulb may simply explode. If you are sure that one of the control wires is connected to ground, then there is no need to fear an explosion.

There are safer devices. By chance you may have an indicator lamp from an old communication equipment at hand. These light bulbs, “inca”, begin to glow if one of the terminals is connected to a phase wire. Single-pole probes are equipped with similar lamps.

A more serious device would be a combination of an LED and a current-limiting resistor connected in series with it. It is clear that this case is for people who are friends with a soldering iron, for example radio amateurs. The resistor should have a resistance of several tens of kiloohms.

To avoid electric shock, you need to follow one simple rule. During measurements, do not touch wires or metal with any part of your body.