The ability to understand wiring is the most important skill for any home master. In order to repair and replace wiring, repair home electrical appliances, install sockets and switches, it is necessary to determine the phase and zero. You can find the phase and neutral wires in a single-phase or three-phase network in different ways - visually, using special tools. The choice of method depends on the conductor itself and the conditions for testing.
Color Marking
The easiest way to find the right core is to determine the color of insulation. The color of the wires in the wiring and its designation are regulated by state standards. According to the international standard IEC, manufacturers are required to paint the insulation of each core in their own color. In a single-phase network, the color of the wires in the electrical wiring 220 V is as follows: zero should have a blue or blue color, the earth should be yellow-green (sometimes in the form of a strip), the phase may have any other shade. Typically a brown color is used for the phase core. In a two-wire wire, zero is blue, the phase of a different color. The color of the phase in the multiphase network depends on the manufacturer. Usually it is black, brown, red.
This method of determination is not reliable. Not all manufacturers adhere to established requirements, so the cores can be designated differently. It is especially dangerous to use a search by color coding in houses of an old building - there all the cores were white.
Using an indicator screwdriver
This is one of the most common household phase search methods. An indicator screwdriver can be bought at any construction or electrical installation store for little money. It is a classic flat-shaped screwdriver with an indicator on the handle. The case is made of dielectric for safe work of the master.
The tip of the indicator screwdriver is a contact tip. It is not recommended to use such a device in complex repair work. This will shorten the life of the product, due to which it will be impossible to determine the phase wire.
To find the phase, the indicator sting needs to touch the stripped conductor. Then you need to touch the contact pad with your finger. If the light on the screwdriver lights up, the sting touched the phase. Otherwise, zero or ground. If both conductors show a phase, a serious malfunction can be judged.
The described algorithm is suitable for simple screwdrivers. On sale you can find advanced products that allow you to ring the chain and carry out other operations. Outwardly, they look like ordinary indicator screwdrivers, but instead of a neon bulb, an LED is used. The method of determination in this case will vary slightly. The master does not need to touch the contact pad - just attach a screwdriver to the core.
Multimeter Detection
Any home electrician should have a multimeter in his toolkit. This is a universal tester that allows you to check the operability of electronic components, measure voltage and current strength, as well as ring the circuit. An inexpensive and high-quality device with the simplest functionality can be bought for 300-500 rubles. Professional electricians use more expensive appliances with additional options and minimal error.
Multimeters are of two types according to the way of work - electronic and analog. Pointer or analogue is a simple device with an arrow. Digital multi-tester shows numbers in numbers. The determination method for both types of devices is the same.
Rules for working with a multimeter:
- Do not take measurements with high humidity.
- Faulty probes are not used.
- The measuring range must exceed the measured value.
- When measuring, it is forbidden to twist the knobs or set other limits.
Currently, it is actively using digital multimeters. The verification algorithm may vary.
Three-wire wiring without marking
You can select an exclusion method. To find the phase, the multimeter should be assembled and put the probes on the left and right - black in the COM connector, red - in the connector for measuring voltage. The switch should be placed in the AC sector V ~ or ACV. The arrow selects the voltage boundary - it must exceed the network voltage. On the tester, you can see the values of 500, 600, 750 W, depending on the model.
Then, voltage measurements are taken between the stripped conductors. There may be 3 options:
- Between zero and phase there should be a voltage close to the mains 220 V.
- There can also be 220 V. between phase and ground. In case of line protection by an RCD system, the machine may trip. If an RCD is absent or there is a minimum leakage current, the displayed voltage will be within the nominal error.
- Between zero and ground, the voltage is zero.
After taking the measurements, the tester turns off, the ends of the conductor are isolated and marked on them. It can be done with colored tape or patch with the appropriate inscriptions.
Checking the contact in the socket by directly measuring the voltage
The multimeter is prepared, a control measurement of the voltage in the outlet is performed. This allows you to make sure that there are no breaks on the line and the operability of the device itself. If the numbers received on the display are correct, the connection is completed correctly.
The red probe should touch the tested conductor. In the case of checking the outlet, the probe is placed in the socket. If the stripped end of the cable is checked, it is recommended to connect through a crocodile clip. The second probe touches the fingers. The display reads the readings. If the black probe is set to zero, the voltage will be zero or close to zero. When it enters the phase, the voltage will reach tens or hundreds of volts.
Touching the probe with your hand in this measurement is safe. Previously, the device was tested for serviceability, so a person will not be struck by an electric shock that is dangerous to life. But even despite the safety of the procedure, not everyone can cross the psychological barrier. Then you can touch the probe with plaster, ceiling or wallpaper. They have a little humidity, so the readings on the tester will be visible. They will be below the required value, but it is realistic to determine the phase in this way. Also, as a second contact, you can use any grounded device (heating radiator, water supply) or a metal frame without grounding.
Search for zero and earth
Phase determination is straightforward. It is harder to distinguish zero from the earth. There are different methods of determination, but they are all not reliable. Accurately identify the purpose of the vein using professional instruments from the arsenal of specialists.
One way is to check with a multimeter. If an RCD trips, it can be judged that the tester was connected between phase and ground. Upon contact with the phase and neutral conductor, the protective device does not work. This is due to the fact that when measuring between a phase and a grounding conductor, a small leakage current is formed, which may not be enough for the protective system to operate.
The second method is ringing with the help of a multitester. The multimeter is put into a resistance measurement state. The range can be set up to 200 ohms. Be sure to turn off the voltage on the shield. After that, check the voltage between the conductors and the grounded object. The resistance value on the grounding conductor should be lower than on the zero.
The described methods are approximate and do not give an absolute guarantee of the correct determination of zero and earth. Compounds can be different, and the difference in measurement in all cases is minimal. If necessary, use special devices to determine.
Grounding busbar in the junction box
This method is better not to use, since its effectiveness and safety are not up to standard. The reliability of the results depends on the method of wiring, as well as switching in the distribution panel.
Disconnect the ground bus from the supply circuit or remove the wire from it that will be tested. After this, the conductors are dialed. As a result, zero and earth come to light.
Prohibited and dangerous methods
The accuracy of the conductor definition directly affects the safety of using home appliances. Therefore, the phase search method must be reliable. There are folk methods for determining the phase conductor, which are forbidden to use. These include the creation of a home-made system with an incandescent lamp. When working, you can get an electric shock.
Some are looking for a phase in a three-wire and two-wire wire using potatoes. This is also a method that is not reliable and unsafe. Find out exactly the purpose of the veins with its help will not work.
The purpose of the conductors can only be determined using special devices. A visual search or application of folk methods can lead to negative consequences for the safety of housing, health and human life.
