Even in the relatively recent past, few people thought about the need for a quality grounding device. And now many do not pay due attention to this, considering the presence of zero and phase sufficient for the normal operation of household appliances. Meanwhile, it provides the necessary protection, especially when an RCD is included in the circuit. When driving into a new apartment, you should check for the presence of tires in the control cabinet. However, this is not the only thing to be done. After all, the fact that there is a bus does not yet guarantee the correct connection in sockets. Today's article will tell you how to check the grounding with a multimeter, as well as with the help of other devices that are always at hand.
Why is a circuit necessary and why is it connected?
There are frequent cases when, due to high humidity, voltage begins to break through the housing of such household appliances as a washing machine or dishwasher. The electric discharge that a person receives in contact with the surface of such a device cannot be called strong, but it is quite unpleasant. If a breakdown of the insulation of the phase wire to the case occurs, everything can be more serious, even fatal.
Protective grounding is switched with a contact connected through a wire to the housing, and the voltage that arises, which is always directed along the path of least resistance, goes through it. It is for this reason that a person is completely safe. If a protective shutdown device is provided in the switchboard, then it picks up this leak and turns off the power supply. But in order to make sure of the existence of such protection, you should know how to check the grounding in the socket with a multimeter or using other devices.
Preliminary visual inspection
First you need to determine whether the ground wire is suitable for the outlet and whether it is connected correctly. To do this, using an indicator screwdriver, check all three contacts of the connection point. The bulb should only light up when it comes into contact with the phase contact. It should be noted - this information will come in handy later. After that, it is necessary to turn off the input circuit breaker and once again check the socket with an indicator, making sure that there is no voltage.
Then the external decorative overlay is removed so that the contacts are visible (often for this you have to remove the device from the "glass"). After making sure that it is the yellow-green wire that is suitable for the grounding contact, and not a jumper between it and the zero terminal, you can assemble everything in the reverse order and resume the power supply. Now we can move on to the question of how to check the grounding with a multimeter.
First steps to check: what you need to know
To do this, you will not need anything but a pen, a piece of paper and a measuring device. It does not matter if it is analog or digital. Before checking the quality of grounding with a multimeter, you should set its switch to the maximum AC current. For various models, it can be 700, 750 or 1000 volts.
One of the probes is connected to the previously noted phase contact. The second is first switched to zero, and then to the ground bracket. The readings in both cases are recorded for comparison. If they are ideally identical, this is a reason to doubt the lack of a neutral conductor connection and grounding in one of the junction boxes or outlets. We have to start a long and painstaking search.
Checking the circuit with an incandescent lamp
After making sure that the yellow-green wire is connected to the desired contact, before checking the grounding with a multimeter, you can test using a conventional cartridge with wires and a lamp. Such work does not require special skills, but you should not forget about attentiveness and accuracy - all checks are performed when the voltage is on. One of the stripped ends of the wire coming from the cartridge with the lamp is connected to the phase contact. The second, to test the performance, is first connected to zero - a glow should appear. Further, instead of a neutral terminal, the core is connected to the ground bracket. Further 3 scenarios:
- Lamp does not light - missing or faulty ground connection.
- The device works at full strength - either the circuit is in order, or there is contact with zero. Further verification is needed with more sophisticated devices.
- A half-lamp brightness is ideal where no further testing is required. It means having a good ground and its proper connection.
Checking the connection of the circuit in the presence of RCD
Everything is much simpler here. To do this, you don’t even need to know how to check the grounding with a multimeter in a private house or apartment. The presence of an RCD that does not work indicates that there is no zero contact with the ground. This means that if the residual current circuit breaker is working properly (you can check by pressing the "test" button - the cut-off should occur), then either the circuit is not connected as expected, or there is no such connection at all, and the wire in the sockets is mounted only for visibility.
For work, you only need a piece of wire with stripped ends. They should connect the zero pin of the socket and the ground bracket. At this point , the residual current circuit breaker should trip by disconnecting the circuit and removing the voltage from the home electrical system.
Testing the ground resistance in a private house
Often the circuit itself turns out to be inoperative. If it is made of steel tires, normal corrosion may render it unusable. However, the question "how to check the grounding resistance with a multimeter" is incorrect. For such tests, another device is used, which is called a megaohmmeter. In order to use it, specialists undergo special training. It can only be noted that the ground resistance for a single-phase voltage of 220 V should be 4 ohms. The same indicator is required for a three-phase network of 380 V.
Residual Current Device Tests
If there is an RCD in the switchboard, before checking the ground loop with a multimeter, it makes sense to make sure that the protection is working. If the home master does not trust the “test” button, you can carry out your tests. For this, the RCD is completely disconnected from the network, and pieces of wire are connected to its input and output contact (one of two). For example, take the upper and lower phase terminal. The flag is set to the "On" position, after which a regular 1.5 V battery is connected to the free ends. The field created on one coil and its absence on the second one creates the appearance of leakage, as a result of which a cut-off should occur. If this does not happen, the device is malfunctioning.
What can be said in conclusion
A properly mounted and connected ground loop is necessary, because once it can save not only health, but also the life of people living in the house. Do not underestimate its role in the protection system of your home electrical network. In addition, according to statistics, household appliances connected to ground outlets last much longer. The main thing is that the circuit is functional and correctly connected to the home network. But one conclusion can be made: every home master is obliged to know how to check the grounding with a multimeter or other devices.