Categories: Electrician Secrets, Automata and RCD
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What to do if an RCD or a difavtomat works when you connect a washing machine
In accordance with current technical standards, the wiring in the apartment must be three-wire, and the outlet networks must be equipped with differential protection. There is no need to once again tell that all this is achievable is far from always. therefore RCD and differential circuit breakers in apartment distribution boards so far can be seen infrequently - mainly for connecting a washing machine, which is usually located in the bathroom.
The fact is that according to the rules of the PUE, protection against leakage currents for power consumers in the bathroom is mandatory. AND, installing a washing machine in the bathroom, experts often put in a shield a separate differential protection device for its connection.
However, a situation where RCD or difavtomat, to which the washing machine is connected, starts to constantly work and, what is called "spoil the nerves."
Let's try to deal with possible causes of differential protection after connecting the washing machine, as well as determine the actions and measures by which you can resolve the situation.
1. The first thought that comes to mind in a similar situation is wrong connection. This primarily concerns the differential protection apparatus. It is hardly possible to make a mistake when connecting the cable cores in the socket: for the “differential” to operate, it would be necessary to connect together the zero working and protective conductor (N and PE). For a two-wire line, the connection of the working neutral conductor and the housing of the washing machine is likely (an attempt to make an unapproved grounding) All this can cause the RCD to trigger, but such incidents are rare, and you should not devote much time to describing them.
More often, you have to deal with the wrong connection of an RCD or a difavtomat. The most typical case is when the phase is “passed” through the apparatus, and the operating zero is duplicated or simply taken directly from the common zero bus. The reason is ignorance of the principle of operation of the RCD, according to which all the current of the zero working and phase conductors must pass through the internal circuit of the device.
If part of the current passes through the common zero bus, bypassing the differential protection device, then the RCD will perceive this as a leak and turn off the power. Therefore, when connecting a differential protection device, it is necessary to strictly follow the labeling of the terminal clamps and follow it. The main requirement is that the zero wire N going to the washing machine must be connected directly to the appliance, there should not be any additional working “zeros”.
2. Malfunction of the RCD itself also should not be ruled out. To check, disconnect all the outgoing wires, apply voltage to the included RCD (or difavtomat) and press the "test" button. The device should turn off only when the button is pressed and nothing else. If the differential protection device is found to be faulty, it is easier to replace than to repair.
3. In the case when the device turned out to be serviceable, we critically evaluate condition of the washing machine itself. If the washing machine is new, then suspicions of it are eliminated immediately. Anything is possible for an old washing machine: damage to the internal wiring, deterioration of the insulation of the windings of the electric motor, damage to the housings of internal appliances and devices.
To check for internal leakage in the washing machine itself, you can use a multimeter. We check the resistance between each plug electrode of the plug and the body of the machine at a limit of 20 kilo-ohms.For a differential protection rating of 30 milliamps to trip, the resistance must be 7.3 kilo-ohms or less. If the resistance exceeds this figure, then it is not a washing machine.
An exception, of course, are those cases when the differential protection is triggered, for example, when the electric motor is turned on, the intake valve is opened, and the drain pump is turned on. At the same time, measuring the insulation resistance of a machine that is not included in the network is pointless. But this is not necessary: there is no doubt already, and the circle of troubleshooting is narrowed to the element of the washing machine, when turned on, the problem is manifested.
It is better to entrust a faulty washing machine to specialists, since it is almost hopeless to look for a leak on your own.
4. If, however, the washing machine is working, then only one version remains: wiring failure. Moreover, a completely new wiring may also be malfunctioning. A self-tapping screw stuck in a working zero core hidden under the sheathing, moisture penetrating into the branch box, damaged by a knife during stripping and tightly laid wires in the shield and the same boxes - these are malfunctions that can occur regardless of the age of insulation.
It is quite difficult to find and fix such malfunctions. If we are talking about open wiring, then it must be revised throughout. It is also advisable to open the junction boxes and check if the neutral working conductor closes to extraneous current-carrying parts.
For hidden wiring, all this is even more complicated. In practice, it is possible to find only damage associated with the complete breakage of one of the cable cores. Locking the working “zero” on nails, screws and other fasteners in the wall can only be found the method of many long trials and errors.
If you do not see a clear prospect for such work, then it will be easier to replace the cable line. Moreover, the triggering of differential protection can be associated not only with damage to the cable, but also with the elementary aging of its insulation. This is true for old aluminum wiring. For the new wiring, it is possible that the cable used during installation was counterfeit, and its insulation allows leakage, even before it has worn out.
Alexander Molokov
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