Knocks out an RCD or automatic machine when the washing machine is turned on

Recommendation points

• Is the connection correct
• Systematic response
• Are the protective devices intact?
• Leakage through wet contacts and insulation
• Heating element problems

What to do if an RCD is triggered in the dashboard when the washing machine is turned on? The answer is obvious: look for the source of the problem, but what if the search excludes wiring defects and points to household appliances? Unfortunately, even a new washing machine can provoke emergency shutdowns, so we will understand.

Is the connection correct

In most cases, the operation of an RCD and even a conventional circuit breaker is the result of an incorrect wiring diagram or a choice of rating. If there is a possibility of an error of this kind, it should be eliminated first..

Washing machines, dishwashers and other household appliances with active heating elements must be connected through a residual current device to prevent electric shock to people. Since such household appliances belong to the category of consumers of increased power, they are powered by a separate line: a three-core cable with one plug socket, to which no other electrical appliances are connected. The protective conductor is connected directly to the common ground bus, while the neutral and phase conductors are connected only to the lower terminals of the RCD with the corresponding marking. Connecting a neutral conductor to a common neutral bus is guaranteed to lead to erroneous operations.

It is advisable to select the RCD leakage current rating of 30 mA – higher values ​​can be dangerous to humans, while a higher sensitivity threshold, for example, 10 mA, can lead to false alarms due to leaks in a rather complex power supply circuit for household appliances. A separate recommendation: to purchase a mechanical type RCD as more reliable.

The current rating of the RCD is selected in accordance with the line load. Since the power of most washing machines is in the range of up to 3 kW, the ability to withstand a current of 16 A will be sufficient for the protective device. A slightly different approach applies when choosing a protective circuit breaker. Its task is to prevent damage to the wiring during overloads or short circuits, for example, when the heating element coil breaks down. The power line of the washing machine is laid with a single-core copper cable with a cross-section of at least 2.5 mm², for such conductors, the current limit is 25A. It is desirable that the power circuit of the washing machine be protected by a two-pole automatic device, which excludes a polarity reversal in the AC network. It is optimal to select the “B” disconnection characteristic, as the most sensitive for household networks.

Systematic response

If during the check it was found that the connection diagram was correct, you should more accurately determine the source of the problem. First you need to understand at what point the protective devices are triggered: when the machine is connected to the outlet, when the power is turned on, or during operation. So, an RCD can work:

1. Immediately upon plugging into the socket – the insulation of the power cable of the device is damaged, or there is wetting of the terminal blocks at the point where the conductors are connected to the converter board;
2. When the device is powered on – breakdown of the insulation of the internal power supply to the grounded housing of the device, or water ingress on the main board;
3. When the engine is turned on – damage to the insulation of the windings or in the place where the power keys are attached to the cooling radiator, or the board gets wet;
4. When the heating element is turned on – violation of the integrity of the heater case or breakdown to the grounding contact.

By analogy, we can distinguish typical malfunctions that lead to the operation of the circuit breaker:

1. When plugged into a socket – short circuit on the converter board, breakdown of transformer insulation or power cable;
2. When the power is turned on, the input converter is faulty;
3. When the engine or heating element is turned on, the windings or the heating coil are closed.

It should be noted that the triggering of protective devices may occur irregularly. So, the circuit breaker can turn off at low voltage when the load current exceeds the set limit. The operation of the RCD from time to time indicates either a periodic ingress of water on live parts, or a malfunction of the device itself. There is an obvious drawback of differential automatic machines: there is no way to determine which type of protection worked. It is possible to recommend a temporary series connection with a diffautomat of a conventional circuit breaker with a lower rating..

Are the protective devices intact?

Erroneous operations can be a sign of defective safety devices. For an RCD, there is no particular problem to establish the fact of a breakdown; first, you need to perform a test operation by pressing the test button. The second stage is plugging into a power outlet of a powerful active consumer that does not have a grounding contact, for example, a conventional electric heater or vacuum cleaner. If at the same time the RCD disconnects, it should be replaced, or check the integrity of the cable insulation in the supply line.

Circuit breakers are subject to aging and wear on the tripping mechanism. The check is carried out in a very primitive way: one or more consumers of fixed power are connected to the outlet of the washing machine. In this case, it is desirable to measure the effective current using a current clamp. If the machine switches off at currents below the rated threshold, the machine should be replaced.

Leakage through wet contacts and insulation

Leakage in the power supply line of a washing machine is usually observed on exposed live parts where condensation may form. Another particular case is the loss of dielectric properties of the insulation of the cable in the wall or the power cord..

The first step in checking for this kind of defects is to disconnect the power line in the shield and from the socket outlet. As a result, there should be three exposed veins on each side of the line. They need to be separated from each other to the sides and measure the resistance between the conductors using a conventional multimeter set in a range of at least 1 megohm. Usually the capabilities of even an inexpensive meter are enough to detect a leak, it is only important that a fresh battery is installed in the multimeter. The power cord is tested in a similar way. It is disconnected from the connecting terminals inside the machine itself and is also checked for reduced resistance between the wires.

If the cause of the leak is the wetting of the board or input terminals, the fact of such a malfunction is determined by periodic visual monitoring of the state of these elements at the time of the RCD tripping. Basically, the ingress of water on live parts is possible if the tightness of the hoses located inside the body of the washing machine is broken. If the reason is the formation of condensation, it is enough to strengthen the insulation of live parts and tracks on the board with a dielectric varnish, or put the electrical circuit of the device in a sealed enclosure.

Heating element problems

The breakdown of the heating element is also a very common reason for the operation of an RCD or a circuit breaker. To make sure of this kind of malfunction, you need to open the inspection hatch on the back of the washing machine to gain access to the heater terminal row. Having unscrewed the central nut, you need to drown the stud in depth, loosening the clamping bracket, and then remove the heating element along with the sealing rubber cuff. Descaling the surface of the heater will allow you to check the integrity of the steel shell and establish the presence of cracks. If water gets inside the heating element, this is guaranteed to trigger the RCD. Also, the presence of a breakdown to the case can be determined by the same method as when measuring the cable insulation resistance.

The presence of a short circuit in the heater coil is established by measuring the resistance. The calculation formula is quite simple: divide the square of the voltage by the power. That is, if according to the washing machine’s passport the power is 1600 W, the resistance of the heater coil should not be less than 30 Ohm.