Today it is very important to ensure the safe functioning of the electrical network and household appliances. This will protect expensive equipment from premature breakdowns. Special protective devices of UZO can cope with this task. An indicator of the quality of their work is the operation of automation. As practice shows, sometimes it works for no apparent reason, as a result of which there is a complete blackout of electricity to the room. And many owners are wondering why the RCD machine is triggered.
What is it?
Residual current circuit breaker (RCD) is a special device that provides a protective function to a person from the effects of currents, and also reduces the risk of fires in the wiring during short circuits by stopping the supply of current to the wiring at certain points. It can be used in combination with other protective devices, as well as separately from them. There are several options why an RCD works. This is an instant reaction to factors such as:
- current leakage;
- voltage overload;
- Short circuit in the wiring system.
The appearance of the electrical protective unit
The geometric shape of the RCD is almost identical to the shape of a circuit breaker. The housing is equipped with a locking lever, a “T” button and the marking. Small holes are formed in its upper and lower parts. The terminals are located in these holes. The product is available in two sizes and differs in the number of holes, there can be 2 or 4 pcs.
The main function of the RCD
The main function of the device is to compare certain indicators of the input and output current of the electric circuit. At the time of the leak, a regular reaction occurs, which is the reason why the RCD worked. It is this action that indicates that a current leak has occurred. Performs its differential transformer, equipped with a core with several windings, arranged in the inner plane of the protective product:
- Two wires having identical indicators of its diameter and turns are “phase” and “zero” conductors. Their winding is made in a certain direction, contributing to the meeting of electromagnetic flux generated during the flow of current.
- One winding serves as a control. As soon as current appears in the winding, its passage is switched off. An electromechanical relay, arranged in the inner plane of the protective unit, is directly connected to this winding.
Distinctive characteristics of RCD
A distinctive property is the type of current used:
- A - sinusoidal variable and pulsating constant;
- AS is a sinusoidal variable;
- B is a constant, pulsating constant and sinusoidal variable.
And:
- Rated load current. This parameter indicates the permissible current flowing through the protective unit. Standard values of a scale of rated current in amperes: 125 A, 100 A, 80 A, 63 A, 40 A, 25 A, 16 A.
- Rated differential current. Differential current is leakage current. Its standard scale in milliamps is 500 mA, 300 mA, 100 mA, 30 mA, 10 mA, 6 mA.
Features of the choice of RCD
Based on the fact that the main function of the unit is to protect a person from electric shock, when choosing it, the differential current rating must be taken into account. This indicator should not exceed 30 mA.
For spaces with high humidity, such as a bathroom, shower, bathroom, so that there are no questions why the RCD worked, the most optimal option would be a device with a nominal value of 10 mA.
For outlet groups and a lighting network in homes, experts recommend using a device with a 30 mA parameter.
Protective devices that perform a fire function will have a differential current value of 100 mA, 300 mA, 500 mA. They perform the task of preventing the occurrence of a fire during a leak in the wiring. These types are strictly forbidden to use for outlet systems, since damage to a person by a differential current of 100 mA will lead to death.
Location and external factors
Quality functioning is directly dependent on location and weather conditions, such as humidity and temperature changes. These factors can lead to a malfunction of the operating mode, which will become the reason why the RCD works without a reason. Installation in a panel located on a street or in an unheated space is likely to result in an abnormal response. Sudden changes in temperature can lead to the formation of condensate in its internal part, as a result of which the automation will react. It should also be borne in mind that microcircuits do not withstand frost. The most optimal arrangement would be a dry, warm room.
The reasons for the operation of the RCD
Current leakage may occur due to various circumstances. Therefore, the most important thing in solving this problem, why RCD works is their correct determination. Let's consider some options:
- Wiring. If the house wiring is not new, but has served a sufficiently long period, then a leak may occur. Insulating tape often acts as a culprit, since its base can lose its elasticity. This will lead to the formation of small cracks, which will be the "path" of small leaks. If the installation of the wiring was carried out recently, then you should check the connection points of the conductors, perhaps their poor connection was made. Damage to the insulation of conductors should not be ruled out, for example, during repair work.
- Household electrical appliances. In the process of using electrical units, very often there are problems with structural violations of the insulation of the cord, providing connection to the mains, as well as the breakdown of internal parts.
- The quality of electrical work. This is the most common reason why RCDs do not work when a zero leak occurs. Poor connection of conductors in the electrical network system, which includes the junction box, switches, sockets, as well as in protective devices.
- Increased humidity. When carrying out repairs near the location of the wiring using liquid mixtures, a protection system may also occur.
The response of the device to any of the above reasons will be a proof of its serviceability, as well as the correct and high-quality connection to the electrical system.
Determining the causes of the operation is not an easy task, but still feasible if you follow the recommendations of specialists and follow the proposed search algorithm.
RCD testing for serviceability
To exclude unsuitability, you need to make sure that the connection protection process is completed correctly. Testing can be done by performing some operations:
- Turn off the machine. Performing this action will eliminate the impact on the RCD of all objects connected to it.
- Disconnect the outgoing conductors by removing them from the pre-weakened terminal.
- Check the locking lever. Set it to the “on” position and easily knock on the case. A spontaneous change in the position of the mechanism at the time of the option indicates a failure of the lever, which implies that the RCD is not suitable for further operation.
- Turn on the machine (the locking mechanism must be in working condition). Automation should not react, since the conductors are disconnected at the output, but its reaction will be the basis for replacing the device.
- Testing by pressing the "T" button. A functioning unit will respond by instant shutdown.
Why RCD works without load
The sequence of actions is as follows:
- Turn off appliances and lighting.
- Connect the wires in the terminal, after turning off the machine.
- Turn on the machine.
Observe the functionality of the device for at least 15 minutes. If it works in the normal mode and the automation does not work, then there is no problem in the wiring. If it works, then there is a leak. Perhaps this will not be one leak, so you should carefully approach this task and fix the problem.
It is strictly forbidden to connect the ground wires and “zero”. These reasons can lead to abnormal operation of automation.
Electrical appliances and their participation in the operation of an RCD
At this stage, it is necessary to carry out the inclusion in the network of each individual appliance (appliances, table lamps and lamps). This will allow you to find out why the RCD is triggered when you turn on one or another device.
The equipment must be plugged in without the use of additional adapters (tee, carrying). This rule should be followed, as sometimes the culprits of the leak are adapter wires. It is necessary to check all the devices, perhaps the leak does not occur in one but in several.
RCD trip when the washing machine is turned on
Very often, when the washing machine is connected to the power supply, current flow is turned off. In this case, you must first make sure that the machine is the cause of the operation. It is necessary to connect another device to the outlet where the machine is turned on. Its amount of energy consumed must correspond to the machine. If the machine does not respond, then the problem is with the previously connected device. The reasons why the RCD is triggered when the washing machine is turned on may be several:
- cord or plug wear;
- the presence of condensation on the internal conductors;
- circuit closure in an electric heater (TEN);
- failure of the "surge protector";
- short circuit of the engine, control board or start button.
Why does an RCD trip when the heater is turned on?
The operation of protection at the moment of switching on this device gives a warning signal about malfunctions in its operation. Water is heated by means of an electric heater, consisting of tubes, with a spiral integrated inside them. Prolonged use of the boiler can lead to a violation of the insulation of the conductors, as well as due to the accumulation of scale on the pipes, which leads to damage to their surface. Small cracks appear on it, through which water penetrates into the middle of the tube. Contact of the water with the spiral will cause a short circuit in the current. In most cases, it is the failure of the heater that causes the RCD to trip. But this is not the only reason.
Other possible reasons why an RCD trips on a water heater:
- wrong choice of boiler power;
- violation of the insulation of the internal conductors;
- incorrect connection to the mains;
- connection to the power supply of several household appliances.
To avoid overloading the power supply network, it is necessary to equip separate sockets for connecting a washing machine, water heater, dishwasher, microwave.
The implementation of a full range of checks of the probable reasons why the RCD is triggered will provide an opportunity to assess the level of condition of the power supply network of house building.