RCDs are an important element of electrical installations. By protecting the installation and its users from electric shock, short circuit, fire and other hazards, they ensure safe operation. What do you need to know about them? In a new article, we write about their applications and types.
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What types of residual current circuit breakers are there?
RCDs are the successors of fuse links and are more reliable. The effectiveness of protection provided by RCDs depends primarily on their correct selection in terms of the specifics of the installation and the type of threats against which these protective devices should protect. One of the most important aspects is the selection of the right type of circuit breaker. These devices are available in the following variants
Differential circuit breakers
They are used to protect against electric shock. They detect the difference between the current entering and leaving the circuit. There are various types available on the market, differing in sensitivity and ability to detect different types of current.
Circuit breakers
Common overcurrent (short-circuit) circuit breakers are designed to disconnect the circuit at currents exceeding the rated value. They are classified based on types or tripping curves.
Selective breakers
These are safety devices installed in circuits before overcurrent breakers. In the event of a current flow with undesirable parameters, their function is to activate the appropriate switch - located closest to the place where the problem occurs. The use of this type of safety device can most often be seen in industrial applications.
Grounded circuit breakers
They use grounding to control electric current and prevent electric shock. They detect stray voltage on the device's housing and interrupt the circuit if a safety level is exceeded.
When is an RCD required?
RCDs are also known as Residual Current Devices (RCDs ). Their job is to detect any differences between the current entering and leaving an electrical circuit, allowing the power supply to be immediately disconnected if an incorrect current flow occurs. Their operation is based on the application of an incorrect current to the trip coil. The use of RCDs is particularly important in the context of protection against electric shock. They can immediately interrupt the circuit when the long-term current capacity of the conductor is exceeded. This minimizes the risk of serious injury or even death as a result of such exposure.
There are several different types of RCDs that vary in their sensitivity and ability to detect different types of current.
- type A – are very sensitive and trigger immediately at currents exceeding 2-3 times the rated current. They are used in very sensitive electrical installations to protect electronic devices sensitive to fluctuations in the intensity of electricity;
- AC type – detect alternating differential current;
- Type B – are very versatile and are available in single and three-phase versions. The short-circuit tripping current can be alternating, variable and direct. Circuit breakers with the B characteristic are used in systems where there is a risk of different types of currents, e.g. in circuits with power supply for electronic devices.
- type C and D – are designed to protect high-power devices. This group includes models with high starting currents, which can be up to 20 times the rated current.
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How to choose a circuit breaker for your home?
The principles of selecting a circuit breaker are regulated by the PN-HD 60364-4-43:2012 standard. The device parameters should be adapted to the design currents of the receivers (Ib) and the long-term current capacity of the conductors (Iz). The overcurrent circuit breakers used should be selected so that they operate not only at typical rated currents (In), but also in situations where a current with a higher intensity flows through them than the long-term current capacity of the conductors.
When selecting a circuit breaker, the current multiplication factor (k) must be taken into account, which is a multiple of the rated current (In). Different k values are assumed for different types of circuit breakers, such as fuses or circuit breakers with characteristics B, C and D. For circuit breakers with characteristics B, C and D, k is usually 1.45. These values ensure that the circuit breaker will operate even in situations where the expected currents exceed the rated standards.
How to connect an RCBO switch?
Installing a circuit breaker is an activity that requires special caution and strict adherence to the rules. The entire process should be preceded by appropriate preparation. Before starting work, of course, disconnect the main power supply in the circuit in which it will be installed. The next step is to prepare the wires that will be connected to the switch and expose the insulation to the appropriate length at the ends of the wires.
The wires should be properly connected to the circuit breaker terminals. It is important to maintain the correct order when connecting the phase, neutral and ground wires. After connecting the wires, make sure that the circuit breaker terminals are properly secured and tightened securely. This prevents the formation of loose connections and the resulting problems.
Once the circuit breaker has been securely installed and all connections are secure, the main power supply to the circuit can be restored. This should be done carefully and under the supervision of a specialist. It is also a good idea to test the circuit breaker in a controlled environment.
Differential circuit breakers at the Onninen wholesaler
At Onninen we offer a wide range of residual current circuit breakers. In our Onninen electrical wholesaler you will find models that will prove themselves in even the most demanding installations and will allow you to implement complex projects. These include:
SCHNEIDER ELECTRIC VigiC120-4-30-AC differential block
The rated current of 125 A and the rated voltage of 400 to 415 V ensure the versatile use of the SCHNEIDER ELECTRIC VigiC 120-4-30-AC residual current circuit breaker . The rated residual current setting is in the range of 0.03 to 0.03 A, so the model can be installed in various installations.
EATON FRCdM differential circuit breaker
The rated voltage of this circuit breaker is 415 V and the operating current of the protective device is 40 A. The shallow depth (70.5 millimetres) allows the EATON AC 4-pole FRCmM-40/4/003 differential circuit breaker to be installed even in a small switchboard.
LEGRAND P304 4P differential circuit breaker
The LEGRAND P304 4P residual current circuit breaker is available in versions with rated currents from 16 to 63 A and differential currents from 10 to 500 mA. It is equipped with a special lower catch and terminal covers for easy installation and is compatible with auxiliary devices (auxiliary and signaling contacts, undervoltage and shunt releases, remote drives, etc.).
Choosing the right residual current circuit breaker for your home electrical installation is very important to ensure its safety and efficient operation. If you have any doubts, you can use the help of our team.
Check the residual current circuit breakers at the Onninen wholesaler