Electrical installations use various types of protection to protect electrical circuits, devices or people from the effects (often tragic) of improper network operation, e.g. electric shock. One of the protection devices commonly used by electricians is a differential circuit breaker, commonly known as a residual current device. What exactly is this device? When should an installation be equipped with one? What type of differential circuit breaker should you choose? And how often is it recommended to replace it? Everything you need to know about differential circuit breakers can be found in the article below, and you can find practically every type of differential circuit breaker in the Onninen wholesaler. We invite you!
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What is a differential?
A differential switch is the common name for a differential switch. It is an electrical safety device that prevents electric shock to a person during direct and indirect contact, minimizes the effects of damage to equipment and reduces the risk of fire.
The phase and neutral wires pass through the differential switch, e.g. in a single-phase circuit it will be the phase wire and the neutral wire. Under normal conditions, the current in the circuit has the same value as the current flowing through the neutral wire. In the event of a failure in the installation, the current "escapes" to the housings of electrical devices, as a result of which the current values in the phase wires and the neutral wire begin to differ (this difference is the differential current). When the electric current flowing out of the circuit is not equal to the current flowing in, the differential switch should detect these irregularities and immediately disconnect the circuit. The power supply is switched off automatically.
Other commonly used names for differential circuit breakers include: residual current circuit breaker, residual current circuit breaker, RCD circuit breaker and RCCB circuit breaker, from the abbreviations of the English names ( residual current device and residual current circuit breaker , respectively) .
When is it advisable to use a differential circuit breaker?
RCDs are used in electrical installations as additional protection against electric shock. They are found in TN-S (most often in houses and apartments), TN-CS (in the section with separated PE and neutral conductors) and TT networks. They appear rarely in IT networks. RCDs cannot be implemented in TN-C installations, because PE and N conductors are not separated in them, so the RCDs would not function properly.
The differential detects even a small current leakage – one that could not cause overcurrent protection to operate. However, the device does not provide absolute protection, i.e. 100% protection regardless of the situation. When you touch a protective conductor with a current flow to ground, the risk of electric shock still exists, but it is usually much lower than in the case of contact with an unprotected conductor and usually does not pose a threat to human life or health.
The question of when it is not so much worth it, but rather when it is necessary to use differential circuit breakers and what parameters they should have is discussed in building regulations and the requirements of Polish Standards relating to electrical installations and electrical devices. The obligation to provide protection against electric shock is regulated by the provision of § 180 of the Regulation of the Minister of Infrastructure of 12 April 2002 on the technical requirements that buildings and their location should meet.
How much power should a differential have?
The basic parameter of each differential switch is the rated differential current I Δn . This is the value declared by the manufacturer (10, 30, 100, 300, 500 mA or 1 A), at which, under specific conditions, a given differential switch should operate. Additionally, the differential switch is structurally adapted (including the size and cross-section of the current paths and the selection of terminals for the wires) to a specific value of the rated current. For example, a 25A differential switch or a 40 A differential switch are available. The power of the differential switch is selected by a qualified electrician, taking into account, among other things, the type of installation and its load, as well as legal regulations and requirements of the standards for a given location.
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What is the difference between differentials?
There are various types of differential circuit breakers available on the market.
Due to the sensitivity (operating current I Δn ) the following circuit breakers are distinguished:
- highly sensitive – they respond to current below 30 mA, so they are most often used in houses and apartments;
- medium-sensitive - responding to a current of 30 to 500 mA;
- low-sensitive - responding to current above 500 mA, they are mainly used in industrial facilities.
Depending on the types of leakage currents detected, the type of tripping or the sensitivity to differential current, several basic types of differential circuit breakers can be distinguished:
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AC type – AC type RCD circuit breakers are sensitive to sinusoidal alternating currents, this is the most popular type of differential circuit breaker in our country; - type A - type A switch is sensitive to the flow of sinusoidal and rectified pulsating current (note: type A is not suitable for installation in circuits responsible for powering e.g. inverters);
- type B – type B differential switch is designed for more advanced electrical installations, it detects sinusoidal alternating current, direct current smoothed to a frequency of 1000 Hz and pulsating direct current;
- F type – F type circuit breakers detect sinusoidal alternating current with variable frequency characteristics, which is why they are implemented together with converters frequencies.
Depending on the number of poles, differential circuit breakers are divided into:
- bipolar – used in single-phase circuits (hence the name single-phase differential );
- four-pole – used in three-phase circuits with a neutral wire (hence the name 3-phase differential ).
Due to the built-in overcurrent protection, differential circuit breakers are distinguished:
- RCCB - unsecured,
- RCBO - with protection.
When choosing a residual current circuit breaker, you should look at the electrical installation as a whole. In particular, you should take into account the expected values of leakage current, the planned load of the installation and the type of receivers in the circuit. The functions that the residual current circuit breakers are to perform in the protected circuit are also important. After all, it does not necessarily have to be only protection against electric shock. If you are not a professional, it is worth seeking advice from a licensed electrician.
How often should a differential be replaced?
RCDs in electrical installations should be inspected periodically to ensure proper protection of electrical equipment and, above all, the safety of household members and employees. The RCD usually has a "TEST" button. Pressing it simulates a fault in the installation, and thus current leakage, which allows you to verify the device's efficiency. If the current is not automatically and immediately cut off, it is recommended to replace the RCD. It is best to contact an electrician. The frequency of testing is specified by the RCD manufacturers. In favorable environmental conditions, it is usually enough to repeat the test once a year.
Is a differential switch a fuse?
No. Differential circuit breakers and electrical fuses (also called fuses/overcurrent circuit breakers and colloquially "plugs") are two different types of protection used in electrical circuits. A fuse protects the installation and electrical receivers from the effects of excessive electrical energy - overload or short circuit, interrupting the flow of current. Its use effectively prevents damage to the installation and electrical equipment connected to it. A differential circuit breaker does not protect against overheating or short circuiting of devices, but detects current leakage, preventing "kicks" that are dangerous to human health and life. Protection should be comprehensive - based on both differential circuit breakers and overcurrent circuit breakers. There should be at least one fuse for each differential circuit breaker.
Differentials at the Onninen wholesaler
In the Onninen electrical wholesaler you will find a wide range of AC, A and other residual current circuit breakers. We offer certified, standard-compliant products from renowned manufacturers and suppliers. You can choose from:
as well as various accessories from the modular equipment range. We also encourage you to familiarize yourself with other available security products.
Don't know which differential switch, fuse or surge arrester will fit your network system? Onninen experts provide professional support in selecting the optimal type of differential switches and other elements. Write, call or visit the nearest branch. We will try to answer every question. Are you a professional? Electricians can count on special conditions of cooperation.
Check the residual current circuit breakers at the Onninen wholesaler