The safety of an electrical installation depends not only on the quality of the wiring and accessories, but above all on appropriate safeguards . These safeguard against the effects of short circuits, overloads, and electric shocks. In this article, we explain the difference between overcurrent and differential protection , how they work and how to select them for your installation - both at home and in an industrial facility.

1. What is overcurrent protection (colloquially "eska")?

Overcurrent protection, commonly known as a "switch" , is a device that automatically disconnects the power supply when too much current flows through the circuit.

Sometimes, several high-power devices, such as a washing machine, dryer, or dishwasher , are connected to a single line. This can cause the current in the circuit to exceed the allowable value, which can lead to overheating of the wiring and even a fire. This is one of the most serious mistakes that can be avoided at the design stage. You can learn about other mistakes to avoid. You can find them -> here .

To prevent this and protect both the installation and the connected equipment , overcurrent circuit breakers are used.
In the event of an overload, the "eska" automatically disconnects the circuit , ensuring that the installation is safe and not damaged.

💡 Worth knowing:
The letter markings on the circuit breakers (e.g. B16, C16, D16 ) determine the characteristics and rated current of the device, more about this later in the article.

2. What types of circuit breakers are there and how to select them for your installation.

To be able to select the right switch, we need to understand its markings.

On each one we will find information about its operating characteristics and rated current, it is a letter + number.

The letter - indicates the operating characteristics, i.e. sensitivity to short-circuit current.

Symbol	Operating range	Application	Description of operation
B	3–5 × In	Home installations, lighting, sockets	Highly sensitive characteristic – the "S" mode operates at a slight overload. Protects installations with low inrush currents.
C	5–10 × In	Standard in most installations	Universal characteristics - good for circuits with moderate inrush currents (e.g. devices with motors).
D	10–20 × In	Industrial installations, engines, compressors	“Slower” start-up response, so it doesn’t shut down during momentary current peaks.
K	8–12 × In	Devices with high starting current (transformers, motors)	Used less frequently, in specific industrial applications.
WITH	2–3 × In	Sensitive electronic systems	Very fast response - protects delicate devices against voltage surges.

💡 In = rated current , e.g. for C16: 16 A × 10 = 160 A - at this current the circuit breaker will trip immediately.

The number indicates the maximum current that can flow in the circuit without tripping the protection. It is given in amps (A).

At home we most often encounter type B or C fuses.

Overcurrent protection can be found on our website at this link.

3. What is differential protection? (colloquially: differential)

Residual current devices (RCDs) – this is the name given to a very important and often overlooked element in home wiring. They protect users and equipment from electric shock. Unlike a circuit breaker, they don't react to overloads or short circuits, but to current leakage that doesn't return to the source.

What exactly does this mean and how does a differential work?

The current leaving the distribution board must be the same as the current returning to it. If there's any damage to the insulation, moisture, or contact with an uninsulated wire, the RCD, often in a fraction of a second, cuts off the power, saving lives.

4. How to select a differential switch for the installation?

There are several types of differential circuit breakers on the market. They differ in their operation and sensitivity to different types of current.

The selection of this element depends on the environment and the type of devices connected to the network.

Type	How it works	Where to use	Examples of devices
AC	Only responds to sinusoidal alternating current	Simple circuits without electronics	Lighting, classic sockets, heaters
AND	Responds to alternating current and pulsating direct current (DC)	Most home installations	Washing machines, dishwashers, TVs, switching power supplies
B	Responds to alternating, pulsating and smooth direct current (DC)	Installations with converters, photovoltaics, EV chargers	PV panels, inverters, electric car chargers
F	Enhanced Type A with Frequency Interference Immunity	Devices with electronic drives	Heat pumps, inverter air conditioners
S (selective)	With delayed action	At the beginning of the installation with several RCDs	Main switchboards, industrial facilities

In addition to the type, another important parameter is sensitivity , i.e. the current value at which it will operate.

Value	Application
10 mA	Very high sensitivity – protection of a single circuit (e.g. bathroom, socket by the sink)
30 mA	Standard protection against electric shock in home installations
100–300 mA	Fire protection – used mainly in industrial and office buildings

In practice, type A, 30mA differential circuit breakers are used in home installations.

How to choose a differential for your installation?

1. Specify the type of circuit and receivers:

   • if it is lighting and sockets – type AC or A (30 mA) ,

   • if there are electronic devices (household appliances, RTV, power supplies) – type A ,

   • if you have photovoltaics or an EV charger – type B.

2. Select the rated current (In)

   • Most often 25 A, 40 A or 63 A – depending on the circuit load.

   • The RCD should not be weaker than the overcurrent protection (i.e. "eska") in the same circuit.

3. Pay attention to your work environment:

   • In humid or outdoor locations, use devices with a higher IP rating (e.g. IP65).

4. Use several differentials

   • instead of one for the entire building – divide the circuits (e.g. kitchen, bathroom, utility rooms).

   • This means that the failure of one device will not cut off the power throughout the house.

You can find differential circuit breakers on our website -> here.

5. Summary.

Both differential and overcurrent protection are essential components of electrical installations. Ideally, our distribution board should include both, as only such a combination ensures operational safety.

The most important thing to remember:

• “ Eska ” (MCB) – disconnects the circuit in the event of an overload or short circuit.

• “ Residual Current Device ” (RCD) – reacts when current “escapes” from the circuit and protects people.

Check out what we have to offer in the home installation security category -> link .

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