EV Charger Protection: Why a Circuit Breaker is Crucial for Safe Charging

Some electric car owners overlook important safety precautions when setting up their wallboxes and often have to deal with the consequences — don’t let this happen to you. In most countries, you are required to install a residual current device (RCD) and a miniature circuit breaker to charge safely. The thing is, EV chargers need reliable protection against electrical faults. But what exactly are these “extras”, and how do they keep you safe?

It might seem a bit technical at first, but it's easier to grasp than you think. By the time you finish reading, you'll know exactly why and how to protect your wallbox with a circuit breaker and RCD.

Yes, EV chargers require circuit breakers to avoid damage from electrical faults, sudden grid voltage shifts, and other unexpected events. Built-in safety features or additional devices in the building’s electrical system safeguard the wallbox, the vehicle, and the entire power network.

Yes, EV chargers require RCD protection for safe operation. Some wallboxes include built-in safety features like DC fault protection or an integrated RCD. Whether you still need an external RCD is not up to the charger manufacturers but depends on local regulations. If you are required to install one, there are two options:

• Type A RCDs detect alternating and pulsating direct currents. This means they are suitable for wallbox with built-in DC fault protection.

• Type B RCDs handle all fault types, including DC currents, and are essential for chargers without DC protection.

If your wallbox has a built-in Type B RCD, you may not need an external one. However, always consult an electrician to ensure compliance and safety.

Many models, including our go-e Charger, have built-in DC fault protection that disconnects during DC fault caused by the car. Simply put, the charger stops charging. However, an RCD Type A in the home’s distribution board is still required for full protection.

In addition to the RCD, a miniature circuit breaker must be installed to protect against overloads and short circuits. If you’re unsure whether you know what this device is about, keep reading — you are about to find out.

A circuit breaker is a safety mechanism for the electrical system in a building. It is designed to protect the system when you use electrical devices, like a wallbox to charge your car. The circuit breaker detects electrical faults and turns off the power to prevent damage or even fire.

It works similarly to a fuse, which is basically a different version of the same concept. When the fuse blows out, you need to replace it. In contrast, the circuit breaker "trips" and stops the electricity in case of an electrical fault, and you can reset it to restore the power.

The miniature circuit breaker in particular supports currents of up to 100 A and has a short-circuit capacity of up to 10 kA. That’s why it’s normally suitable for residential and commercial settings. In contrast, other types of circuit breakers are designed for higher-voltage applications.

The size of a circuit breaker depends mostly on the maximum charging power of your wallbox. The safety device should be dedicated solely to the EV charger, which means the supply cable to the charging station should not be connected to any other electricity consumers. Therefore, you only need to consider the power requirements of the wallbox itself when selecting the appropriate breaker.

For an 11 kW EV charger, you need a type A circuit breaker with a rated current of 16 amps, as this is usually the optimum choice for such installations.

The circuit breaker ensures that the charging cable does not overheat. However, it only helps if a cable with the correct cross-section is used. If it is too thin, the protection may trigger more frequently or, worse still, fail to protect the system in time.

The higher the charging power, the more protection is needed. Therefore, we recommend using a 32 A circuit breaker for a 22 kW EV charger because of the higher power requirements.

The mentioned circuit breaker is designed to trip quickly if there is an issue and offers great protection, especially when many wallboxes are operating simultaneously.

Yes, technically you can have a wallbox without a circuit breaker. However, if something were to happen to the electrical system in your house, the insurance would likely refuse to cover the damage, as it would be considered your deliberate decision to ignore the requirement of using a safety device.

When you're setting up your wallbox, choosing the right supply cable is vital. First, it keeps everything safe, and second, it minimises power losses while charging. 

An 11 kW EV charger requires a cable cross-section of between 2.5 mm² and 6 mm². A 22 kW EV charger should have a cable cross-section of between 6 mm² and 10 mm². The thickness of the cable should therefore correspond to the power requirement of your wallbox.

Note: You can also see cable cross-sections written like this: 5x2.5 mm² or 5x10 mm². The "5" refers to the number of individual wires inside the cable. This value is always the same for wallbox supply cables.