Wallbox with residual current device (RCD) – correctly protecting type A or type B

When installing an electric vehicle charging station, residual current protection (RCD) is crucial for safety and cost. We'll explain step by step which type of circuit breaker is truly mandatory and where you can save money during installation. This way, you'll know exactly what to look for before you buy.

Here's how to protect your wallbox with the appropriate residual current device (RCD).

A wallbox with a residual current device (RCD) is essential for any safe home charging solution. This device cuts off the power supply as soon as a fault occurs in the charging station or vehicle, protecting you from dangerous electric shocks. At PVundSO, experienced electrical engineers will advise you on the most suitable protection for your charging station, ensuring it meets all relevant standards and is also cost-effective. This guide explains why this protection is mandatory, the differences between various RCD types, and how choosing the right one can save you money. This way, you can make an informed decision when purchasing your wallbox and avoid costly mistakes.

Why your wallbox needs a residual current device (RCD).

A residual current device (RCD) for the wallbox interrupts the circuit instantly as soon as a fault current occurs. Such fault currents arise from damaged insulation, moisture ingress, or a defect in the charging cable. If the current then flows through your body to the ground, it becomes life-threatening. The RCD detects even the slightest deviations between the incoming and outgoing current and trips within milliseconds. An RCD for the wallbox trips at a differential current of just 30 mA, long before the current becomes dangerous to humans.

A charging station places higher demands on the system than a regular wall socket. Your car is charged at high power for hours, often outdoors and in all weather conditions. This continuous load increases the risk of a fault occurring at some point. That's why effective residual current protection (RCD) is mandatory for every wallbox.

The residual current device (RCD) complements the miniature circuit breaker (MCB), which only protects against overload and short circuits. Only the combination of both components makes your charging solution safe. Therefore, when it comes to wallbox RCDs, the focus is always on personal protection, not on protecting the wiring. A wallbox with an RCD is thus not an optional extra, but the foundation for safe operation.

Comparison of Type A and Type B RCDs

When it comes to residual current protection (RCDs) for charging stations, you'll primarily encounter two types. They differ in the type of residual current they can reliably detect. This difference will ultimately determine the cost of your installation and the selection of suitable components.

What a Type A RCD detects

A Type A residual current device (RCD) detects sinusoidal alternating fault currents and pulsating direct fault currents. This is perfectly sufficient for most household circuits. However, when charging an electric car, smooth direct fault currents can also occur because the charging electronics in the vehicle convert the current. A standard Type A RCD cannot detect these smooth direct fault currents.

A Type A residual current device (RCD) wallbox is therefore only compliant with standards if an additional device monitors smooth DC fault currents. This task is performed by a so-called DC fault current detector, which trips at 6 mA.

When a Type B residual current device (RCD) is needed

A Type B residual current device (RCD) additionally detects smooth DC fault currents and thus covers all relevant fault types on its own. A wallbox with a Type B RCD is therefore particularly versatile, but also significantly more expensive. A Type B RCD wallbox module can easily cost several times more than a comparable Type A.

For most private households, the more expensive option is only worthwhile if the charging station doesn't monitor DC fault currents itself. If the wallbox has its own built-in detection, the extra cost for Type B is unnecessary.

What DIN VDE 0100-722 prescribes

The relevant standard for charging infrastructure is DIN VDE 0100-722. It requires that every charging point be protected against fault currents and safely disconnect in the event of a smooth DC fault current of 6 mA or higher. A simple AC protection system, as was common in older installations, is therefore no longer sufficient.

Specifically, the residual current device (RCD) must trip at a rated residual current of less than 30 mA AC and 6 mA DC. Therefore, if an RCD is required for a wallbox, it's not just any RCD that's needed, but a solution that covers both types of residual current. A standard household RCD does not meet this requirement. This is precisely where many older installations fail, as they were planned without considering the requirements of e-mobility. Before connecting a charging station, the existing electrical circuit should therefore be thoroughly inspected.

The standard gives you two options. You can either use a Type B residual current device (RCD) or a Type A RCD in combination with a 6 mA DC residual current detector. Both options offer the same level of safety, but differ significantly in price. Which option is cheaper depends solely on the features of your wallbox.

Wallbox with integrated residual current device (RCD) or external solution?

Many modern charging stations already come with the necessary protection. A wallbox with an integrated residual current device (RCD) saves you additional components in the fuse box, thus saving space and money. Nevertheless, you should carefully check the data sheet to see exactly what's integrated, as manufacturers use different solutions.

Advantages of integrated DC fault current detection

Some devices include a wallbox with an integrated Type B residual current device (RCD), while others rely on integrated 6 mA DC residual current detection. In the latter case, an inexpensive external Type A RCD is sufficient because the charging station itself monitors the critical DC component. This design has become the standard in the residential sector.

The integrated detection provides the same level of protection as a Type B fuse, but costs significantly less. You save money on installation without compromising safety. Additionally, your fuse box remains more organized because an expensive Type B component is no longer needed. This is precisely why this solution is the most economical choice for most homes.

The Sofar Solar Wallbox with integrated DC detection

A good example is the Sofar Solar Wallbox from our product range. This 11 kW wallbox with integrated residual current device (RCD) features a built-in 6 mA DC fault current detection system and a Type 2 connector. This means that a Type A RCD is sufficient for protection; a more expensive Type B RCD is not required.

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The Sofar Solar Wallbox charges your car with up to 11 kilowatts and is particularly suitable for charging with your own solar power. The control unit allows you to adjust the charging power to your needs and prioritizes the use of electricity from your own roof. Because DC protection is already integrated into the device, installation is simpler and more cost-effective.

Choosing a Type A wallbox with integrated DC detection combines safety and cost-effectiveness. You meet all the requirements of the standard while saving yourself the expense of a Type B component. For the vast majority of homes, this is the ideal combination of protection and price.

Which residual current device (RCD) is right for your wallbox?

Which type of residual current device (RCD) is suitable for wallbox connections depends primarily on the features of your charging station. If it doesn't have its own DC detection, you need a Type B RCD. If it has 6 mA detection, a Type A RCD is sufficient, saving you money on materials.

For electric vehicles, experts recommend a Type A EV or Type F EV residual current device (RCD). These circuit breakers are specifically designed for the loads encountered during charging and are more robust than a standard RCD for wallbox installations. Also, ensure the rated current matches the charging power; for 11 kilowatts, this is typically 40 amps. A dedicated circuit solely for the wallbox is another essential part of a proper installation.

If you're planning on getting a second vehicle or expanding your charging system in the long term, it's worth investing in a well-designed electrical connection. A residual current device (RCD) for wallbox installations should then offer sufficient capacity for additional loads. This way, you avoid having to reconfigure the fuse box every time you expand your charging system.

Installation and registration of your wallbox

Only a qualified electrician may connect a wallbox. They will check the meter cabinet, select the appropriate cable cross-section, and correctly install the residual current device (RCD) for wallbox systems. This ensures that your residual current protection operates according to standards and trips reliably in an emergency.

You must also register any charging station up to 11 kilowatts with the grid operator. More powerful connections even require explicit approval. Your electrician will usually assist you with these formalities and complete the necessary paperwork. Properly documented installation is also important later for subsidies and insurance. The costs for circuit breakers and connections are usually in the low three-figure range, depending on the complexity. If you save on the expensive Type B residual current device (RCD) by using a wallbox with an integrated RCD, the final bill will be significantly lower.

Charging with your own solar power is particularly cost-effective. Combined with our PV systems, you can charge your electric car with solar energy from your own roof instead of buying expensive grid electricity. Our guide on charging your electric car with a balcony power plant shows you how this works in everyday life. Our PV system checklist will help you plan the right system.

Frequently asked questions about the wallbox with residual current device (RCD).

Is a residual current device (RCD) necessary for a wallbox?

Yes. A wallbox with a residual current device (RCD) is mandatory, as every charging station must protect against AC and DC residual currents. Without this protection, operation is neither safe nor compliant with standards.

Is a Type A residual current device (RCD) sufficient for the wallbox?

A Type A residual current device (RCD) is sufficient if the charging station has integrated 6 mA DC fault current detection. If this is missing, a Type B RCD is required, which detects smooth DC fault currents itself.

Why is a Type B residual current device (RCD) often more expensive?

A Type B residual current device (RCD) must cover all types of fault currents on its own, including smooth DC fault currents. This technology is more complex and makes the component significantly more expensive than the combination of a Type A RCD with integrated DC detection.

Am I allowed to install the residual current device (RCD) myself?

No. Installation should be carried out by a qualified electrician. They will ensure that the protection is correctly sized, properly connected, and documented according to standards.

Conclusion

A wallbox with a residual current device (RCD) is essential for safe home charging. DIN VDE 0100-722 requires protection that also detects smooth DC residual currents from 6 mA upwards. You have two options for this. You can either opt for a more expensive Type B RCD or the more affordable combination of a Type A RCD with integrated DC residual current detection. Modern devices like the Sofar Solar Wallbox already include this detection feature, saving you installation costs. Our electrical engineers will be happy to discuss which protection option is best suited to your specific situation.