RCD Type A vs. Type B: When Do I Need Which?
Comparison of all RCD types (AC, A, A-SI, B, F) for Belgian electrical installations according to AREI/RGIE standards.
RCD Type A vs. Type B: When Do I Need Which?
The AREI prescribes at least an RCD Type A as the minimum. Type B is required when smooth DC fault currents can occur — typically with EV chargers without an integrated DC fault current sensor or heat pumps with a frequency inverter. Choosing the correct RCD type is critical for safety and inspection compliance.
Overview of All RCD Types
| Type | Detects | Application | Price (approx.) |
|---|---|---|---|
| AC | Only pure AC fault currents | Obsolete, no longer permitted for new installations | ~€25–40 |
| A | AC + pulsating DC fault currents | Standard for residential use | ~€40–60 |
| A-SI | Same as Type A, selective (time-delayed) | Main RCD (300 mA), prevents cascade tripping | ~€80–120 |
| B | All fault currents including smooth DC | EV charger, heat pump with inverter | ~€150–250 |
| F | Same as A + frequency-controlled fault currents | Variable-frequency drives (motors) | ~€100–180 |
When Is Type B Required?
Type B is necessary when a device can generate smooth DC fault currents. This primarily applies to:
- EV charger (charging station) without integrated DC fault current sensor: Simple charging stations without 6 mA DC detection require a Type B RCD
- Heat pump with inverter (frequency converter): The frequency converter can generate DC fault currents
- PV inverter without transformer: Transformerless inverters can feed DC components into the grid
When Is Type A Sufficient?
Type A is sufficient for:
- EV charger WITH integrated DC fault current sensor (6 mA): The AREI (Art. 7.22.4) requires Type B or equivalent (e.g., Type A + RDC-DD). A simple Type A alone is not sufficient for an EV charger — the charger must have an integrated DC 6 mA sensor that detects DC fault currents from 6 mA and interrupts charging
- Normal household appliances: Washing machine, dishwasher, cooktop, lighting
- Socket circuits: Standard 30 mA RCD Type A
AREI Requirements
| AREI Article | Requirement |
|---|---|
| Art. 4.2.4.3 | RCD is mandatory for every circuit (TT system) |
| Art. 4.2.4.3_b | Maximum 8 final circuits per 30 mA RCD |
| Art. 5.3.5.3_a | Residual-current devices in residential installations must be at least Type A; at the feed point at least 40 A rated current |
| Art. 7.22 | EV charger: Dedicated circuit with appropriate RCD |
Ensuring Selectivity
For correct selectivity, the installation should be structured as follows:
- Main RCD: 300 mA, Type A-SI (selective, time-delayed)
- Group RCDs: 30 mA, Type A (for normal circuits)
- Special RCD: 30 mA, Type B (for EV charger/heat pump, if no DC sensor present)
This way, in case of a fault, only the responsible group RCD trips, not the main RCD — the rest of the installation remains operational.
Price Difference and Recommendation
The price difference between Type A (€40–60) and Type B (€150–250) is substantial. Therefore, always first check whether your EV charger or heat pump has an integrated DC fault current sensor. If so, a less expensive Type A RCD is sufficient. The manufacturer's documentation provides this information.
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