RCD Types Explained: AC, A, F, B
Modern electrical loads produce fault currents that Type AC RCDs cannot detect. Here's what each type detects and when the regulations require it.
Why the RCD type matters
An RCD (Residual Current Device) measures the difference between line and neutral current. If the difference exceeds the trip threshold (typically 30 mA), it trips — indicating current is flowing to earth through an unintended path (fault, person contact).
The problem: different loads create different types of fault current. A Type AC RCD only detects sinusoidal AC fault current. Modern electronics (LED drivers, inverters, EV chargers) can produce fault currents with DC components — which a Type AC RCD cannot detect at all, providing zero protection.
⚠️ Type AC is now prohibited for new installations in most EU countries
Germany (VDE 0100-530:2023), France (NF C 15-100:2023) and other national standards now require Type A as the minimum for all circuits in new residential buildings.
The four RCD types
Detects: Sinusoidal AC fault current only
- • Detects: pure sinusoidal AC fault current
- • Does NOT detect: pulsating DC, smooth DC, high-frequency
- • Permitted in existing retrofits only in some countries
- • Still available but should not be specified for new work
Typical use: Not recommended — use Type A or higher
Detects: AC + pulsating DC fault currents
- • Detects: sinusoidal AC AND pulsating DC (up to 6 mA smooth DC)
- • Required for: washing machines, dishwashers, microwave ovens (all have SMPS with DC components)
- • Required for: LED drivers, most modern consumer electronics
- • IEC 62423 / EN 61008 Type A
Typical use: Default for all domestic circuits, sockets, lighting
Detects: AC + pulsating DC + composite HF currents
- • Detects everything Type A detects, plus:
- • Composite high-frequency fault currents from VFDs (variable frequency drives)
- • Required for single-phase VFDs (dishwasher inverter motors, washing machine inverters)
- • Type F is supersensitive to HF components — prevents nuisance tripping with inverter-controlled appliances
Typical use: Single-phase VFD loads, high-end washing machines, heat pumps with inverters
Detects: AC + pulsating DC + smooth DC fault currents
- • Detects ALL fault current types including smooth DC
- • Required for: EV Type 2 chargers (7–22 kW) — 3-phase rectifier produces smooth DC fault current
- • Required for: PV inverters, three-phase VFDs, UPS systems
- • Required for: medical equipment (SELV/PELV circuits)
- • Significantly more expensive than Type A
Typical use: Mandatory for EV chargers, 3-phase drives, PV inverters
Quick selection guide
| Load / Circuit | Minimum RCD type | Why |
|---|---|---|
| General sockets (domestic) | Type A | SMPS in modern appliances |
| Lighting (LED drivers) | Type A | LED drivers have DC components |
| Kitchen appliances | Type A | Inverter-driven appliances |
| Washing machine (inverter) | Type F | HF composite fault currents |
| EV charger (Type 2, 7kW+) | Type B | 3-phase rectifier, smooth DC |
| PV inverter | Type B | DC fault currents |
| 3-phase VFD motor | Type B | Smooth DC fault current |
| Fire alarm, emergency lighting | Type A / as specified | Low leakage, sensitive |
| Medical equipment | Type B | IEC 60364-7-710 |
Sensitivity ratings
RCDs are available in different trip current thresholds for different purposes:
Bathrooms, supplementary protection for socket circuits in bathrooms (IEC 60364-7-701)
Standard for all socket circuits and most final circuits. Protects against lethal shock.
Selective (time-delayed) upstream RCDs for discrimination. Does not protect against shock — used for fire protection only.
Main incomer discrimination RCD in commercial buildings. Fire protection only.
RCD selection handled for your project
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