Residual current rating (IΔn)
| IΔn | Purpose |
|---|---|
| 6–10 mA | The most sensitive personal protection - individual critical points: bathroom, nursery, a socket for one specific appliance. |
| 30 mA | The main protection of people against electric shock: socket circuits, wet rooms, outdoors. The household standard. |
| 100 mA | Fire protection, main and group panels. No longer protects a person from shock. |
| 300–500 mA | Fire protection at the service entrance of large buildings and for selectivity between cascaded RCDs. |
Type by leakage current waveform
| Type | Responds to | Where it is used |
|---|---|---|
| AC | Sinusoidal AC leakage current | Legacy type, for simple loads without electronics. Often no longer recommended. |
| A | AC + pulsating DC | The modern household standard: sockets, washing machines, dishwashers, anything with electronics. |
| F | Like A + high-frequency components | Appliances with variable-frequency drives, some household equipment. |
| B | Like A/F + smooth DC | EV chargers, solar panels, three-phase electronics. |
Natural leakage current calculator
Natural leakage = 0.4 mA per amp of load + 0.01 mA per metre of cable. The rating should exceed three times the natural leakage, otherwise nuisance tripping is likely.
RCD current rating
A plain RCD has no overload or short-circuit protection - it is paired with a circuit breaker, and the RCD's current rating must be at least the breaker's rating (e.g. a C25 breaker - a 40 A RCD). The wire and breaker calculator helps pick the breaker.
RCD or RCBO
An RCBO is a breaker and an RCD in one case: it protects against overload, short circuit and leakage, and saves panel space. A separate RCD + breaker take more space, but when something trips you immediately see the cause (leakage or overload), and replacing a single module is cheaper.
Selectivity
With cascaded RCDs (at the entrance and on groups), the upstream one should be type S (time-delayed) with a rating at least 3× the downstream ones - otherwise a leakage trips the whole panel instead of one line.
Important
Reference material, per IEC 61008/61009 and local wiring codes. Ratings, mandatory application areas and selectivity depend on the specific installation; design and installation should be done by a qualified electrician.