RCD Type A or Type B? The AREI Rule in 2026
In Belgian homes every RCD is at least Type A. When you need Type B or Type A with RDC-DD – EV charger, heat pump, PV – and why A-SI does not mean selective.
AuthorStephan BehmShort answer: at least Type A, Type B only for smooth DC fault current
Every RCD in a Belgian domestic installation must be at least Type A (AREI Book 1, subsection 5.3.5.3(a)). You need Type B where smooth DC fault currents can occur and no other permitted combination covers them. For EV chargers the rule is fixed: either an RCD that keeps working with a DC fault component (for example Type B), or an RCD together with a residual direct-current detecting device, for example Type A plus an RDC-DD in the charging station (7.22.4.1(b)).
For every other appliance the datasheet decides: which fault-current waveforms are possible, is DC monitoring built in, which external RCD does the manufacturer specify? "Has an inverter" is not on its own a reason for Type B.
This article covers domestic AC installations under Book 1, version 06, applicable since 1 April 2026. Earthed DC systems, which version 06 now regulates, are a separate topic.
Type, high immunity and selectivity are three different things
- AC, A, F or B states the fault-current waveforms for which tripping is guaranteed.
- High immunity (manufacturer codes such as SI, HI or AP-R) reduces nuisance tripping under certain disturbances.
- Selectivity or time delay describes timing relative to a downstream RCD. What counts is an S marking or a documented time characteristic.
A "Type A-SI" is therefore not automatically selective. Some A-SI devices trip instantaneously.
All RCD types at a glance
| Type | Detects | Use in Belgian homes |
|---|---|---|
| AC | Pure AC fault currents only | Does not meet the minimum Type A requirement |
| A | AC and pulsating DC fault currents | Minimum class (5.3.5.3(a)); appliance requirements still apply |
| A-SI | Same waveforms as Type A | Higher immunity to disturbances; not automatically selective |
| F | Additionally certain mixed frequencies | For certain single-phase inverter loads per the manufacturer |
| B | Additionally smooth DC fault currents | When the protection concept or the manufacturer requires it |
New in version 06: sensitivity classes now distinguish AC or pulsating DC from smooth DC. "High sensitivity" means more than 10 mA up to 30 mA for AC, and more than 20 mA up to 80 mA for smooth DC (2.6.4).
Four ratings on the device you must not confuse
- Type (A, F, B …): detected fault-current waveform.
- IΔn (for example 30 or 300 mA): sensitivity to residual current.
- In (for example 40 or 63 A): the current the RCD may carry continuously. It does not trip on overload, so a plain RCD needs coordinated overcurrent protection.
- Short-circuit withstand or conditional short-circuit current: must suit the installation point (5.3.5.3(a)).
Number of poles, supply voltage and wiring matter too: all live conductors of the protected circuit pass through the core-balance transformer, and neutrals of different RCD groups are never mixed. The test button checks the internal mechanism – not the earthing resistance and not the complete protective measure. Only the measurements during inspection do that.
When do you need Type B?
Type B comes into play when smooth DC fault currents are possible and no other combination permitted by AREI and the manufacturer covers that risk. Check the actual appliance:
| Appliance | What decides |
|---|---|
| EV charger | 7.22.4.1(b): Type B or RCD plus coordinated RDC-DD (in the installation, the charger or both) |
| Heat pump | Datasheet of compressor drive, backup heater and controls; specified external RCD |
| PV inverter | Inverter topology, internal residual-current monitoring, manufacturer's requirement for the external RCD |
| Several inverters on one RCD | Assess the sum of normal leakage currents and possible DC components together |
"Transformerless" or "has an inverter" does not create a general Type B obligation. Conversely, Type B or F is not simply "better": a wider waveform range does not replace correct sensitivity, rated current, disconnection time, overcurrent protection or proper wiring.
When is Type A enough?
- Socket and lighting circuits: the usual 30 mA Type A RCD.
- Ordinary household appliances such as washing machine, dishwasher, cooker and lighting, unless the manufacturer specifies otherwise.
- EV charger with built-in RDC-DD: each charging circuit gets its own RCD of no more than 30 mA (7.22.4.1(b)). If the charging station has a residual DC detecting device coordinated with the external RCD, Type A is sufficient there. The charger's datasheet documents that coordination.
New, modified or existing?
"At least Type A" is the selection basis for new domestic installations. For an existing installation, also check when it was built, which Part 8 deviations apply and whether a renovation or extension triggers current requirements for the modified part. An existing Type AC is therefore neither acceptable without review nor automatic proof that the whole installation is unusable.
Nuisance tripping: cause first, device second
If an RCD trips for no apparent reason, "fit an A-SI" is not a diagnosis. First check insulation faults, moisture, swapped or shared neutrals, leakage currents and wiring errors. Only then assess whether a device with documented high immunity is suitable. High immunity must not weaken protection of persons.
A combined RCD/circuit breaker (RCBO) provides residual-current and overcurrent protection for a single final circuit. Its type must still match the load, and coordination with the upstream RCD remains necessary. Record the actual device reference in the dossier – datasheet, wiring diagram and installation instructions – not just "30 mA Type A".
Selectivity: 300 mA ahead of 30 mA is not enough
Grading 300 mA ahead of 30 mA does not guarantee selectivity. Check the ratio of rated residual currents, an explicitly selective or time-delayed characteristic on the upstream device, the manufacturer-approved combination, disconnection times and normal leakage currents. High immunity does not replace time/current coordination. Only with that evidence does a fault reliably trip just the group RCD.
AREI references at a glance
| AREI Book 1 | Requirement |
|---|---|
| 2.6.4 | Sensitivity classes for AC/pulsating DC and for smooth DC |
| 4.2.4.3(b) | No more than 300 mA at the origin; downstream, sensitive protection for the listed circuits |
| 4.2.4.3(b) | Max. 8 final circuits per high- or very-high-sensitivity RCD |
| 5.3.5.3(a) | In homes at least Type A; origin RCD at least 40 A; short-circuit withstand suited to the location |
| 7.22.4.1(b) | EV charger: own RCD ≤ 30 mA per charging circuit; DC-proof RCD or RCD plus DC detection |
Selection in six steps
- Identify the circuit and every connected appliance.
- Set the AREI minimum protection and sensitivity.
- Check manufacturer documents for fault waveform, DC detection and the specified external RCD.
- For cascades, prove time/current coordination of the actual models.
- Document type, sensitivity, rated current and delay in the single-line diagram.
- Have the completed installation inspected by the approved inspection body.
Record and check RCD data in PlanElec
In PlanElec you record type, sensitivity and rated current for every RCD; the data appear in the single-line diagram and the PDF. The AREI/RGIE self-check flags, among other things, a main RCD below 40 A, an EV charger without its own RCD, a charger RCD that is neither Type B nor paired with an RDC-DD confirmed in the inspector, and – as a practice recommendation based on IEC 60364-5-53 – an upstream RCD without time delay. The full scope is in What the self-check verifies. Manufacturer coordination and measurements are verified on the real device; the inspection is carried out by the approved inspection body.
Related articles
Legal basis: AREI/RGIE Book 1, version 06, section 2.6.4 and subsections 4.2.4.3(b), 5.3.5.3(a) and 7.22.4.1(b). The official text published by the FPS Economy prevails.