RCD Type A vs. Type B in 2026: Which Protection Do You Need?
RCD types for Belgian domestic installations under AREI/RGIE Book 1 Version 06: Type A, Type B, DC detection, immunity and selectivity.
RCD Type A vs. Type B in 2026: Which Protection Do You Need?
For a Belgian domestic AC installation, AREI/RGIE Book 1 Version 06 requires residual-current devices to be at least Type A. That does not make Type A suitable for every load or Type B mandatory for every electronic appliance. Possible residual-current waveforms, protection inside the equipment and the exact model instructions must be assessed together.
This guide covers domestic AC installations. Earthed DC systems added from 1 April 2026 are a separate application.
Waveform class, immunity and selectivity
AC, A, F or B describes the residual-current waveforms covered. SI, HI or AP-R are manufacturer labels for enhanced immunity to specified disturbances. Selectivity or delay describes timing relative to a downstream device and needs an S classification or documented time characteristic. An A-SI device can be instantaneous and is not automatically selective.
Overview of All RCD Types
| Type | Detects | Application |
|---|---|---|
| AC | Only pure AC fault currents | Does not meet the minimum Type A class for new domestic installations |
| A | AC and pulsating DC residual currents | Domestic minimum class; equipment instructions still apply |
| A-SI | As Type A | Enhanced immunity; not automatically selective |
| B | Also smooth DC residual current | Where equipment and protection design require it |
| F | Certain additional mixed frequencies | For specified single-phase converter loads |
Four independent ratings
The type only answers the waveform question. IΔn (for example 30 or 300 mA) is residual-current sensitivity. In (for example 40 or 63 A) is the current the device can carry continuously; it is not an overload trip setting. An RCD without overcurrent protection therefore needs a suitably coordinated overcurrent device. Breaking capacity or conditional short-circuit current must also be suitable at the installation point.
Pole count, system voltage and wiring matter as well. Every active conductor of the protected circuit passes through the summation transformer, and neutrals from different RCD groups must not be mixed. The test button checks an internal device function; it does not measure earth resistance or prove the entire protection measure. The required inspection uses additional tests and measurements.
New, altered or existing?
“At least Type A” is the baseline for new domestic work. For an existing part, establish its date, any Part 8 deviations and whether an alteration or extension triggers current requirements for the changed portion. An installed Type AC must therefore not be called generally acceptable without that analysis, but its presence alone does not prove that the whole legacy installation is unusable.
Start with the circuit and equipment, not a slogan
“PV means Type B” and “domestic means Type A” are not design rules. A heat pump may combine a compressor drive, backup heater and controls with different manufacturer conditions. For PV, inverter topology, internal monitoring and the connection arrangement matter. For an EV charging point, establish whether an RDC-DD is built in and which external RCD may be coordinated with it. Where several electronic loads share an RCD, assess their combined normal leakage and possible DC components.
Type F or B is not simply “better” than Type A. Wider waveform coverage does not replace correct sensitivity, rated current, disconnection time, overcurrent protection or wiring. Nor should an instruction for one item be applied automatically to the whole board. The complete protective chain from supply origin to load must be coherent.
Investigate unwanted tripping before changing type
Replacing a device with an SI-labelled version is not a diagnosis. First check insulation faults, moisture, mixed neutrals, cumulative leakage and wiring errors. Enhanced immunity can then be considered where the manufacturer's documentation covers the disturbance, without weakening the required protection against electric shock.
For cascaded RCDs, manufacturer coordination data is more meaningful than the labels 300 mA and 30 mA alone. The upstream selective device needs an appropriate time characteristic and the downstream device must still disconnect within the required time. Keeping sufficient margin between cumulative normal leakage and the operating range can improve robustness, but cannot guarantee that an installation never trips.
A combined RCBO can provide residual-current and overcurrent protection for one final circuit. Its waveform class must still match the load, and coordination with an upstream RCD remains necessary. With a separate RCD, the In rating does not provide overload protection. Upstream protection, board arrangement and possible load currents must be designed together. Record the exact product reference and instructions, not only “30 mA Type A”, so later work is based on verifiable characteristics.
When Is Type B Required?
Type B is relevant where smooth DC residual current can occur and no other permitted combination covers it. For a heat pump or PV inverter, check the waveforms identified by the manufacturer, internal DC monitoring, the specified external type and coordination of multiple converters. “Inverter” or “transformerless” does not establish a universal Type B requirement.
When Is Type A Sufficient?
Type A is sufficient for:
- Charging point with coordinated DC detection: AREI 7.22.4.1.b requires an individual RCD of no more than 30 mA for each separate AC circuit, plus either a device that remains effective under the disruptive DC component, such as a suitable Type B, or an RCD coordinated with residual DC detection, such as Type A plus an RDC-DD. Protection may be in the installation, charger or both.
- 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_b | No more than 300 mA at the origin, followed by high-/very-high-sensitivity protection for the listed domestic circuits |
| 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
Placing 300 mA upstream of 30 mA does not guarantee selectivity. Assess the ratio of rated residual currents, an explicitly selective or suitably delayed upstream characteristic, permitted product combinations, disconnection times and normal leakage currents. Enhanced immunity does not replace coordination. Without evidence, do not promise that only the downstream device will trip.
A six-step selection sequence
- Identify the circuit and connected equipment.
- Establish AREI baseline protection and sensitivity.
- Read each manufacturer's waveform, DC-detection and external-RCD requirements.
- Verify time/current coordination for exact cascaded models.
- Document type, sensitivity, rated current and any delay.
- Have the completed installation inspected by an approved body.
Sources and related guides
- AREI/RGIE Regulations 2026
- Do you need 30 mA for every socket?
- Plan an EV charger under AREI
- Start in PlanElec
Primary sources: AREI/RGIE Book 1 Version 06, 4.2.4.3.b, 5.3.5.3.a and 7.22.4.1.b, plus the Directorate-General for Energy FAQ on the Royal Decree of 5 March 2023. PlanElec records protection data, includes it in the diagram and PDF, and flags supported cases in an indicative self-check. It does not replace professional design or official inspection.