Is a Main Switch Mandatory? What AREI Requires
Yes: every main distribution board needs a main switch-disconnector that breaks all line conductors at once – at least 40 A in homes (AREI 5.3.5.1(b)). All requirements at a glance.
AuthorStephan BehmShort answer: yes, at least 40 A in homes
Yes, a main switch is mandatory in Belgium. Under AREI Book 1, subsection 5.3.5.1(b), every main distribution and switching board is fitted with a main switch-disconnector that breaks all line conductors and, where applicable, the neutral simultaneously. Its rated current suits the installation and is at least 25 A in general, at least 40 A in domestic installations.
Unlike a plain disconnector, a switch-disconnector may be operated under load. That is exactly what makes it the main switch: one action and the whole installation is dead.
The requirements at a glance
| Requirement | What AREI requires | Reference |
|---|---|---|
| Present | Main switch-disconnector on the main distribution and switching board | 5.3.5.1(b) |
| All line conductors at once | One operation breaks all line conductors and, where applicable, the neutral | 5.3.5.1(b) |
| Rated current | suited to the installation; at least 25 A, at least 40 A in homes | 5.3.5.1(b) |
| Exception | The network operator's overcurrent device may perform the function if designed to provide isolation | 5.3.5.1(b) |
| Accessible | Board easy to operate and maintain; in homes reachable without special aids | 5.3.5.1(c) |
In practice "all line conductors and, where applicable, the neutral" means: two-pole on a single-phase supply, four-pole on 3N~400 V and three-pole on 3×230 V without neutral. AREI sets no fixed mounting height; what matters is that you can reach the board without a ladder, tools or moving furniture.
What the main switch is for
- Emergency disconnection: in a fire, flood or electrical accident, any occupant switches off the whole installation with one action – no expertise needed.
- Isolation for work: anyone working on the installation first separates it safely from the grid.
Typical findings at inspection
In older installations the main switch is sometimes missing entirely, or there is only a single-pole switch that does not break the neutral. Check these points before the inspection:
- Is a main switch present?
- Does it break all line conductors (and the neutral where present) at once?
- Is its rated current at least 40 A in a home and suited to the installation?
- Is the board freely accessible – not behind furniture or in a locked room?
Main switch and main fuse are two different things
The main switch is not overcurrent protection. It isolates; it does not protect. Overcurrent protection comes from the network operator's device ahead of the meter and the circuit breakers in the board. Conversely, the network operator's device may take over the main-switch function only if it is expressly designed for isolation (5.3.5.1(b)). The breaking capacity needed downstream is explained in Breaking capacity of circuit breakers.
Main switch and the RCD at the origin
At the origin of a domestic installation there is also at least one RCD of at most 300 mA, at least Type A and rated at least 40 A (4.2.4.3(b), 5.3.5.3(a)). It provides the isolating function under 5.3.3.1 a.3. That is a requirement on this device, not an exception to 5.3.5.1(b): as a substitute for the main switch-disconnector, the AREI expressly names only the network operator's overcurrent device. Whether a single device fulfils both roles is shown by its ratings. In any case, the single-line diagram must make clear which device performs the main switch-disconnector function.
Planning the main switch in PlanElec
In PlanElec you place the main switch with its number of poles and rated current in the single-line diagram and the board. The AREI/RGIE self-check reports a missing main switch and a main switch below 40 A in a home as errors. The full scope is in What the self-check verifies. The inspection of the completed installation is carried out by the approved inspection body.
Related articles
- Inspection checklist: what the inspector verifies
- A 30 mA RCD for every socket?
- Electrical inspection in Belgium
Legal basis: AREI/RGIE Book 1, version 06, subsection 5.3.5.1(b) and (c), supplemented by 4.2.4.3(b), 5.3.3.1 a.3 and 5.3.5.3(a). The official text published by the FPS Economy prevails.