Protection: RCDs, earthing and fault safety
How AREI Book 1 protects against electric shock through basic protection, fault protection, RCDs, earthing and equipotential bonding.
Uitleg
This page summarizes AREI rules about protection against electric shock and fault safety.
Looking for the meaning of a breaker, RCD or RCBO first? See Protection devices.
In short
- Basic protection prevents contact with live parts.
- Fault protection prevents exposed conductive parts from remaining dangerously live.
- Household installations have at least one RCD of at most 300 mA at the origin of the installation.
- Additional high- or very-high-sensitivity RCD protection is used for sensitive circuits and special environments.
- Earthing and the protective conductor remain necessary: an RCD does not replace the earthing arrangement and its conductors.
What AREI means by protection
AREI distinguishes between two types of danger:
Direct contact
Someone touches a live part that normally carries voltage.
- Protection uses insulation, enclosures, barriers or placing parts out of reach.
- A high- or very-high-sensitivity RCD can provide additional protection.
Indirect contact
Someone touches an exposed conductive part that became live because of a fault.
- Protection disconnects the fault current quickly enough.
- This requires earthing, protective conductors and suitable protection.
RCD protection in homes
For household low-voltage installations, AREI requires at least one residual-current protective device with a residual operating current of no more than 300 mA at the origin of the installation.
Additional high- or very-high-sensitivity RCDs are used where the risk is higher or the rules require them. In practice this often means 30 mA protection for socket circuits, mixed circuits, wet rooms, outdoor circuits, EV and certain technical systems.
| Protection level | Practical role | What to show on the diagram |
|---|---|---|
| Main RCD | Fire and fault protection at the origin of the installation | Position, sensitivity, rated current and type |
| Additional 30 mA RCD | Personal or additional protection for specific circuits | Which final circuits are downstream |
| RCBO | Overcurrent and RCD protection per circuit | The circuit is protected and disconnected separately |
| Earthing | Reference path for fault currents | Earthing connection, protective conductors and equipotential bonding |
Earthing and equipotential bonding
The earthing installation is more than an earth electrode or earth loop. It includes the earth connection, earthing conductor, main earthing terminal, protective conductors and, where needed, equipotential bonding.
Every building requires main equipotential bonding. It connects extraneous conductive parts, such as metal pipes, to the main earthing terminal so dangerous potential differences are limited.
What should you check on a diagram?
Protection must be visible in the dossier. Do not check only whether “an RCD” has been drawn.
| Question | Why it matters |
|---|---|
| Is there an RCD at the origin of the installation? | AREI expects at least 300 mA protection there |
| Are sensitive circuits grouped logically under 30 mA protection? | This limits risk and nuisance trips |
| Are all exposed conductive parts connected through protective conductors? | Otherwise fault protection cannot work correctly |
| Is the earthing structure understandable? | Inspection and fault analysis rely on it |
| Are PV, battery and EV included in the protection logic? | Sources and heavy consumers change fault and supply paths |
Common errors
- Drawing a 30 mA RCD without showing which circuits it protects.
- Adding an EV charger or PV inverter without revisiting the RCD structure.
- Leaving protective conductors or earthing out of the dossier logic.
- Treating old parts as if exceptions automatically remain after new modifications.
- Putting too many final circuits under one sensitive RCD, causing nuisance trips.