Three-phase residential consumer unit with 37 circuits and AFDD protection

A distribution board for a home on a three-phase supply, built in a Schrack Modul 160 Compact enclosure. It feeds 37 circuits, every one of them protected at 30 mA residual current, with arc fault detection on six circuits and surge protection at the incomer.

Incoming section

• Four-pole main switch-disconnector — isolates the whole board from a single point.
• Surge protective devices — limit transient overvoltages from the network before they reach the equipment in the home.
• Voltage monitoring relay with display, driving a four-pole contactor — if the voltage leaves the permitted range or a phase is lost, the contactor disconnects the supply and protects the connected equipment.
• Distribution blocks on each phase and on neutral, feeding the circuit groups.

Circuit layout

The circuits are split into independent groups, so a fault on one circuit does not leave the whole home without power:

• Three groups of 8 single-phase circuits, each group behind its own 63 A / 30 mA RCD.
• Four RCBOs (circuit breakers with built-in residual current protection), for circuits that must not depend on any other group.
• Six arc fault detection (AFDD) circuits, spread evenly across the three phases and fed from a three-phase busbar.
• Three four-pole C20 / 30 mA RCBOs, for the home's three-phase loads.

Circuits were assigned to phases to keep the load as balanced as possible, and spare rail space was left for future additions.

Wiring and identification

Every conductor carries an identification marker, and the connection to the home's installation runs through numbered terminal rows on dedicated rails, with separate terminals for neutral (blue) and protective earth (green-yellow). Any circuit can be traced, disconnected or changed later without disturbing the rest of the wiring.

For what a residential consumer unit should contain in general, see our article What a residential consumer unit should contain.