Distribution Board / Panel
Switchgear
A metal or plastic enclosure that splits incoming mains power into multiple protected circuits. Each outgoing circuit has its own breaker or fuse, with a common neutral and earth busbar.
Schematic symbol
Switch (SPST)
How distribution board / panel appears in a circuit diagram.
Types & variants
Key specs
Rated current
AMain incomer rating: 63A, 100A, 125A residential; up to 1000A industrial.
Voltage rating
V240V single-phase, 415V three-phase. 600V class typical.
Number of ways
—How many breaker slots. Common: 4, 8, 12, 16, 24-way.
Fault rating
kAMax short-circuit current the board can clear: 6kA residential, 10–25kA commercial.
IP rating
—Ingress protection. Indoor: IP40. Outdoor / damp: IP65.
Markings
Incomer rating (e.g. 100A), voltage (240/415V), manufacturer (Hager, Schneider, ABB, Legrand), fault rating (e.g. 6kA), IP rating. Each breaker slot numbered for circuit identification.
Standard values
Residential main incomer: 63A or 100A single-phase. Outgoing: 6A (lighting), 16A (sockets), 32A (water heater / cooker), 40A (EV charger). DIN-rail modules: 17.5mm wide per module.
How to choose
1) Calculate total load + 20% headroom → main incomer rating. 2) Count circuits → number of ways (allow spares). 3) Match breaker type to wiring (RCBO per circuit is best practice). 4) Choose IP rating for environment. 5) Use three-phase if total load > ~15kW. 6) Always hire a licensed electrician — this is not DIY work.
Pinout & package
DIN-rail mounted in a wall box. Top: main isolator / incomer. Below: rows of MCBs / RCBOs on busbar. Neutral and earth busbars on the side. Knockouts at top/bottom for cable glands.
Example circuits
- Residential split-load consumer unit (lights on RCD side, sockets on another)
- Garage sub-panel fed from main house panel
- Workshop three-phase distribution for machinery
- Solar PV AC distribution board (with isolation + surge protection)
- EV charger dedicated circuit on RCBO
Common failures
Busbar overheating from loose connections (most common cause of fires). Breaker failure to trip on overload. Corrosion on busbar contacts in damp environments. RCD nuisance tripping from accumulated leakage.
How to test
POWER OFF and isolated. Tighten all terminal screws to specified torque. Insulation resistance test between phases, phase-neutral, phase-earth (megger at 500V — should read >1MΩ). RCD trip test with built-in test button annually.
Substitutes
Cannot be substituted — a panel is required. Older fused wire boards can be upgraded to MCB distribution boards for better protection.