Types of Circuit Breakers and How to Choose Them

A circuit breaker is the first line of protection for a circuit: it disconnects the supply on overload, short circuit or earth leakage. Choosing the right type and rating has a direct effect on building safety and the life of the installation. Here are the common types and how to read their specifications.

Types of circuit breakers

MCB (miniature circuit breaker)

Protects a circuit against overload and short circuit. Used in residential and commercial distribution boards with common ratings from 6 A to 63 A.

RCCB / RCD (residual current device)

Monitors the difference between outgoing and returning current and trips when current leaks to earth. It protects people from electric shock, typically with 30 mA sensitivity on residential circuits. It does not protect against overload on its own, so it is used together with MCBs.

RCBO

Combines MCB and RCCB protection in one device per circuit, so only the affected circuit trips.

MCCB (moulded-case circuit breaker)

Higher ratings, with adjustable settings on some models; used for main feeders and larger boards in commercial buildings.

Trip curves B, C and D

Curve	Typical use
B	Normal domestic loads and lighting with low inrush current
C	Commercial loads, small motors and AC units with moderate inrush
D	Motors and transformers with high inrush current

Poles and breaking capacity

Breakers come as single-pole (1P) for single-phase circuits, double-pole (2P) to switch phase and neutral together, and three- or four-pole (3P / 4P) for three-phase circuits. Breaking capacity (kA) is the maximum short-circuit current the breaker can safely interrupt, set by the designer according to the fault level at the board.

Indicative breaker selection table

Circuit	Common wire size	Common breaker*
Lighting	1.5 mm²	MCB 10 A, curve B
General sockets	2.5 mm²	MCB 16–20 A, curve B
Water heater	4 mm²	MCB 20–25 A
AC unit	4 – 6 mm²	MCB 25–32 A, curve C
Personal protection in wet areas	—	RCCB or RCBO, 30 mA

* Indicative only. Breaker selection must match the cable size, actual load and circuit design, and be decided by an engineer or licensed electrician in line with the Saudi Building Code.

See the breakers and boards we supply on our breakers and distribution boards page, and match breakers to wire sizes with our electrical wire sizes guide.