All component comparisons
MCB vs RCCB
MCB (Miniature Circuit Breaker) and RCCB / RCD / GFCI compared — what each is better at, and which one the job actually calls for.
These are not alternatives, and treating them as such is the mistake worth avoiding: they protect different things. An MCB trips on overcurrent and short circuit — it protects the wiring from melting. An RCCB trips when the current going out does not match the current coming back, which is the signature of current leaking to earth through something, possibly a person. A consumer unit normally needs both, which is why the combined RCBO exists.
What each one is
MCB (Miniature Circuit Breaker)
A resettable mains circuit breaker that trips on overload or short circuit, protecting house/building wiring. Replaces rewireable fuses; just switch it back on after a trip.
RCCB / RCD / GFCI
A device that quickly cuts power when it detects leakage current to ground, protecting against electric shock and fire hazards.
Key specs
MCB (Miniature Circuit Breaker)
- Rated current (In)(A)
- Continuous current, e.g. 6, 10, 16, 20, 32A.
- Trip curve(B/C/D)
- Magnetic trip multiple for short-circuit response.
- Breaking capacity (Icn)(kA)
- Max fault current it can interrupt, e.g. 6kA/10kA.
- Poles(-)
- 1P (live), 2P (live+neutral), 3P/4P for three-phase.
RCCB / RCD / GFCI
- Trip current(mA)
- Current level at which the device trips (typically 10mA, 30mA, or 40mA).
- Breaking capacity(kA)
- Maximum fault current the device can safely interrupt without damage.
- Response time(ms)
- Time to trip when leakage current exceeds threshold (typically <30ms).
- Voltage rating(V)
- Maximum system voltage the device is designed to protect.
Types you will meet
MCB (Miniature Circuit Breaker)
- Type B (trips 3-5x, lighting/sockets)
- Type C (5-10x, motors/inductive)
- Type D (10-20x, high inrush)
- 1P / 2P / 3P / 4P
RCCB / RCD / GFCI
- Type A (AC only)
- Type A-S (AC and pulsating DC)
- Type B (AC and smooth DC)
- 40mA sensitivity
- 30mA sensitivity
- 10mA sensitivity
- Combined RCBO (with overload protection)
How to choose
MCB (Miniature Circuit Breaker)
Size In to the cable's safe current (not the load) and coordinate with wire gauge. Type B for general/lighting, C for motors/AC, D for heavy inrush. Breaking capacity >= prospective fault current. Pair with an RCD/RCBO for shock protection.
RCCB / RCD / GFCI
1) Select trip current based on application (30mA for general use). 2) Ensure voltage rating matches your supply. 3) Check breaking capacity for your circuit's fault level. 4) Choose Type A for most residential/commercial use, Type B for specialized DC applications.
How each one fails
MCB (Miniature Circuit Breaker)
Nuisance tripping (under-rated or faulty), fails to trip (dangerous - replace), worn contacts, loose terminals causing heat.
RCCB / RCD / GFCI
Failure to trip when needed (mechanical wear or contamination), nuisance tripping (moisture or dust), internal circuit damage. Test button should be used monthly to verify functionality.
Full reference for each part
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