Electrical guide · 2026-08-11
RCB, RCCB and MCB: A Simple Singapore Homeowner Guide
Homeowners often use RCB, RCCB and MCB interchangeably, but these labels can refer to different protective functions. The important question during a fault is which device operated and why.
Lightweight service animation
Electrical concept at a glance
Trip → diagnose → reset or repair
MCB: circuit overcurrent protection
An MCB is commonly associated with protecting a circuit against excessive current conditions. If one MCB repeatedly trips, the affected circuit and connected loads need investigation.
RCCB / residual-current protection
Residual-current protection is intended to respond to leakage-type fault conditions. If this device will not stay on, the fault can involve wiring, equipment, moisture or another issue that requires testing.
Why the label alone does not tell you the fault
A tripped device identifies where protection operated; it does not automatically identify the failed component. Diagnosis should test the circuit and connected equipment rather than replacing the breaker first.
What to photograph
A straight-on photo of the DB labels and the device that has moved to the off/tripped position can be useful, provided the cover remains closed and there are no exposed parts.
Related questions
Should I replace an MCB because it trips?
Not automatically. The cause of the trip should be identified first; the breaker may be responding correctly to a circuit or load problem.
What does RCCB mean?
It is a common term for a residual-current protective device. Exact devices and installation arrangements vary.