Posted by Greg Allan.

Difference Between an RCD and a Circuit Breaker

RCD means Residual Current Device and MCB means Multiple Circuit Breaker. As their name suggests, RCDs have got to do with current and MCBs are concerned with circuits. Let’s learn more about them!

If you live in a building constructed after 2009, then the chances are that your home or property most probably has RCDs and MCBs. RCDs were mandated by law in 2009 and every home in Western Australia is required to have 2 RCDs installed before it could be sold, leased, or rented.


Even though the RCDs and the MCBs are quite similar in their look and structure, they perform different types of function altogether. An RCD will save your life by ensuring that in case of a current leakage or an imbalance in current, which could result in electrocution, the current is cut off. It is as easy as that. An MCB will save your home from electrical fires by ensuring that the wires are not overheating and that there is no overload on the various electric circuits.

You need to ensure that you have both of them in your house. The harsh truth about electricity is that even a 30mA of current is enough to cause a cardiac arrest or can cause some irreversible damage to your body. That’s why RCD trips at 30mA limit ensuring that no damage is done and that no one is killed. MCBs have a higher breakpoint of 10, 16, or 32A because it is mostly concerned with the electrical equipment, power consumption, wiring, and cabling of your home. The moment it detects that there’s too much overload on a circuit it will break. Thus it protects your home from the risk of electrical fire by ensuring that the wires don’t overheat and cause any massive damage.


It is required by law to have 2 RCDs installed in your home such that they protect the power and light circuits. For circuit breakers, you need to have one MCB per circuit.

The RCDs are usually installed near the main switchboard. The new MCBs are usually installed above or below the existing circuit breakers.

The RCDs can be tested for their functionality by pushing a button and seeing if it trips or what. There is no sure-shot effective way of testing an MCB.

So, everytime you rent a property, buy a new property, or live someplace new, make sure to check that there are at least TWO RCDs installed in it for your (and your family’s) safety.

Difference Between an RCD and an MCB | | Perth Electricians

Posted by Greg Allan.