Difference between an RCD and circuit breaker

Question

What's the difference between an RCD and a circuit breaker? Or are they the same thing?

Bill · Accepted Answer

An MCB is an overload device, designed to operate if there is a short circuit fault or if the current being used on the circuit exceeds the rated current of the device. For instance, you have too many appliances being used at the same time, or if a cable is damaged causing a direct short between live and earth, or live and neutral. 
 An RCD on the other hand is not an overload device, it is designed operate under current leakage faults, it limits the amount of current that can flow in the event of an electric shock. If electricity if flowing down an unintended path, like yourself, the RCD will detect this and trip out. In households the RCD is limited to 30mA, as it only takes 50mA to stop your heart.

Craig · Answer

The circuit breaker protect the electrical wiring and system in the property,
the RCD or RCBO protects  people from getting an electric shock or electrocution

Lee · Answer

A circuit breaker trips out when there's a live to earth/ live to neutral fault or on overload

An RCD trips out when there is an earth to neutral fault

Ian · Answer

An RCD is short for residual current device and protects against electric shock in the event if a fault on either the circuit or applicance. A circuit breaker protects the circuit from current overload and will trip if it's maximum stated current (e.g. 32 amp) is exceeded.

Jason · Answer

They are both generic terms, and each one can mean more than one thing, however generally in a domestic setting, an RCD is a device which disconnects the supply when a residual current is detected (hence R C D) but a circuit breaker (for example an MCB) is a device which disconnects the supply when an overcurrent is detected.  Usually RCDs don't protect from overcurrent and need to be used in conjunction with an MCB.

However nowadays, most electricians tend to fit RCBOs instead, which are a combination of an RCD and an MCB.  These protect you from earth leakage as well as overcurrent.  This avoids having an RCD protecting several different circuits which isn't ideal as accumulative minor faults can cause nuisance tripping.

Mujib · Answer

Both forms of protection however a breaker will only trip out on overload or short circuit

And a rcd will only trip out on earth leakage or earth related faults

To get the best of both worlds use either rcbo's or mcbs which are protected by rcds

Simon · Answer

Hi 
A rcd protect a person from accidents a circuit breaker protect the wiring

Chris · Answer

rcbos are a circuit breaker version of a rcd.... They are not the same thing.... Rcbos and rcds are very similar if not almost the same in practical terms.

Ryan · Answer

Rcd is fault protection.

Basic protection is mcbs

Mitch · Answer

A residual current device is a safety device that must be in place in order to work on any circuit be it an RCD additional to a MCB or RCBO.

Trevor · Answer

An RCD will activate on fault current therefore protecting the user from a potential fatal shock, and MCB will work on overload protecting the installation. There's a device called an RCBO which combines the duty of both the MCB and RCD.

hope you find this information useful.

Difference between an RCD and circuit breaker

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