What is difference between an ELCB and RCCB?

Answer 1

What is an ELCB?

An Earth Leakage Circuit Breaker was the first name given to what is now called a Ground Fault Circuit Interrupter (GFCI) . The original type of ELCB or GFCI was designed only to detect a current flowing in the safety "ground" or "earth" wire.

If there is no fault anywhere in a circuit supplying single-phase alternating power to a unit such as an electrical appliance, machine or other equipment, the current flowing to the unit at any instant in the "hot" or "live" wire should exactly match the current flowing away from the unit in the neutral wire. Similarly, there should be no current flowing in the unit's safety "ground" or "earth" wire.

It is a basic fact of electrical engineering design that all current flowing to an electrical appliance, machine or other equipment from the power generation station via its supply circuit's "hot" or "live" wire should only return to the power station via that same circuit's "neutral" wire.

So, as a result of that basic fact, if any current isflowing in the ground wire, it must be caused by a fault condition and the supply of current to the circuit needs to be stopped urgently. Many years ago, before today's electronic RCDs or GFCIs were designed, much simpler electro-mechanical relays called Earth Leakage Circuit Breakers (ELCBs) were invented so that, if any such ground current exceeding just a few milliamps was detected, they would "trip" - meaning "operate" - to break the current supply to the circuits for which they were installed to protect.

The original type of ELCB or GFCI did not check for any difference in current flowing in the live and neutral wires, which is another indication of a very serious fault condition - even if no current can be detected flowing in the ground wire - because the "missing current" may actually be flowing to ground via someone's body!

When RCDs were invented, most manufacturers of GFCIs adopted the same technology because it offers so much more protection to users than the original GFCI could ever give. In the US and Canada such devices are still commonly known as "GFCIs" or "GFIs" even though they have the additional "residual current detector" functionality, whilst in Europe and elsewhere the more accurate name of "Residual Current Detector" or RCD has been widely adopted for general use instead of using the name of the much simpler GFCI device.

What is an MCB? A Miniature Circuit Breaker. An MCB is a device designed to protect a circuit's wiring from the serious damage which would be caused if it has to carry a current which is too high for the diameter of its wires. Such a current could easily heat up the wires so much that their insulation melts. If that situation were allowed to develop further it would soon cause the wires in a cable to short out and to burn so hot that they could easily cause a house fire.

Before circuit breakers were invented, simple wire fuses were used: the wire in the fuses was deliberately made much thinner than the wires in the circuits they were intended to protect. Thus, if a fault condition occured, as the current in the circuit grew higher and higher, a point would be reached at which the thin wire of the fuse would get so hot that it would melt - all safely contained within the body of the fuse - and thus break the flow of current in the circuit it was protecting. The problem with fuses is that - depending on their design, as some are faster-acting than others - it can take a significantly longer amount of time for them to operate compared with today's very-fast-acting circuit breakers. That fact means that, if a circuit overload current fault condition occurs, considerable damage can still occur both to the circuit wiring and/or to the unit it is supplying with power. Then, after the fault condition has been fixed, the melted or "blown" fuse wire in a rewireable type of fuse has to be replaced or - if it is a "disposable cartridge" fuse - the blown fuse cartridge has to be thrown away and replaced by a new one. A circuit breaker, if it is still in good condition, only needs to be reset.

It is no joke to say if it is still in good condition...! One more fact needs to be mentioned: a significant design feature built into today's circuit breakers is their ability to "self-destruct on a crowbar fault ". A "crowbar fault" is a very serious overload condition, so bad that it would cause many thousands of amps to flow, just as if someone had thrown down a heavy metal crowbar tool onto power lines to connect both hot and neutral wires... Such a fault condition can only be stopped by what is the ultimate fail-safe function of all modern circuit breakers: by using electro-magnetic technology similar to that of a simple relay, they are designed to self-destruct at least as fast as - if not faster than - the fastest acting fuses!

In brief, wherever electrical equipment - and the wiring which supplies it - need to be protected from overload current fault conditions then: a) if the physical space available allows circuit breakers to be installed, and

b) if the higher initial costs of deploying circuit breakers can be afforded

then it is significantly better to deploy circuit breakers instead of fuses.

For more information on all these topics see the answers to the Related Questions shown below.

Answer 2

ELCB is a device that is used to detect leaking currents from an installation when the power is cut while RCCB is an electric device that disconnects power when the flow of power is not balanced at phase.

Answer 3

RCCB - Residual Current Circuit Breaker. Works by sensing the current exiting the live and returning via the neutral wire. If the difference passes a threshold (marked on the device) the RCCB will register a fault and trip.

ELCB - Earth Leakage Circuit Breaker. Works by sensing the current in the earth wire. If the difference passes a threshold, the ELCB will register a fault and trip.

Although both just about do the same thing, all modern circuit breakers are RCCB types. The ELCB will only trip if the current leaks to Earth, meaning the electrical item must be earthed. That also means the electrical item must be wired with a 3 prong plug.

An RCCB, current out must equal current back in, or that current is leaking somewhere else (maybe through you....) and it is a fault.

Answer 4

Elecb is voltage operated device where as RCCB is current operated device. RCCB is the preferred one. ELCB is outdated.