Full form of ELCB – Full form of ELCB is Earth Leakage Circuit Breaker.

What is ELCB – Definition of ELCB is given below –

Definition –

ELCB is a device that is used in electrical circuit to protect a person from an earth fault.

What is an earth fault –

An earth fault occurs when a live wire touches the body of the equipment (due to insulation failure etc) which causes metallic body of the equipment gets charged. When a person touches the charged body of equipment, he will get shock &person may die. Therefore, function of ELCB is to trip/interrupts the circuit when live wire touches the body of the equipment.

Types of ELCB –

There are two types of ELCB – A) Voltage operated ELCB & B) Current operated ELCB. The current operated ELCB is also called RCCB (or RCD)

Working Principle of ELCB–

It consists of a voltage operated coil (called search/sensing coil), fixed & moving contacts. This coil has two terminals, one terminal is connected with the metal body of the equipment while other terminal is connected with the earth.

Under normal condition, the voltage between metal body & earth is 0V, hence ELCB carries the normal current of the load. When earth fault occurs, it means phase wire touches the metal body of the equipment, the metal body gets charged & leakage current flows from body to earth. The search coil gets voltage difference across its terminals& actuates its tripping mechanism & trips the circuit. If fault is temporary, we may switch on ELCB again, but if fault persists, then ELCB will not be switched on again and we will have to rectify the fault first, then ELCB can be switched on.

(Note – For a human being 30mA current is a safe current & beyond this current is harmful so ELCB must trip on or less than 30mA current.)

Selection of ELCB –

• It should be capable to carry the rated current of load,
• Check ELCB is required for single phase or 3 phase load.
• Check number of poles – SP, SPN, DP,TP, TPN, 4P where SP = Single Pole which means only phase wire will be connected, DP = Double Pole which means phase & neutral wires will be connected, TP = Triple pole which means three phases will be connected, 4P = Fore pole which means 3 phases & a neutral will be connected.
• Fault current rating(in mA) on which relay should trip/interrupts the faulty circuit, for ex – 30mA, 100mA, 300mA etc

Ex – 40A DP ELCB with 30mA fault current.

LIMITATIONS OF VOLTAGE OPERATED ELCB–

• To operate ELCB, proper earthing is required. ELCB will not work If there is no body earthing of the equipment.
• ELCB works on metal body equipment,

(Note:-Due to above limitations ELCBs are not being used and should be replaced with RCCBs because earthing is not required for earth fault protection in RCCBs.)

Frequently Asked Questions (FAQs) on ELCB– 

Q1) What is the difference between ELCB & RCCB?

Ans) The main difference between ELCB & RCCB is that ELCB is a voltage operated device & earth connection is required to operate it. On the other hand, RCCB is a current operated device & no need of earthing connection for the operation. ELCB works on metal body while RCCB works on leakage of current on metallic or non-metallic body.

Detail of ELCB is given in above sections of this page & details of RCCB is given in a separate chapter.

Q2) What is the difference between ELCB & MCB/MCCB?

Ans) The difference – ELCB is used for the protection from earth leakage in the system while MCB/MCCB is used for protection from overloading & short circuit in an equipment / electrical circuit.

Click on MCB & MCCB to get more details about these circuit breakers.

Q3) When does an ELCB trip?

Ans) ELCB tips when an earth fault occurs in an equipment or electrical circuit. Complete working principle of ELCB is given in above section of this page.

Q4) What type of current protection is not provided by ELCB?

Ans) ELCB provides protection against earth leakages only & it doesn’t provide protection against over-loading & short circuit.

Q5) Why 30mA ELCB used in electrical system?

Ans) 30mA ELCB is used in electrical system to protect user/operator/human being from earth fault. Beyond 30mA capacity ELCB is harmful for user, that is why we should ensure that ELCB of 30mA capacity must be used in lighting/power DBs for domestic purpose.

Q6) What is the purpose of ELCB?

Ans) The purpose of installation of ELCB in electrical system is to provide protection of user against earth fault which occur in an electrical equipment or electrical circuit. The leakage current is dangerous if it reaches on the metal enclosure of the equipment. The user will get shock if he touches metal body of the equipment. If earth leakage is there circuit then it will charge metallic part in which it is laid, if user will come in contact with than metallic part, he/she will get shock. In such situations / faults ELCB will trip & stop power supply to that equipment/circuit.

Q7) Why ELCB trips frequently?

Ans) ELCB trips only when earth leakage/ earth fault is there in either equipment/circuit. If ELCB is tripping again & again & not getting reset, it means fault persists in the system. Therefore, it is important to clear the fault from the system by identifying the problem. If it is not possible to clear the fault immediately, then identify the main circuit which has this fault & isolate it from the DB or turn off MCB which is connected with faulty circuit so that ELCB doesn’t trip & power could be available for healthy circuits. (Note- The faulty circuit should be properly taken care before putting it in use again).

Q8) How to check the working of ELCB?

Ans) there are two methods through which health of ELCB could be checked –

1. a) ELCB comes with a test knob, ELCB will trip when knob is pressed manually. This process will work when power supply is connected to ELCB, without power this knob will not work.
2. b) ELCB testing instruments (digital) are available in market. These instruments help to check whether ELCB is tripping on its rated fault current such as 30mA /100mA/300mA….etc. Process is very simple, instrument comes with a lead whose one end is connected with the instrument & other end has a plug which is to be connected with the socket/circuit whose ELCB is to be tested. Once both the ends are connected, then switch on digital device & set the fault setting which you want to test & press test button, ELCB will trip on its rated fault current if it is OK. If ELC is not tripping on rated fault current then check again, if again same status is their then replace ELCB with new one.

Q9) How sensitivity of ELCB is measured?

Ans) Sensitivity of ELCB can be checked with the help of hand-held/portable instrument which operates the ELCB on its rated fault capacity (in mA). Complete detail is given in above Q8.

Q10) What is ELCB Switch?

Ans) ELCB switch is nothing but ELCB itself which is called Earth Leakage Circuit Breaker. It is installed in electrical system to protect the user from earth fault which occurs in the equipment or electrical circuit. It trips automatically on earth fault, but can be operated manually.