A test button is incorporated in each MCB + ELCB & RCCB / ELCB to enable the electrical and mechanical operation of the device to be checked .it is advised that MCB + ELCB & RCCB/ELCB is tested periodically.

 

1.       Against indirect human contact.

2.       Against direct human contact.

3.       Earth faults due to corrosion.

4.       Protection against fire due to electrical faults

 

SELECTION

30mA

A 30 mA ELCB will provide a high degree of protection against electrocution in an accidental shock hazard situation. The current flowing through human body could be between 80 mA and 240mA depending on the resistance of the human body and the voltage across it.

 

Zone  Physiological Effects

Zone 1 Usually no reactions

Zone 2 Usually no harmful physiological effects

Zone 3 Usually no organic damage to be expected. Likelihood of muscular contraction and difficulty in breathing. Reversible disturbances of formation and conduction of impulse in the heart and transient cardiac arrest without ventricular fibrillation increases with current magnitude and time.

 

Zone 4 In addition to teh effects of Zone 3, probability if ventricular fabriliation increased upto 5% (curve C2) upto 50% (curve C2) and above 50% beyond curve C3. It increases with magnitude and time, and pathophysiological effects such as cardiac arrest, breathing arrest and heavy may occur.

 

To be within zone of the IEC curve as shown above. It is necessary for the ELCB operate within 50ms at 240 mA and 150ms at 80mA Both these conditions are satisfied by 30mA ELCB.

For household, individual outlets, wet areas and temporary installations, ELCB with sensitivity not exceeding 30mA is advisable 100mA

A 100mA ELCB will normally give high degree of protection against electrocution but there is a possibility that the shock current could fall below the tripping level of ELCB This could occur if additional resistances to that of human body are included in the earth path.

 

The 100mA RCCB protects against leakage currents and indirect contact with earth loop impedance upto 500 Ohms.

 

A 300/500 mA ELCB may be used where only fire protection is required. Eg., on lighting circuits, where the risk of electric shock is small. 300/500 mA ELCB will not give any protection against electrocution.