Why cannot an ELCB function if its N input is not grounded?

What is ELCB?

ELCB - Earth Leakage Circuit Breaker

Earth Leakage Circuit Breaker (ELCB), often referred to as a Residual Current Device (RCD), is made to prevent electric shocks and fires caused on by earth leakage currents. It operates by spotting electrical current imbalances flowing between a circuit’s live (L) & neutral (N) conductors. An immediate trip and interruption of the current flow occurs when an imbalance is identified, protecting both people and equipment from potential danger.

Why cannot an ELCB function if its N input is not grounded?

An ELCB’s N input is essential for optimal performance.

If N input has no connection to ground, an ELCB might not function as follows:

1). Detecting Imbalance

Imbalances are identified by the ELCB by comparing the current flow in the live (L) & neutral (N) conductors. The currents flowing across both conductors must be equal when everything is operating as it intended. Some of the current can flow via the ground or any other conducting material instead of following the intended path if there is an earth leakage (or) fault in the circuit. The ELCB detects an imbalance as a result.

2). Reference Point

The neutral (N) conductor serves as an indication for the live (L) conductor’s current. The ELCB can identify even slight imbalances in a balanced electrical system since the currents in the L & N conductors are equal & opposing. The ELCB will not have an accurate reference point to identify these imbalances efficiently if the N input is not linked to ground.

3). Safe Tripping

The ELCB could not be able identify the imbalance if a fault occurs & the N input is not grounded, or it may not trip at all. As a result, people in that position would be at risk of electrical shocks or flames because the defect would be undetected & the electrical hazard might continue.

4). Grounding Safety

In electrical systems, grounding is a critical safety measure. It gives the fault current a way to escape from electrical equipment & into the earth, preventing any defective machinery or leakage currents from endangering people and property.


In conclusion, for an ELCB to work properly and deliver the desired safety benefits, the N input should be connected to ground. The ELCB would be unable to identify imbalances without this grounding connection, failing to offer adequate protection from electric shocks & fire risks.