The minimum permissible size of the earth continuity conductor is 6 sq. mm.

Explanation:
The earth continuity conductor, also known as the protective conductor or the earth wire, is an essential component of electrical installations. It is responsible for providing a low impedance path for the flow of fault currents to the earth, ensuring the safety of the electrical system and protecting individuals from electric shock.

The size of the earth continuity conductor is determined by various factors, including the maximum fault current that may flow through it. The larger the fault current, the larger the size of the conductor required to carry it safely.

In most electrical installations, the minimum permissible size of the earth continuity conductor is specified by regulations or standards. These standards are designed to ensure that the conductor can safely carry the fault current without overheating or causing voltage drops that could affect the operation of protective devices.

In the case of the given question, the minimum permissible size of the earth continuity conductor is stated as 6 sq. mm. This means that for the specific installation in question, the earth continuity conductor must have a cross-sectional area of at least 6 sq. mm.

It is important to note that this minimum size is a general guideline and may vary depending on the specific requirements of the installation and the applicable regulations. Factors such as the type of electrical system, the maximum fault current, and the length of the conductor may need to be considered when determining the appropriate size.

In conclusion, the minimum permissible size of the earth continuity conductor is 6 sq. mm. This ensures that the conductor can safely carry fault currents and provide effective protection against electric shock and other electrical hazards.