Part P Earthing and Bonding

Question 1

What is the minimum cross-sectional area of the main protective bonding conductor for a domestic installation with a 25mm² line conductor?

Accepted Answer

10mm²

Answer

4mm²

Answer

6mm²

Answer

16mm²

Question 2

Which of the following services must be connected to the main protective bonding?

Accepted Answer

All metallic services entering the building: water, gas, oil, and any other metallic service pipes

Answer

Only the water pipe

Answer

Only the gas pipe and water pipe

Answer

Plastic pipes do not require bonding, and neither do metal ones

Question 3

In a TT earthing system, what provides the earth fault return path?

Accepted Answer

The general mass of earth via a local earth electrode

Answer

The supply neutral conductor (PEN)

Answer

A metallic sheath on the supply cable

Answer

The water pipe network

Question 4

What is the purpose of equipotential bonding in a domestic installation?

Accepted Answer

To ensure all simultaneously accessible metallic parts are at the same potential, eliminating dangerous touch voltages

Answer

To provide a low-impedance path for fault current to flow back to the source

Answer

To increase the current-carrying capacity of the cables

Answer

To improve the power factor of the installation

Question 5

Where should the main earthing terminal be located in a domestic installation?

Accepted Answer

At or near the consumer unit (origin of the installation)

Answer

In the garage

Answer

At the earth electrode

Answer

In the bathroom

Question 6

What is the maximum resistance of an earth electrode in a TT installation protected by a 100mA RCD?

Accepted Answer

500Ω

Answer

50Ω

Answer

100Ω

Answer

200Ω