Part P Earthing & Bonding

Question 1

What is the primary purpose of earthing in an electrical installation?

Accepted Answer

To provide a low-impedance return path for fault current so that protective devices operate quickly, limiting the duration of dangerous touch voltages

Answer

To improve power factor

Answer

To prevent voltage surges

Answer

To provide a reference for measuring current

Question 2

What is the main earthing terminal (MET)?

Accepted Answer

The central connection point in the installation where the earthing conductor, main bonding conductors and circuit protective conductors are all connected

Answer

The earth rod in the ground

Answer

The earth terminal in the consumer unit only

Answer

The earthing point at the electricity meter

Question 3

What is an earthing conductor?

Accepted Answer

The conductor connecting the main earthing terminal to the earthing arrangement (e.g., earth terminal at the supply, earth electrode or PME neutral)

Answer

The earth conductor within each circuit cable

Answer

The bonding conductor to gas pipes

Answer

The earth terminal in a socket outlet

Question 4

What minimum size is required for an earthing conductor in a typical domestic installation connected to a PME (TN-C-S) supply?

Accepted Answer

16 mm² if unprotected, or 10 mm² if protected (buried or in conduit)

Answer

2.5 mm² copper

Answer

4 mm² copper

Answer

6 mm² copper

Question 5

What is extraneous conductive part?

Accepted Answer

A conductive part that is not part of the electrical installation but can introduce a potential (e.g., metallic water pipes, gas pipes, structural steelwork)

Answer

Any metal part of an electrical accessory

Answer

The armour of a cable

Answer

The neutral conductor

Question 6

What is the main bonding conductor's connection point on a metallic gas installation pipe?

Accepted Answer

As close as practicable to the point of entry into the building, upstream of any meter or stop valve

Answer

At any convenient point along the pipe

Answer

At the gas appliance

Answer

At the meter only