Part P Earthing and Bonding 2

Question 1

A domestic property has a PME (TN-C-S) supply. The electrician notices the gas pipe entering the building is plastic. Is main bonding of the gas supply still required?

Accepted Answer

No — bonding is only required for metallic services that could introduce an earth potential

Answer

Yes — all gas supplies must always be bonded regardless of material

Answer

Only if the gas meter is metallic

Answer

Bonding must be applied to the plastic pipe using special clamps

Question 2

What is the minimum cross-sectional area of the earthing conductor connecting the MET to the earth electrode in a TT system?

Accepted Answer

6mm² copper if mechanically protected, 16mm² if not

Answer

2.5mm² copper

Answer

10mm² copper

Answer

25mm² copper minimum

Question 3

What test is used to measure the resistance of an earth electrode?

Accepted Answer

Earth electrode resistance test using the fall-of-potential method

Answer

Insulation resistance test

Answer

Continuity test with a low-resistance ohmmeter

Answer

Loop impedance test

Question 4

In a bathroom, supplementary equipotential bonding connects which parts?

Accepted Answer

All simultaneously accessible exposed-conductive-parts and extraneous-conductive-parts within the location

Answer

Only the bath and shower tray

Answer

Only the light switch and shaver socket

Answer

The toilet cistern and towel rail only

Question 5

What is the consequence of a broken PEN (combined protective earth and neutral) conductor in a PME (TN-C-S) supply?

Accepted Answer

Dangerous voltages can appear on all earthed metalwork in the installation, including bonded pipework

Answer

The lighting dims slightly

Answer

The RCD will trip immediately

Answer

The electricity supply will be cut off automatically

Question 6

What size bonding conductor is required for supplementary bonding between two extraneous-conductive-parts (e.g., two metal pipes)?

Accepted Answer

2.5mm² if mechanically protected, 4mm² if not

Answer

1.0mm²

Answer

6mm² minimum

Answer

10mm² minimum