Part P Inspection & Testing 1

Question 1

What is the purpose of initial verification (inspection and testing) of a new electrical installation?

Accepted Answer

To confirm that the installation complies with BS 7671 and is safe for use before it is energised for the first time

Answer

To issue an invoice for the work

Answer

To register the installation with the electricity supplier

Answer

To obtain planning permission for the work

Question 2

What does 'dead testing' mean in electrical installation testing?

Accepted Answer

Tests performed with the installation isolated from the supply (de-energised), such as continuity and insulation resistance tests

Answer

Tests performed on decommissioned circuits only

Answer

Tests using low-voltage probes only

Answer

Tests for the presence of voltage

Question 3

What is the minimum insulation resistance acceptable under BS 7671 for a 230 V circuit?

Accepted Answer

1 MΩ (1,000,000 ohms)

Answer

100 kΩ

Answer

10 kΩ

Answer

500 kΩ

Question 4

What is the purpose of the ring continuity test?

Accepted Answer

To confirm that the ring circuit is correctly wired as a ring (both conductors return to the consumer unit) and to identify crossed or broken conductors

Answer

To test insulation resistance of the ring circuit

Answer

To measure the earth fault loop impedance

Answer

To confirm the MCB rating is correct for the circuit

Question 5

What test instrument is used for insulation resistance testing?

Accepted Answer

A dedicated insulation resistance tester (megohmmeter or 'megger') applying a DC test voltage

Answer

A multimeter on resistance range

Answer

An RCD tester

Answer

A loop impedance tester

Question 6

What is the maximum earth fault loop impedance (Zs) for a 16 A Type B MCB?

Accepted Answer

2.87 Ω (as per BS 7671 Table 41.3 for TN systems at 0.4 s disconnection)

Answer

1 Ω

Answer

10 Ω

Answer

0.5 Ω