Part P Testing and Inspection 2

Question 1

During an RCD test, what trip times are acceptable for a 30mA Type AC RCD when tested at rated residual current (IΔn)?

Accepted Answer

Must trip within 300ms

Answer

When tested at rated residual current (IΔn = 30mA), a general-purpose (non-time-delayed) RCD must trip within 300ms. When tested at 5 × IΔn (150mA), it must trip within 40ms. The 300ms limit at rated current ensures reliable operation, while the faster 40ms at 5× ensures rapid disconnection for more serious fault currents.

Question 2

What does a Periodic Inspection Report (PIR/EICR) code C2 signify?

Accepted Answer

Potentially dangerous — urgent remedial action required

Answer

Code C2 (Potentially Dangerous) indicates a fault that, while not presenting immediate danger, could become dangerous if not addressed. Urgent remedial action is required. Code C1 indicates immediate danger requiring urgent action. Code C3 indicates an improvement is recommended. Code FI means further investigation is needed.

Question 3

When performing a continuity test on a protective conductor, what type of instrument is used?

Accepted Answer

A low-resistance ohmmeter (typically using a test current of at least 200mA DC)

Answer

Continuity testing uses a low-resistance ohmmeter that delivers a test current of at least 200mA DC. This ensures that the measurement can detect poor connections and resistive joints that would not be revealed by a high-impedance instrument. The instrument must be calibrated and the test lead resistance nulled (zeroed) before taking measurements.

Question 4

At what maximum interval does BS 7671 recommend periodic inspection and testing of a domestic electrical installation?

Accepted Answer

Every 10 years or at change of occupancy

Answer

IET Guidance Note 3 recommends periodic inspection and testing of domestic installations every 10 years or at change of occupancy (tenancy or ownership). For rented properties, the interval is 5 years as required by the Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020. Regular inspection identifies deterioration before it becomes dangerous.

Question 5

During initial verification, the polarity test confirms which critical safety feature?

Accepted Answer

That single-pole switching devices are connected in the line conductor only, and that the line and neutral are correctly identified throughout

Answer

Polarity verification ensures that all single-pole switches and protective devices are connected in the line (live) conductor, that socket outlets are correctly wired (line to line terminal, neutral to neutral terminal, earth to earth terminal), and that the line and neutral conductors are correctly identified throughout. Reversed polarity is a serious safety hazard.

Part P Electrical Practice Test

Part P Electrical Practice Test

Part P Testing and Inspection 2