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Inspection & Testing Flashcards

6 cards from real PART P practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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

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

    Initial verification ensures a new installation complies with the design and with BS 7671, identifying any errors in construction before the installation is put into use, preventing danger to the occupier.

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

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

    Dead testing refers to tests carried out with no electrical supply connected (de-energised), including continuity (CPC, bonding, ring), insulation resistance, and polarity (initial check) — all performed safely with no live parts.

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

    Answer: 1 MΩ (1,000,000 ohms)

    BS 7671 Table 61 specifies a minimum insulation resistance of 1 MΩ (measured at 500 V DC) for circuits with nominal voltages up to 500 V, confirming the insulation between conductors is sound.

  4. What is the purpose of the ring continuity test?

    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

    The ring continuity test uses three measurements to confirm the ring is correctly formed (not broken, bridged or incorrectly cross-connected), using the phase, neutral and CPC conductors in sequence.

  5. What test instrument is used for insulation resistance testing?

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

    An insulation resistance tester (megohmmeter) applies a specified DC test voltage (500 V for 230 V circuits) and measures the resistance of the insulation; a multimeter cannot apply sufficient voltage for this test.

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

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

    BS 7671 Table 41.3 specifies maximum Zs values for each device; for a 16 A Type B MCB on a socket circuit (0.4 s disconnection), the maximum Zs is 2.87 Ω at the standard table temperature of 20°C.