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.
Read the first 6 Inspection & Testing flashcards as text
What is a 'prospective fault current' (PFC) test and why is it performed?
Answer: It measures the maximum fault current at the consumer unit origin to verify the breaking capacity of the main fuse and all protective devices exceeds the available fault current
The PFC test measures the maximum available short-circuit and earth fault current at the origin; this value must be within the breaking capacity of the protective devices, and must be considered when selecting devices throughout the installation.
What happens to Zs as cable temperature increases?
Answer: Zs increases (copper resistance increases with temperature) so the measured cold Zs must be corrected to operating temperature using a correction factor
Copper conductor resistance increases with temperature (approximately 0.4% per °C); Zs measured at ambient (cold) conditions must be multiplied by a temperature correction factor to obtain the Zs at operating temperature for comparison against BS 7671 limits.
What is the purpose of the 'verification of voltage drop' in a new installation?
Answer: To confirm that the voltage drop in circuit cables under design load current does not exceed the BS 7671 limits (typically 3% for lighting, 5% for other circuits)
Excessive voltage drop in long cables can affect the performance of connected equipment; BS 7671 limits are 3% for lighting circuits and 5% for other circuits from the origin of the installation.
What does the term 'electrode resistance testing' involve?
Answer: Measuring the resistance between an earth electrode and the general mass of earth using a dedicated earth electrode resistance tester (3-probe fall-of-potential method)
Earth electrode resistance testing uses the fall-of-potential method, injecting current between the electrode under test and a remote current electrode, measuring voltage between the electrode and a probe electrode, and calculating resistance from V/I.
What is the purpose of recording serial numbers and test instrument calibration dates on an EIC or EICR?
Answer: To ensure the test instruments used were calibrated and traceable, validating the accuracy of the test results
Recording calibration details provides traceability and confidence that the test instruments were accurate at the time of testing; calibration certificates must be current, typically renewed annually.
How often should test instruments used for electrical inspection and testing be recalibrated?
Answer: At minimum every 12 months (or as specified by the instrument manufacturer and the engineer's certification scheme)
BS 7671 and Competent Person scheme requirements specify that test instruments should be calibrated regularly (typically annually) to ensure measurement accuracy; the calibration certificate provides traceability of measurement.