📋 Test Instruments, RCD Testing and Certification (Part 6)

1. When a general (non-delay) type RCD is tested at its rated residual operating current (1× IΔn), what is the maximum permitted operating time under BS 7671:2018+A2:2022?

1. 300 ms
2. 40 ms
3. 150 ms
4. 500 ms

A general non-delay RCD tested at 1× IΔn must operate within a maximum of 300 ms. (BS 7671:2018+A2:2022, Regulation 643.7.1 (notes))

2. A 30 mA RCD provides additional protection under Regulation 415.1.1. When tested at 5× its rated residual operating current, within what time must it disconnect to be deemed effective?

1. 40 ms
2. 300 ms
3. 200 ms
4. 130 ms

For additional protection, a 30 mA RCD must disconnect within 40 ms when tested at 5× IΔn. (BS 7671:2018+A2:2022, Regulations 415.1.1 and 643.8)

3. You test a 30 mA RCD that provides additional protection. The test current applied to confirm the 40 ms operating-time criterion must be at least what value?

1. 150 mA
2. 30 mA
3. 15 mA
4. 60 mA

5× IΔn for a 30 mA RCD equals 150 mA, the current at which the ≤ 40 ms criterion is verified. (BS 7671:2018+A2:2022, Regulations 415.1.1 and 643.8)

4. When an RCD is tested at 0.5× IΔn (half the rated residual operating current), what is the expected and correct result?

1. The RCD should not trip
2. The RCD must trip within 300 ms
3. The RCD must trip within 40 ms
4. The RCD must trip within 130 ms

At 0.5× IΔn the RCD should remain stable and not operate, confirming it does not trip below its rated residual current. (BS 7671:2018+A2:2022, Regulation 643.7.1; IET Guidance Note 3)

5. Following Amendment 2 to BS 7671:2018, which RCD test requirement was removed?

1. The requirement to test at 5× IΔn and at both half-cycles
2. The requirement to test at 1× IΔn
3. The requirement to test the no-trip condition at 0.5× IΔn
4. The requirement to record results on the schedule of test results

Amendment 2 removed the previous requirement to test general RCDs at 5× IΔn and at both half-cycles; a single AC test at IΔn now demonstrates compliance. (BS 7671:2018+A2:2022; IET Wiring Matters, July 2022)

6. A time-delayed (S-type) RCD is tested at its rated residual operating current (IΔn). Within which range must its operating time fall?

1. 130 ms to 500 ms
2. 0 ms to 40 ms
3. 40 ms to 300 ms
4. 500 ms to 1000 ms

An S-type (time-delayed) RCD tested at IΔn must operate within the range 130 ms to 500 ms. (BS 7671:2018+A2:2022, Regulation 643.7.1 (notes); BS EN 61008/61009)

7. An S-type RCD operates in 90 ms when tested at IΔn. How should this result be interpreted?

1. Unsatisfactory — it is below the 130 ms lower limit for an S-type RCD
2. Satisfactory — faster operation is always better
3. Satisfactory — it is within the 40 ms limit
4. Unsatisfactory — it exceeds the 500 ms upper limit

An S-type RCD must operate between 130 ms and 500 ms; tripping in 90 ms is below the lower limit and is not acceptable for a time-delayed device. (BS 7671:2018+A2:2022, Regulation 643.7.1 (notes); BS EN 61008/61009)

8. What type of test current is applied to a general AC-type RCD when verifying compliance under Amendment 2?

1. An alternating (AC) test current at IΔn
2. A pulsating direct test current at 5× IΔn
3. A smooth direct current at 0.5× IΔn
4. A high-frequency current at 1000 Hz

Under Amendment 2 an RCD is tested with an alternating test current applied at the rated residual operating current (IΔn). (BS 7671:2018+A2:2022, Regulation 643.7.1 (notes); Wiring Matters July 2022)

9. A 30 mA RCD used for additional protection on a socket-outlet circuit is tested and trips at 1× IΔn in 250 ms, and at 5× IΔn in 35 ms. Which conclusion is correct?

1. Both results are acceptable — within 300 ms at 1× and within 40 ms at 5×
2. Only the 1× result is acceptable; the 5× result fails
3. Both results fail because they exceed 40 ms
4. The 5× result fails because it exceeds 30 ms

At 1× IΔn the limit is 300 ms (250 ms passes) and at 5× IΔn the additional-protection limit is 40 ms (35 ms passes); both results are satisfactory. (BS 7671:2018+A2:2022, Regulations 643.7.1, 415.1.1 and 643.8)

10. Why is the 0.5× IΔn (no-trip) test still useful when commissioning an RCD?

1. It confirms the RCD does not nuisance-trip at currents below its rated residual operating current
2. It confirms the RCD disconnects within 40 ms
3. It measures the earth fault loop impedance of the circuit
4. It verifies the prospective fault current at the origin

Applying 0.5× IΔn and confirming no operation demonstrates the device is correctly rated and will not trip below its rated residual current. (BS 7671:2018+A2:2022, Regulation 643.7.1; IET Guidance Note 3)

11. A 100 mA general (non-delay) RCD is used solely for fault protection, not additional protection. When tested at 1× IΔn, what is the maximum permitted operating time?

1. 300 ms
2. 40 ms
3. 130 ms
4. 500 ms

Any general non-delay RCD tested at 1× IΔn must operate within 300 ms; the 40 ms criterion applies only to 30 mA devices providing additional protection at 5× IΔn. (BS 7671:2018+A2:2022, Regulation 643.7.1 (notes))

12. How many separate signatures/declarations does an Electrical Installation Certificate (EIC) for new installation work require?

1. Three — design, construction, and inspection & testing
2. One — a single combined declaration
3. Two — design and testing only
4. Four — design, construction, testing and maintenance

An EIC for new work requires three declarations covering design, construction (installation), and inspection & testing. (BS 7671:2018+A2:2022, Regulation 644.4 and Appendix 6)

13. Which two schedules must accompany a completed Electrical Installation Certificate?

1. A Schedule of Inspections and a Schedule of Test Results
2. A Schedule of Defects and a Schedule of Maintenance
3. A Schedule of Loads and a Schedule of Cables
4. A Schedule of Observations and a Schedule of Recommendations

An EIC must be accompanied by a Schedule of Inspections and a Schedule of Test Results. (BS 7671:2018+A2:2022, Regulation 644.4 and Appendix 6)

14. An electrician adds a new ring final circuit to an existing consumer unit. Which certificate is required?

1. An Electrical Installation Certificate (EIC)
2. A Minor Electrical Installation Works Certificate (MEIWC)
3. An Electrical Installation Condition Report (EICR)
4. No certificate is required for additions

Because a new circuit has been installed, the work must be certified with an EIC, not a Minor Works Certificate. (BS 7671:2018+A2:2022, Regulations 644.1 and 644.4)

15. A spur is added from an existing socket-outlet to feed one additional socket, with no new circuit created. Which document is appropriate?

1. A Minor Electrical Installation Works Certificate (MEIWC)
2. An Electrical Installation Certificate (EIC)
3. An Electrical Installation Condition Report (EICR)
4. A Schedule of Test Results only

Additions or alterations that do not include a new circuit are certified using a Minor Works Certificate. (BS 7671:2018+A2:2022, Regulation 644.1; Appendix 6 model forms)

16. Which document is used to report on the condition of an existing electrical installation?

1. An Electrical Installation Condition Report (EICR)
2. An Electrical Installation Certificate (EIC)
3. A Minor Electrical Installation Works Certificate
4. A Building Regulations compliance notice

The EICR is the document used to report on the condition of an existing installation. (BS 7671:2018+A2:2022, Regulation 644.4; Appendix 6 model forms)

17. On an EICR, what does an observation coded C1 indicate?

1. Danger present — immediate risk of injury, report Unsatisfactory
2. Improvement recommended but not dangerous
3. Potentially dangerous but no immediate risk
4. Further investigation required without delay

C1 means danger is present with immediate risk of injury, which results in an Unsatisfactory report. (BS 7671:2018+A2:2022, Appendix 6; IET Guidance Note 3)

18. An EICR records only one observation, coded C3 (improvement recommended). What overall assessment should the report carry?

1. Satisfactory
2. Unsatisfactory
3. Conditional
4. Pending further investigation

A C3 code alone does not warrant an Unsatisfactory outcome; the installation can be reported as Satisfactory. (BS 7671:2018+A2:2022, Appendix 6; IET Guidance Note 3)

19. An EICR lists three observations: one C2, one C3 and one FI. What overall outcome should be recorded?

1. Unsatisfactory — because a C2 and an FI are present
2. Satisfactory — because a C3 is present
3. Satisfactory — because there is no C1
4. Conditional — pending the FI only

Any C1, C2 or FI code makes the report Unsatisfactory; here both a C2 and an FI require an Unsatisfactory result. (BS 7671:2018+A2:2022, Appendix 6; IET Guidance Note 3)

20. On an EICR, what does the code FI signify?

1. Further investigation required — report Unsatisfactory
2. Fully insulated — no action needed
3. Final inspection completed satisfactorily
4. Fault isolated and rectified on site

FI means further investigation is required without delay, and its presence results in an Unsatisfactory report. (BS 7671:2018+A2:2022, Appendix 6; IET Guidance Note 3)

21. During an EICR you find an accessible exposed live terminal posing an immediate risk of electric shock. Which classification code applies?

1. C1 (danger present)
2. C2 (potentially dangerous)
3. C3 (improvement recommended)
4. FI (further investigation)

An immediate risk of injury, such as an accessible live part, is coded C1 (danger present). (BS 7671:2018+A2:2022, Appendix 6; IET Guidance Note 3)

22. A defect that is potentially dangerous but presents no immediate risk of injury, such as the absence of supplementary bonding where it is required, is most appropriately coded as which observation?

1. C2 (potentially dangerous)
2. C1 (danger present)
3. C3 (improvement recommended)
4. FI (further investigation)

A potentially dangerous condition with no immediate risk is coded C2, and its presence makes the report Unsatisfactory. (BS 7671:2018+A2:2022, Appendix 6; IET Guidance Note 3)

23. Which document specifies the recommended maximum interval before the first periodic inspection and testing of a completed installation?

1. The Electrical Installation Certificate, which records the recommended date of the next inspection
2. The Minor Works Certificate only
3. The local authority Building Control notice
4. The manufacturer's instructions for the consumer unit

The EIC includes a field for the recommended date by which the installation should next be inspected and tested. (BS 7671:2018+A2:2022, Regulation 644.4 and Appendix 6)

24. For a domestic dwelling occupied by the owner, the IET commonly recommends periodic inspection and testing at a maximum interval of how long, or on change of occupancy?

1. 10 years
2. 1 year
3. 3 years
4. 25 years

IET guidance recommends a maximum interval of 10 years for owner-occupied domestic premises, or on change of occupancy. (IET Guidance Note 3 (Inspection & Testing), Table of recommended intervals)

25. What is the recommended maximum interval between periodic inspections for tenanted domestic rented accommodation in England, as reflected in current guidance?

1. 5 years, or on change of occupancy
2. 10 years
3. 1 year
4. 20 years

Privately rented domestic accommodation is recommended to be inspected at least every 5 years, or on change of tenancy, consistent with the Electrical Safety Standards in the Private Rented Sector regulations. (IET Guidance Note 3; Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020)

26. A caravan (leisure accommodation vehicle) and a swimming pool installation are two locations with shorter recommended inspection intervals. What is the recommended maximum interval typically given for these?

1. 1 year
2. 10 years
3. 5 years
4. 3 years

Higher-risk locations such as caravans and swimming pools carry a recommended maximum interval of 1 year in IET guidance. (IET Guidance Note 3 (Inspection & Testing), Table of recommended intervals)

27. Where an installation is subject to a formal periodic inspection programme, what is the primary basis on which the actual interval should be set?

1. The type of installation, its use, condition and external influences (frequency assessed by the inspector)
2. A fixed interval of exactly 10 years for every installation
3. The age of the test instruments used
4. The number of circuits in the distribution board

Recommended intervals are guidance maxima; the actual frequency is determined by the installation type, use, condition and external influences, as judged by the competent person. (BS 7671:2018+A2:2022, Regulation 651; IET Guidance Note 3)

28. For a 30 mA RCD providing additional protection in accordance with Regulation 415.1.1, what is the maximum disconnection time permitted when the device is tested at a current of 5 times its rated residual operating current?

1. 40 ms
2. 200 ms
3. 300 ms
4. 500 ms

Additional protection by a 30 mA RCD is verified where it disconnects within 40 ms when tested at 5 times its rated residual operating current. (BS 7671:2018+A2:2022, Regulations 415.1.1 and 643.8)

29. Following Amendment 2, at what current is a general-purpose non-delay RCD tested to confirm it operates correctly, and what is the maximum permitted operating time?

1. At its rated residual operating current, with a maximum of 300 ms
2. At five times its rated residual operating current, with a maximum of 40 ms
3. At half its rated residual operating current, with a maximum of 2 s
4. At its rated residual operating current, with a maximum of 40 ms

A general non-delay type RCD is tested at one times its rated residual operating current and must operate within a maximum time of 300 ms. (BS 7671:2018+A2:2022, Regulation 643.7.1 (notes))

30. What change to RCD testing requirements did Amendment 2 of BS 7671 introduce?

1. It removed the requirement to test at five times the rated residual operating current and at both half-cycles
2. It increased the maximum operating time for a non-delay RCD to 500 ms
3. It introduced a mandatory test at half the rated residual operating current
4. It removed all requirements to functionally test RCDs

Amendment 2 removed the previous requirement to test RCDs at five times the rated residual operating current and at both half-cycles; a single AC test at the rated residual operating current now demonstrates compliance. (BS 7671:2018+A2:2022 (vs. earlier editions); IET Wiring Matters, July 2022)

31. You test a 30 mA RCD providing additional protection on a socket-outlet circuit. At 5 times the rated residual operating current the device disconnects in 33 ms. What should you record?

1. The result is satisfactory, as it is within the 40 ms limit
2. The result is unsatisfactory, as the limit is 300 ms
3. The result is unsatisfactory, as it should not trip below 40 ms
4. The result is satisfactory only if it also trips at one times within 40 ms

For 30 mA additional protection the device must disconnect within 40 ms at 5 times the rated residual operating current, so 33 ms is satisfactory. (BS 7671:2018+A2:2022, Regulations 415.1.1 and 643.8)

32. For a time-delayed (S-type) RCD tested at its rated residual operating current, within what range must the operating time fall?

1. 130 ms to 500 ms
2. 0 ms to 40 ms
3. 40 ms to 300 ms
4. 500 ms to 1000 ms

A time-delayed S-type RCD tested at its rated residual operating current must operate within the range 130 ms to 500 ms. (BS 7671:2018+A2:2022, Regulation 643.7.1 (notes); BS EN 61008/61009)

33. An RCD ramp test gradually increases the residual current applied to the device. What does this test primarily establish?

1. The actual residual current at which the RCD trips
2. The earth fault loop impedance of the circuit
3. The insulation resistance of the protective conductor
4. The prospective fault current at the origin

A ramp test slowly increases the residual current until the RCD operates, revealing the actual trip current of the device rather than its operating time. (IET Guidance Note 3 (Inspection & Testing); BS 7671:2018+A2:2022, Regulation 643.7)

34. A 30 mA RCD is subjected to a ramp test. At what range of residual current would you expect a correctly functioning device to operate?

1. Between 50% and 100% of the rated residual operating current
2. Below 10% of the rated residual operating current
3. Exactly at 5 times the rated residual operating current
4. Above twice the rated residual operating current

A correctly functioning RCD should not trip below 50% of its rated residual operating current and must trip by 100%, so the ramp trip current lies between 15 mA and 30 mA for a 30 mA device. (BS EN 61008/61009; IET Guidance Note 3 (Inspection & Testing))

35. Under Amendment 2, what type of test current is applied when verifying an AC-type RCD at its rated residual operating current?

1. An alternating test current
2. A pulsating direct test current
3. A smooth direct test current
4. A high-frequency square wave

An AC-type RCD is tested with an alternating test current applied at the rated residual operating current. (BS 7671:2018+A2:2022, Regulation 643.7.1 (notes))