Part 6 - Inspection and Testing

Overview

Part 6 of BS 7671 sets out the requirements for the inspection and testing of electrical installations, both at initial verification upon completion of new work and at periodic intervals throughout the life of an installation. With an exam weighting of 7%, this topic is moderately weighted but consistently produces questions that candidates find challenging.

The critical concept in Part 6 is that every installation must be verified as compliant before being put into service. This verification comprises a detailed visual inspection followed by a defined sequence of tests. The order of these tests is not arbitrary — it is specified to ensure that each test builds upon the results of the preceding one and that safety is maintained throughout the testing process.

Key Sections

Chapter 61 - Initial Verification (Regulations 610-622)

Initial verification must be carried out on every:

• New installation
• Addition to an existing installation
• Alteration to an existing installation

…before it is put into service.

Visual Inspection (Regulation 611)

A detailed visual inspection must be carried out before testing begins and, where practicable, with the installation de-energised. The inspection must confirm:

• Correct selection and erection of equipment
• Adequate accessibility for operation and maintenance
• Correct labelling and identification of circuits
• Appropriate connection of conductors
• Presence of fire barriers, seals, and protective devices
• Suitability of equipment for the environmental conditions

Testing Sequence (Regulation 612)

The testing sequence for initial verification must be followed in order because each test may depend on the satisfactory results of previous tests:

1. Continuity of protective conductors (including main and supplementary bonding) — Reg 612.2
2. Continuity of ring final circuit conductors — Reg 612.2
3. Insulation resistance — Reg 612.3
4. SELV and PELV verification (where applicable) — Reg 612.4
5. Polarity — Reg 612.6
6. Earth electrode resistance (for TT systems) — Reg 612.7
7. Earth fault loop impedance — Reg 612.9
8. Additional protection (RCD testing) — Reg 612.10
9. Prospective fault current — Reg 612.11
10. Check of phase sequence (for multi-phase circuits) — Reg 612.12
11. Functional testing — Reg 612.13
12. Voltage drop (where required by measurement) — Reg 612.14

Insulation Resistance Test Values (Regulation 612.3)

Circuit Voltage	Test Voltage	Minimum Resistance
SELV and PELV	250V DC	≥ 1.0 MΩ
Up to and including 500V	500V DC	≥ 1.0 MΩ
Above 500V	1000V DC	≥ 0.5 MΩ

The 500V DC test voltage yielding a minimum of 1.0 MΩ for standard circuits is one of the most commonly tested figures in the exam.

Chapter 62 - Periodic Inspection and Testing (Regulation 631)

Every installation must be subject to periodic inspection and testing at intervals determined by:

• The type of installation
• Its use and occupancy
• The external influences to which it is subjected
• The condition of the installation

Recommended Inspection Intervals

Installation Type	Recommended Interval
Domestic	Every 10 years (or on change of occupancy)
Commercial	Every 5 years
Industrial	Every 3 years
Swimming pools	Annually
Construction sites	Every 3 months
Caravan parks	Annually

During periodic inspection, it is not always necessary to carry out every test in the initial verification sequence. The scope of testing is determined by the inspector based on available records and the condition observed during visual inspection.

Important: These intervals are recommendations, not mandatory fixed periods. The decision on frequency is based on the type, use, and condition of the installation.

Chapters 63-65 - Certification and Reporting (Regulations 641-651)

Upon completion of verification, the appropriate certification must be issued. There are three principal forms:

Electrical Installation Certificate (EIC) — Regulation 641

• Required for all new installations
• Certifies that the installation complies with BS 7671
• Must be signed by three responsible persons:
  • The designer
  • The installer
  • The inspector (who may be the same person for smaller installations)

Minor Electrical Installation Works Certificate (MEIWC)

Issued for minor works such as:

• Adding a socket outlet to an existing circuit
• Replacing a consumer unit where the circuit design is unaffected
• Adding a lighting point to an existing circuit

Electrical Installation Condition Report (EICR) — Regulation 651

Issued following periodic inspection and testing. It records the condition of the existing installation using a coding system to classify deficiencies:

Code	Meaning	Action Required
C1	Danger present	Immediate remedial action required
C2	Potentially dangerous	Urgent remedial action required
C3	Improvement recommended	Advisory — no immediate action
FI	Further investigation required	Cannot be fully assessed without further work

Important Regulation Numbers

• 611 - Visual inspection requirements (before testing, supply de-energised)
• 612 - Testing sequence for initial verification
• 612.2 - Continuity of protective conductors and ring final circuits
• 612.3 - Insulation resistance testing (minimum 1.0 MΩ at 500V DC)
• 612.6 - Polarity verification
• 612.9 - Earth fault loop impedance measurement
• 612.10 - RCD testing (additional protection verification)
• 621-622 - Initial verification procedures and requirements
• 631 - Periodic inspection and testing
• 641 - Electrical Installation Certificate (EIC) requirements
• 651 - Electrical Installation Condition Report (EICR) requirements

Common Exam Topics

• The correct testing sequence as defined in Regulation 612 (tested in almost every exam sitting)
• Minimum insulation resistance values and the corresponding test voltages
• When to issue an EIC versus a MEIWC versus an EICR
• The EICR condition coding system (C1, C2, C3, FI) and what each code means
• Whether visual inspection comes before or after testing (always before)
• Recommended periodic inspection intervals for different installation types
• Who must sign an Electrical Installation Certificate
• Earth fault loop impedance testing and its relationship to disconnection times in Part 4

Study Tips

• Memorise the testing sequence in Regulation 612. A useful mnemonic for the first tests is: “Continuity, Continuity (ring), Insulation, SELV/PELV, Polarity, Earth electrode, Loop impedance, RCD.” Questions frequently ask what comes before or after a specific test.
• Know the insulation resistance minimum values and test voltages as a pair: 500V test voltage → minimum 1.0 MΩ for most standard circuits.
• Understand the difference between the three certificate types. A common exam question describes a scenario and asks which certificate is appropriate.
• Link the earth fault loop impedance test back to the disconnection times in Regulation 411.3.2 (Part 4). The measured Zs must be low enough to ensure the protective device disconnects within the required time.
• Remember that periodic inspection intervals are recommendations, not mandatory fixed periods.

Related Topics

• Part 4 - Protection for Safety
• Part 5 - Selection and Erection of Equipment
• Part 1 - Scope, Object and Fundamental Principles
• Part 7 - Special Installations or Locations