Inspection and Testing 2391 Quiz: Master Essential Skills

The City and Guilds 2391 qualification in Inspection and Testing is one of the most important certifications an electrician can hold. Whether you are preparing for the exam or simply want to refresh your knowledge, testing yourself on key concepts is an excellent way to build confidence. This article covers the essential topics you should know and provides quiz-style questions to check your understanding.

Why Inspection and Testing Matters

Every electrical installation needs to be inspected and tested to verify that it is safe and compliant with BS 7671. This applies to new installations before they are energised, existing installations that require periodic verification, and any installation that has been altered or extended.

Qualified inspection and testing professionals are in high demand because this work is essential to the electrical safety chain. Without competent testing, dangerous faults can go undetected, putting lives and property at risk.

Key Topics to Master

Before testing your knowledge, make sure you are comfortable with these core areas:

• Initial verification requirements for new installations, including the sequence of tests
• Periodic inspection and testing including the criteria for determining inspection intervals
• Test instruments and their correct use, calibration, and limitations
• Continuity testing of protective conductors and ring final circuits
• Insulation resistance testing including acceptable values and test voltages
• Earth fault loop impedance and its relationship to protective device operation
• RCD testing including trip times, test currents, and documentation requirements
• Documentation including electrical installation certificates, minor works certificates, and condition reports

Sample Quiz Questions

Test yourself with these questions that reflect the type of knowledge assessed in the 2391 exam:

Question 1: What is the minimum acceptable insulation resistance value for a circuit operating at 230V? The answer is 1 megohm. BS 7671 specifies minimum insulation resistance values based on the circuit voltage, and for circuits up to and including 500V, the minimum value is 1 megohm when tested at 500V DC.

Question 2: In what order should tests be carried out during initial verification? The correct sequence begins with continuity of protective conductors, followed by continuity of ring final circuits, insulation resistance, polarity, earth fault loop impedance, prospective fault current, and finally RCD testing. Dead tests are always completed before live tests.

Question 3: What coding system is used in Electrical Installation Condition Reports? The coding system uses C1 (danger present, requiring immediate action), C2 (potentially dangerous, requiring urgent remedial action), C3 (improvement recommended), and FI (further investigation required).

Understanding the 2391 Variants

The 2391 qualification comes in different variants to suit your experience level:

• 2391-50 is designed for those who have limited experience in inspection and testing and need comprehensive training from the ground up
• 2391-51 is aimed at experienced electricians who already carry out inspection and testing work and need the formal qualification to evidence their competence
• 2391-52 combines both initial verification and periodic inspection into a single, broader qualification

Choosing the right variant depends on your existing experience and career goals. Your training provider can advise on which option best suits your circumstances.

Preparing for Success

The 2391 exam is widely regarded as one of the more challenging qualifications in the electrical sector. Successful preparation involves:

• Thorough study of BS 7671 and the IET Guidance Note 3
• Regular practice with test instruments to build practical competence
• Completing mock exams under timed conditions
• Attending all course sessions and engaging with practical workshops

Frequently Asked Questions

How long does the 2391 course take? Course duration varies by variant and provider, but typically ranges from five to ten days of classroom and practical training, plus additional self-study time.

Can I take the 2391 without the 18th Edition? It is strongly recommended that you hold the 18th Edition qualification before starting the 2391, as the inspection and testing process relies heavily on knowledge of BS 7671. Some training providers may make it a formal prerequisite.

What equipment do I need for the practical assessment? You will need access to a calibrated multifunction tester, a two-pole voltage indicator with proving unit, and appropriate PPE. Most training centres provide equipment during the course, but you should have your own instruments for professional work.