Study for the C&G 2391 Online
AI-powered study assistant, mock exams, scenario walkthroughs, and regulation lookup. Everything you need to prepare for the Inspection and Testing qualification.
What Is the C&G 2391 Qualification?
The City & Guilds 2391 — officially titled "Level 3 Award in Initial and Periodic Inspection and Testing of Electrical Installations" — is the recognised qualification for electricians who carry out inspection and testing of electrical installations. It demonstrates that you have the knowledge and practical skills to inspect new installations before they are energised (initial verification) and to periodically inspect existing installations that are already in service (periodic inspection and testing).
The 2391 is a combined qualification that replaced the older C&G 2394 (Initial Verification) and C&G 2395 (Periodic Inspection and Testing). The 2394 covered the inspection and testing required before a new installation is connected to the supply — ensuring it has been designed, constructed, and tested in accordance with BS 7671. The 2395 covered the periodic inspection of existing installations, identifying deterioration, damage, and departures from the current edition of the regulations. The 2391 covers both areas in a single qualification.
For working electricians, the 2391 is one of the most important qualifications after the 18th Edition (C&G 2382) and the Level 3 NVQ. Without it, you cannot join a competent person scheme (NICEIC, NAPIT, ELECSA) as a qualified supervisor, and you cannot independently sign off Electrical Installation Certificates (EICs) or Electrical Installation Condition Reports (EICRs). If you want to work as a self-employed electrician and certify your own work, the 2391 is not optional — it is essential.
Why You Need the 2391 Qualification
The 2391 is required for several critical career milestones in the electrical industry. Understanding these requirements helps you plan your career progression effectively.
- NICEIC/NAPIT/ELECSA membership: All major competent person schemes require the 2391 (or equivalent) for qualified supervisors. Without scheme membership, you cannot self-certify notifiable electrical work under Part P of the Building Regulations.
- Signing off EICRs: To issue an Electrical Installation Condition Report, you must be competent in periodic inspection and testing. The 2391 is the standard evidence of this competence. Landlord EICR work is a growing market since the 2020 regulations made them mandatory for rented properties in England.
- JIB Approved Electrician (Grade Card): The Grade Card requires the 2391 in addition to the Gold Card qualifications. It demonstrates a higher level of competence and is valued by employers in commercial and industrial work.
- Career advancement: Many electrical contracting firms require the 2391 for senior electrician roles, site supervisor positions, and contracts manager positions. It is also valuable for electricians moving into consultancy, training, or compliance roles.
What the 2391 Course Covers
The 2391 course content covers every aspect of electrical inspection and testing that a competent person needs to know. The syllabus is divided into several key areas, each of which is tested in both the written examination and the practical assessment.
Safe isolation procedures form the foundation of all inspection and testing work. Before any dead testing can be carried out, the circuit or installation must be safely isolated and proved dead using a GS 38 compliant voltage indicator and proving unit. The correct procedure is: test the voltage indicator on a known live source (or proving unit), test the circuit for dead on all conductors, then test the voltage indicator again to confirm it is still working. This three-step procedure must be followed every time without exception.
Initial verification covers the inspection and testing required before a new installation or alteration is connected to the supply. This includes a detailed visual inspection of the installation against the design documentation and BS 7671 requirements, followed by a sequence of electrical tests. The documentation produced is the Electrical Installation Certificate (EIC), which confirms that the installation has been designed, constructed, inspected, and tested in accordance with BS 7671.
Periodic inspection covers the assessment of existing installations that are already in service. This involves a thorough visual inspection, followed by testing, to identify any deterioration, damage, defects, or non-compliance with the current edition of BS 7671. The documentation produced is the Electrical Installation Condition Report (EICR), which includes observation codes (C1, C2, C3, FI) and an overall assessment of the installation condition.
The GN3 Testing Sequence Explained
Guidance Note 3 (GN3) published by the IET specifies the correct sequence of tests for both initial verification and periodic inspection. The tests must be carried out in a specific order because each test validates the results of the previous one and confirms that it is safe to proceed to the next. Understanding this sequence is essential for both the 2391 exam and real-world practice.
Continuity of Protective Conductors
This test confirms that the circuit protective conductors (CPCs) provide a continuous low-resistance path from every exposed-conductive-part back to the main earthing terminal. A low-resistance ohmmeter is used to measure the R1+R2 value for each circuit. This test is done first because a functioning earth path is essential for safety before any further tests are carried out.
Continuity of Ring Final Circuit Conductors
For ring final circuits, this test confirms that the line, neutral, and CPC are all continuous rings without breaks, and that no interconnections or spurs exist where they should not. The three-step test method (end-to-end, cross-connect, test at each socket) is the standard approach. The measured values at each socket outlet should be reasonably consistent, indicating a healthy ring.
Insulation Resistance
This test applies a DC test voltage (typically 500V for standard 230V circuits) between live conductors and earth, and between line and neutral, to confirm that the insulation of the cables and accessories is in good condition. The minimum acceptable value is 1 megohm, though in practice healthy insulation should read significantly higher. This test is done after continuity tests because it requires the circuit to be isolated and all loads disconnected.
Polarity
This test confirms that single-pole switching and protective devices are connected in the line conductor only, not the neutral. It also confirms that socket outlets are correctly wired (line to the correct terminal, neutral to the correct terminal, earth connected). Polarity is typically confirmed during the R1+R2 continuity test using the wander lead method.
Earth Fault Loop Impedance (Zs)
This live test measures the total impedance of the earth fault loop for each circuit. The measured Zs value must not exceed the maximum permitted value for the protective device on that circuit (as tabulated in BS 7671). This ensures that in the event of an earth fault, sufficient current will flow to operate the protective device within the required disconnection time (0.4 seconds for final circuits, 5 seconds for distribution circuits).
Prospective Fault Current (PSCC)
This test measures the maximum prospective short-circuit current and prospective earth fault current at the origin of the installation. The measured value must not exceed the rated breaking capacity of the protective devices. This is important because if the fault current exceeds the device rating, the device may fail to interrupt the fault safely.
RCD Testing
Residual Current Devices (RCDs) are tested to confirm they operate within the required time at their rated residual operating current. A 30mA RCD protecting a socket outlet must trip within 300ms at the rated current and within 40ms at five times the rated current. The test also confirms the RCD does not trip at 50% of the rated current (to avoid nuisance tripping). This is the final test because it requires the supply to be live.
The 2391 Practical Assessment
The practical assessment is the component that many candidates find most challenging. It requires you to demonstrate that you can carry out a real inspection and testing procedure on an actual or simulated installation, following the correct sequence and producing accurate documentation.
The practical typically involves two scenarios. The first is an initial verification of a newly installed or altered circuit. You inspect the installation visually, carry out the full testing sequence, and complete an Electrical Installation Certificate (EIC) with accurate test results and any observations about departures from BS 7671.
The second scenario is a periodic inspection of an existing installation. You carry out a visual inspection and testing of an installation that has been in service, identify any defects or non-compliance, assign appropriate observation codes (C1, C2, C3, or FI), determine the overall assessment (Satisfactory or Unsatisfactory), and complete an Electrical Installation Condition Report (EICR).
In both scenarios, assessors are looking for several things: that you follow the correct testing sequence, that you perform safe isolation properly, that your test instrument readings are accurate and consistent, that you identify defects correctly, that you assign the appropriate observation codes, and that your documentation is complete and accurate. Elec-Mate scenario walkthroughs simulate both types of assessment so you arrive prepared and confident.
How Elec-Mate Helps You Pass the 2391
Studying for the 2391 alongside a full-time job is challenging. You need a study method that fits around your work schedule and gives you access to the information you need when you need it. Elec-Mate provides exactly that.
The AI study assistant is available 24/7 and can answer any question about inspection and testing procedures, BS 7671 regulations, GN3 guidance, or documentation requirements. Unlike a textbook, the assistant explains concepts in plain language and can give you examples relevant to the specific type of installation you are studying. Ask it to explain the difference between Zs and Ze, to walk you through the ring final circuit continuity test, or to clarify when an FI code is appropriate instead of a C2. It responds instantly with clear, regulation- referenced answers.
The mock exam questions are drawn from the full 2391 syllabus and are designed to mirror the style and difficulty of the real examination. Each question includes a detailed explanation of the correct answer, with references to the relevant regulations and guidance notes. Timed practice exams help you build the speed and confidence needed for the real assessment.
AI Study Assistant
Ask questions about any regulation, testing procedure, or scenario. The AI study assistant provides detailed explanations with BS 7671 regulation…
GN3 Testing Sequence
Learn the correct order of tests from Guidance Note 3. Interactive walkthroughs explain why each test is performed in sequence and what the results mean.
Mock Exam Questions
Hundreds of practice questions covering the full 2391 syllabus. Timed mock exams simulate the real written assessment with instant marking and detailed…
Scenario Walkthroughs
Realistic inspection scenarios covering domestic, commercial, and industrial installations. Work through each scenario step by step with AI guidance and…
Certificate Practice
Practise completing EICs and EICRs accurately. The app validates every field and flags common documentation mistakes before you encounter them in the…
Regulation Lookup
Instant access to BS 7671 regulation references and GN3 guidance. Search by topic, regulation number, or keyword.
How to Prepare for the 2391 Using Elec-Mate
Follow these steps to build your knowledge and confidence before the C&G 2391 examination and practical assessment.
Start with the GN3 testing sequence
Open the Inspection and Testing study module in Elec-Mate and begin with the GN3 testing sequence. This covers the correct order of tests as specified in Guidance Note 3: continuity of protective conductors, continuity of ring final circuits, insulation resistance, polarity, earth fault loop impedance, prospective fault current, and RCD testing. Understanding why the tests are done in this order is fundamental to the 2391.
Work through practical scenario walkthroughs
The app presents realistic inspection scenarios — a domestic rewire, a commercial installation, a periodic inspection of an older property. Each scenario walks you through what to inspect, what to test, and how to document your findings. The AI study assistant explains the reasoning behind each step and answers your questions in real time.
Practise completing certificates and reports
Practise filling in EICs and EICRs using the Elec-Mate certificate forms. The 2391 assessment requires you to complete the documentation accurately, so being comfortable with every section of the form before the exam is essential. The app validates your entries and flags any errors or omissions.
Take mock exams under timed conditions
Use the mock exam feature to test your knowledge under realistic time constraints. The questions cover the full syllabus including BS 7671 regulation references, GN3 procedures, testing instrument operation, and documentation requirements. Review your results to identify weak areas that need more study.
Book and prepare for the practical assessment
Once you are confident with the theory, book your practical assessment at an approved centre. Use the Elec-Mate pre-assessment checklist to ensure your test instruments are calibrated, your leads are compliant with GS 38, and you have all the necessary documentation. The app provides a final revision summary covering the most common practical assessment tasks.
Study for the C&G 2391 with Elec-Mate
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Frequently Asked Questions About the C&G 2391
What is the difference between C&G 2391, C&G 2394, and C&G 2395?
Do I need the 2391 to carry out EICRs?
How long does the C&G 2391 course take?
What test instruments do I need for the 2391 practical?
Can I study for the 2391 online?
What observation codes are used on an EICR and what do they mean?
Pass the 2391 with confidence
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