Written practice means writing your answer out in full and then marking it against a list of points. A multiple-choice simulator, like our free 2391-52 mock exam, tests whether you can recognise the right option; it does not show you how many marks your own wording would earn. This page gives you one complete written scenario from our book, 2391-52 mock exam papers, exactly as it appears in the book, followed by the model answer and the marking points. Sit it first, then mark yourself.
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The book has 16 written scenarios like this one, two 60-question multiple-choice papers, and a model answer with marking points for every written question.
How to use this page
- Cover the model answer and read the scenario below.
- Write your answer to parts (a), (b) and (c) on paper, in your own words. Give yourself a fixed time, for example ten minutes for the ten marks, and stop when it is up.
- Then read the model answer and tick each marking point you covered.
- Note the points you missed. They are usually the same few habits, such as proving the detector before and after use.
Worked scenario: safe isolation of a final circuit (10 marks)
Set A, Scenario 1. The scenario and questions, word for word from the book:
You are asked to replace a damaged socket-outlet on a ring final circuit in an occupied two-storey house. The consumer unit has a double-pole main switch and an RCBO for each circuit. You have locking-off devices, padlocks, warning notices, a two-pole voltage detector and a proving unit.
Total: 10 marks
- (a) Describe, in order, a safe isolation procedure for this circuit, up to the point where work can start. [7 marks]
- (b) State two things that could leave the conductors live, or make them live again, after the RCBO has been locked off. [2 marks]
- (c) Explain why a non-contact voltage indicator must not be used to prove the circuit dead. [1 mark]
Model answer and marking points
This is the model answer as it appears in the book. Award one mark for each marking point you covered.
(a) 7 marks
Identify the correct circuit and do not rely on the labels. Where it is safe to do so, check with the voltage detector that the socket-outlet is live with the RCBO ON, so you know the circuit is controlled by it. Switch the RCBO OFF, fit a locking-off device and padlock with a unique key, and keep the key. Fit a caution or prohibition notice at the point of isolation. Prove the voltage detector on the proving unit. At the point of work, test between all conductors (line, neutral and cpc) to prove them all dead. Prove the detector again on the proving unit, then start work.
Marking points (1 mark each, 7 total):
- Identify the circuit; do not trust labels alone
- Check the circuit is live and controlled by the device (ON then OFF), where safe
- Switch OFF and secure with a locking-off device and padlock with a unique key
- Keep the key and fit a caution or prohibition notice at the point of isolation
- Prove the voltage detector on a proving unit before testing
- Test between all conductors at the point of work to prove line, neutral and cpc dead
- Re-prove the detector on the proving unit after testing
(b) 2 marks
A borrowed neutral from another circuit can make the neutral live. A secondary source such as PV or battery storage, or an automatic or app-controlled device, can re-energise circuits.
Any 2 of (1 mark each):
- A borrowed neutral shared with another circuit
- A secondary source (for example PV or battery storage) or an inverter in island mode
- Automatic or remote controls (time switches, photocells, app-controlled devices)
- Diverted neutral current on earthing and bonding from a fault elsewhere
(c) 1 mark
It only indicates that something may be live. No indication does not prove the conductor is dead; only a device that makes contact with the conductor may be used to prove dead.
Marking points (1 mark each, 1 total): No indication does not prove dead; only a contact device may prove dead
How the pack marks your written answers
The book states its own marking rule: “Award one mark for each marking point covered. Where a list says ‘any’, award one mark for each listed point up to the marks available. Model answers show one good way of answering; other correct wording earns the marks.” So you do not need to match the model answer word for word. You need to make each point.
Every written question in the pack has a model answer and marking points, in the same layout as above, so you can see where each mark came from.
What the 16 written scenarios cover
The scenarios are in four sets. These are the titles as they appear in the book.
- Set A, domestic inspection and testing (40 marks): 1. Safe isolation of a final circuit; 2. Interpreting a schedule of test results; 3. Recording extent, limitations and installation details; 4. Testing a new radial circuit
- Set B, rented homes, rings and instruments (38 marks): 5. Coding findings in a rented flat; 6. Ring final circuit test results; 7. Test instruments and test leads; 8. Choosing the right document
- Set C, TT systems, live testing and reports (40 marks): 9. A TT installation; 10. Justifying live testing; 11. An EICR for a landlord; 12. Insulation resistance at a modern consumer unit
- Set D, small commercial and alterations (40 marks): 13. Agreeing the extent of a periodic inspection; 14. Results at a café distribution board; 15. A dangerous situation in an office; 16. Replacing a consumer unit without an EICR
What else is in the book
- Two full 60-question multiple-choice practice papers
- An explanation for every multiple-choice answer, with a reference line naming its source
The book does not time you or mark your answers for you. Set your own timer if you want timed practice, and confirm the current assessment details with your centre.
Get the full pack
2391-52 mock exam papers: Inspection and Testing Exam Practice (paperback £14.99 or Kindle £9.99, on Amazon): 16 written scenarios with model answers and marking points, and two 60-question multiple-choice papers. See what is inside.
Independent publication. Not produced, endorsed or approved by City & Guilds, EAL, the IET or BSI. Not a past paper and contains no assessment questions.
Written by a City & Guilds 2391-51 qualified electrician.