The C&G 2391 Practical Exam - Initial Verification

In this guide the qualification we are covering is the C&G 2391 2391-52 Level 3 Award in Initial and Periodic Inspection and Testing of Electrical Installations , which is the combined or full Inspection and Testing qualification.

The practical exam required for this qualification is broken into two separate parts:
- Initial Verification of a brand new installation
- Periodic Inspection of an existing installation.

On this page, we are covering the first one - Initial Verification and everything that is associated with that part of the practical exam.

C&G 2391 practical exam - Initial Verification

This part of the practical exam consists of three tasks:
1. Visual inspection
2. Fault finding with Insulation Resistance testing
3. A full Inspection and Testing procedure with the completion of the Electrical Installation Certificate

Visual Inspection

On the day of the C&G 2391 practical exam the first task for delegates to complete is a visual inspection of a model electrical installation. The installation consists of only a few demo circuits and of a single phase consumer unit.

Within 30 minutes the delegate will be required to visually identify 12 faults/non compliments with BS 7671.

The faults can be some of these, but the list is far from complete:

• Incorrect polarity
• Exposed live parts
• Wrong choice of circuit breakers
• Wrong circuit arrangements inside the consumer unit (Neutrals and Earths not in order in their respective terminal bars)
• Wrong choice of colour coding
• Missing earth
• Twisted cables
• Missing protective bonding conductor
• Missing danger notices or other warning notices
• Incorrect or missing labelling of protective devices, switches and terminals
• Wrong selection of conductors for current-carrying capacity
• Connection of conductors (exposed copper)
• Physical damage to accessories
• Missing earth sleeving
• Loose SWA cleats
• Missing identification of switch wires

Remember this is a visual inspection only! You are expected to find faults without the use of hands or other methods.

Fault finding with Insulation Resistance testing

At this stage of the practical exam the delegate will be required to perform a fault finding procedure on a “black box” simulating a circuit under various and adjustable fault conditions.

The delegate will be required to select the appropriate tester (insulation resistance tester) and after visually inspecting the tester for faults, setting it up for the correct voltage.
Since the simulated circuit will be a single phase low voltage circuit, the required test voltage with which the tests must be undertaken is 500V with accordance of BS 7671.

Test sequence is as follows:

• Test between L-N
• Test between L-E
• Test between N-E

Possible test results:

• > 2 M ohm – open circuit (no electrical connection between conductors which is as it should be)
• < 2 M ohm but not 0 Ohm - possible electrical connection between conductors (faulty condition which needs further investigation)
• 0 ohm – short circuit between conductors (faulty condition)

The examiner will “insert” one or more of these faults into the “black box” and the delegate will be required to identify and explain the possible causes and solutions.

Read more about insulation resistance testing under the section C&G 2391 – Insulation resistance test.

Inspection and testing procedure

The delegate will be required to perform a full Inspection and Testing procedure on a sample electrical installation with Certification after completion. The term "full" indicates that the inspection must cover 100% of the electrical installation.

The given time for this task is 120 minutes.

The delegate will be presented with a sample electrical installation consisting of:

- 3 Phase&Neutral board supplying:

• 3 phase motor supply in SWA cable (DOL starter, no motor connected)
• Sockets supplied by a ring circuit
• Radial circuit to a FCU with MI cable
• Sub-main supply to the single phase consumer unit

- Single Phase&Neutral consumer unit supplying:

• Lighting circuit with intermediate switching
• Lighting circuit with a dimmer switch
• Socket outlet supplied by a radial circuit.

Before anything else the delegate will be expected to perform a Safe Isolation Procedure.

The sequence of the inspection and testing is as follows:

• Assessment of general characteristics
• Continuity of protective conductors, including p rotective bonding
• Continuity of ring final circuit conductors
• Polarity dead tests
• Insulation resistance test
• Polarity live tests
• Earth fault loop impedance tests
• Prospective fault current test
• Phase sequence test
• RCD test
• Functional testing

The delegate will be expected to perform a 100% correct inspection and testing procedure in the correct sequence.

If any faults found, it must be reported to the examiner and recorded on the Electrical Installation Certificate.

On our next pages we will cover each of the tests in full detail.