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View Unit : Carrying Out Fault Diagnosis on Electrical Equipment and Circuits

Unit Reference Number
Qualification Framework
Carrying Out Fault Diagnosis on Electrical Equipment and Circuits
Unit Level
Level 3
Unit Sub Level
Guided Learning Hours
Unit Credit Value
Date of Withdrawal
4.1 Engineering
Unit Grading Structure
Assessment Guidance

This unit must be assessed in a work environment and must be assessed in accordance with the ‘Common Requirements for National Vocational Qualifications (NVQ) in the QCF’ which can be downloaded from Semta’s website: http://www.semta.org.uk/training_providers__awarding/national_occupational_standard/qca_assessment_requirements.aspx

Additional assessment requirements have been published by Semta. These additional assessment requirements are set down in Semta’s Engineering Maintenance Level 3 unit assessment strategy which can be downloaded from Semta’s website: http://www.semta.org.uk/training_providers__awarding/national_occupational_standard/qca_assessment_requirements.aspx

Learning Outcomes and Assessment Criteria
Learning Outcome - The learner will:Assessment Criterion - The learner can:

1a. Carry out fault diagnosis on electrical equipment and circuits


Work safely at all times, complying with health and safety and other relevant regulations and guidelines


Carry out all of the following during the fault diagnostic activity:

• plan the fault diagnosis, based on the available information about the fault

• obtain and use the correct issue of company and/or manufacturers drawings and maintenance documentation

• adhere to procedures or systems in place for risk assessment, COSHH, personal protective equipment and other relevant safety regulations and procedures to realise a safe system of work

• ensure the safe isolation of equipment (such as electricity, mechanical, gas, air or fluids)

• provide and maintain safe access and working arrangements for the fault finding/maintenance area

• carry out the fault diagnostic activities using approved procedures

• collect equipment fault diagnostic evidence from ‘live’ and isolated circuits

• disconnect or isolate components or parts of circuits, when appropriate, to confirm diagnosis

• identify the fault and ...


... determine appropriate corrective action

• dispose of waste items in a safe and environmentally acceptable manner, and leave the work area in a safe condition


Carry out fault diagnosis on six of the following types of equipment:

• single-phase power circuits

• three-phase power circuits

• direct current power circuits

• switchgear and distribution panels

• motors and starters

• control systems and components

• electrical plant

• luminaires


Find faults that have resulted in two of the following breakdown categories:

• intermittent action or circuit failure

• partial failure or reduced performance

• complete breakdown


Review and use all relevant information on the symptoms and problems associated with the products or assets


Investigate and establish the most likely causes of the faults


Select, use and apply diagnostic techniques, tools and aids to locate faults


Collect fault diagnostic evidence from four of the following sources:

• the person or operator who reported the fault

• test instrument measurements (e.g. watt meters, multimeter, earth-loop impedance testers)

• circuit meters (such as voltmeter, power factor meter, ammeter)

• recording devices

• sensory input (sight, sound, smell, touch)

• plant/equipment records

• condition of end product

• equipment self-diagnostics


Use a range of fault diagnostic techniques, to include two of the following:

• half-split technique

• input/output technique

• injection and sampling

• six point technique

• equipment self-diagnostics

• emergent sequence

• unit substitution

• function/performance testing


1b. Carry out fault diagnosis on electrical equipment and circuits (continued)


Use a variety of diagnostic aids and equipment to include two of the following:

• logic diagrams

• flow charts or algorithms

• manufacturers’ manuals

• equipment self-diagnosis

• fault analysis charts (such as fault trees)

• trouble shooting guides

• electronic aids


Use all of the following fault diagnosis procedures:

• inspection (such as breakages, wear/deterioration, signs of overheating, missing parts, loose fittings)

• operation (such as manual switching off and on, RCD test buttons, automatic switching/timing/sequencing, desired outputs)

• measurement (such as voltage, current, continuity, power, temperature, luminescence)


Use three of the following types of test equipment to aid fault diagnosis:

• multimeter

• watt meter

• voltmeter

• ammeter

• earth-loop impedance tester

• insulation resistance tester

• portable appliance tester

• light meter

• other specific test equipment


Complete the fault diagnosis within the agreed time and inform the appropriate people when this cannot be achieved


Determine the implications of the fault for other work and for safety considerations


Use the evidence gained to draw valid conclusions about the nature and probable cause of the fault


Record details on the extent and location of the faults in an appropriate format


Provide a record of the outcome of the fault diagnosis, using one of the following:

• step-by-step analytical report

• preventative maintenance log/report

• corrective action report

• company-specific reporting procedure


2a. Know how to carry out fault diagnosis on electrical equipment and circuits


Describe the health and safety requirements of the area in which the fault diagnosis activity is to take place, and the responsibility these requirements place on the learner


Describe the isolation and lock-off procedure or permit-to-work procedure that applies


Explain how to recognise and deal with victims of electric shock (to include methods of safely removing victim from power source, isolating the power source, and methods of first aid resuscitation)


Describe the importance of wearing protective clothing and other appropriate safety equipment during fault diagnosis activities


Describe the Hazards associated with carrying out fault diagnosis on electrical equipment (such as live electrical components, stored energy, misuse of tools), and how to minimise these and reduce any risks


Describe the procedure to be adopted to establish the background of the fault


Explain how to evaluate the various types of information available for fault diagnosis


Explain how to use the various aids and reports available for fault diagnosis


Explain how to use various items of fault diagnostic equipment to investigate the problem


Describe the various fault finding techniques that can be used, and how they are applied (such as half-split, input-to-output, emergent problem sequence, six point technique, function testing, unit substitution, injection and sampling techniques and equipment self-diagnostics)


Explain how to evaluate sensory information (sight, sound, smell, touch)


Explain how to analyse evidence and evaluate possible characteristics and causes of specific faults/problems


Explain how to relate previous reports/records of similar fault conditions


2b. Know how to carry out fault diagnosis on electrical equipment and circuits (continued)


Describe the care, handling and application of electrical test instruments (such as multimeters, insulation resistance testers)


Explain how to calibrate electrical test instruments and check that they are free from damage and defects


Explain how to obtain and interpret drawings, circuit and physical layouts, charts, specifications, manufacturers’ manuals, history/maintenance reports, graphical electrical symbols, BS7671/IEE wiring regulations, and other documents needed in the maintenance process


Describe the basic principles of how the circuit functions, the operating sequence, the purpose of individual units/components and how they interact


Describe the different types of cabling (such as multi-core cables, single-core cables, SWA cables, MI cables, screened cables), their associated fittings, and their application


Describe the different types of motors and starters, and their operation


Describe the different types of control systems and components, and their operation


Describe the different types of electrical components (such as plugs, switches, lighting and fittings, junction boxes, consumer units), and their operation


Explain how to evaluate the likely risk to themselves and others, and the effects the fault could have on the overall process or system


Explain how to prepare and produce a risk analysis report, where appropriate


Explain how to prepare a report or take follow-up action which satisfies the company policy on concluding fault diagnosis


Describe the extent of their own authority and to whom they should report if they have problems that they cannot resolve

Equivalent Units
There are no equivalences to display.