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City and Guilds 2330 Certificate in Electrotechnical Technology Level 3 Unit 3 Outcome 1 Session 4 List and describe the stages of fault diagnosis and rectification B & B Training Associates


Unit 3

Installation (Buildings and Structures) Fault Diagnosis and rectification

Outcome 1

Select and apply fault diagnosis and rectification techniques

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Outcomes from this session At the end of this session you should be able to


List and describe the stages of logical fault diagnosis and rectification

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Review of previous sessions 

There are different types of circuits in both three-phase and single-phase supplies

Power circuits are almost all circuits other than lighting and emergency circuits

Control circuits deal with the controlling of motor starters etc.

Lighting circuits deal with lighting

Fire and emergency lighting circuits are easy to recognise.

Faults occur for many reasons, they need to be understood and rectified.

The person who is working must be competent to do the task

Tasks should be planned so that no live working takes place

An approved voltage tester and a voltage proving unit are required for testing of a potentially live piece of equipment.

There are three key aspects to good fault finding practice, good technical knowledge, good personal experience and a logical approach

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Data Collection When fault finding, data is essential. The data can come from 

The client – What happens – Flashes bangs etc » The client will often be able to provide clues as to the nature of the fault. Careful questioning can provide a starting point for the investigation

Previous test schedule sheets – These are not immediately useful for a specific fault, but they can be an indicator of an underlying fault

Prior reports – This report may give you some indication on the nature of the fault

Test results – This may indicate changes that have taken place over time.

Manufacturers data sheet – These are useful when trying to determine issues with specific items of equipment

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Re-energising a Supply It is essential when dealing with any faults in a in electrical installation that a set process is followed. You cannot simply turn on a supply and wait for the ‘bang’. The order in dealing with any fault is; 

Find the fault

Rectify the fault

Re-test prior to any further progression.

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Checks To Be Done Before Turning On The Supply 

Check – make sure the covers are back on and screwed back.

Switch off loads –

Never put a fuse in when the load is connected –

loads can cause a protective device to trip or blow because the inrush current causes a very large level of current to flow for a short duration of time. this can cause an arc to occur.

Try to avoid making a circuit breaker when the load is connected. – This can cause someone a surprise

Remember –

remember that turning a supply on is no substitute for a proper inspection and test of an installation. End of session 4

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List the stages of fault diagnosis  

List the stages of fault diagnosis

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