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City and Guilds 2330City and Guilds 2330

Certificate in Electrotechnical Certificate in Electrotechnical TechnologyTechnology

Level 3Level 3Unit 3 Outcome 1 Session 4Unit 3 Outcome 1 Session 4

List and describe the stages of fault List and describe the stages of fault diagnosis and rectification diagnosis and rectification

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Unit 3 Unit 3 Installation (Buildings and Installation (Buildings and

Structures) Fault Diagnosis and Structures) Fault Diagnosis and rectificationrectification

Outcome 1Outcome 1Select and apply fault diagnosis and

rectification techniques

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Outcomes from this sessionOutcomes 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 sessionsReview 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 CollectionData CollectionWhen 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 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 Checks To Be Done Before Turning On The SupplyTurning On The Supply

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

Switch off loads– 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.

Never put a fuse in when the load is connected– 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