Tuesday, 10 July 2007

C&G 2391 Inspection and Testing Day Questions for Roger 2

A few more questions for Roger in respect of C&G 2391 Inspection and Testing


  1. What does the letters IP stand for. What is the minimum IP rating for the top of an electrical enclosure? Finally what size particle does the IP rating relate to.
  2. What document assigns an inspector the legal status of Duty Holder?
  3. Where a single person is not responsible for a new electrical installation what title roles would need to sign the certificate?
  4. What notice would not need to be present on a 230V DB but would be required on a 400Volt DB?
  5. An insurance company requires a report on an electrical installation, which report would need to be produced and what additional pages would be required?
  6. What is meant by the terms SELV and PELV.
  7. What two methods can be employed for measuring the earth electrode on a TT system.
  8. What is meant by the term TN-C-S?
  9. Explain what is meant by direct contact and indirect contact. Name three methods of protection against direct contact.
  10. When testing equipotential bonding what is the minimum resistance allowed? What is meant by equipotential?
  11. Name three precautions to be taken when carrying out insulation tests.
  12. What voltage setting needs to be selected when testing SELV and what voltage when testing a 230 Volt circuit.
  13. Between what voltages must a low resistance ohm meter produce?
  14. When using 2 30mA RCDs in series how can discrimination be achieved?
  15. The mechanical operation of an RCD should be tested at what interval?
  16. A domestic installation contains no CPCs on the lighting circuit, how old could you assume the electrical installation to be?
  17. Explain what is meant by the 3/4 rule of thumb in relation to Zs.
  18. Where an instrument is not capable of testing above 230volts, what calculation can be used to work out the phase to phase prospective fault current in a three phase circuit.
  19. Explain what is meant by the 'touch voltage' and what is the maximum allowed?
  20. Why is important to obtain the prospective fault current?
  21. When carrying out a stage three test on ring final circuit the resistance rises around the ring and then begins to drop towards the end what is the likely cause.
  22. Stage three of a ring final circuit obtains (R1+R2) but what else does it check.
  23. On a ring final circuit the first and last socket gives 0.4 ohms but further round the ring the value drops to 0.2 ohms, what could be the cause?
  24. In a standard twin and earth PVC cable, which conductor(s) will have the lowest resistance and which will have the highest?
  25. Given an insulation resistance of 1.8 Meg ohms obtained from an overall test carried out on a 230 volt six way consumer unit. If 5 of the circuits have insulation resistances of 50, 50, 30, 50, 40 what is the insulation resistance of the sixth circuit and would this meet the minimum required for the installation?

More to come later?

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