City and Guilds 2395 Exam Questions 2

To pass your electrical course work your best point of attack is to work out question papers. These questions are the basic knowledge you should posses for inspection and testing and you can expect to get similar questions in you r multiple choice exams. The answers however will be in a multiple choice format, but the questions will be similar to the ones below.

1. List two statutory documents applying to the conduct of inspection and testing and one statutory document requiring installations to meet the standards set out in BS 7671. 

2. List two main things to be agreed with the client prior to inspecting and testing an existing installation and state where these should be recorded. 

3. List five things to check before using a test instrument and its leads. 

4. State the instruments which would have the following ranges:- 

  • a) 0-2Ω
  • b) 0-200 MΩ
  • c) 0-20 kA

5. An insulation resistance test is to be carried out on a lighting circuit. State the action to be taken in respect of : 

  • a) lamps
  • b) light switches
  • c) two-way light switches

6. An insulation resistance test is to be carried out on a lighting circuit. State the action to be taken in respect of vulnerable equipment including smoke detectors and self-contained emergency lighting luminaries. 

7. Explain briefly why it is desirable to minimise the amount of dismantling during a periodic inspection and test. 

8. Outline the dangers which could arise during the following tests: 

  • a) insulation resistance test
  • b) earth fault loop impedance test
  • c) RCD test

9. A SELV circuit in zone 0 of a bathroom is being inspected. State:- 

  • a) the BS number of the safety isolating transformer
  • b) the maximum voltages allowed ( both ac and dc )
  • c) where the transformer should be located

10. State the maximum rating of a RCD used for:- 

  • a) protecting a 63A socket outlet on a construction site
  • b) fire protection in an area with a high risk of fire due to the materials
  • being processed
  • c) protecting a socket outlet supplying a caravan.

11. State the test currents and the maximum acceptable tripping times for a 10 mA, BS EN 61008 RCD used for Additional Protection. 

12. Describe briefly how to measure the prospective fault current at a three-phase distribution board. 

13. A circuit breaker to BS 3871 is marked “M6” explain what this marking means and describe how the same information would be marked on a circuit breaker to BS EN 60898

14. State the minimum IP rating for an enclosure:

  • a) for protection against direct contact
  • b) in zone 0 of a bathroom
  • c) in zone 1 of a public shower room where a hose would be used for cleaning 

15.

a) State the upper limit for the resistance of bonding conductors given as a rough guide in IEE Guidance Note 3. 
b) Explain how the effects of parallel paths can be avoided when checking the continuity of main protective bonding conductors. 
c) State the safety precaution required when taking the action recommended in b) above.

16. Earth fault loop impedance can be calculated from measured values of Ze, R1 and 
R2. 

  • a) state the equation to be used
  • b) explain why a measured value of earth fault loop impedance may be less than a value calculated as above. 

17.

  • a) State the practical advantage that measuring Rl +R2 has over the alternative method of measuring c.p.c. continuity. 
  • b) Say when it is necessary to use the alternative method.
  • c) State the percentage rise in the resistance of a copper conductor between 20°c and 70 °c.

18. A continuity test is being carried out on a lighting circuit using the Rl + R2 
method.

State:

  • a) the check to be made on light switches during the R1 + R2 test and explain how 
  • b) the check to be made on any Edison Screw lampholders
  • c) the BS number of Edison Screw lampholders for which the checks in b) are not required. 

19. The continuity of the conductors of a ring final circuit is checked using the method given in IEE Guidance Note 3. List four things which arc confirmed by satisfactory readings. Assume that testing has been done through the front of the sockets using a test lead with a plug.

20.

  • a) List two factors affecting the measured value of earth fault loop impedance of a given circuit. 
  • b) State a simple rule for taking account of the factors in a) above when comparing measured values of Zs with the maximum values given in BS 7671.

 

 

 

Answers

 

 

1. Two statutory documents relating to the conduct of inspection and testing:

  •  Health and Safety at Work etc. Act 1974
  •  Electricity at Work Regulations 1989

Electricity Safety, Quality and Continuity Regulations 2002 requires installations to meet requirements of BS 7671. 

2. Two things to be agreed with client:      

  • 1) Extent,
  • 2) Limitations

Record these on the Electrical Installation Condition Report form.

3. Five points should be given. See GS 38.
Instrument :

  • in good condition
  • calibrated
  • battery o.k.
  • suitable for voltage it is to be used on
  • suitable ranges for the measurement to be taken.

Leads:

  • in good condition
  • adequately insulated for the voltage they are to be used on
  • fused and/or fitted with resistors to limit current
  • probes fitted with finger guards
  • probe tips with bare minimum of exposed metal (2mm or less) or
  • else covered by retractable spring loaded shrouds
  • adequate length
  • coloured to aid identification

4.

  • a) low resistance ohmmeter,
  • b) insulation resistance ohmmeter, prospective fault current meter

5.

  • a) remove lamps or switch off locally if removal is not possible
  • b) put light switches ‘on* unless the switch is being used to isolate lamps which cannot be removed
  • c) operate two-way switches alternately while applying the test voltage to ensure that both strappers and the switch wire are tested

6. Isolate the vulnerable equipment or disconnect it. If this is not possible then only test between all live conductors connected together and earth.

7. Dismantling introduces the risk of:

  • a) damage
  • b) incorrect reassembly
  • c) forgetting to reassemble

8.

  • a) The use of high voltages creates a risk of shock and the risk of damaging vulnerable equipment.
  • b) If the c.p.c. is broken then every exposed conductive part downstream from the break will be live during the test and present a shock risk.
  • c) Danger is the same as for b)

9.

  • a) BS EN 61558-2-6 is latest standard. ( Previous standards BS EN 60724 and BS 3535 )
  • b) 12Vacor30Vdc
  • c) Outside zones 0, 1 and 2

10.

  • a) 500 mA
  • b) 300 mA
  • c)   30 mA
11.
  • At 5 mA the RCD should not trip.
  • At 10 mA it should trip in 300 ms or less.
  • At 50 mA it should trip in 40 ms or less.

12. Measure the prospective short-circuit current between each line and neutral. 
Take the highest reading and double it to get the prospective fault current. 

13. M6 means the circuit breaker has a breaking capacity of 6kA. On a BS EN 60898 
circuit breaker it would be marked as the figure 6000 inside a rectangular box. 
14.
  • a)IP2X
  • b)IPX7
  • c)IPX5
15.
  • a) 0.05Ω
  • b) Measure the continuity with one end of the bond disconnected.
  • c) The installation must be isolated from the supply.

16.

  • a) Zs = Ze + Rl +R2
  • b) Ze is measured with the earthing conductor disconnected from the main earthing terminal. Zs is measured with all bonding connected and this may provide parallel paths which reduce the apparent value of Zs. 

17.

  • a) Measuring R1 + R2 requires meter leads of standard length whereas the alternative long lead method, measuring R2, requires a lead the length of the circuit. 
  • b) The alternative ‘long lead’ method must be used for checking the continuity of bonding conductors. 
  • c) 20%

18.

  • a) Check that the light switches arc in the line conductor and not the neutral. Check this by measuring R1 + R2 at the lamp and checking that the reading becomes infinite when the switch is opened. 
  • b) Ensure that the outer contact is connected to neutral and the centre contact to line. 
  • c) Check in (b) not required for E14 and E27 lampholders to BS EN 60238.

19.

  • 1. the ring is continuous
  • 2. the value of R1 and R2
  • 3. there are no interconnections in the ring
  • 4. socket outlets are correctly connected
20.
  • a)   circuit loading and ambient temperature
  • b)   Measured values of Zs should not exceed 80% of the maximum given in the tables in Chapter 41 of BS 7671. (Appendix 14 of BS 7671)