2391 questions sample1

Section - Answer all twenty questions.
1. Three single socket outlets have been added to a ring final circuit.
State the:
a. inspection and test certificate that will need to be completed
b. title in law given to the inspector
c. legal status of the inspector
2. State the: a. statutory document that is relevant to Inspection and Testing b. non-statutory document that is relevant to electrical test equipment c. non-statutory document that is relevant to The Requirements for Electrical Installations
3. Give one example of the circumstances that would require the issue of each of
the following
a. electrical installation certificate.
b. periodic test report.
c. minor works certificate.
4. State:
a. the meaning of indirect contact b. two methods of protecting against indirect contact
5. State the form of protection that is offered by each of the following:
a. placing out of reach
b. SELV
6. Give one example of each of the following
a. an exposed conductive part b. an extraneous conductive part c. direct contact.
7. State the earthing systems that use the following as earth return paths
a. PEN conductor b. cable sheath c. general mass of earth
8. State the measuring instruments that indicate each of the following units
a. MΩ
b. kA
c. ms.
9. From the BS 7671 2001 schedule of Inspections, state three checks to be made on conductors / cables
10. The initial values recorded between the ends of individual P and N loops during
a ring final circuit test were both 0.6ohms. If the cable is flat twin with c.p.c.,
state the;
a. approximate resistance value of the c.p.c. loop
b. approximate values that would be obtained between P and N at each socket after cross-connections bad been made c. reason why P to c.p.c. readings will increase slightly to the mid-point of the ring and then decrease again.
11. The continuity of a lighting circuit protective conductor is to be tested. If the test method uses a temporary link between phase and earth in the distribution board, state
a. at which points in the circuit the test should be conducted
b. the conductors between which the test should be made
c .the significance of the reading at the end of the circuit
12. The insulation resistance of a 12V PELV installation is to be tested. State
a. the instrument that should be used
b. minimum acceptable value of insulation resistance
c. test voltage to be applied.
13. Give three reasons for carrying out a polarity test on an
Installation as required by BS7671 2001.
14. With regards to BS 7671 identify
a. two special locations that require reduced disconnection times for
protective devices
b. one special location that prohibits the use of socket outlets other than
SELV socket outlets.
15. State the
a. important check to be made regarding equipotential bonding before
carrying out a loop impedance test on a circuit
b. action to be taken regarding the earthing conductor prior to conducting
an external loop impedance test
c. precaution that should be taken before conducting the test in b.
16. State the maximum disconnection times appropriate to the following
a domestic socket outlet circuit
b. site hut lighting on a construction site
c. 110v reduced low voltage system.
17. An earth electrode resistance test is to be performed using an earth electrode resistance tester. Name the three electrodes involved in the test.
18. For a TNC-S system, state three parts of the earth fault loop path external to the installation.
19. State three reasons for the use of a 5OOmA r.c.d. in an installation
20. State three methods of ascertaining the value of prospective short circuit current at the origin of a TNC-S system.
Section B Questions 21 to 26 all refer to the following scenario.
A small, 10 year-old, commercial/office premises at 27 Old Street, Littleton, has been sold and the new owner/occupier, Mr. A.N. Other, has requested an electrical inspection and test for insurance purposes. The installation has remained unaltered since new but the original certificates/documents have been mislaid
The supply system is single phase, 2-wire, 230V 50Hz, TN-C-S with measured values for PFC and Ze of 3000A and 0.08Ω respectively.
The suppliers’ protective device is a 100A BS 1361 fuse and the copper, earthing and main equipotential bonding conductors (16mm2) and 10mm2) respectively, have been correctly connected. The other services to the premises are Gas and Water.
The main 230V/100A 2-pole switch is incorporated in a six-way split load distribution board incorporating & 63A/3OmA RCD. This unit is fully accessible and located in the entrance lobby.
The installation comprises 3 No. 32A 4.Omm2 radial socket outlet circuits ( 1 and 2 are RCD protected), a 16A 2.5mm2 radial water heater circuit and 2 - 6A 1.0mm2 lighting circuits (circuit5 supplies an exterior PIR controlled luminaire). All are wired in thermoplastic (pvc) single conductors enclosed in pvc conduit (cpc’s same size as lives) All protective devices are Type ‘2’ BS3871 (M6) miniature circuit breakers.
The client requests that radial S/0 circuit 3 should not be isolated for testing, as it feeds important IT equipment.
The only installation fault revealed during an inspection process was the omission of red sleeving on lighting switch conductors and two-way lighting strappers.
Polarity has been proven to be correct for all circuits, and all functional tests were satisfactory
The test instrument used was a 4in 1 multi. Function tester serial No. A8B489.
The following table indicates the test results obtained
Circuit R1+R2 Max. Zs Test Zs L/L Ins. Res. L/E RCD IΔn RCD 5xIΔn
Ω Ω Ω MΩ MΩ Ms. Ms.
1.Sockets 0.33 1.07 0.42 200 200 260 80
2.Sockets 0.25 1.07 0.35 200 200
3.Sockets ? 1.07 0.7 ? ?
4. Lighting 1.1 5.71 1.2 200 50
5. Lighting 1.3 5.71 3.7 200 50
6. Water H 0.35 3.75 0.46 200 50


21. Complete the attached Schedule of Inspection (Form 3), indicating only those items that are relevant to this installation.
22. State:
a. if the measured values of Zs are acceptable (show all calculations)
b. any value of Zs that maybe suspect, indicating why and giving a possible
reason.
c. why it may not have been possible to obtain values for Zs for circuits 1 and 2
d. how the situation in c) may be overcome.
23. If an Insulation Resistance test on the whole installation had been possible, and the overall value between live conductors was greater than 200MΩ, and that between live conductors and earth was 9MΩ, calculate the theoretical values for circuit 3 (show all calculations).
24. Explain why
a) a 3OmARCD has been used on circuits 1 and 2 rather than one of a higher IΔn value
b) the installed RCD is unsuitable.
25 Complete the attached Schedule of Inspections (Form 4), making appropriate comments in the remarks column.
26 Complete the attached Periodic Inspection Report (Form 6).