FINAL - IT 30 ELECTRICAL INSPECTOR EXAMINATION ANSWER SCHEDULE Notes:1. (1 mark) means that the preceding statement/answer earns 1 mark. 2. This schedule sets out the expected answers to the examination questions. The marker can exercise their discretion and decide on the overall accuracy of any answer that is presented in the candidate s own words. 3. Symbols and terms - alternatives Power W or P Voltage V or E or U Phase Active Question 1 Marks Reference Marking notes (a) The work is undertaken under such control and direction of a person authorised under the Act to do the work and is sufficient to ensure: That the work is performed competently. That while the work is being undertaken, appropriate safety measures are adopted. That the competed work complies with the requirements of the regulations. (2 marks) EA 2 (b) Use the associated equipment and person protective equipment that is necessary to ensure his or her safety and the safety of other person within the vicinity of the work. (2 marks) ESR 103(2) (c) Any TWO of: The use of a key or tool is required. An interlocking device is fitted. An intermediate barrier is provided. (2 marks) AS/NZS 3000: 1.5.4.4(b) Exception (d) Any TWO of: Where the electrical equipment operates under conditions of fluctuating or intermittent loading, or a definite duty cycle Where the electrical installation is large and complex Where special types of occupancy exist. (2 marks) AS/NZS 3000: 2.2.2(b) FINAL - IT30 ANSWERS 15 NOVEMBER 2014 1
Question 1 Marks Reference Marking notes (e) Any TWO of: The neutral pole of a multi-pole switch or circuit breaker having an appropriate short-circuit breaking and making capacity is linked and arranged to switch substantially together with all active poles. The switch or circuit breaker is linked with corresponding switches so that the neutral contact cannot remain open when the active contacts are closed. A switched neutral pole shall not open before and shall not close after the active pole(s). Where an item of switchgear is required to disconnect all live conductor of a circuit, it shall be of a type such that the neutral conductor cannot be disconnected or reconnected without respective active conductors also being connected or reconnected. (2 marks) AS/NZS 3000 2.3.2.1.1 (b)(ii)(a) AS/NZS 3000 2.3.2.1.1 (b)(ii)(b) AS/NZS 3000 2.3.2.1.1(b)(ii) AS/NZS 3000 2.3.2.1.1(b)(iii) (f) Any ONE of: (2 marks) The minimum size of the main earthing conductor may be determined in relation to the crosssectional area of the minimum cable size required to carry the maximum demand The minimum cross-sectional area determined by calculation shall not be less than the value determined by the following equation. AS/NZS 3000 5.3.3.2 Exception (b) AS/NZS 3000 5.3.3.1.3 (g) An electricity generation system shall be arranged so that it cannot supply energy upstream of the point of connection to the installation either directly or indirectly. (2 marks) AS/NZS 3000: 7.3.3 (h) Any TWO of: Shall not accept plugs of other voltage systems. Shall not have a contact for a protective earthing conductor. Shall have their voltage conspicuously marked. Shall be of a form that will prevent insertion of an extra-low voltage (2 marks) AS/NZS 3000: 7.5.10(b) AS/NZS 3000: 7.5.10(c) AS/NZS 3000: 4.4.1.2(a) AS/NZS 3000: 4.4.1.2(b) FINAL - IT30 ANSWERS 15 NOVEMBER 2014 2
Question 1 Marks Reference Marking notes plug into a socket-outlet connected to a circuit of greater than extralow voltage. The nominal voltage shall not be capable of exceeding the limits for extra-low voltage (50V a.c. or 120V ripple-free d.c.) and the source of supply is arranged so it cannot exceed those values. Circuits shall be electrically segregated from each other and from circuits of higher voltages. Live parts of SELV circuits shall not be connected to earth or to protective earthing conductors that are part of other circuits or to other live parts. Live parts of PELV circuits shall be protected from direct contact by barriers or insulation unless the voltage does not exceed 25Va a.c. or 60V ripple-free d.c. in dry areas where a large contact area with the human body is not expected or 6V a.c. or 15V d.c. in all other areas.. (i) (i) It has a fusing factor between 1.25 and 1.5 AS/NZS 3000: 1.5.7(a) AS/NZS 3000: 1.5.7(b) AS/NZS 3000: 1.5.7(c) AS/NZS 3000: 1.5.7(d) (1 mark) GK (ii) A gg type fuse (1 mark) GK (j) This is the maximum current that can be safely interrupted under short circuit conditions. (2 marks) GK FINAL - IT30 ANSWERS 15 NOVEMBER 2014 3
Question 2 Marks Reference Marking notes (a) (i) The owners and operators of the caravan park. (1 mark) ESR 75(1)(a) (ii) 5 years (1 mark) ESR 75(1)(a) (iii) A periodic assessment may be undertaken only by a person who is authorised to assess prescribed electrical work in a caravan park. (1 mark) ESR 75(2) (iv) (A) The person supplying electricity to the caravan. (1 mark) ESR 76(1) (B) A current warrant of electrical fitness. (1 mark) ESR 76(1) (b) (i) A/NZS 3001 Appendix C4 and C5 (1 mark) AS/NZS 3001 (iii) IEC 60309 AS/NZS 3001 Appendix C4.5 A rating not less than 16A AS/NZS 3001 2.2.7.2(c) AS/NZS 3112 AS/NZS 3001 Appendix C4.5 A rating not less than 15A AS/NZS 3001 Appendix C4.5 (c) The use of 0.4s disconnection times for protective devices fitted to caravan park socket-outlets is to ensure adequate touch voltage control is provided for all transportable structures or vehicles installations connected to those socket-outlets. (2 marks) AS/NZS 3001 2.2.4.2.2 Note FINAL - IT30 ANSWERS 15 NOVEMBER 2014 4
Question 3 Marks Reference Marking notes (a) (i) Final subcircuits supplying one or more socket outlets. Final subcircuits supplying lighting points Final subcircuits supplying directly connected hand-held electrical equipment AS/NZS 3000 2.6.3.1(a) AS/NZS 3000 2.6.3.1(b) AS/NZS 3000 2.6.3.1(c) (ii) 30 ma. AS/NZS 3000 2.6.3.1 (iii) At the switchboard where the final subcircuit originates (1 mark) AS/NZS 3000 2.6.3.1 (b) (i) Type AC AS/NZS 3000 2.6.2.2 Note 1(a) (ii) Tripping is ensured for residual AS/NZS 3000 sinusoidal alternating currents. 2.6.2.2 Note 1(a) (iii) Because tripping is not ensured for residual pulsating direct currents. (2 marks) GK (c) (i) Type A. AS/NZS 3000 2.6.2.2 Note 1(b) (ii) Tripping is ensured for residual sinusoidal alternating currents. Tripping is ensured for residual pulsating direct currents. AS/NZS 3000 2.6.2.2 Note 1(b)(i) (1 mark) AS/NZS 3000 2.6.2.2 Note 1(b)(ii) FINAL - IT30 ANSWERS 15 NOVEMBER 2014 5
Question 3 Marks Reference Marking notes (d) Tripping is ensured for residual sinusoidal alternating currents. Tripping is ensured for residual pulsating direct currents. With rated residual current not exceeding 10 ma with an interrupting time not exceeding 40 ms at rated residual current. AS/NZS 3000 2.6.2.2 Note 1(c)(i) AS/NZS 3000 2.6.2.2 Note 1(c)(i) (1 mark) AS/NZS 3000 2.6.2.2 Note 1(c)(i) FINAL - IT30 ANSWERS 15 NOVEMBER 2014 6
Question 4 Marks Reference Marking notes (a) Living Unit Calculations 5 units = 116A (given) 6 units Load Group Calculation Load (A) Group A Lighting and track 5 + (6 x 0.25) = 6.5 (1 mark) Group B Socket outlets 15 + (3.75 x 6) 37.50 (1 mark) Group C Range 6 x 2.8 16.80 Group E Instantaneous hot water 6 x 6 36.00 Group F Storage water heaters 6 x 6 36.00 Total 132.8 (1 mark) Unit load allocated across the three phases: Red White Blue 132.8 132.8 116 FINAL - IT30 ANSWERS 15 NOVEMBER 2014 7
Question 4 Marks Reference Marking notes (b) Communal Areas Three-phase Allocation of three-phase loads Load Group Calculation Load (A) Group J(i) Hot water cylinders /phase (2000 230)x 0.5 4.35 Group L Water pump /phase Name plate rating 10.8 Red White Blue 15.15 15.15 15.15 (c) Communal areas single phase loads Load Group Calculation Load (A) Group A(ii) Tennis court lighting 0 0 Group H Lighting (30 x 56) 230 7.3 Group I 9 Socket outlets 15.00 Group J(i) Clothes dryers (6000 230)x 0.5 13.05 FINAL - IT30 ANSWERS 15 NOVEMBER 2014 8
Question 4 Marks Reference Marking notes (d) Balancing the loads across the three-phases Red White Blue Living units 132.8 132.8 116 Three-phase loads Tennis court lighting Communal lighting Communal socket outlets Communal clothes driers 15.15 15.15 15.15 0 0 0 7.3 5 5 5 4.35 4.35 4.35 Totals 157.3 157.3 147.8 (1 mark) FINAL - IT30 ANSWERS 15 NOVEMBER 2014 9
Question 5 Marks Reference Marking notes (a) (i) 25 x 1.5 = 37.5A (ii) The fuse would operate in 10,000 second or 2.78 hours (1 mark) (b) (i) The minimum current that needs to flow to enable the fuse to operate within 0.4s is 150A (1 mark) Values between 135 and 160A acceptable. (ii) Z = V I = 230 150 = 1.53Ω (1 mark) (c) To ensure the protective devices operate with 0.4s To ensure that touch voltages do not rise to dangerous levels. (d) The 20A HRC fuse operated within 0.019s with 200A flowing. It would take the 32A fuse 0.4s to operate with 200A flowing. Correct discrimination occurred because the 20A HRC fuse operated 21 times quicker than the 32A would have. (1 mark) (1 mark) (1 mark) (1 mark) (1 mark) FINAL - IT30 ANSWERS 15 NOVEMBER 2014 10
Question 6 Marks Reference Marking notes (a) Load 1 kva = kw pf x 1000 = 9200 1 x 1000 = 9.2 kva Load 2 kva = kw pf x 1000 = 3450 0.75 x 1000 = 4.6 kva Load 3 kva = kw pf x 1000 = 2300 0.92 x 1000 = 2.5 kva kva = 9.2 + 4.6 + 2.5 = 16.3 kva (1 mark) (b) Load 1 Q = 0 (1 mark) Load 2 Q = S 2 - P 2 = 4600 2 -- 3450 = 3042.61 VAr Load 3 Q = S 2 - P 2 = 2500 2 -- 2300 2 = 979.8 VAr Q = 0 + 3042.61 + 979.8 = 4022.41 VAr (c) A 20 kva transformer (1 mark) FINAL - IT30 ANSWERS 15 NOVEMBER 2014 11
Question 7 Marks Reference Marking notes (a) A certified design is required because it does not comply with Part 2 of AS/NZS 3000. (1 mark) GK (b) It must identify the location of the installation It must identify the standards with which the installation is intended to comply The person who prepared the design must sign and date it. ESR 58(1)(a) ESR 58(1)(b) ESR 58(1)(c) (c) Any TWO of: (2 marks) If the installation is a 2-wire or a 4- wire installation in which no conductor is earthed: * switched and circuit breakers must be fitted in all conductors used in the installation. * all poles must operate substantially together. Switches fuse links or circuit breakers must not be inserted into an earthing conductor or any earthing connection. The voltage drop must not be more than 5% under maximum load conditions between the point of supply and any socket outlet within an installation operating at standard low voltage The voltage drop must not be more than 5% under maximum load conditions between the supply terminals of any fixed wired appliance connected to an installation operating at standard low voltage. ESR 61(2) ESR 61(3) ESR 61(4) ESR 61(4) (d) The installation will comply with the regulations. The installation will be electrically safe, as required by regulation 14. (1 mark) ESR 58(2)(a) (1 mark) ESR 58(2)(b) (e) All of it GK FINAL - IT30 ANSWERS 15 NOVEMBER 2014 12
Question 7 Marks Reference Marking notes (f) The work is high-risk prescribed electrical work All high-risk prescribed electrical work is required to be inspected. (1 mark) ESR 6A(2)(a) (1 mark) ESR 70(1) (g) That the installation is safe to use on the grounds that it is electrically safe and complies with the regulations. (1 mark) ESR 74A(1) FINAL - IT30 ANSWERS 15 NOVEMBER 2014 13
Question 8 Marks Reference Marking notes (a) Luminaire starting current 70W = 0.63A Luminaire starting current 250W = 1.9A Maximum voltage drop = 230 x 5% = 11.5V Vd for each section of cable, commencing at the switchboard mv/a.m = V d x 1000 A x m Vd = mv/a.m x A x L 1000 Vd1 = (1.9 + (4 x 0.63)) x 18.02 x 40 1000 = 3.19V Vd2 = (1.9 + (3 x 0.63)) x 18.02 x 30 1000 = 2.05V Vd3 = (1.9 + (2 x 0.63)) x 18.02 x 30 1000 = 1.71V Vd4 = (1.9 + 0.63) x 18.02 x 30 1000 1.37V Vd5 = 1.9 x 18.02 x 30 1000 = 1.03V Total Vd = 3.19 + 2.05 + 1.71 +1.37 +1.03 = 9.35V (1 mark) (b) Yes Because the 250W light will not (1 mark) start if the volt drop is more than 11.5V FINAL - IT30 ANSWERS 15 NOVEMBER 2014 14
Question 9 Marks Reference Marking notes (a) A domestic electrical installation that has a maximum demand at or below 80A per phase if single-phase A domestic electrical installation that has a maximum demand at or below 50A per phase if multi-phase (1 mark) ESR 57(2)(a) (1 mark) ESR 57(2)(b) (b) The person does not enter (whether directly, or by holding any material or equipment, or otherwise) any enclosure where live conductors are likely to be present. (1 mark) ESR 57(3)(e)(i) (c) Lighting circuit. 1 mm 2 ECP 51: Table 3 Socket outlet circuit 2.5 mm 2 ECP 51: Table 3 The permanently connected hot water cylinder 1.5 mm 2 ECP 51: Table 3 The permanently connected room heater 2.5 mm 2 ECP 51: Table 3 (d) It must have an isolating switch next to it. The isolation switch must have a minimum rating of 15A The cable and flexible cord must be three-core and include an earth wire. The wire insulation for flexible cord in the element enclosure must have a minimum temperature rating of 85 0 C ECP 51 5.4.1 ECP 51 5.4.1 ECP 51 5.4.2 ECP 51 5.4.3 (e) Minimum size of 0.75 mm 2 ECP 51: 5.3.3 Flexible cord of the sheathed, rounded type ECP 51: 5.3.3 (f) (i) A person authorised to inspect mains work. ESR 57(3)(e)(ii) (ii) AS/NZS 3000 ESR 57(3)(e)(ii) (iii) Any TWO of: (1 mark) FINAL - IT30 ANSWERS 15 NOVEMBER 2014 15
Question 9 Marks Reference Marking notes Earth continuity test AS/NZS 3000: 8.3.5 Insulation resistance test AS/NZS 3000: 8.3.6 Polarity test AS/NZS 3000: 8.3.7 Correct circuit connections test AS/NZS 3000: 8.3.8 FINAL - IT30 ANSWERS 15 NOVEMBER 2014 16