IT 28 ELECTRICAL INSPECTOR EXAMINATION ANSWER SCHEDULE Notes:1. 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 person does not enter any enclosure where live conductors are likely to be present. The work is tested and certified in accordance with Part 2 of AS/NZS 3000 before being connected to a power supply, by a person authorised to inspect mains work ESR 57(3)(e)(i) ESR 57(3)(e)(ii) (b) To eliminate the need for the use of cord extension sets, electrical portable outlet devices and adaptors (2 marks) AS/NZS 3003 2.7.1 (c) At a switchboard: 3.10.2.2(a) By means of a suitable device that provided for the complete 3.10.2.2(b) protection of the conductor insulation and for continuity of conductive wiring enclosures. (d) It shall be supplied by a separate secondary winding of an isolating transformer complying with AS/NZS 61558.2.6. It shall be protected by an RCD with a maximum residual current rating of 30 ma which operates in all live conductors. AS/NZS 3004.1 2.4.2.4.5(a) AS/NZS 3004.1 2.4.2.4.5(a) (e) A random selection of socket outlets, light switches and light fittings. NZECP 51 1.6.4 All socket outlets rated above 10A. NZECP 51 1.6.4 All permanently connected NZECP 51 appliances and fittings. 1.6.4 All fittings, electrical appliances and light fittings associated with damp NZECP 51 1.6.4 IT28 - ANSWERS 16 NOVEMBER 2013 1
Question 1 Marks Reference Marking notes locations. (f) That the RCCB: Will operate in the specified time. At the rated residual a.c. current. (g) Any ONE of: To ensure equipment is operationally safe. To verify that the voltage drop within the installation is within acceptable limits. (2 marks) (h) AS/NZS 3112 IEC 60309 Earth Phase or active Neutral Neutral Phase or active Earth One mark for each correct set Candidates have to get both fully correct to get 2 marks) (i) Isc = 230 GK 0.38 = 605.26 A GK (j) To ensure the protection can clear the earth fault current To ensure the protection operates within the required time. (2 marks) GK IT28 - ANSWERS 16 NOVEMBER 2013 2
Question 2 Marks Reference Marking notes (a) (i) Marker tape at the correct depth Mechanical protection system correct size Mechanical protection system at the correct depth Mechanical protection system in correct position Bedding above the cable correct Bedding below the cable correct 3.11.4.5 Figure 3.14 3.11.4.3(d) Figure 3.14 AS/NZS 3000 Table 3.6 Figure 3.14 (1½ marks) AS/NZS 3000 3.11.4.3 (a), (b), (c) Figure 3.14 3.11.4.2 Figure 3.14 3.11.4.2 Figure 3.14 (ii) Marker signs shall be at the points where the cable enters or leaves the building. 3.11.4.6(b) (ii) The plan shall be located at the switchboard from which the cable IT28 - ANSWERS 16 NOVEMBER 2013 3
Question 2 Marks Reference Marking notes originates. 3.11.4.6(a) (b) Where the wiring system is inherently suitable for installation below ground and no further mechanical protection is required 3.11.2 (c) Where the wiring system is laid within a channel chased in the surface of rock 3.11.2 IT28 - ANSWERS 16 NOVEMBER 2013 4
Question 3 Marks Reference Marking notes (a) (i) Zones 1, 2 and 3 AS/NZS 3000 6.2.4.3 (ii) Zone 1 IPX4 AS/NZS 3000 6.2.4.1(b) Above 0.3 m from the floor AS/NZS 3000 6.2.4.3 Zone 2 IPX4 AS/NZS 3000 6.2.4.1(b) Above 0.3 m from the floor AS/NZS 3000 6.2.4.3 Zone 3 No degree of protection required AS/NZS 3000 6.2.4.1(b) Above 0.3 m from the floor AS/NZS 3000 6.2.4.3 (b) (i) Zone 2 of the hand basin AS/NZS 3000 6.2.4.3 (ii) Zone 2 IPX4 AS/NZS 3000 6.2.4.1(b) Above 0.3 m from the floor AS/NZS 3000 6.2.4.3 IT28 - ANSWERS 16 NOVEMBER 2013 5
Question 3 Marks Reference Marking notes (c) Must be installed above 0.3m of any floor or surface where the floor or surface is likely to become wet. Can only be for the connection of pool equipment. AS/NZS 3000 6.3.4.3 6.3.4.3(b) A minimum degree of protection of IPX5 AS/NZS 3000 6.3.4.1(b) Any ONE of: * Located at a height not less that 0.45m above ground level at a horizontal distance not less that 1.25m from the internal rim of the water container * Located beneath and not less than 0.5m from the edge of a fixed continuous horizontal barrier that is not less than 1.25m wide measured from the internal rim of the water container. Any ONE of: * Supplied individually as a separated circuit in accordance with clause 7.4. * Protected by a RCD with a fixed rated residual current not exceeding 30mA. Controlled by a switch that required manual operation and does not operate automatically by the insertion of withdrawal of a plug AS/NZS 3000 6.3.4.3(b)(ii)(A) AS/NZS 3000 6.3.4.3(b)(ii)(B) AS/NZS 3000 6.3.4.3(b)(iii)(C) AS/NZS 3000 6.3.4.3(b)(iii)(E) 6.3.4.3(b)(iv) IT28 - ANSWERS 16 NOVEMBER 2013 6
Question 4 Marks Reference Marking notes (a) To prevent load current flowing in protective earthing conductors (2 marks) GK (b) (i) Switchboard 1 HRC fuses GK MCBs GK (ii) Switchboard 2 HRC fuses GK Any ONE of: GK * Air circuit breakers * MCCBs * MCBs backed up by HRC fuses (c) (i) I = P V x Cos Φ = 9.2 x 10 3 230 x 0.8 = 50A (ii) (A) PSC - 3ǿ = S 3 x V x Imp = 500 x 10 3 3 x 400 x 0.04 = 18042.75A PSC - 1ǿ = 18042.75 3 = 10419A (B) 15 ka IT28 - ANSWERS 16 NOVEMBER 2013 7
Question 5 Marks Reference Marking notes (a) A patient area is a location where it is intended that low-voltage medical equipment will be used on a patient. A patient environment is the space extending 1500 mm around all possible patient locations in a cardiac protected area. (b) Low voltage isolation transformers complying with AS/NZS 4510 Type I low-voltage residual current devices (RCDs) complying with AS/NZS 3190, AS/NZS 61008.1 or AS/NZS 61009.1 (c) (i) The boundaries of the cardiacprotected area is clearly and permanently inlaid on the floor. Each socket outlet in the cardiac protected electrical area is separated by not less than 4000 mm from the nearest socket outlet in the body-protected electrical area. The nominal patient location centres are separated by not less than 4000 mm (ii) Socket outlets complying with AS/NZS 3112 Socket outlets complying with AS/NZS 3123 or IEC 60309 Socket outlets complying with AS/NZS 60320.1 Cord extension sockets complying with AS/NZS 3120 (iii) The shall be insulated and segregated from contacting other conductive items except at the EP junction The resistance of the protective earthing conductor between each socket outlet and the EP junction shall not exceed 0.1Ω 1.4.17 1.4.17 AS/NZS 3003 1.4.12(a) AS/NZS 3003 1.4.12(b) 2.1(a) 2.1(b) 2.1(c) AS/NZS 3003 4.4.2.4.1(b)(i) AS/NZS 3003 4.4.2.4.1 (b)(ii) AS/NZS 3003 4.4.2.4.1 (b)(iii) AS/NZS 3003 4.4.2.4.1 (b)(iv) 4.4.2.4.3 4.4.2.4.3 IT28 - ANSWERS 16 NOVEMBER 2013 8
Question 6 Marks Reference Marking notes (a) (i) It identifies the location of the installation. It identifies the standards with which the installation complies. The person who prepared the design has signed and dated it. (ii) The installation complies with the regulations. The installation is electrically safe as required by regulation 14. ESR 58(1)(a) ESR 58(1)(b) ESR 58(1)(c) ESR 58(2)(a) ESR 58(2)(b) (b) (i) (A) New mains, new main ESR 6A(2) switchboard of a larger size and new main earthing system ( mains work ) (B) Three new final subcircuits ESR 6A(3) (C) All lighting that was been ESR 6A(1) replaced with more up-to-date equipment (ii) New mains, new main switchboard of a larger size and new main earthing system ( mains work ) ESR 70(1) (c) (i) The record of inspection. ESR 72(1) The electrical safety certificate ESR 74A(1) (ii) Any FOUR of: (2 marks) The work has been done in ESR 67(1)(a) accordance with Part 2 of AS/NZS 3000: If the work was required to ESR 67(1)(c) comply with standards other than Part 2 of AS/NZS 3000 which standards were complied with Whether the work done relied ESR 67(1)(d) on any manufacturer s instructions: The type of supply system that ESR 67(1)(e) the installation is safe to connect to. Which parts of the installation ESR 67(1)(f) are safe to connect to a power supply. identify the location of the ESR 67(2)(a) IT28 - ANSWERS 16 NOVEMBER 2013 9
Question 6 Marks Reference Marking notes installation on which prescribed electrical work was done Describe the work done ESR 67(2)(b) Give the name of the person issuing the certificate, along with the name of any person who, acting under the supervision of that person, performed any of the prescribed electrical work referred to in the certificate Give the registration number (if any) of every person referred to in paragraph (c) Give the date or dates on which the work was done, or the period within which it was done. Be signed and dated by the person issuing the certificate ESR 67(2)(c) ESR 67(2)(d) ESR 67(2)(e) ESR 67(2)(f) IT28 - ANSWERS 16 NOVEMBER 2013 10
Question 7 Marks Reference Marking notes (a) As the current through a fuse increases beyond its current rating, the time taken to operate decreases. GK (b) (i) Pre-arcing time Arcing time (ii) * The pre-arcing time is the time taken for a fault current large enough to operate the fuse * To initiate the arc that will melt the fuse. * The arcing time is time taken from the initiation of the arc * Until the fuse elements have opened and the arc extinguished (c) (i) 32 x 1.25 Answers can = 40A range between 40A and 51.2A 32 x 1.6 = 51.2A (ii) From the graph the time taken will be between 2000 and 10,000 seconds. The time taken depends on the fusing factor stated in (c)(i) (iii) From the graph the minimum fault current is 210A (iv) When a fault occurs a minimum fault current of 90A needs to flow to operate the 20A fuse in 0.4s. A minimum fault current of 210A is required to operate the 32A fuse in 0.4s A current in the 200 to 210A range is acceptable. IT28 - ANSWERS 16 NOVEMBER 2013 11
Question 8 Marks Reference Marking notes (a) (i) Certificate of compliance ESR 65(1) (ii) An electrical warrant of fitness ESR 78(1) (b) Yes Regulation 78(1)(c) states that the person who did the certification under regulation 66 can also issues the warrant of electrical fitness at the same time. (1½ marks) (c) (i) The appliance inlet shall comply with IEC 6039, AS/NZS 3123 or AS/NZS 3120 All fittings shall be visually inspected for mechanical damage or damage due to water ingress AS/NZS 3001 C6.6 AS/NZS 3001 C6.6 (ii) A minimum of 10 metres AS/NZS 3001 C6.8 (iii) Any TWO of: Be in one length AS/NZS 3001 C6.8(a) Comply with the crosssectional AS/NZS 3001 requirements of Table 5.1 C6.8(b) Have provision for strain relief for the supply lead connection. AS/NZS 3001 C6.8(d) (d) The supply shall be protected by an overcurrent circuit breaker. The circuit breaker must be located within the caravan. The maximum rating of the circuit breaker shall not exceed the maximum current rating of the supply lead or supply lead fittings, whichever is the smallest. AS/NZS 3001 3.3.1.1 AS/NZS 3001 3.3.1.1 AS/NZS 3001 3.3.1.1 IT28 - ANSWERS 16 NOVEMBER 2013 12
Question 9 Marks Reference Marking notes (a) 5% of 230V = 11.5V AS/NZS 3000: 3.6.2 (b) Proposed total maximum demand = 30 = 14 = 45A V d = mv/a.m x I x m 1000 = 2.81 x 45 x 20 1000 = 2.53V (c) V d = mv/a.m x I x m 1000 = 18.02 x 15 x1 1000 = 0.27V (d) Volt-drop available for submain = 11.5 (2.53 + 0.27) = 8.70V V d = mv/a.m x I x m 1000 mv/a.m = V d x 1000 I x m = 8.7 x 1000 15 x 30 = 19.33 The minimum size submain cables is 2.5 mm 2 Cu IT28 - ANSWERS 16 NOVEMBER 2013 13