it 28 | electrical inspectors examination question and … questions – 16 november 2013 7 question...

IT 28

Candidate Code No.

For Board Use Only

Result Date Int

Result Date Int

ELECTRICAL INSPECTOR EXAMINATION 16 November 2013

QUESTION AND ANSWER BOOKLET Time Allowed: Three hours

INSTRUCTIONS – READ CAREFULLY You have 10 minutes to read this paper but do not start writing until you are told to do so by the supervisor. Write your Candidate Code Number in the box provided above. Your name must NOT appear anywhere in this paper. Answer all questions. The pass mark for this examination is 60 marks. Use a pen for written answers. Do not use pencils or red pens. Drawing instruments and pencils may be used when diagrams are required. Marks are allocated on the basis of correctness. Do not use correcting fluid or correcting tape. Non-programmable calculators may be used. It is recommended that the reference source for your answers be included in the space provided if a question can be answered from the Act, Regulations, Standard or Code of Practice. However, just stating a reference only will earn no marks. For calculation questions all workings, including formulae, must be shown to gain full marks. Warning – You could get 0 marks for any question, or part of a question, if you show anything hazardous or dangerous in your answer. You will need to use the following documents in this examination: ● Electricity (Safety) Regulations 2010 reprinted at 1 July 2013 ● AS/NZS 3000:2007 and Amendments 1 and 2 ● AS/NZS 3001:2008 and Amendment 1 ● AS/NZS 3003:2011 ● AS/NZS 3004.1:2008 ● NZECP 51 PLEASE HAND THIS PAPER TO THE SUPERVISOR BEFORE LEAVING THE ROOM

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IT28 QUESTIONS – 16 NOVEMBER 2013

2

Question 1 (a) Refer to the Electricity (Safety) Regulations 2010 and state the TWO

conditions under which a homeowner can extend an existing final subcircuit. (2 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

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(2) ________________________________________________________

________________________________________________________

________________________________________________________

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Ref: ……………………………………..

(b) Refer to AS/NZS 3003 and state the main reason for determining the

number and disposition of socket outlets in patient areas. (2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: ……………………………………..

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3

Question 1 continued (c) AS/NZS 3000 permits one type of wiring enclosure to be changed to

another type of wiring enclosure. Refer to AS/NZS 3000 and state the TWO locations where the change of

wiring enclosure can occur. (2 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

Ref: ……………………………………..

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4

Question 1 continued (d) Refer to AS/NZS 3004.1 and state the TWO methods either of which can

used to provide additional protection against electric shock for a socket outlet on a marina service pillar.

(2 marks)

(1) ________________________________________________________

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________________________________________________________

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(2) ________________________________________________________

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Ref: ……………………………………..

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5

Question 1 continued (e) An electrical inspector is required to test wiring installation work carried out

by a homeowner. Refer to NZECP 51 and state the FOUR categories of work that the

electrical inspector must test. (2 marks)

(1) ________________________________________________________

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(2) ________________________________________________________

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(3) ________________________________________________________

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(4) ________________________________________________________

________________________________________________________

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Ref: ……………………………………..

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6

Question 1 continued (f) An RCCB is being tested by using an RCD tester. What is the testing verifying?

(2 marks) ____________________________________________________________

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(g) State ONE reason why a test load is connected to a new electrical

installation following the initial connection to the electricity supply. (2 marks)

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7

Question 1 continued (h) Label the polarity of the socket outlet connections on each of these figures.

(2 marks)

(i) An earth-loop impedance test on a single phase 230V socket outlet adjacent

to a distribution board is measured at 0.38. Calculate the fault current that would flow when a short circuit of negligible

impedance occurs between the phase conductor and the protective earthing conductor at the socket outlet.

(2 marks)

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8

Question 1 continued (j) An earth-fault loop impedance test is carried out on an electrical installation

to verify the impedance of the fault loop. State TWO reasons why it is important to verify the impedance of the fault

loop. (2 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

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9

Question 2 (a) The figure below represents a 16 mm2, 4 core TPS consumers main cable.

The diameter of the cable is 25mm. The cable is to be installed: ● In an area subject to vehicular traffic. ● As a Category B system. There is no poured concrete at ground level, before or after the cable is

laid. (i) Refer to AS/NZS 3000 and on the figure, show all of the cable

installation requirements, including all dimensions. (6 marks)

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GROUND LEVEL _____________________ _ _ _ _ _ _ _ _ _ _ _ _ _ __________________

CABLE


10

Question 2 continued (ii) Refer to AS/NZS 3000 and state the requirements relating to the

marking and recording of the consumers main cable location using cable marker signs.

(1 mark)

________________________________________________________ ________________________________________________________

________________________________________________________

________________________________________________________

Ref: ……………………………………..

(iii) Refer to AS/NZS 3000 and state the requirements relating to the

marking and recording of the consumers main cable location using plans.

(1 mark)

________________________________________________________ ________________________________________________________

________________________________________________________

________________________________________________________

Ref: ……………………………………..

(b) Refer to AS/NZS 3000 and define the term Category A system as it

relates to underground cables. (1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: ……………………………………..

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11

Question 2 continued (c) Refer to AS/NZS 3000 and define the term Category C system as it

relates to underground cables. (1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: ……………………………………..

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12

Question 3 (a) AS/NZS 3000 permits light switches to be installed in bathrooms in

domestic residences. (3½ marks)

(i) Refer to AS/NZS 3000 and state the shower zone or zones in a

bathroom where light switches can be installed.

________________________________________________________

Ref: ……………………………………..

(ii) Refer to AS/NZS 3000 and state the requirements for installing a light switch in each of the shower zone or zones stated in (a)(i).

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

Ref: ……………………………………..

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13

Question 3

(b) AS/NZS 3000 permits light switches to be installed in bathrooms in

domestic residences. (1½ marks)

(i) Refer to AS/NZS 3000 and state the hand basin (capacity less than

45 litres) zone or zones in a bathroom where light switches can be installed.

________________________________________________________

Ref: ……………………………………..

(ii) Refer to AS/NZS 3000 and state the requirements for installing a light switch in each of the hand basin (capacity less than 45 litres) zone or zones stated in (b)(i).

________________________________________________________

________________________________________________________

________________________________________________________

Ref: ……………………………………..

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14

Question 3 continued (c) Refer to AS/NZS 3000 and state the circumstances in which a 230V socket

outlet can be installed in Zone 1 of a swimming pool. (5 marks)

____________________________________________________________

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Ref: ……………………………………..

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15

Question 4 (a) A large low voltage electrical installation incorporates various MEN

switchboards and distribution switchboards with one building structure. State the main technical reason why a distribution switchboard must not

be used to supply a MEN switchboard. (2 marks)

____________________________________________________________

____________________________________________________________

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(b) The fault levels on separate three-phase main switchboards are recorded as

follows: ● Switchboard 1 2.75kA ● Switchboard 2 20 kA (i) State TWO typical protective devices, either of which will provide an

electrically safe environment for Switchboard 1. (1 mark)

________________________________________________________

________________________________________________________

(ii) State TWO typical protective devices, either of which will provide an electrically safe environment for Switchboard 2.

(1 mark) ________________________________________________________

________________________________________________________

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16

Question 4 continued (c) A new 230V, single-phase commercial installation has a maximum demand

of 9.2 kW and a power factor of 0.8 lag. The installation is protected by a main circuit breaker.

The installation is supplied from a 400V, 500 kVA, three-phase transformer

with a 4% impedance. (i) Calculate the minimum current rating of the main circuit breaker.

(2 marks) (ii) A MCB is to be installed as the short-circuit protection device at the

main switchboard. (A) Calculate the minimum breaking capacity of the MCB.

(3½ marks) (B) The MCBs available are: 4.5 kA breaking capacity 6 kA breaking capacity 10 kA breaking capacity 15 kA breaking capacity State the most suitable MCB for this situation

(½ mark) ____________________________________________________

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17

Question 5 AS/NZS 3003 states that all patient areas shall be body-protected areas or cardiac-protected areas. (a) Refer to AS/NZS 3003 and explain the difference between a patient area

and a patient environment. (2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

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____________________________________________________________

____________________________________________________________

____________________________________________________________

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Ref: ……………………………………..

(b) Refer to AS/NZS 3003 and state the TWO types of devices that are known

as leakage protective devices (LPDs). (1 mark)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

Ref: ……………………………………..

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18

Question 5 continued (c) You are to carry out an inspection of a new cardiac-protected area in a

hospital. (i) The cardiac-protected area is in the same room as a body-protected

area. Refer to AS/NZS 3003 and state the THREE requirements relating to

the cardiac-protected area in relation to the body-protected area. (3 marks)

(1) ____________________________________________________

____________________________________________________

____________________________________________________

____________________________________________________

____________________________________________________

(2) ____________________________________________________

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____________________________________________________

____________________________________________________

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(3) ____________________________________________________

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Ref: ……………………………………..

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19

Question 5 continued (ii) Refer to AS/NZS 3003 and state the FOUR types of socket outlets that

are required to be connected to an EP junction in a cardiac protected area.

(2 marks) (1) ____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

(3) ____________________________________________________

____________________________________________________

(4) ____________________________________________________

____________________________________________________

Ref: ……………………………………..

(iii) Refer to AS/NZS 3003 and state TWO requirements for protective

earthing conductors used to connect socket outlets to an EP junction in a cardiac-protected area.

(2 marks) (1) ____________________________________________________

____________________________________________________

____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

____________________________________________________

____________________________________________________

Ref: ……………………………………..

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20

Question 6 Prescribed electrical work has been completed on two buildings in a commercial development. ● Each building has its own three-phase, 400V, supply from the local

distribution system ● Each building has its own point of supply and revenue metering. (a) Building 1 Building 1 is completely new and has a certified design in accordance with

Part 1 of AS/NZS 3000. (i) Refer to the Electricity (Safety) Regulations 2010 and state the THREE

aspects that show that the design is a certified design. (3 marks)

(1) ____________________________________________________

____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

____________________________________________________

(3) ____________________________________________________

____________________________________________________

____________________________________________________

Ref: ……………………………………….

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21

Question 6 continued (ii) Refer to the Electricity (Safety) Regulations 2010 and state the TWO

situations with which the installation must comply after it is installed, tested, inspected and connected in accordance with the certified design.

(2 marks)

(1) ____________________________________________________

____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

____________________________________________________

Ref: ……………………………………….

(b) Building 2 Building 2 is an existing building. The following work was carried out. ● New mains, new main switchboard of a larger size and new main

earthing system ● Three new final subcircuits. ● All lighting has been replaced with more up-to-date equipment The alterations and additions were designed and installed in accordance

with Part 2 of AS/NZS 3000. (i) Refer to the Electricity (Safety) Regulations 2010 and state: (A) Which of the prescribed electrical work carried out on Building 2

is classified as high-risk prescribed electrical work. (½ mark)

____________________________________________________

____________________________________________________

Ref: ……………………………………….

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22

Question 6 continued (B) Which of the prescribed electrical work carried out on Building 2

is classified as general prescribed electrical work. (½ mark)

____________________________________________________

Ref: ……………………………………….

(C) Which of the prescribed electrical work carried out on Building 2

is classified as low-risk prescribed electrical work. (½ mark)

____________________________________________________

Ref: ……………………………………….

(ii) Which of the prescribed electrical work carried out on Building 2 is

required to be inspected? (½ mark)

________________________________________________________

Ref: ……………………………………….

(c) ONE document was given to the owner of Building 2 after all work was

completed and the installation was connected to the supply. This document contained all the information required by the Electricity (Safety) Regulations 2010.

(i) One section of the document contains the certificate of compliance. Refer to the Electricity (Safety) Regulations 2010 and state what the

TWO other sections of the document must be. (1 mark)

(1) ____________________________________________________

(2) ____________________________________________________

Ref: ……………………………………….

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23

Question 6 continued (ii) Refer to the Electricity (Safety) Regulations 2010 and state FOUR

pieces of information that must be recorded on the certificate of compliance section of the document.

(2 marks)

(1) ____________________________________________________

____________________________________________________

____________________________________________________

____________________________________________________

(2) ____________________________________________________

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____________________________________________________

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(3) ____________________________________________________

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(4) ____________________________________________________

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Ref: ……………………………………….

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24

Question 7 Introduction Characteristic curves for HRC fuses are published by their manufacturers. The graph below shows typical characteristic curves for various HRC fuse sizes.

Use the information in the introduction to this question to answer parts 7(a), 7(b) and 7(c).

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25

Question 7 continued

(a) State what is meant by the term inverse time-current characteristic as it relates to HRC fuses.

(1 mark) ____________________________________________________________

____________________________________________________________

____________________________________________________________

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(b) The total time taken for a HRC fuse to operate is defined as the total

operating (or clearance) time. (i) The total operating (or clearance) time comprises TWO parts.

State those TWO parts. (1 mark)

(1) ____________________________________________________

(2) ____________________________________________________

(ii) Explain how the two parts stated in (b)(i) make up the total operating (or clearance) time.

(4 marks) ________________________________________________________

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26

Question 7 continued (c) A 32A gG type HRC fuse on an MEN switchboard protects a submain

supplying a distribution board. (i) Calculate the fusing current of the 32A fuse.

(1 mark)

(ii) Refer to the graph and determine the time taken for the 32A fuse to operate when the fusing current calculated in (c)(i) flows.

(½ mark) ________________________________________________________

________________________________________________________

(iii) Refer to the graph and determine the minimum fault current that

needs to flow if the 32A fuse will operate in 0.4 S. (½ mark)

________________________________________________________

________________________________________________________

(iv) A 20A gG type HRC fuse protects a final subcircuit at the distribution

switchboard. Refer to the graph and state why there is correct discrimination

between the 32A and 20A HRC fuses, when a fault occurs in the final subcircuit.

(2 marks) ________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

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27

Question 8 Introduction An electrical inspector has purchased a caravan for personal use. The caravan is to be used at various camping grounds. ● There is an existing switchboard and wiring to various appliances in the

caravan. ● There is no warrant of electrical fitness for the caravan and there is no

indication as to its age. The inspector has decided to: ● Assess the caravan to determine whether it complies with current

requirements ● Install two new 230V socket outlets in the caravan. Use the information in the introduction to this question to answer parts 8(a), 8(b), 8(c) and 8(d). (a) Documents are required to be issued for work on the caravan. (i) Refer to the Electricity (Safety) Regulations 2010 and state the type of

document that must be issued for the new socket outlets. (½ mark)

________________________________________________________

Ref: ……………………………………….

(ii) Refer to the Electricity (Safety) Regulations 2010 and state the type of document that must be issued for re-inspection of the caravan.

(½ mark) ________________________________________________________

Ref: ……………………………………….

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28

Question 8 continued (b) The electrical inspector has issued a certificate of compliance for the two

new socket outlets. Refer to the Electricity (Safety) Regulations 2010 and state whether the

electrical inspector can carry out the re-inspection of the caravan if the inspector also installed and certified the new socket outlets. State a reason to support your answer.

(2 marks) ____________________________________________________________

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Ref: ……………………………………….

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29

Question 8 continued (c) For the re-inspection of the caravan. (i) Refer to AS/NZS 3001 and state TWO requirements relating to the

caravan appliance inlet for the caravan. (2 marks)

(1) ____________________________________________________

____________________________________________________

____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

____________________________________________________

____________________________________________________

Ref: ……………………………………….

(ii) Refer to AS/NZS 3001 and state the minimum length of the supply lead.

(1 mark) ________________________________________________________

Ref: ……………………………………….

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30

Question 8 continued

(iii) Refer to AS/NZS 3001 and state TWO requirements for the supply

lead, apart from the minimum length. (1 mark)

(1) ____________________________________________________

____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

____________________________________________________

Ref: ……………………………………….

(d) Refer to AS/NZS 3001 and state the requirements for limiting the current of

the incoming supply of the caravan (3 marks)

(1) ________________________________________________________

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(2) ________________________________________________________

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(3) ________________________________________________________

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________________________________________________________

Ref: ……………………………………….

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31

Question 9 Introduction The figure below shows a 230V, single phase domestic electrical installation. ● The consumer mains and main switchboard are existing. ● The submain, distribution switchboard (within a detached garage) and the

16A socket outlet are going to be installed

● The installation has a maximum demand of 30A when measured by a

maximum demand indicator over a period of two weeks before the new submain and socket outlet were installed.

● The battery charger has a maximum demand of 15A. This is also the

maximum demand at the distribution switchboard ● All cables are either clipped to the surface (touching) or buried

underground. Thermal insulation is not an issue. ● Cable details are:

Cable mV/A.M (single phase) Current rating 2.5 mm2 Cu 18.02 30 4 mm2 Cu 11.22 39 6 mm2 Cu 7.50 50 16 mm2 Cu 2.81 91

● The voltage drop between the point of supply and the 16A socket outlet

cannot exceed the limit in AS/NZS 3000. Use the information in the introduction to this question to answer parts 9(a), 9(b), 9(c) and (9)(d).

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32

Question 9 continued (a) Refer to AS/NZS 3000 and state the maximum voltage drop permitted at

the 16A socket outlet. State a reference to support your answer. (1 mark)

____________________________________________________________

____________________________________________________________

(b) Calculate the voltage drop in the consumers mains when the proposed

total maximum demand is being supplied. (3 marks)

(c) Calculate the voltage drop in the proposed final subcircuit cable that is

to run between the distribution board and the 16A socket outlet. (1½ marks)

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33

Question 9 continued (d) Calculate the minimum cable size of the proposed submain cable that

is to run between the main switchboard and distribution board. (4½ marks)


34

For Candidate’s Use For Examiner’s Use Only Questions

Answered Marks

In the box, write the number of EXTRA sheets you have used. Write NIL if you have not used any

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