ELECTRICAL APPLIANCE SERVICEPERSON EXAMINATION 19 November 2016 QUESTION AND ANSWER BOOKLET

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1 Candidate Code No. EAS 1081 For Board Use Only Result Date Int Result Date Int ELECTRICAL APPLIANCE SERVICEPERSON EXAMINATION 19 November 2016 QUESTION AND ANSWER BOOKLET INSTRUCTIONS READ CAREFULLY Time Allowed: 2 Hours You have 10 minutes to read this paper but do not start writing until instructed 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 a pencil or a red pen. Drawing instruments and pencils may be used when diagrams are required. Marks are allocated based on correctness. Do not use correcting fluid or correcting tape. If a question can be answered from the Act, Regulations, Standard or Code of Practice it is recommended that the relevant clause or regulation number be stated in the reference space provided. For calculation questions, all workings, including formulae, must be shown to gain full marks. For calculation questions, all workings, including formulae, must be shown to gain full marks. You will need to use the following documents in this examination: AS/NZS 3760:2010 PLEASE HAND THIS PAPER TO THE SUPERVISOR BEFORE LEAVING THE ROOM

2 Question 1 Each part in this question is worth 2 marks. Write your answer for each part in the box provided (a) In an electrical appliance that has two elements connected in series, the element with the lowest voltage drop also has the: 1. Highest resistance 2. Highest current flow 3. Lowest current flow 4. Lowest resistance (b) On the nameplate of an electrical appliance which of the following would indicate that the appliance is required to be earthed. 1. The New Zealand Standards symbol. 2. The term Class I 3. The symbol square within a square 4. The Electrical Workers Registration Board logo (c) The flexible cord supplying a double insulated 230V, 2 kw electrical appliance is to be replaced. The most appropriate type of flexible cord to use would be: 1. Twisted conductor three core unsheathed 2. Two single core conductors, unsheathed 3. Standard duty three core tough plastic sheathed 4. Light duty two core tough plastic sheathed EAS 1081 QUESTIONS 19 NOVEMBER

3 Question 1 continued (d) Which of the following three core flexible cords has the least conductor resistance? 1. 5 metres of 0.75 mm² cord metres of 1.0 mm² cord 3. 5 metres of 1.0 mm² cord metres of 0.75 mm² cord (e) Which of the following documents specifies the tests to be carried out on an electrical appliance which is for hire or lease? 1. AS/NZS NZ AS AS/NZS 3760 (f) The Electricity Act 1992 requires that a registered electrical appliance serviceperson who carries out prescribed electrical work must hold a licence. The name of that licence is: 1. A Schedule 2 Licence 2. A Practising Licence 3. A Registration Licence 4. A Workers Licence EAS 1081 QUESTIONS 19 NOVEMBER

4 Question 1 continued (g) A 230V heater comprises two elements connected in series with the supply. If one element becomes open-circuited, what is the voltage across the other element? V V 3. 0V V (h) The main reason for carrying out an insulation resistance test on a Class II electrical appliance is to: 1. Check that the electrical appliance will operate properly 2. Verify that the insulation of current carrying components can withstand the normal supply voltage 3. Verify that the insulation resistance does not exceed 1 MΩ 4. Ensure there is no exposed primary insulation. (i) On the nameplate of an electrical appliance which of the following would indicate that the appliance is a Class II appliance: 1. The New Zealand Standards symbol. 2. The term Class I 3. The symbol square within a square 4. The Electrical Workers Registration Board logo EAS 1081 QUESTIONS 19 NOVEMBER

5 Question 1 continued (j) A portable isolating transformer designed for personal protection is required to be tested after a new flexible cord has been fitted. What is the minimum insulation resistance test value which would be acceptable for the transformer when measured between the supply conductors and its metal case? 1. 1 MΩ Ω MΩ 4. 1Ω EAS 1081 QUESTIONS 19 NOVEMBER

6 Question 2 (a) An insulation resistance test is being carried out on a 230V, Class I plug-in electrical appliance that has semi-conductor devices components. The semi-conductor devices cannot be disconnected or shorted-out. Describe how to carry out an insulation resistance test on the appliance using an insulation tester that has 1000V d.c., 500V d.c and 250V d.c. ranges. Include a test result that will permit the appliance to returned to service. (4 marks) (b) Following repairs to the electric motor and flexible supply cord of a 230V, Class I, concrete mixer a test of the integrity of the insulation is to be carried out while the mixer is live. (i) What instrument is used to make this test? (1 mark) (ii) Describe how this test is carried out. EAS 1081 QUESTIONS 19 NOVEMBER

7 Question 2 continued (iii) Refer to AS/NZS 3760 and state a test result that will permit the mixer to be returned to service. (1 mark) (c) Explain why an ohmmeter is not the correct instrument to carry out an insulation resistance test on a portable electrical appliance. EAS 1081 QUESTIONS 19 NOVEMBER

8 Question 3 (a) State TWO safety reasons why the main switch on a switchboard should be turned off before removing or replacing a fuse carrier into a fuse base. (1) (2) (b) A socket outlet final subcircuit is protected by an MCB on a switchboard. The MCB has tripped. An electrical appliance supplied from the socket outlet has been disconnected. When the MCB is reset, it trips again. (i) What is the probable cause of the fault? (1 mark) (ii) Who should be called to repair the fault? (1 mark) (c) State TWO electrical safeguards that can be used with a 230V, Class I electrical appliance to provide personal safety when operating outdoors. (1 mark) (1) (2) EAS 1081 QUESTIONS 19 NOVEMBER

9 Question 3 continued (d) The protective earthing conductor resistance of a 230V, Class I electrical appliance must be 1Ω or less. State ONE reason why the low resistance of protective earthing conductor contributes to electrical safety when the appliance is being used. (e) You have completed repairing a plug-in, Class I electrical appliance and the protective earthing conductor test result was 15Ω. State the sequence of actions you would take to ensure that the electrical appliance is safe and can be returned to service. (3 marks) EAS 1081 QUESTIONS 19 NOVEMBER

10 Question 4 (a) When selecting a flexible cord for fitting to a single phase electrical appliance, it is necessary to consider various factors that may affect the performance of the appliance. List THREE factors that may need to be considered when selecting the cord (3 marks) (1) (2) (2) EAS 1081 QUESTIONS 19 NOVEMBER

11 Question 4 continued (b) A mineral insulated metal sheathed (MIMS) element and flexible cord have been replaced in a Class I portable oven. Two instruments tests are to be carried out with the oven disconnected from the electricity supply. Refer to AS/NZS 3760 and for each test state: The name of the test. The test instrument used. A test result that will permit the oven to be returned to service. (3 marks) Ref:. EAS 1081 QUESTIONS 19 NOVEMBER

12 Question 4 continued (c) A Class A, Type II portable RCD has been installed in a flexible cord. (i) Refer to AS/NZS 3760 and state the test current and maximum permitted tripping time for the RCD. Ref:. (ii) Explain why the portable RCD is voltage dependent. EAS 1081 QUESTIONS 19 NOVEMBER

13 Question 5 (a) A 230V, Class I, plug-in electrical appliance is controlled by a single pole switch. You are testing the appliance with an ohmmeter and find that the neutral is switched. Describe the ONE situation that could cause the neutral to be switched instead of the phase in the appliance. (b) State ONE unsafe effect in an electrical appliance a phase and neutral transposition could create. (1 mark) EAS 1081 QUESTIONS 19 NOVEMBER

14 Question 5 continued (c) A 230V, 500W, Class I single-phase plug-in washing machine is faulty. When the homeowner plugged the washing machine into a live socket outlet and turned it on, they received an electric shock. Tests showed a protective earthing conductor resistance of 3.85Ω and a resistance in the phase to frame fault of 5.25Ω. (i) Calculate the total current that flowed under the fault condition, when the washing machine was operating. (5 marks) (ii) Calculate the voltage on the frame of the appliance that caused the homeowner to receive an electric shock, when the washing machine was operating. EAS 1081 QUESTIONS 19 NOVEMBER

15 Question 6 (a) The figure below represents the metal frame of a 230V, Class I, portable appliance. Within the frame, draw and label the following components: * A fuse that protects the whole circuit. * A single-pole switch that controls the circuit. * Element 1 is 30Ω and is connected closest to the switch. * Element 2 is 40 Ω and element 3 is 50 Ω. These two elements are connected in parallel after element 1 Show the supply to the appliance and on to the components. (5 marks) Metal frame of the Class I Appliance EAS 1081 QUESTIONS 19 NOVEMBER

16 Question 6 continued (b) From the figure in (a), calculate the current drawn by the appliance while it is operating. (5 marks) EAS 1081 QUESTIONS 19 NOVEMBER

17 Question 7 Rewireable fuses, HRC fuses and MCBs may be found on switchboards. (a) It is important to replace a blown HRC fuse with one of the correct current rating. (i) Define the term current rating as it relates to an HRC fuse (ii) An HRC fuse cartridge protecting a final subcircuit has blown. State the effect of replacing the fuse cartridge with a cartridge of a lower current rating. (iii) An HRC fuse cartridge protecting a final subcircuit has blown. State the effect of replacing the fuse cartridge with a cartridge of a higher current rating. EAS 1081 QUESTIONS 19 NOVEMBER

18 Question 7 continued (b) State TWO advantages that HRC fuses have when compared to rewireable fuses. (1) (2) (c) State TWO safety reasons why the terminals of HRC fuse carriers must not be bridged with fuse wire of the same current rating as the blown fuse cartridge. (1) (2) EAS 1081 QUESTIONS 19 NOVEMBER

19 Question 8 Introduction A 240V/230V plug-in heater has two elements of the same resistance controlled by a three-heat switch with low, medium and high settings. An ohmmeter shows a resistance of 26.45Ω when the three-heat switch is in the high position. Use the information in the introduction to this question to answer parts 8(a), 8(b), 8(c) and 8(d). (a) Calculate the power consumed when the heater switch is in the medium position and the operating voltage is 230V. (3 marks) (b) Calculate the power consumed in kw when the heater switch is in the high position and the operating voltage is 240V. EAS 1081 QUESTIONS 19 NOVEMBER

20 Question 8 (c) AS/NZS 3000 states that the maximum voltage-drop on a socket outlet in an electrical installation cannot exceed 5%. (i) Calculate the voltage at the socket outlet when the maximum voltage drop occurs when operating at 230V. (ii) Calculate the power consumed in kw when the heater switch is in the high position and the maximum voltage drop occurs when operating at 230V (d) Will the current drawn consumed by the heater increase or decrease when operating at 240V? (1 mark) EAS 1081 QUESTIONS 19 NOVEMBER

21 Question 9 Introduction In an office, a 16A MCB protects a final subcircuit consisting of three socket outlets supplying various 230V plug-in electrical appliances. The appliances were operating normally until the MCB tripped. When the MCB was reset, it tripped again. The appliances are not overloading the final subcircuit There are TWO types of faults in an electrical appliance that could cause the MCB to trip. Use the information in the introduction to this question to answer parts 9(a) and 9(b). (a) For the first type of fault state: The name of the fault. How to test to locate the fault in an appliance. The test instrument used. The test result if the fault is in an appliance. (5 marks) EAS 1081 QUESTIONS 19 NOVEMBER

22 Question 9 continued (b) For the second type of fault state: The name of the fault. How to test to locate the fault in an appliance. The test instrument used. The test result if the fault is in an appliance. (5 marks) EAS 1081 QUESTIONS 19 NOVEMBER

23 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 TOTAL MARKS EAS 1081 QUESTIONS 19 NOVEMBER