ASSOCIATED TRADESPERSONS EXAMINATION … TRADESPERSONS EXAMINATION 26 June 2010 PLUMBERS/GASFITTERS...

AT 156A

Candidate Code No.

For Board Use Only

Result Date Int

Result Date Int

ASSOCIATED TRADESPERSONS EXAMINATION

26 June 2010

PLUMBERS/GASFITTERS

QUESTION AND ANSWER BOOKLET Time Allowed Two hours and 30 minutes

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 on this paper

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 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. 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 some of the following documents in this examination:

Electricity Act 1992 reprint dated 19 August 2005 and the Electricity Amendment Act 2006 or Electricity Act 1992 reprint dated 2008 and the Electricity Amendment Act 2006 or the Electricity Act 1992 reprint dated 1 April 2010

Electricity Regulations 1997 reprint dated 2 September 2005 or the Electricity (Safety) Regulations 2010

AS/NZS 3000:2000 and Amendments 1, 2, 3 and A or AS/NZS 3000:2007 and Amendment No 1

AS/NZS 3760:2003 and Amendment No 1 AS 60529 or AS 1939 Supplement 1-1990

PLEASE HAND THIS PAPER TO THE SUPERVISOR BEFORE LEAVING THE ROOM

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AT 156A QUESTIONS – 26 JUNE 2010 2

Question 1

(a) A 230V, two-core and earth flexible cord with the standard colour coding is

to be fitted to a single-phase Class I, electrical appliance.

List TWO aspects that need to be considered when selecting the cord.

(2 marks)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

(b) A 230V, fixed wired electrical appliance draws 8.7A on full load. Calculate

the power consumed drawn by the appliance on half full-load.

(2 marks)

(c) The sheath of a flexible cord supplying an electrical appliance has been

damaged and the basic insulation has become exposed. Explain the main

reason why you would replace the flexible cord

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

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Question 1 continued

(d) The cores of a flexible cord are being terminated in an electrical appliance.

State TWO reasons why it is important to remove only sufficient basic

insulation to allow the cores to be terminated.

(2 marks)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

(e) Refer to AS/NZS 3760 and briefly explain what the term basic insulation

means:

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(f) When an HRC fuse cartridge is replaced, the replacement cartridge must

have four characteristics similar to the original. Two of those characteristics

are “category of duty (rupturing capacity) and utilisation category (fusing

factor). State the other TWO characteristics.

(2 marks)

(1) ________________________________________________________

(2) ________________________________________________________

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(g) A Class I electrical appliance is controlled by a single-pole switch. State

why safety could be affected if the switch was placed in the neutral

conductor.

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

(h) An HRC fuse, that protects a circuit, blows every time the correct fuse link

is inserted. State TWO undesirable effects that may occur if the fuse link is

replaced with one of a higher current rating.

(2 marks)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

(i) An electrical appliance has been repaired. The repair included the

replacement of the flexible cord to the appliance. When the appliance is

operated, the cord overheats. State TWO reasons, either of which would

cause this to happen.

(2 marks)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

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(j) State TWO characteristics an insulating material must possess to be

suitable for use as insulation in a flexible cord.

(2 marks)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

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Question 2

(a) The figure below represents the metal frame of a 230V, Class I, heater.

Within the frame, draw and label the following components:

* A fuse that protects the whole circuit.

* A single-pole switch that controls the circuit.

* Two elements, one of 15 ohms and the other of 60 ohms.

* A two-position selector switch to connect the supply to either of

the elements.

Draw and label the supply to the heater.

(5 marks)

Frame of the Class I electrical appliance

(b) For the heater in (a), calculate the maximum current drawn.

(2 marks)

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(c) For the heater in (a), calculate the maximum power consumed.

(2 marks)

(d) For the heater in (a), state the most suitable rating for the fuse.

(1 mark)

____________________________________________________________

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Question 3

A plug-in electrical appliance that has been repaired is is required to be checked

and tested in accordance with AS/NZS 3760 before being returned to service.

(a) Refer to AS/NZS 3760 and state FOUR visual checks (inspections) that

must be carried out.

Note: The visual checks (inspections) must relate to a Class I plug-in

electrical appliance.

(4 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

(3) ________________________________________________________

________________________________________________________

________________________________________________________

(4) ________________________________________________________

________________________________________________________

________________________________________________________

Ref: ……………………………………………

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Question 3 continued (b) Refer to AS/NZS 3760 and complete the following in relation to the tests

using test instruments:

Note: 1. A PAT tester is not to be used 2. An earth leakage tester is not to be used 2. The appliance does not contain MOV or EMI components

Test No.1

(1) Type of test

(1 mark)

________________________________________________________

(2) Instrument used

(1 mark)

________________________________________________________

(3) Acceptable test result

(1 mark)

________________________________________________________

Ref: ……………………………………………

Test No.2

(1) Type of test

(1 mark)

________________________________________________________

(2) Instrument used

(1 mark)

________________________________________________________

(3) Acceptable test result

(1 mark)

________________________________________________________

Ref: ……………………………………………

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Question 4

(a) You intend to remove the supply to a single-phase fixed wired appliance at

a three-phase switchboard by removing the HRC fuse carrier. On that

switchboard, what is the nominal voltage between:

(i) Active (phase) No.1 and active (phase) No.2.

(½ mark)

________________________________________________________

(ii) Active (phase) No.1 and active (phase) No.3.

(½ mark)

________________________________________________________

(iii) Active (phase) No.2 and active (phase) No.3.

(½ mark)

________________________________________________________

(iv) Any active (phase) and neutral.

(½ mark)

________________________________________________________

(v) Any active (phase) and earth.

(½ mark)

________________________________________________________

(vi) Neutral and earth.

(½ mark)

________________________________________________________

(b) Refer to the Electricity Regulations and state what is meant by the term

“standard low voltage” for a single phase MEN system.

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: ……………………………………………..

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(c) In an electrical installation, metallic gas or water pipes are often required to

be bonded (joined) electrically to other metallic pipe services or the

installation earthing system. State TWO reasons why this bonding is

necessary.

(3 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

(d) State TWO reasons why a reliable protective earthing conductor in a Class I

portable electrical appliance contributes to the electrical safety of the

appliance.

(2 marks)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

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Question 5

(a) Refer to AS/NZS 3000 and state what is meant by the term “damp

situation”.

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: ……………………………………………

(b) Electrical fittings installed in damps situations have an IP rating. How can it

be established that an electrical fitting has an International Protection

Rating?

(2 marks)

____________________________________________________________

____________________________________________________________

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(c) Refer to AS1939, AS 60529 or AS/NZS 3000 and briefly describe:

(i) The type of protection offered by first number after the letters IP.

(1 mark)

________________________________________________________

________________________________________________________

________________________________________________________

Ref: ……………………………………………

(ii) The type of protection offered by second number after the letters IP.

(1 mark)

________________________________________________________

________________________________________________________

________________________________________________________

Ref: ……………………………………………

(d) Refer to AS1939 or AS 60529 or AS/NZS 3000:2007 and describe the

specific levels of protection offered by fittings rated at IP23.

(4 marks)

2 ________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

3 ________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

Ref: ……………………………………………

(turn over)


Question 6

(a) An HRC fuse on a switchboard has blown because of an overload. You need

to replace a fuse cartridge but it is not practical to turn off the main switch.

State TWO precautions that should be taken when replacing the fuse

cartridge.

(2 marks)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

(b) You are replacing a length of leaking galvanised iron water mains with a

section of new polybutylene pipe.

(i) State the safety precaution you would take before cutting the leaking

galvanised pipe.

(1 mark)

________________________________________________________

________________________________________________________

(ii) State the reason why the precaution in (b)(i) is necessary?

(2 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

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(c) (i) Explain the main purpose of using a Danger Tag system.

(1 mark)

________________________________________________________

________________________________________________________

(ii) Describe the main information that should be on a danger tag

(2 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(iii) State TWO circumstances where an isolating switch would carry two

danger tags.

(2 marks)

(1) ____________________________________________________

____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

____________________________________________________

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Question 7

(a) You have repaired a Class I, 230 volt, plug-in electrical appliance. The

appliance incorporates a single-pole switch.

Describe how you would carry out a protective earthing conductor test on

the Class I, 230 volt, plug-in electrical appliance. The answer must include

the type of test instrument used.

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(b) You have repaired a Class I, 230 volt, plug-in electrical appliance. The


Describe how you would carry out an insulation resistance test on the Class

I, 230 volt, plug-in electrical appliance. The answer must include the type

of test instrument used.

(3 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

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(c) You have repaired a Class I, 230 volt, plug-in electrical appliance. The


Briefly explain why a multimeter set on the low ohms scale should not be

used to carry out an insulation resistance test on this appliance.

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(d) You have repaired a Class I, 230 volt, plug-in electrical appliance. The


State TWO reasons why you would carry out a polarity test on this

appliance.

(2 marks)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

(e) You have repaired a Class I, 230 volt, plug-in electrical appliance. The


State ONE reason why you would not use a 500V insulation tester, set on

MΩ scale, to carry out a protective earthing conductor test on this

appliance.

(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

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Question 8

Note Read the entire question before answering.

A 230V, fixed-wired, boiler in a kitchen is connected via a flexible cord to a

permanent connection unit and is supplied from a fuse on a three-phase

switchboard.

You have been requested to disconnect the boiler from the supply and remove it

for major servicing work. The flexible cord is to remain with the boiler.

Warning: If any part of your answer is dangerous or hazardous, you

will get no marks for that part.

(a) Describe how you would safely isolate and disconnect the boiler.

(6 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

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(b) State TWO tests using test instruments that you would carry out on the

repaired boiler to ensure it is safe to reconnect to the permanent

connection unit.

(1 mark)

(1) ________________________________________________________

(2) ________________________________________________________

(c) Tests on the boiler confirm that it is safe to connect to the supply. Describe

the actions you would take to ensure that you can safely re-connect the

boiler to the permanent connection unit.

(3 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(turn over)


Question 9

(a) State TWO reasons why you should not complete a permanent isolation of

a circuit by only removing the carrier of a fuse.

(2 marks)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

(b) One reason why covers must be in place and secured before returning a

repaired electrical appliance to service is to prevent basic insulation being

exposed. State THREE other reasons why covers must be in place and

secured.

(3 marks)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

(3) ________________________________________________________

________________________________________________________

(turn over)



(c) A fixed wired Class I electrical appliance is supplied from a surface mounted

isolating switch via PVC conduit wire enclosed in PVC flexible conduit.

(i) State THREE possible causes of exposed basic insulation in this

situation.

(3 marks)

(1) ____________________________________________________

____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

____________________________________________________

(3) ____________________________________________________

____________________________________________________

____________________________________________________

(ii) State TWO reasons why the PVC flexible conduit must be securely

clamped.

(2 marks)

(1) ____________________________________________________

____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

____________________________________________________


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

Answered

Marks

1

2

3

In the box, write the

number of EXTRA

sheets you have

used. Write NIL if

you have not used

any

4

5

6

7

8

9

TOTAL

ASSOCIATED TRADESPERSONS EXAMINATION … TRADESPERSONS EXAMINATION 26 June 2010 PLUMBERS/GASFITTERS...

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