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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
(turn over)
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)
____________________________________________________________
____________________________________________________________
____________________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 3
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) ________________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 4
Question 1 continued
(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) ________________________________________________________
________________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 5
Question 1 continued
(j) State TWO characteristics an insulating material must possess to be
suitable for use as insulation in a flexible cord.
(2 marks)
(1) ________________________________________________________
________________________________________________________
(2) ________________________________________________________
________________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 6
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)
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 7
Question 2 continued
(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)
____________________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 8
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: ……………………………………………
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 9
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: ……………………………………………
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 10
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: ……………………………………………..
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 11
Question 4 continued
(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) ________________________________________________________
________________________________________________________
________________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 12
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)
____________________________________________________________
____________________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 13
Question 5 continued
(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)
AT 156A QUESTIONS – 26 JUNE 2010 14
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)
________________________________________________________
________________________________________________________
________________________________________________________
________________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 15
Question 6 continued
(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) ____________________________________________________
____________________________________________________
____________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 16
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
appliance incorporates a single-pole switch.
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)
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 17
Question 7 continued
(c) You have repaired a Class I, 230 volt, plug-in electrical appliance. The
appliance incorporates a single-pole switch.
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
appliance incorporates a single-pole switch.
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
appliance incorporates a single-pole switch.
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)
____________________________________________________________
____________________________________________________________
____________________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 18
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)
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
(turn over)
AT 156A QUESTIONS – 26 JUNE 2010 19
Question 8 continued
(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)
AT 156A QUESTIONS – 26 JUNE 2010 20
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)
AT 156A QUESTIONS – 26 JUNE 2010 21
Question 9 continued
(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) ____________________________________________________
____________________________________________________
____________________________________________________