MARKING GUIDELINE
NATIONAL CERTIFICATE
NOVEMBER EXAMINATION
INSTALLATION RULES
(Second Paper)
29 NOVEMBER 2016
This marking guideline consists of 7 pages.
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MARKING GUIDELINE -2- T760(E)(N29)T
INSTALLATION RULES
(Second Paper)
QUESTION 1
SANS 10142 PART 1 OF 2008: REGULATION 6.2.8.5: SUSTAINED CURRENT
CARRYING CAPACITY OF A CABLE BURIED IN THE GROUND
(I = Is x F1 x F2 x F3 x F4)
1.1 Depth of burial
Soil temperature
Soil thermal resistivity
Grouping of cables (4)
1.2 I = 66 A
F1 = 0,98
F2 = 0,94
F3 = 0,83
F4 = 0,81
I
Is
F1 F 2 F 3 F 4
66 66
Is :
0,98 0,94 0,83 0,81 0,619
Is = 106,6 A
Look up column 2 on table 6.8 for 106 amps
& nearest cable size will be 16mm2 (4)
1.3 5% of 230 = 11,5V
5% of 400 = 20V (2)
[10]
QUESTION 2: SANS 10142 PART 1 OF 2008: INSTALLATION OF CONDUCTORS AND
CABLES: CONSTRUCTION
2.1 conductors of mineral-insulated metal-sheathed cables;
internal connections of distribution boards, switchgear and
industrial controlgear; busbars;
aerial conductors;
aluminium conductors of nominal cross-sectional area 16 mm2 or
more; and
copper conductors of nominal cross-sectional area 16 mm2 or less that are
used in multicore cables. (6)
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MARKING GUIDELINE -3- T760(E)(N29)T
INSTALLATION RULES
(Second Paper)
2.2 2.2.2 Black only
2.2.2 Green/yellow or bare conductor
2.2.3 A colour other than green/yellow, green or black
2.2.4 “0”
(4 × 1) (4)
[10]
QUESTION 3: SANS 10142 PART 1 OF 2008: VERIFICATION AND CERTIFICATION
(PROSPECTIVE SHORT-CIRCUIT CURRENT)
3.1 EB
PSCC
RBBr
E B 1,05 100 2 : 210V
RBBr 0,9 RB RBL RY
L 0.022 45
RY : : 0,025
A 40
RBBr 0,9 0,011 100 1 0,025
RBBr 0,99 1 0,025 : 2,015
210
PSCC : 104 A
2,015 (7)
3.2 V EB
I :
R RBBr RL
210
I
2,015 110
210
I : 1,87 A
112,056 (3)
[10]
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MARKING GUIDELINE -4- T760(E)(N29)T
INSTALLATION RULES
(Second Paper)
QUESTION 4: SANS 10142: PART 1 OF 2008: POSITIONING OF CABLES
4.1 In the same trench or wire-way as a supplier's cable except with the
supplier's permission.
In the same wireway as the cables or wires of telecommunication, radio &
signalling circuits.
Where it is likely damaged by liquids such as oil, acid, acetone and alkali
or by gases such as sulphur dioxide.
Within 150 mm of hot surfaces such as hot pipes and flues if the heat is
likely to damage the cable. unless the cable is cooled or shielded from
heat.
In a position where it likely to be damaged unless it is mechanically
protected. (5)
4.2 Under thatched or wood-shingle roofs
In parts of a roof space where working height is less than 750 mm
In parts of a roof spaces that are intended to be used (or not used) for
storage, unless the wiring is suitably protected against mechanical
damaged
Within 1m of a trap door unless the wiring is suitably protected against
mechanical damage
Where it will be in contact with flammable material (5)
[10]
QUESTION 5: SANS 10142 PART 1 OF 2008: SECTION 6.3 (INSTALLATION OF
CONDUCTORS AND CABLES)
5.1 on the surface,
under plaster,
under a raised floor,
in hollows (such as in walls and partitions) (no additional protection being
needed),
in roof spaces,
direct in the ground (see 6.4.4.2, unarmoured buried cables),
outdoors or exposed to water (but unless the manufacturer proves that the
cables can withstand ultraviolet radiation, the cable shall be out of sight of
the sky), and
under screed if protected by an earth leakage protection device with a
rated earth leakage (Any SIX) (6)
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MARKING GUIDELINE -5- T760(E)(N29)T
INSTALLATION RULES
(Second Paper)
5.2 5.2.1 current-carrying capacity or the insulation resistance or the earth
continuity of the cable, core or conductor.
(Any ONE of the above underlined)
5.2.2 connector or bend or elbow or tee-piece
(Any ONE of the above underlined)
5.2.3 allow the strands of a stranded conductor to spread
5.2.4 to be cut away
(4 × 1) (4)
[10]
QUESTION 6: SANS 10142: PART 1 OF 2008: SECTION 8.7.8.1: INSULATION RESISTANCE
TEST
6.1 1. ensure supply is switched off.
2. ensure that all fuses are in place and switches and circuit-breakers.
3. are in the closed positions.
4. Loads may be disconnected – remove all sensitive electronic devices,
SPD's etc.
5. ensure circuit under test is discharged.
6. use an a.c. or d.c. voltage of at least twice the nominal voltage, with a
minimum of 500 V,
NOTE: The working voltage is taken as the maximum of the voltages
measured
7. in the case of a.c., between each phase conductor and either the neutral
or the earthing conductor, and
8. in the case of d.c., between positive and negative conductors.
9. restore supply to normal when test is completed.
(Any FIVE) (5)
6.2 dimmer switches,
touch switches,
time delay devices,
power controllers,
electronic starters for fluorescent lamps,
earth leakage units,
surge arresters
and certain appliances are disconnected so that they are not subjected to
the test voltage. (Any FIVE in any order)
(5)
[10]
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MARKING GUIDELINE -6- T760(E)(N29)T
INSTALLATION RULES
(Second Paper)
QUESTION 7: SANS 10142 PART 1 OF 2008 (GENERAL)
7.1 B
7.2 B
7.3 B
7.4 B
7.5 A
7.6 A
7.7 A
7.8 B
7.9 B
7.10 B
(10 × 1) [10]
QUESTION 8: SANS 10142 PART 1 0F 2008 (CERTIFICATE OF COMPLIANCE)
8.1 Elevated voltage on neutral
No load voltage (main DB)
On load voltage (main DB)
Voltage at available load in worst condition
Operation of earth leakage test button
Operation of earth leakage unit
PSCC
Earth loop impedance (Any FIVE) (5)
8.2 Continuity of all bonding conductors
Resistance of earth continuity conductor
Continuity of ring circuit (if applicable)
Earth electrode resistance
Insulation resistance
Polarity of points of consumption
All switching devices, make & break circuits (Any FIVE) (5)
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QUESTION 9: SANS 10142 PART 1 OF 2008 (PROTECTION)
9.1 EARTH LEAKAGE PROTECTION
in a new installation for circuits that supply SANS 164-1 or SANS 164-2
type socket-outlets, =
in an existing installation for all the circuits that supply socket-outlets when
any such circuit or circuits are rewired or extended (2)
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MARKING GUIDELINE -7- T760(E)(N29)T
INSTALLATION RULES
(Second Paper)
9.2 EARTH LEAKAGE PROTECTION
socket-outlets connected to a safety supply
a socket-outlet that complies with SANS 164-4 and that is intended only for
the connection of an appliance for critical application (such as emergency
lighting, a deep-freeze, a burglar alarm or data processing equipment);
circuits that supply fixed socket-outlets positioned out of normal reach,
rated at less than 16 A and intended for the connection of luminaires (see
6.14.1.4); and
a stove coupler that complies with SANS 60309-1/IEC 60309-1 and of
dimensions as given in SANS 337 (Any THREE) (3)
9.3 BONDING
All accessible extraneous conductive parts associated with a water pump
motor shall be bonded to the earth continuity conductor.
These parts include the suction pipe, delivery pipe and pump casing (3)
9.4 SURGE PROTECTION
transient over voltages and surge currents such as those due to switching
operations or those induced by atmospheric discharges (lightning). (2)
[10]
QUESTION 10: SANS 10142 PART 1 OF 2008: ANNEXURE E (CALCULATION OF
VOLT DROP)
10.1 VD from DB to joint A
VD = I × R × 2
VD = 60 × 50 × (0,63/1000) × 2: = 3,78V
VD from joint A to Joint B
VD = 60 × 30 × (1,4/1000) × 2: = 5,04V
VD from joint B to load
VD = 60 × 10 × (2,2/1000) × 2: = 2,64V
Total VD = 3,78 + 5,04 + 2,64 = 11,469V (7)
10.2 % VD = (11,469/230) × (1)
10.3 TV = (2 × Icb) × RECC
TV = (2 x 63) × (2,2/1000) × 90: = 24,948V
A minimum area of 10 mm2 must be used (2)
[10]
TOTAL: 100
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