Design of Building Electrical Systems

1. BEE 4213
UTILISATION OF
ELECTRICAL ENERGY
By: DR. KOK BOON CHING
(JEK@2012)
CHAPTER
2DESIGN OF
BUILDING
ELECTRICAL SYSTEMS

2. Design Team
Landscap
e
Architect
Architect

3. Building Electrical Systems
Utility
Transform
er
Main
Distributio
n Panel
Panel
Board

4. Design Methodology
Electrical Schematic
Calculate
Panelboar
d Ampere
Rating
Architectur
al Plan
Assembly
load data

5. Electrical Wiring in Residential
Buildings
• Electricity Supply Specifications (MS IEC
60038 standards)
1. Single phase supply with nominal voltage of
230V, range +10%, -6%;
2. Three phase supply with nominal voltage of
400V, range +10%, -6%;
3. Permitted frequency is 50Hz + 1%;
4. Earthing system type (TT System)

6. SINGLE PHASE METERING
ARRANGEMENT

7. 3-PHASE OVERHEAD
INCOMING

8. SINGLE PHASE GROUP
METERING

9. 3-PHASE GROUP METERING

10. Supply Voltage Options
• Low Voltage
i. Single-phase, two-wire, 240V, up to 12 kVA
maximum demand
ii. Three-phase, four-wire, 415V, up to 45 kVA
maximum demand
iii. Three-phase, four-wire, C.T. metered, 415V,
up to 1,000 kVA maximum demand

11. Supply Voltage Options
• Medium Voltage & High Voltage
i. Three-phase, three-wire and 11 kV for load
of 1,000 kVA maximum demand and above
ii. Three-phase, three-wire, 22kV or 33kV for
load of 5,000 kVA maximum demand and
above
iii. Three-phase, three-wire, 66kV, 132kV and
275kV for exceptionally large load of above
25 MVA maximum demand

12. Demand Estimation
• Range of maximum demand (M.D.) for
domestic consumer sub-classes or premises

13. Demand Estimation
• Range of maximum demand (M.D.) for types
of shop-houses

14. Group Diversity
• Group diversity is applied in the computation
of unit/individual demand and group demand.

15. Planning
flow
chart
for
building
wiring
installations

16. Domestic Electrical System Design
(Building)
• Type of Electrical Load Source
• Lighting
• Ceiling Fan
• Switched Socket 13A
• Switched Socket 15A
S/S/O (Switched Socket Outlet) 13A
S/S/O (Switched Socket Outlet) 15A

17. Domestic Electrical System Design
(Building)
• Type of Electrical Load Source (Con’t…)
• Water Heater
• Air-Con
• Electric Motor
• Exhaust Fan
• Cooker Point
• The portable appliances like TV, radio, washing
machine, computer etc are the sub-loads to the
switched socket.

18. Domestic Electrical System Design
(Building)
• Type of PVC covered copper cable:
• Cable 1.5sqmm – red and yellow-blue colours, for load source
like lighting and ceiling fan wiring use.
• Cable 2.5sqmm – red and yellow-blue colours, for load source
like switch socket 13A and 15A, heater, air-con etc.
• Cable 4.0sqmm – red and yellow-blue colours, for load source
like electrical motors etc.
• Cable 6.0sqmm – for earthing purpose.
• Cable 25.0sqmm – for wiring between kWh meter and DB.

19. Domestic Electrical System Design
(Building)
• Types of DB
• PVC c/w plastic cover
• Metal clad c/w cover
• Rating of the 1ø DB – 30A SPN and 63A SPN.
• Rating of the 3ø DB – 30A TPN, 60A TPN,
100A TPN, 150A TPN.

20. Distribution Board (Residential)

21. Distribution Board (Commercial)

22. Domestic Electrical System Design
(Building)
• Types of circuit Protection Components:
• Switch Fuse – 30A, 60A SPN.
• Moulded Case Circuit Breaker (MCCB)
• Earth Leakage Circuit Breaker (ELCB) or Residue Current
Circuit Breaker (RCCB) – 32A/ 60A with 100mA/ 30mA
(sensitivity).
• Over current Miniature Circuit Breaker (MCB) – 6A, 10A,
and 20A.
• 1 outgoing MCB ≈ 10 lighting point/ fan point
• 1 outgoing MCB ≈ 3 power point (S/S/O 13/15A)
• 1 outgoing MCB ≈ 1 air-con point
• 1 outgoing MCB ≈ 1 water heater point

23. Domestic Electrical System Design
(Building)
• Calculations of connected load and maximum demand
load:
• Loads estimated Watts:
No. Electrical Load Estimated Watt
1. Lighting Point 60 – 100W
2. Fan Point 60W
3. S/S/O Point 13A 250W
4. S/S/O Point 15A/20A 500W
5. Air-Conditioner Point 1.0 hp = 746W
6. Water Heater Point 1000W
7. Cooker Point 1500W

24. Domestic Electrical System Design
(Building)
• Example:
Type of Electrical Load
Estimate
Power
(Watt)
No.
(NOS)
Total Power
(Watt)
Lighting Point 100W 10 1000W
S/S/O – 13A 250W 6 1500W
Air-Con 746W 2 1492W
Water Heater Point 1000W 1 1000W
Total Connected Load, CL 4992W

25. Domestic Electrical System Design
(Building)
• In order to find the actual maximum total
electrical load, we use demand factor (DF),
Nominal Value, DF = 0.6.
• Example:
PMD = 4992W x 0.6 = 2995.2W.
PMD = PCL x DF

26. Domestic Electrical System Design
(Building)
• Calculation for Maximum Total Load Current:

27. Basic Electrical Symbols-Layout
Descriptions Symbol Mounting Height
Lighting point Follow ceiling level
Ceiling fan point or Follow ceiling level
S/S/O 13 A 300 mm or 1450 mm
S/S/O 15 A 300 mm or 1450 mm
Air-Con point or 2050 mm (min.) adj.
Switch (1-way) 1500 mm
Switch (2-way) 1500 mm
Switch (Intermediate) 1500 mm
Heater point or 2050 mm
Exhaust fan point 2600 mm
Distribution board 2100 mm
TNB kWh meter 2650 mm
A
C
AC
2g 3g 4g 5g
WH
M

28. Basic Electrical Symbols-Schematic
M
E
TNB Meter Panel ELCB/ RCCB Earth Chamber
Switch Fuse MCB/ MCCB
Cut-out
Fuse
Neutral
Link

29. Symbols
From
Energy
Commission
of
Malaysia
(Suruhanjaya
Tenaga
Malaysia)

30. Example of a Single-phase
Consumer Electrical Wiring

31. Example
of
a
Three-phase
Consumer
Electrical
Wiring

32. Example (Architectural Plan 1)

33. Example (Architectural Plan 2)

34. Examples of Lighting Circuits
Schematic Wiring
SINGLE LIGHT POINT controlled by a ONE WAY SWITCH

35. Examples of Lighting Circuits
Schematic Wiring
TWO LIGHT POINTS controlled by a ONE WAY SWITCH

36. Examples of Lighting Circuits
Schematic Wiring
TWO LIGHT POINTS controlled separately by TWO ONE WAY
SWITCHES

37. Examples of Lighting Circuits
Schematic Wiring
SINGLE LIGHT POINT controlled by a TWO WAY SWITCH

38. Examples of Lighting Circuits
Schematic Wiring
THREE LIGHT POINTS controlled by TWO WAY SWITCHES AND
INTERMEDIATE SWITCH

39. Intermediate Switch

40. Examples of Lighting Circuits
Schematic Wiring
SINGLE FLUORESCENT LIGHT POINT controlled by a ONE WAY
SWITCH

41. Examples of Socket Outlet
Schematic Wiring
Socket Outlet – SINGLE SOCKET

42. Examples of Socket Outlet
Schematic Wiring
Socket Outlet – RADIAL CONNECTION

43. Examples of Socket Outlet
Schematic Wiring
Socket Outlet – RING CIRCUIT CONNECTION

44. Final Circuit For 13A Socket
Outlets
Circuit
Type
Over Current Protection
Rating (Fuse or MCB)
(Ampere)
Minimum Size of Copper
Conductor in PVC or Rubber
Insulation
(mm2)
Maximum Floor
Area
(m2)
Ring 30 or 32 2.5 100
Radial 30 or 32 4.0 50
Radial 20 2.5 20

45. Minimum Cross Sectional Area
Rating of Wiring Conductors
Conductor Cross Sectional Area
in mm2
Material Application
1.5 mm2 Copper Lighting/Fan Circuit
2.5 mm2 Copper 13A Socket Outlet Circuit
4.0 mm2 - 6.0 mm2 Copper General Power Circuit (example:
water heater, cooker unit,
motor/pump)
16.0 mm2 – 25.0 mm2 Copper Main Circuit

46. Some Electrical Accessories...
LAMP
• Fluorescent lamps using magnetic ballasts (watt
loss not exceeding 6 watts) shall be equipped with
dry paper type capacitor;
• Fluorescent lamps using electronic ballasts or high
frequency electronic ballasts do not need
capacitors;
• Outdoor domestic lamp installations shall use
weather proof and water proof lamps;
• Submerged light installations (example in
swimming pools, fountains, etc.) shall have water
proof lamps with a voltage not exceeding 12 Volt

47. Some Electrical Accessories...
ELECTRIC WATER HEATERS
• Divided into 2 types, namely instantaneous water
heaters and stored water heaters (storage tank
type)
• Instantaneous water heaters shall be equipped
with a 2 pole control switch and its own residual
current device. Storage water heaters (storage
tank type) shall be installed with an isolator and its
own residual current device; and
• Water heaters exceeding 3kW shall be
permanently connected to a 20A/30A rated circuit
breaker/fuse with an isolator switch and residual

48. Some Electrical Accessories...
ELECTRIC COOKERS
• Exceeding 3kW shall have its own circuit
connected permanently to a 30A rated circuit
breaker or fuse with an isolator switch and
cooker control unit incorporated with a 13A
socket outlet.
• Two or more cooker appliances may be
installed in the same room within a distance of
2 meters.

49. Some Electrical Accessories...
ELECTRIC MOTORS
• Fence gate, air conditioners, fountains, swimming
pools, fish ponds, water pumps exceeding 373W
but not exceeding 2238W, shall be connected
permanently to a 20A/30A rated circuit
breaker/fuse together with an isolator, motor
starter and 15A socket outlet.
• The motor starter shall be of Direct-On-Line type
with the appliance together with the contactor,
overload relay and on-off control.
• The circuit breaker/fuse which controls the motor
circuit shall be capable of withstanding the starting

50. Some Electrical Accessories...
ELECTRIC BELLS
• The circuit shall have a push button switch and
a AC/DC transformer.
CEILING FANS
• Shall conform to clause 21.101 of the MS
1219:2002 standard with regards to test on the
suspension system of ceiling fans.

51. Industrial Electrical System Design
Design
componen
ts
Non-Motor
Circuits
Motor
Circuits
Circuit
Serving
Several
Motors
Panelboard
s and
Switchboar
ds
Transforme
rs

52. Non-Motor Circuits
• For non-motor loads, the MCCBs or fuses are
not allowed to carry 100% rated current on a
continuous basis, it is normally limited to 80% of
the breaker rating.
• OC = 1.25 X Load Amperes
• Wire = 1.25 X Load Amperes
• Example: A 240 V circuit carries a load of 1200
VA. What is the correct MCCB size?

53. Motor Circuits
• Motor’s inrush current during startup (5-7 FLA).
• 2 protective devices: MCCB and time delay
fuse.
• For MCCB,
OC = 1.75 X FLA
Wire = 1.25 X FLA
• For time delay fuse,
OC = 1.25 X FLA
Wire = 1.25 X FLA

54. FLA for 1-φ AC Motors
HP 115 V 200 V 208 V 230 V
1/6
1/4
1/3
1/2
3/4
4.4
5.8
7.2
9.8
13.8
2.5
3.3
4.1
5.6
7.9
2.4
3.2
4.0
5.4
7.6
2.2
2.9
3.6
4.9
6.9
1
11/2
2
3
16
20
24
34
9.2
11.5
13.8
19.6
8.8
11
13.2
18.7
8
10
12
17
5
71/2
10
56
80
100
32.2
46
57.5
30.8
44
55
28
40
50

55. Motor Circuits
• Example: Design a circuit to serve a 10 HP,
240 V, single-phase AC motor. The
overcurrent device is a MCCB.
Solution:
From previous table, FLA = 50 A.
OC = 1.75 X 50 = 87.5 A (100 A/ 1P)
Wire = 1.25 X 50 = 62.5 A

56. Circuits Serving Several Motors
• For MCCB,
OC = 1.75 X FLA (Largest Motor) + Sum of FLA
for smaller motors
Wire = 1.25 X FLA (Largest Motor) + Sum of
FLA for smaller motors
• For time delay fuse,
OC = 1.25 X FLA (Largest Motor) + Sum of FLA
for smaller motors
Wire = 1.25 X FLA (Largest Motor) + Sum of
FLA for smaller motors

57. Circuits Serving Several Motors
• Example: An air conditioning unit has two
motors, a 5 HP compressor and a 1.0 HP
condensing fan. Both motors are rated at 240 V,
single-phase. Design a circuit for this unit using
a MCCB as the OC device.
Solution:
From table, FLA (5 HP) = 28 A and FLA (1 HP) =
8 A.
OC = 1.75 X 28 + 8 = 57 A (60 A/ 1P MCCB)
Wire = 1.25 X 28 + 8 = 43 A.

58. Transformers
• Transformer must have OC device protection on
both the primary and secondary sides.
• OC (Pri) = 1.25 X FLA (Pri)
• OC (Sec) = 1.25 X FLA (Sec)
• The FLA is determined from the transformer’s
rated kVA and voltage, not the load current.

59. Transformers
• Example: A 50 kVA step-down transformer with
a 3.3 kV three-phase primary and 415Y/240 V
secondary is selected to serve a lighting panel.
Select the correct OC device for this
transformer.
Solution:

60. Transformers
Solution (Cont…)
OC (Pri) = 1.25 X 8.75 = 10.94 A
(15 A/ 3P MCCB)
OC (Sec) = 1.25 X 69.56 = 86.95 A
(90 A/ 3P MCCB)
kVA / (1.732 x Voltage
trasformer)

61. Panelboards and Switchboards
No. Connected Load Demand Factor Remarks
1. Lighting 1.25 Continuous
2. Receptacles
1st 10 kVA@100%
Remainder@50%
1.00
0.50
3. Resistance Heat 1.00 or 0.00 Seasonal
4. Heat Motor 1.00 or 0.00 Seasonal
5. Air Conditioning Motors 1.00 or 0.00 Seasonal
6. Motors 1.00 Non Seasonal
7. Other Loads 1.00 or 1.25* *If Continuous
8. Water Heating 1.00
9. Kitchen 0.65 to 1.00
10. Spare Capacity 1.00
11. Largest Motor 0.25

62. Example
A 415Y/240 V panelboard serves the following loads.
Compute the total connected load and the demand load.
No. Load Rating
1. Lighting 15.0 kVA @ PF=0.95
2. Receptacles 22.0 kVA @ PF=0.90
3. Resistance Heat 9.0 kW
4. Air Conditioning 12.0 kVA @ PF=0.88
5. Motors 6.0 kVA @ PF=0.88
6. Water Heating 4.5 kW
7. Spare Capacity 10.0 kVA @ PF=0.90

63. Solution
No. Load Connected Load
1. Lighting 14.25 + j4.68
2. Receptacles 19.80 + j9.59
3. Resistance Heat 9.00 + j0.00
4. Air Conditioning 10.56 + j5.70
5. Motors 5.28 + j2.85
6. Water Heating 4.50 + j0.00
7. Spare 9.00 + j4.36
Total 72.39 + j27.18 or 77.32 kVA
The total connected load is:

64. Solution
The computed demand load will be:
No. Load Demand Load
1. Lighting (14.25 + j4.68) X 1.25 = 17.81 + j5.85
2. Receptacles (9.00 + j4.36) X 1.00 = 9.00 + j4.36
(10.80 + j5.23) X 0.50 = 5.40 + j2.62
3. Resistance Heat 0.00
4. Air Conditioning (10.56 + j5.70) X 1.00 = 10.56 + j5.70
5. Motors (5.28 + j2.85) X 1.00 = 5.28 + j2.85
6. Water Heating (4.50 + j0.00) X 1.00 = 4.50 + j0.00
7. Spare (9.00 + j4.36) X 1.00 = 9.00 + j4.36
8. Largest Motor 5 HP (3.28 + j1.77) X 0.25 = 0.82 + j0.44
Total 62.37 + j26.18 or 67.64 kVA

65. Solution
The total demand load of 67.64 kVA can then be
converted to current as follows:
So, the circuit serving the panelboard will be protected
by a 100 A/ 3P circuit breaker.