Conduct an electrical installation design for a typical villa house
(20m x 15m = 300m2) with the following parameters:
Here are some examples of the range of nameplate wattages for various household appliances:
1. Lighting
a) Lighting-Living Room = 12 x 18 Watt = 216 Watts
b) Dining-Room = 4 x 11 Watt = 44 Watts
c) Lighting-Bedrooms = 12 x 11 Watt = 132 Watts
d) Lighting-Kitchen = 4 x 18 Watt = 72 Watts
e) Lighting-Corridor = 4 x 18 Watt = 72 Watts
f) Bath-Room = 4 x 18 Watt = 72 Watts
g) Lighting-Store = 2 x 18 Watt = 36 Watts
h) Garage = 2 x 50 Watt = 100 Watts
i) Lighting-Outdoor = 4 x 50 Watt = 200 Watts
Total power rating for lighting = 944 Watts
2. Kitchen Appliances
a) Toaster = 800 Watts
b) Electric-Mitad = 3500 Watts
c) Electric stove = 2500 Watts
d) Microwave-Oven = 1400 Watts
e) Pancake maker = 1500 Watts
f) Coffee-Maker = 900 Watts
g) Refrigerator-Standard size = 725 Watts
h) Refrigerator-Dorm size = 350 Watts
Total power rating for kitchen appliances = 11,675 Watts
3. Home Electronics
a. Personal computer
CPU = 120 Watts
Monitor = 150 Watts
Laptop = 80 Watts
Printer = 300 Watts
b. Radio (stereo) = 70 Watts
c. Televisions (color)
43" = 130 Watts
55" = 170 Watts
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d. Tape player (stereo) = 750 Watts
e. Video Cassette Recorder (VCR)/DVD = 60 Watts
Total power rating for electronics appliances = 1,830 Watts
4. Laundry Appliances
a. Washing-Machine = 700 Watts
b. Clothes-Dryer = 3500 Watts
c. Dishwasher = 3000 Watts
d. Iron = 1000 Watts
e. Water-Heater (100 liter) = 3500 Watts
Total power rating for laundry appliances = 11,700 Watts
5. Personal Items
a) Hair Dryer = 1250 Watts
b) Shaver = 30 Watts
c) Garage door opener = 500 Watts
Total power rating for personal item appliances = 1,780 Watts
6. Air Quality
a) Vacuum cleaner = 1000 Watts
b) Water pump = 1100 Watts
Total power rating for air quality = 2,100 Watts
Consider total length of cable from energy meter to MDB and SDB is 25 meters and the loads have
an average distance of 50 meters from the SDBs.
1) Determine the total load attached to the utility supply
2) Circuit Breaker size (CB) of the main feeder and select the cable size
3) Select the cable size and circuit breaker of the sub main feeder
4) Check that the voltage drop is acceptable
5) Determine the Main Distribution Board (MDB) scheduling and associated feeders & CBs
6) Determine the Sub Distribution Board (SDB) scheduling and associated feeders & CBs
Consider a diversity factor (D), efficiency (η) and power factor of 0.6, 90% and 0.90
respectively.
Consider total length of cable from energy meter to sub circuit distribution board an
average of 50 meter.
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Consider the following correction factors
Ambient temperature (Ca) = 0.92
Cable grouping (Cg) = 0.65
Thermal insulation (Ci) = 0.85
Solution
A. Main Distribution Board
1) The total load demand
Total Load = 944watt + 11,675watt + 1,830watt + 11,700watt + 1,780watt + 2,100watt
= 30.03 kW
25% additional load = 30.03 kW x (25/100) = 7.51 kW
Total load connected to the system = 30.03 kW + 7.51 kW = 38 kW
The total demand = Total load * Diversity factor = 38 kW * 0.6 = 22.8 kW
2) Circuit Breaker size (CB) of the main feeder and select the cable size
2.1 Design current Ib will be:
PDemand 22.8 *103
Ib 42.8 A
3 *V * * pf 3 * 380 * 0.9 * 0.9
The corresponding minimum circuit breaker size chosen from EBCS is In = 50A
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2.2 Size of a cable
To calculate the size of the conductor, let’s calculate the current by considering ambient temperature (Ti),
grouping (Cg) and thermal insulation (Ci)
In 50
It 98.4 A
Ca * Cg * Ci 0.92 * 0.65 * 0.85
Cable size based on tabulated current-carrying capacity is obtained and is given 4x16 mm2.
Check that the voltage drop is acceptable
The actual voltage drop is given by
mV * Ib * L 2.3 * 42.8 * 25
VD 2.461V
1000 1000
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Well it is below the maximum voltage of 2.5% x220 = 5.5V given by EBCS and the cable is size
acceptable.
B. Select the cable size and circuit breaker of the sub main feeder
As the system should be balanced the total load should be equally divided to the three phases and
can be grouped into six parts as:
a) Total load demand for sub distribution board one (SBD1) = 6216W
b) Total load demand for sub distribution board two (SBD2) = 5362W
c) Total load demand for sub distribution board three (SBD3) = 6219W
d) Total load demand for sub distribution board four (SBD4) = 3430W
e) Total load demand for sub distribution board five (SBD5) = 4708W
f) Total load demand for sub distribution board six (SBD6) = 3644W
A. The total load demand for sub distribution board (SBD1) for phase R
Total Load = 6.216 kW
25% additional load = 6.216 kW x (25/100) = 1.554 kW
Total load connected to the system = 6.216 kW + 1.554 kW = 7.77 kW
The total demand = Total load * Diversity factor = 7.77 kW * 0.6 = 4.662 kW
1) Circuit Breaker size (CB) of the main feeder and select the cable size
2.2 Design current Ib will be:
PDemand 4.662 *103
Ib 26.16 A
V * * pf 220 * 0.9 * 0.9
The corresponding minimum circuit breaker size chosen from EBCS is In = 32A
2.3 Size of a cable
To calculate the size of the conductor, let’s calculate the current by considering ambient temperature (Ti),
grouping (Cg) and thermal insulation (Ci)
In 32
It 51.15 A
Ca * Cg * Ci 0.92 * 0.8 * 0.85
Cable size based on tabulated current-carrying capacity is obtained and is given 3x6 mm2.
Check that the voltage drop is acceptable
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The actual voltage drop is given by
mV * Ib * L 6.9 * 26.16 * 25
VD 4.513V
1000 1000
It is above the maximum voltage of 2% x220 = 4.4V given by EBCS and the cable is not size
acceptable. Therefore we select the next conductor with higher size and is given by 3x10 mm2
The actual voltage drop is given by
mV * I b * L 4.2 * 26.16 * 25
VD 2.75V
1000 1000
It is below the maximum voltage of 2% x220 = 4.4V given by EBCS and the cable size is acceptable.
2) The total load demand for branches of sub distribution board one (SBD1)
Total Load = 6.216 kW
25% additional load = 6.216 kW x (25/100) = 1.554 kW
Total load connected to the system = 6.216 kW + 1.554 kW = 7.77 kW
The total demand = Total load * Diversity factor = 7.77 kW * 0.6 = 4.662 kW
3) Circuit Breaker size (CB) of the branch feeder 1 of SDB1 and determining cable size
For lighting PLDemand = 270 W
2.4 Design current Ib will be:
PLDemand 270
Ib 1.515 A
V * * pf 220 * 0.9 * 0.9
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
2.5 Size of a cable
To calculate the size of the conductor, let’s calculate the current by considering ambient temperature (Ti),
grouping (Cg) and thermal insulation (Ci)
In 16
It 25.58 A
Ca * Cg * Ci 0.92 * 0.8 * 0.85
Cable size based on tabulated current-carrying capacity is obtained and is given 2x1.5 mm2.
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Check that the voltage drop is acceptable
The actual voltage drop is given by
mV * I b * L 28 *1.515 * 50
VD 2.12V
1000 1000
It is below the maximum voltage of 1% x220 = 2.2V given by EBCS and the cable size is acceptable.
For PLDemand1 = 3500 W
2.6 Design current Ib will be:
PLDemand 3500
Ib 19.64 A
V * * pf 220 * 0.9 * 0.9
The corresponding minimum circuit breaker size chosen from EBCS is In = 20A
2.7 Size of a cable
To calculate the size of the conductor, let’s calculate the current by considering ambient temperature (Ti),
grouping (Cg) and thermal insulation (Ci)
In 20
It 36.54 A
Ca * Cg * Ci 0.92 * 0.7 * 0.85
Cable size based on tabulated current-carrying capacity is obtained and is given 3x4 mm2.
Check that the voltage drop is acceptable
The actual voltage drop is given by
mV * I b * L 9 *19.64 *10
VD 1.77V
1000 1000
It is below the maximum voltage of 1% x220 = 2.2V given by EBCS and the cable size is acceptable.
For PLDemand2 = 2500 W
2.8 Design current Ib will be:
7
PLDemand 2500
Ib 14.03 A
V * * pf 220 * 0.9 * 0.9
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
2.9 Size of a cable
To calculate the size of the conductor, let’s calculate the current by considering ambient temperature (Ti),
grouping (Cg) and thermal insulation (Ci)
In 16
It 29.23 A
Ca * Cg * Ci 0.92 * 0.7 * 0.85
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
Check that the voltage drop is acceptable
The actual voltage drop is given by
mV * I b * L 14 *14.03 *15
VD 2.946V
1000 1000
It is above the maximum voltage of 1% x220 = 2.2V given by EBCS and the cable size is not
acceptable. Therefore we select the next conductor with higher size and is given by 3x4 mm2
The actual voltage drop is given by
mV * Ib * L 9 *14.03 *15
VD 1.894V
1000 1000
It is below the maximum voltage of 1% x220 = 2.2V given by EBCS and the cable size is acceptable.
For PLgeneralsocket1 = 800 W
2.10 Design current Ib will be:
PLgeneralso cket 1 800
Ib 4.6363 A
V * * pf 220 * 0.9 * 0.9
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
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2.11 Size of a cable
To calculate the size of the conductor, let’s calculate the current by considering ambient temperature (Ti),
grouping (Cg) and thermal insulation (Ci)
In 16
It 29.23 A
Ca * Cg * Ci 0.92 * 0.7 * 0.85
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
Check that the voltage drop is acceptable
The actual voltage drop is given by
mV * Ib * L 14 * 4.49 * 30
VD 1.885V
1000 1000
It is below the maximum voltage of 1% x220 = 2.2V given by EBCS and the cable size is acceptable.
For PLgeneralsocket2 = 800 W
2.12 Design current Ib will be:
PLgeneralso cket 1 800
Ib 4.6363 A
V * * pf 220 * 0.9 * 0.9
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
2.13 Size of a cable
To calculate the size of the conductor, let’s calculate the current by considering ambient temperature (Ti),
grouping (Cg) and thermal insulation (Ci)
In 16
It 29.23 A
Ca * Cg * Ci 0.92 * 0.7 * 0.85
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
Check that the voltage drop is acceptable
The actual voltage drop is given by
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mV * Ib * L 14 * 4.49 * 30
VD 1.885V
1000 1000
It is below the maximum voltage of 1% x220 = 2.2V given by EBCS and the cable size is acceptable.
B. The total load demand for sub distribution board (SBD2) for phase S
The corresponding minimum circuit breaker size chosen from EBCS is In = 32A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x10 mm2.
For lighting PLDemand = 168 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 2x1.5 mm2.
For PLDemand1 = 3000 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 20A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x4 mm2.
For PLDemand2 = 1250 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given by 3x4 mm2
For PLgeneralsocket1 = 900 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
For PLgeneralsocket2 = 800 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given by 3x2.5 mm2.
C. The total load demand for sub distribution board (SBD3) for phase T
The corresponding minimum circuit breaker size chosen from EBCS is In = 32A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x10 mm2.
For PLDemand1 = 3500 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 20A
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Cable size based on tabulated current-carrying capacity is obtained and is given 3x4 mm2.
For PLDemand2 = 1875 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given by 3x4 mm2
For PLgeneralsocket1 = 800 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
D. The total load demand for sub distribution board (SBD4) for phase R′
The corresponding minimum circuit breaker size chosen from EBCS is In = 25A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x6 mm2.
For lighting PLDemand = 252 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 2x1.5 mm2.
For PLDemand1 = 1500 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
For PLDemand2 = 1000 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
For PLgeneralsocket1 = 800 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
For PLgeneralsocket2 = 800 W
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The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
E. The total load demand for sub distribution board (SBD5) for phase S′
The corresponding minimum circuit breaker size chosen from EBCS is In = 25A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x6 mm2.
For lighting PLDemand = 144 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 2x1.5 mm2.
For PLDemand1 = 3500 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 20A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x4 mm2.
For PLgeneralsocket = 800 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
F. The total load demand for sub distribution board (SBD6) for phase T′
The corresponding minimum circuit breaker size chosen from EBCS is In = 25A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x6 mm2.
For lighting PLDemand = 200 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 2x1.5 mm2.
For PLDemand1 = 1200 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
For PLDemand2 = 1400 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
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For PLDemand = 1100 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
For PLgeneralsocket = 800 W
The corresponding minimum circuit breaker size chosen from EBCS is In = 16A
Cable size based on tabulated current-carrying capacity is obtained and is given 3x2.5 mm2.
Distribution Board Schedule
Panel: MDB
Voltage: 380 V, 50 Hz
Load (kW)
No Description Wire size (mm2) CB rating (A)
R S T
1 SDB1 3x10 32 7.87
2 SDB2 3x10 32 6.703
3 SDB3 3x10 32 7.594
4 SDB4 3x6 25 5.131
5 SDB5 3x6 25 5.479
6 SDB6 3x6 25 5.223
Spare
Spare
Sub Total 13.001 12.18 13.07
kW Connected 38
Diversity Factor 0.6
kW Demand 22.8
Line Current (A) 42.8
2
Cable size (mm ) 4x16
CB size (A) 50
Power Source Utility
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Distribution Board Schedule Distribution Board Schedule
Panel: SDB1 Panel: SDB2
Voltage: 220 V, 50 Hz Voltage: 220 V, 50 Hz
Wire size Load Wire size
Load (kW)
No Description (mm2) CB rating (A) (kW) No Description (mm2) CB rating (A)
1 Lighting 2x1.5 16 0.27 1 Lighting 2x1.5 16 0.168
2 Socket Outlet 3x2.5 16 0.8 2 Socket Outlet 3x2.5 16 0.8
3 Socket Outlet 3x2.5 16 0.8 3 Socket Outlet 3x2.5 16 0.9
4 Electric Stove 3x4 20 2.5 4 Hair Dryer 3x4 16 1.25
5 Electric Mitad 3x4 20 3.5 5 Dish Washer 3x4 20 3
Spare Spare
Spare Spare
Sub Total 7.87 Sub Total 6.118
kW Connected 7.87 kW Connected 6.118
Diversity
0.6 Diversity Factor 0.6
Factor
kW Demand 4.66 kW Demand 3.6708
Line Current
26.16 Line Current (A) 20.6
(A)
Cable size
3x10 Cable size (mm2) 3x6
(mm2)
CB size (A) 32 CB size (A) 25
Power Source MDB Power Source MDB
Distribution Board Schedule Distribution Board Schedule
Panel: SDB3 Panel: SDB4
Voltage: 220 V, 50 Hz Voltage: 220 V, 50 Hz
Wire size Load Wire size
Load (kW)
No Description (mm2) CB rating (A) (kW) No Description (mm2) CB rating (A)
1 Socket Outlet 3x2.5 16 0.8 1 Lighting 2x1.5 16 0.252
2 Socket Outlet 3x4 20 1.875 2 Socket Outlet 3x2.5 16 0.8
3 Close Dry 3x4 20 3.5 3 Socket Outlet 3x2.5 16 0.8
Spare 4 Vacuum Cleaner 3x4 20 1
Spare 5 Pancake Maker 3x4 20 1.5
Spare
Spare
Sub Total 6.175 Sub Total 4.352
kW Connected 6.175 kW Connected 4.352
Diversity
0.6 Diversity Factor 0.6
Factor
kW Demand 3.705 kW Demand 2.6112
Line Current
20.8 Line Current (A) 24.42
(A)
Cable size
3x6 Cable size (mm2) 3x6
(mm2)
CB size (A) 25 CB size (A) 25
Power Source MDB Power Source MDB
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Distribution Board Schedule Distribution Board Schedule
Panel: SDB5 Panel: SDB6
Voltage: 220 V, 50 Hz Voltage: 220 V, 50 Hz
Wire size Load Wire size
Load (kW)
No Description (mm2) CB rating (A) (kW) No Description (mm2) CB rating (A)
1 Lighting 2x1.5 16 0.144 1 Lighting 2x1.5 16 0.2
Socket
3x2.5 16 0.8 3x2.5 16 0.8
2 Socket Outlet 2 Outlet
Socket
3x4 20 3.5 3x2.5 16 1.1
3 Water Heater 3 Outlet
Socket
3x2.5 16 1.2
Spare 4 Outlet
Microwave
3x2.5 20 1.4
Spare 5 Oven
Spare
Spare
Sub Total 4.444 Sub Total 4.7
kW kW
4.444 4.7
Connected Connected
Diversity Diversity
0.6 0.6
Factor Factor
kW Demand 2.6664 kW Demand 2.82
Line Current Line Current
24.94 26.16
(A) (A)
Cable size Cable size
3x10 3x10
(mm2) (mm2)
CB size (A) 32 CB size (A) 32
Power Source MDB Power Source MDB
Fig. 1 Floor plan of a residential building
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