Electrical System Design and Estimationn

Electrical System Design and Estimation

1. HOUSE WIRING (1Φ):
DesignanddrawtheElectricalSchematic(SinglelineDiagram)ofahouse
wiringconnectedwith1ΦKSEBsupplybyproviding1ΦLTMeter
ConnectedLoads.
LIGHTLOAD:Incandescentlamps(5nos,40W);FluorescentLamps(5nos,
40W);CFL(5nos,20W);CeilingFan(4nos,60W),ExhaustFan(2nos,60W),
6Aplug(4nos,100W)
POWERLOAD:16APowerPlug(2nos,1000W),Waterpump(1nos,0.5HP=
373W);WaterHeater(1nos,1000W).
19Prepared by Prasanth K G,MBC CET,Peermade
CASE STUDY

2. Step 1:Load Calculation
EQUIPMENT WATTAGE(watts) NUMBER TOTAL POWER(watts)
IncandescentLamp 40 5 200
FluorescentTube 40 5 200
CFL 20 5 100
CeilingFan 60 4 240
Exhaust Fan 60 2 120
6A plug 100 4 400
TOTAL25 1260
Light Loads
20Prepared by Prasanth K G,MBC CET,Peermade

3. Power Loads
EQUIPMENT WATTAGE NUMBER TOTAL POWER
16A PowerPlug 1000 2 2000
Water Pump 746/2=373 1 373
Water Heater 1000 1 1000
TOTAL3373
Total Connected Load = Light Load + Power Load = 4633 W
Since total Connected Load is less than 5kW single Phase supply can be Provided
21Prepared by Prasanth K G,MBC CET,Peermade

4. Step 2-Determining Number of sub circuits
In domestic dwellings total load is divided into two sub circuits, for load
calculation and ease to design of circuits. They are Light sub-circuit and
Powersub-circuit
Light subcircuit
Light, fan and 6A sockets are connected in a common circuit called Light sub
circuit. According to IS codes load on each light sub-circuit shall be restricted to
800 watts or 10 points. A good engineering practice is using 8 points per light sub
circuits.
Number of light sub circuits=No of light points/8
=25/8=4.1(5 circuits )
22Prepared by Prasanth K G,MBC CET,Peermade

5. Power subcircuit
Two number of 16A Power plugs can be connected in a single power sub circuit.
separate power sub circuit must be provided for all other power loads
Total number of power sub circuits= 1 for 16A PP+1 for water Heater+1 for Pump
=3
Total number of sub circuits=light circuits + Power Sub circuits
=5+3
=8
Select 230V,single phase 8 way DB(standard DB )
Step 3: selection of Distribution Board
23Prepared by Prasanth K G,MBC CET,Peermade

6. Single Phase DB connection(6 way DB)
24Prepared by Prasanth K G,MBC CET,Peermade

7. Incomer: 25A RCBO or RCCB with 30mA sensitivity
Outgoing MCBs: 5 number of 6A MCBs (Bclass) for 5 light sub circuits
3 number of 16A MCBs (Bclass) for 3 Power Sub circuits
MCBs are selected based on maximum current flowing in sub circuit
Maximum current in a light sub circuit
??????=
??????
????????????????????????∅
=
800
230∗1
=3.47A
Maximum current in a Power sub circuit
??????=
??????
????????????????????????∅
=
3000
230∗1
=13.04A
Hence it is a thumb rule to use 6A MCB for light sub circuit and 16A MCB for Power
sub circuit. In case of motor load, we may use MCB with Ampere rating greater than
starting current.
25Prepared by Prasanth K G,MBC CET,Peermade

8. Step 4: selection of Main switch Fuse Unit (SFU)
Fuse is selected based on total load current
??????=
??????
????????????????????????∅
=
4633
230∗1
=20.1A
25A fuse is selected. SFU rating must be greater than fuse rating. Hence 32A,Iron Clad
Double Pole SFU with 25A fuse can be used.
For light sub circuits : 1.5mm sqrCopper wire
For Power sub circuits : 2.5mm sqrCopper wire
For earth wiring : 4 mm sqrCopper wire
Step 5: selection of cables/wires
26Prepared by Prasanth K G,MBC CET,Peermade

9. 27Prepared by Prasanth K G,MBC CET,Peermade

10. HOUSE WIRING (3Φ):
DesignanddrawtheElectricalSchematic(SinglelineDiagram)ofahouse
wiringconnectedwith3ΦKSEBsupplybyproviding3ΦLTMeter
ConnectedLoads.
LIGHTLOAD:FluorescentLamps(10nos,40W);LED(2nos,9W);Ceiling
Fan(5nos,60W),ExhaustFan(2nos,45W),6Aplug(9nos,100W)
POWERLOAD:16APowerPlug(5nos,1000W)
28Prepared by Prasanth K G,MBC CET,Peermade

11. Step 1:Load Calculation
EQUIPMENT WATTAGE(watts) NUMBER TOTAL POWER(watts)
FluorescentTube 40 10 400
LED 9 2 18
CeilingFan 60 5 300
Exhaust Fan 45 2 90
6A plug 100 9 900
TOTAL28 1708
Light Loads
29Prepared by Prasanth K G,MBC CET,Peermade

12. Power Loads
EQUIPMENT WATTAGE NUMBER TOTAL POWER
16A PowerPlug 1000 5 5000
TOTAL5000
Total Connected Load = Light Load + Power Load = 6708 W
Since total Connected Load is greater than 5kW 3 Phase supply can be Provided
30Prepared by Prasanth K G,MBC CET,Peermade

13. Step 2-Determining Number of sub circuits
According to IS codes load on each light sub-circuit shall be restricted to 800
watts or 10 points. A good engineering practice is using 8 points per light sub
circuits.
Number of light sub circuits=No of light points/8
=28/8=3.5(4 circuits )
Two number of 16A Power plugs can be connected in a single power sub circuit
Total number of power sub circuits= 5/2=2.5(3 circuits)
Total number of sub circuits=light circuits + Power Sub circuits=7
Select 3 phase,415V, 4 way DB which can accommodate up to 12 MCBs
31
Step 3: selection of Distribution Board
Prepared by Prasanth K G,MBC CET,Peermade

14. 3 Phase DB connection(6 way DB)
32Prepared by Prasanth K G,MBC CET,Peermade

15. Incomer: 40A RCBO or RCCB with 30mA sensitivity
Outgoing MCBs: 4 number of 6A MCBs (Bclass) for 4 light sub circuits
3 number of 16A MCBs (Bclass) for 3 Power Sub circuits
63A TPN SFU with 40A fuse
For light sub circuits : 1.5mm sqrCopper wire
For Power sub circuits : 2.5mm sqrCopper wire
For earth wiring : 4 mm sqrCopper wire
33
Step 4: selection of Main switch Fuse Unit (SFU)
Step 5: selection of cables/wires
Prepared by Prasanth K G,MBC CET,Peermade

16. 34
spare spare Spare
To
16A
PC5Prepared by Prasanth K G,MBC CET,Peermade