Cable Size and Current Rating Selection:
In our country usually 1.5 sq mm to 2.5 sq mm PVC copper or aluminum wire is used for lighting circuit. And for power circuit, 2.5 sqmm to 4 sqmm PVC copper or aluminum wire is used. Cable size for main line is 4 sq mm to 6 sq mm or more.
Cable size and current carrying capacity of the cable are shown in table form below:
| Cable size Sq mm/rm | Cable Diameter mm | Single Phase Cable | Three Phase Cable | ||
| Copper Amp | Aluminum Amp | Copper Amp | Aluminums Amp | ||
| 1.3 | 1/1.12 | 11 | 8 | 9 | 7 |
| 1.5 | 1/1.40 | 15 | 11 | 12 | 9 |
| 2.5 | 1/1.80 3/1.06 | 18 | 14 | 15 | 12 |
| 4 | 1/2.24 7/0.85 | 24 | 19 | 21 | 16 |
| 6 | 1/2.80 7/1.06 | 31 | 24 | 25 | 20 |
| 10 | 1/3.55 7/1.40 | 42 | 32 | 36 | 28 |
| 16 | 7/1.70 | 57 | 45 | 49 | 38 |
| 25 | 7/2.24 | 73 | 56 | 62 | 48 |
| 35 | 7/2.50 | 88 | 69 | 75 | 58 |
| 50 | 7/3.00 19/1.80 | 108 | 84 | 93 | 72 |
| 70 | 19/2.24 | 133 | 1.03 | 114 | 88 |
| 95 | 19/2.50 | 164 | 127 | 139 | 108 |
Circuit Breaker Selection:
The value of current is determined by calculating the power of all types of loads used in one or more rooms, the current value is again multiplied by the safety factor to calculate the current rating of the circuit breaker.
For example, a one-room shop where 4 20w LED lights are used, a 500 watt drip fridge, a ceiling fan and 3 sockets of 300 watt and an AC of 1500 watt will be used. Selection has to be done.
Mathematical Solution:
- 4 light of 20 watt=20X4= 80watt
- A deep frizzed =500watt
- A selling fan = 80 watt
- 3 socket of 300watt=3 X300= 900 watt
- A Air Condition =1500 watt
Total Loads Power= 80+500+80+900+1500=3060watt
P=V X I COSØ
I= P/V X COSØ (COSØ=.8)
I=3060/220 X .8= 18 Amp
Circuit Broker(CB) Value= 18X2=36~40 Amp, Here, Safety Factor is = 2
Cable size for this shop=Get from above chart that is=10 sqmm/rm
Classification of Electrical Wiring:
