Il give an Example of a light circuit
1. Calculated the area of let's say Pool lighting.
2. Then used the formula N = Eavg*Area /F*Mf
This will give me the number of lights required. then go to select suitable lights
3. Next will be calculating the "Ib" so to calculate that the formula will be I = P/V
4. Draw the circuit diagram and measure the length of the circuit.
5. Select the suitable size breaker "In". It will be a 6A breaker for lights.
6. Select TYPE of breaker(B/C). For large luminaries it's mostly C.
7. Reference Method. For the pool, it will be B.
8. "Ca" refer to OSG table F1. For pool lighting, it will be 0.87. Should say in the question.
9. "Cg" refer to OSG tableF3. For pool lighting, it will be 0.70. Should say in the question.
10. Calculate "It". formula for that is It = In/Ca*Cg
11. Select Cable c.s.a. Refer OSG F4(i)
12. For the cable size selected need to select the V.D. refer OSG F4(ii).
13. Length of the circuit.
14. Calculate voltage drop. V.D. for whole cable=Length*V.D.*Ib/1000
For Lights, max drop is 6.9V and for socket, it will be 11.5V
15. Disconnection time will be 0.4s for all apart from Pool and Pump, Summer house which will be 5sec
16. (R1+R2) for the cable. refer OSG I1.
17. (R1+R2)at 70Degree C. formula for that is 1.2*(R1+R2)*Length/1000.
18. Calculate Zs. The formula will be Zs=Ze +(R1+R2)at 70Degree C
19. Max Zs. I don't have the Reg book so had a copy of the table. The Measured Zs should be lower than Max Zs.
Hope this helps.