Common circuit breaker sizes 
3A 6A 10A 16A 20A 32A 40A 63A
How to work out calculated theoretical ZS 
ZS = (r1+ r2) X L X max temp D rating factor /
1000
(r1+r2) is in m ohm
L in metres m
Max temperature de rating factor C
Watch page and table of the on-site guide and validate calculated maximum ZS values 
B6 ,145
How to calculate IZ
Protective device size over normal degrading factors 
R1+R2 calculation
R1+R2 X L
/ 1000
How to calculate the maximum for fault current for a RCD too trip 
In x 1.95 / 230 =Ans x 0.8
How do you calculate Zs
(R1 + R2 )+ze = Zs
Which appendix will you go to if you want to find information about types of circuit e.g. A1 A2 A3?
Appendix H and it’s tapped in blue
What are the three types of circuits in appendix H that you will find in a installation?
A1 ring A2Radial A3 radial 
In a A1 Ring circuit, what is the overcurrent protective rating the cop conductor size? For all but mineral insulated cables and the maximum floor area served.
30 or 32 A
2.5 mm²
And 6 m² 
In a A2 Riadial circuit, what is the overcurrent protective rating the cop conductor size? For all but mineral insulated cables and the maximum floor area served
30 or 32 A
4 mm²
And 75 m²

In a A3 Riadial circuit, what is the overcurrent protective rating the cop conductor size? For all but mineral insulated cables and the maximum floor area served
20 A
2.5 mm²
50 m² 
