Radial Voltage Drop Calculation?... By Load or MCB Rating?

0.285% Voltage drop seems a remarkably low allowance.

5% is commonly allowed, though remember that this is the TOTAL voltage drop from origin to point of use. So if most of this has already been used in a sub main such a low allowance is possible.


I do however consider it possible that you have mis understood the wording "total voltage drop" 

Total means the total voltage drop from origin to point of use.

It does not mean the total over a number of circuits. 


In my view if a circuit is used for a fixed load, then voltage drop calculations may be based upon the actual load. 16 amp circuit with a 10 amp load, base the voltage drop on 10 amps.

It might be better practice to design for 16 amps in case needs change.

If a circuit supplies one or more socket outlets, then voltage drop calculations should presume full load, who knows what might be plugged into the outlet(s) in future.

0.285% Voltage drop seems a remarkably low allowance.

5% is commonly allowed, though remember that this is the TOTAL voltage drop from origin to point of use. So if most of this has already been used in a sub main such a low allowance is possible.


I do however consider it possible that you have mis understood the wording "total voltage drop" 

Total means the total voltage drop from origin to point of use.

It does not mean the total over a number of circuits. 


In my view if a circuit is used for a fixed load, then voltage drop calculations may be based upon the actual load. 16 amp circuit with a 10 amp load, base the voltage drop on 10 amps.

It might be better practice to design for 16 amps in case needs change.

If a circuit supplies one or more socket outlets, then voltage drop calculations should presume full load, who knows what might be plugged into the outlet(s) in future.