chapter  21
3 Pages

Verification of voltage drop (regulation 612.14)

WithKevin Smith

The concept of volts drop is a very simple one to understand. The distribution and final circuit live conductors have resistance and, although this resistance is only small, Ohm's law tells that where current flows through a conductor having even a small resistance, there will be a potential difference between the ends of that conductor. Calculation is naturally the easier option and for new installations where this work has already been done by the installation's designer, no additional inspection and testing is required to confirm volts drop beyond confirming that the installation work has been carried out in accordance with the original design. The measurement is performed as a dead test with the installation safely isolated from its supply. With all loads disconnected, a temporary link is placed between the live conductors under test at the distribution board and a measurement is made between these conductors with a low resistance ohmmeter at all points on the circuit.