But who wants to do math in a trench or on a roof? Use a calculator. If you don't have a calculator handy, memorize these "Rough as guts" rules for Copper V-90HT (Standard building wire):
On a 415V 3-phase motor, you calculate voltage drop for one conductor, but the total loss affects the motor's torque. Always use a calculator with a "3-phase" toggle. The Best Tool for the Job Instead of breaking out the slide rule, use our Australian Voltage Drop Calculator [Link to your tool]. voltage drop calculator australia
Why Every Australian Electrician Needs a Voltage Drop Calculator (And How to Use It) But who wants to do math in a trench or on a roof
Pro Tip: If your run is over 100 meters, (e.g., from 2.5mm² to 6mm²) rather than one. 3 Critical Mistakes Aussies Make 1. Forgetting the Return Path When using a calculator, do you double the distance? Yes. The current travels down the active AND back the neutral. If your shed is 50m from the switchboard, the total circuit length is 100m . Most good calculators ask for "One-way distance" and do this math for you. Always use a calculator with a "3-phase" toggle
Ignoring voltage drop doesn’t just make your lights dim; it burns out motors, voids warranties, and fails compliance under .
Next time a customer asks, "Why can't I just use 1.5mm² cable for my 200-meter driveway light?" send them here.
