How to choose the right cable size for a circuit
When it comes to cable there is a pretty simple rule to follow, more current, more copper. Just like a street water pipe carries more water than your household tap, the same concept applies to power down a cable.
Cable Sizing Terminology
Although we live in a metric world, most cables are still measured in American Wire Gauge or AWG. We list all of our cables in AWG (such as 8G, 4G etc) and their metric equivalent conductor area, typically shown in mm2. Our cables also show strand number and size, for example "24/0.20" implies 24 strands of 0.20mm diameter copper.
Below is a cross reference table showing the characteristics of each AWG size including typical current handling (shown as "ampacity" on the table).
If you know how long a cable run you require and the current flow needed, you can also use the cross reference chart below. This gives you a quick visual guide including the ability to cater for voltage drop (also explained below). This information is published as a guide only and can vary for extreme situations where temperature might come into play, such as use inside boat engine rooms etc. But for most applications this chart provides a good indicator for cable sizing required.
What is Voltage Drop?
Shown in the guide above are two voltage drop levels of 3% and 10%. Its important to note that as distance increases, voltage decreases and this must be factored in when cabling your equipment. 3% is used for "critical" or voltage sensitive equipment. 10% is used for "non critical" equipment with wider operating voltage ranges. Check your device specifications to determine which applies to your installation
Important Note about Fuse Protection
Please ensure your power circuits are appropriately fused or connected to a resettable circuit breaker to ensure safety at all times. Positive cabling "going to earth" is a common cause of vehicle fires and your insurance may not cover your loss if wiring is proven to be faulty by an assessor. When in doubt, always consult a professional when adding DC power circuits to your vehicle or caravan.
See our other guides on choosing the correct fuse rating and our guide to automotive fuses.