QUICK ANSWER
There is no distance-only sizing rule. Voltage drop depends on the circuit, conductor characteristics, current and operating conditions.
01Explain what the length means
Distinguish the physical one-way route from the total length of all conductors purchased. Identify DC, single-phase or three-phase operation and the arrangement of the conductors. A length without circuit context can produce an incorrect comparison.
02Provide load conditions
Include voltage, design current and, for relevant AC calculations, power factor and conductor impedance. Consider starting or changing loads where the design requires it. Use the project’s permitted voltage-drop criterion rather than assuming one percentage applies everywhere.
03Compare the approved options
Ask the designer to compare compliant sizes or alternative arrangements, then obtain quotations for those defined options. Recheck terminations, route capacity and protection if the size changes. The cheapest price per metre is not necessarily the lowest cost for the complete route.
Before you send an enquiry
- Specify the circuit type
- State one-way route length
- Provide load and permitted drop
- Review the whole route cost
References & further reading
An introductory buying guide, not a project design or a claim of certification. Confirm current standards, local requirements and the exact product documentation with the designer and supplier.