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How it is calculated
Voltage drop = 2 x length x current x 0.0175 / cross-section (mm2) for copper, where 0.0175 is copper resistivity in ohm mm2 per metre and the factor 2 counts the go and return conductors. Keep drop under 5% (3% for sensitive loads). Use pure copper cable, not copper-clad aluminium.
Results are estimates for planning. Real systems depend on site conditions; Qyvea surveys and quotes before installation.
Tips from our installers
- Low-voltage runs lose far more than mains runs: doubling the length doubles the drop.
- For long runs, power the device locally or use a higher voltage.
- Gate motors and locks draw peak current when they start: size for the peak.
Frequently asked questions
What drop is acceptable?
About 5% or less is a common guideline for low-voltage loads.
Why do cheap cables fail?
Many are copper-clad aluminium, which has higher resistance than the label suggests.
Does this apply to AC mains?
The same formula applies with different limits; use proper electrical design for mains.
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