The Problem Index → Power
My pump won't start at the end of a long wire run
This is voltage drop, and at low voltage it punishes distance brutally. The counterintuitive fix is usually not thicker wire.
What actually works
◆ Proven
Raise the voltage instead
Doubling the voltage quarters the loss. If a 12 V run is forcing you into enormous cable, the real answer is 24 V or 48 V.
◆ Proven
Design to 3% drop
3% is the usual target, 5% the outer limit. Motors are the least forgiving load — starting current is several times running current.
◆ Proven
Code is not optional
Voltage drop is usually the binding constraint at low voltage, but ampacity, breakers, conduit fill and burial depth are code matters. An electrician signs off on anything touching the house.
Run the numbers
- Wire size & voltage drop → — free calculator, works offline.
Also searched as
voltage drop · wire size for pump · motor hums wont start · long cable run 12v · what gauge wire · lights dim at the barn · pump far from house