Well Pump Wire Sizing Guide | SCWS

Proper wire sizing ensures your well pump runs efficiently and safely. Undersized wires cause voltage drop, motor overheating, and premature failure. Learn how to verify your system has adequate wiring.

Why Wire Sizing Matters

Electricity loses voltage as it travels through wire—this is called voltage drop. The longer the wire run and the smaller the wire diameter, the more voltage is lost. Well pumps are sensitive to voltage: even a 5% drop reduces efficiency, and a 10% drop can cause motor overheating and failure. Proper wire sizing keeps voltage drop under 3%.

Factors That Determine Wire Size

Three factors determine the correct wire size: motor amperage (based on horsepower), distance from the electrical panel to the pump, and whether you're using single-phase or three-phase power. Most residential wells use single-phase power, which requires larger wire than three-phase for the same motor size.

Common Wire Sizes by Application

For typical residential wells with single-phase power: 1/2 HP motors usually need 12-gauge wire up to 100 feet, 3/4 HP needs 10-gauge, and 1 HP needs 10-gauge up to 200 feet or 8-gauge for longer runs. Deep wells with 2 HP or larger motors often require 6-gauge or heavier wire. Always verify with wire sizing charts for your specific situation.

Signs of Wire Problems

Symptoms of inadequate wiring include the pump tripping its breaker during startup, running but not producing normal flow, or running hot and shutting off on thermal overload. If your pump has failed multiple times, check the wire sizing—many homes have original wiring that was adequate for the original pump but too small for a replacement with a larger motor.

We service all major pump brands including Franklin Electric, Grundfos, Goulds (Xylem), and Sta-Rite (Pentair). Our trucks carry common parts and components for same-day repairs.

Frequently Asked Questions