Submersible Well Pump Wire Size & Breaker Calculator

Submersible motors operate under high starting torque at the bottom of a water-filled casing. Sizing drop cable correctly prevents motor burnout, starting capacitor failures, and nuisance breaker tripping.

⚡ Quick Rule: Submersible Cable Sizing (230V Single-Phase)
  • 0.5 HP (1/2 HP): 14 AWG up to 400 ft | 12 AWG up to 650 ft | 15A Breaker
  • 0.75 HP (3/4 HP): 14 AWG up to 300 ft | 12 AWG up to 480 ft | 15A Breaker
  • 1.0 HP (1 HP): 14 AWG up to 250 ft | 12 AWG up to 400 ft | 20A Breaker
  • 1.5 HP (1-1/2 HP): 14 AWG up to 190 ft | 12 AWG up to 310 ft | 25A Breaker
  • 2.0 HP (2 HP): 12 AWG up to 250 ft | 10 AWG up to 390 ft | 30A Breaker
ft
Depth from wellhead to pump
ft
Wellhead to house breaker panel
MINIMUM COPPER WIRE GAUGE 14 AWG Copper 14/2 Submersible Cable with Ground (Internal Motor Capacitor)
CIRCUIT BREAKER RATING 20A 2-Pole Full Load Amps: 8.1A FLA
TOTAL CIRCUIT LENGTH 250 ft Total
MAX ALLOWABLE RUN 250 ft Max

How to Calculate Submersible Pump Wire Size

Submersible cables run long distances through cold well water and underground trenches. Wire sizing is dictated by continuous full-load operating current (FLA) and maximum allowable voltage drop (under 5% total circuit loss):

⚡ Single-Phase Conductor Voltage Drop Formula:

V_drop = (2 × K × I × D) / CM

Where:
• K = 12.9 ohms-cm/ft (direct-current electrical resistivity constant for copper at operating temperature).
• I = Motor Full Load Amps (FLA).
• D = One-way circuit length in feet (pump depth plus horizontal surface distance to panel).
• CM = Cross-sectional area of the conductor in circular mils (e.g., 14 AWG = 4,110 CM; 12 AWG = 6,530 CM; 10 AWG = 10,380 CM; 8 AWG = 16,510 CM).

Franklin Electric Submersible Cable Maximum Length Chart (230V, 1-Phase)

Maximum one-way distance in linear feet from the breaker panel to the submerged motor (75°C copper cable):

Motor HP FLA Amps 14 AWG 12 AWG 10 AWG 8 AWG 6 AWG Breaker Size
0.5 HP (1/2 HP) 4.9 A 400 ft 650 ft 1,020 ft 1,610 ft 2,510 ft 15A (2P)
0.75 HP (3/4 HP) 6.2 A 300 ft 480 ft 760 ft 1,200 ft 1,870 ft 15A (2P)
1.0 HP (1 HP) 8.1 A 250 ft 400 ft 630 ft 990 ft 1,540 ft 20A (2P)
1.5 HP (1-1/2 HP) 10.4 A 190 ft 310 ft 480 ft 770 ft 1,200 ft 25A (2P)
2.0 HP (2 HP) 12.5 A 150 ft 250 ft 390 ft 620 ft 970 ft 30A (2P)
3.0 HP (3 HP) 17.0 A — 120 ft 190 ft 300 ft 470 ft 40A (2P)
5.0 HP (5 HP) 27.5 A — — 110 ft 180 ft 280 ft 60A (2P)

2-Wire vs. 3-Wire Submersible Cable: Which Do You Need?

  • 2-Wire Submersible Cable (Black, Red, Green): The motor has built-in electronic start components inside its sealed housing. Requires no control box on the surface. Lower initial hardware cost, but if the internal start capacitor fails, the entire pump must be pulled from the well.
  • 3-Wire Submersible Cable (Black, Red, Yellow, Green): The starting capacitor, running capacitor, and motor starter relay are housed in a surface control box mounted inside the home or garage. When a capacitor degrades over time, it can be tested and swapped in 10 minutes without pulling hundreds of feet of wet pipe.

Need Hydraulic Pump Sizing?

Calculate your Total Dynamic Head, friction loss, and flow with our Master Well Pump Sizing Calculator, or review our Engineering Standards & Methodology.