Well Pump: Complete Wiring Guide
Bill of materials
Well pumps are motor loads governed by NEC Article 430. Wire sizing uses the motor FLC (full-load current) from NEC Table 430.248, not the nameplate current. The critical factor for well pumps is voltage drop: runs of 200-500 feet from the panel to the wellhead are common, and undersized wire causes motor damage.
Size wire using FLC from NEC Table 430.248, not nameplate amps. For long runs (200+ ft), voltage drop is the controlling factor - you may need to upsize 1-2 gauges above minimum ampacity. Use submersible pump cable rated for wet locations. The control box (for 3-wire systems) must be sized to the motor HP. GFCI is not required for well pump circuits but a disconnect within sight is required per 430.102.
1/2 HP submersible (10A 240V)
| Component | Specification | NEC basis |
|---|---|---|
| Wire (copper) | 14 AWG THHN | Table 310.16, 110.14(C) |
| Breaker | 15A double-pole | 240.4 |
| Voltage | 240V single-phase | |
| Conduit (EMT) | 1/2" EMT | Chapter 9 Table 4 |
| Max distance (3% VD) | 143 ft at 240V copper | 210.19(A) Note 4 |
1 HP submersible (12A 240V)
| Component | Specification | NEC basis |
|---|---|---|
| Wire (copper) | 12 AWG THHN | Table 310.16, 110.14(C) |
| Breaker | 20A double-pole | 240.4 |
| Voltage | 240V single-phase | |
| Conduit (EMT) | 1/2" EMT | Chapter 9 Table 4 |
| Max distance (3% VD) | 181 ft at 240V copper | 210.19(A) Note 4 |
2 HP submersible (20A 240V)
| Component | Specification | NEC basis |
|---|---|---|
| Wire (copper) | 10 AWG THHN | Table 310.16, 110.14(C) |
| Breaker | 25A double-pole | 240.4 |
| Voltage | 240V single-phase | |
| Conduit (EMT) | 1/2" EMT | Chapter 9 Table 4 |
| Max distance (3% VD) | 181 ft at 240V copper | 210.19(A) Note 4 |
Installation notes
GFCI is not specifically required for this application by NEC, though local amendments may differ. Check with your local building department before starting work.
For the wire run, you have two options: NM-B cable (Romex) for interior runs through framing, or individual THHN conductors in conduit for exposed runs, outdoor installations, or runs through unfinished spaces. NM-B is faster to install but cannot be used outdoors or in conduit. For conduit, use EMT (metallic) or PVC Schedule 40.
Run length matters: every foot of wire adds voltage drop, reducing power to your equipment. The table below shows the exact voltage drop at common distances. If your run exceeds the 3% threshold, upsize one gauge.
Voltage drop by distance
Percentage voltage drop at common run lengths. NEC recommends 3% maximum for branch circuits and 5% for combined feeder plus branch.
| Distance | 14 AWG Co | 12 AWG Co |
|---|---|---|
| 25 ft | 0.5% | 0.3% |
| 50 ft | 1.1% | 0.7% |
| 75 ft | 1.6% | 1.0% |
| 100 ft | 2.1% | 1.3% |
| 150 ft | 3.1% | 2.0% |
| 200 ft | 4.2% | 2.6% |
Common products for 14 AWG Copper circuits
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Related wire data
Detailed ampacity: 14 AWG copper. Wire size lookup: 15A circuit. Calculators: voltage drop · panel load calculator.
Frequently asked questions
What wire size do I need for well pump?
Use 14 AWG copper or 14 AWG aluminum on a 15A breaker at 240V. This is based on NEC 2023 Table 310.16 ampacity with 110.14(C) termination limits and 125% continuous load sizing per 210.19(A)(1).
Does well pump require GFCI?
No. GFCI is not required for this application.
NEC 2023 references verified April 2026