NEC Article 430 (Motors)
What Size Wire for a Well Pump?
A well pump is a motor, so it follows NEC Article 430, not the flat appliance rule. Here is the code-minimum wire and breaker by horsepower, why the wire is almost always upsized for voltage drop, and the calculator for your run.
Motor Sizing: Two Rules, Two Different Numbers
A motor branch circuit sizes the conductor and the breaker separately, and both start from the table full-load current (FLC) in NEC Table 430.248, not the nameplate amps (NEC 430.6(A)(1)). The conductor only has to carry 125% of the FLC (NEC 430.22). The breaker may be as large as 250% of the FLC (NEC 430.52), because it has to pass the motor's starting inrush without tripping. That is why a well pump can legally have small wire on a much larger breaker: NEC 240.4(G) exempts motor conductors from the small-conductor limits, and a separate overload device (430.32), usually inside the pump or its control box, protects the conductor from an overworked motor.
Well Pump Wire and Breaker by Horsepower (240V)
| Pump HP | FLC (430.248) | Min Wire (430.22) | Max Breaker (430.52) | Ground |
|---|---|---|---|---|
| 1/2 HP | 4.9 A | #14 | 15 A | #14 |
| 3/4 HP | 6.9 A | #14 | 20 A | #14 |
| 1 HP | 8 A | #14 | 20 A | #14 |
| 1-1/2 HP | 10 A | #14 | 25 A | #14 |
| 2 HP | 12 A | #14 | 30 A | #14 |
“Min Wire” is the code minimum by ampacity at the 60°C column (always-safe / NM-B). The breaker is the maximum inverse-time size; a smaller standard breaker is fine if it reliably starts the pump. Almost every real well install uses a larger conductor than the minimum because of voltage drop, so treat the table as a floor.
Voltage Drop Usually Sets the Wire, Not Ampacity
A submersible pump sits at the bottom of the well, so the cable run is the drop depth plus the horizontal run to the panel, often 150 to 400+ feet. Over that distance the code-minimum #14 would lose far more than the 3% target and the motor would run hot and short-lived. That is why pump manufacturers (Franklin, Grundfos, Goulds) publish wire-size charts by horsepower and total run length, and why #12 or #10 is the norm even on a small pump. Enter your run below to size the conductor for voltage drop, then use the larger of that and the NEC 430.22 minimum.
Enter the motor FLC as the load and your one-way run to check voltage drop, or open the voltage drop calculator →
Frequently Asked Questions
What size wire do I need for a well pump?
A well pump is a motor load, so the wire follows NEC Article 430, not the appliance rule. The branch-circuit conductor only has to carry 125% of the motor's full-load current from NEC Table 430.248 (430.22), which for a typical 1/2-1 HP 240V submersible is a code-minimum of #14 copper. In practice, though, well pump wire is almost always upsized to #12 or #10 copper, because the cable runs down the well and the voltage drop over that depth would starve the motor. Pump manufacturers publish wire charts by horsepower and total run length; size to that, and never smaller than the NEC 430.22 minimum.
What size breaker for a well pump?
Size the breaker from the motor's table full-load current (FLC), not the nameplate. An inverse-time breaker may be as large as 250% of the FLC (NEC 430.52, Table 430.52), rounded up to the next standard size. A 1/2 HP 240V pump (4.9A FLC) lands on a 15A breaker; 3/4-1 HP on 20A; 1.5 HP on 25A; 2 HP on 30A. The breaker is intentionally larger than the wire's ampacity so the motor can start; the pump's own thermal overload or the control-box overload protects the conductor (430.32), not the branch breaker.
Why is the well pump breaker bigger than the wire can handle?
Because motor circuits split the two jobs. The branch-circuit breaker (NEC 430.52) only provides short-circuit and ground-fault protection, and it has to pass the motor's starting inrush without tripping, so it is sized up to 250% of the FLC. Overload protection, the part that actually protects the small conductor from a stalled or overworked motor, is a separate device sized at 115-125% of the nameplate FLA (430.32), usually built into the pump or its control box. NEC 240.4(G) specifically exempts motor conductors from the small-conductor breaker limits of 240.4(D), so #14 copper on a 30A motor breaker is code-correct.
Is a well pump 120V or 240V?
Most residential submersible well pumps are 240V, and jet pumps are commonly dual-voltage (wired 120V or 240V). Running a pump at 240V halves the current and the voltage-drop loss over a long cable run, which is why submersibles are almost always 240V. Check the motor or control-box label for the connected voltage before sizing.
Does a well pump need a disconnect?
Yes. NEC 430.102 requires a disconnecting means within sight of the pump motor (or its controller), and the pressure switch is not a disconnect. Submersible pumps are controlled by a pressure switch and often a control box (for a 3-wire pump), but a lockable breaker or a separate disconnect still has to serve as the motor disconnect.
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