We're always going to suggest that you consult with a licensed electrician if you're uncomfortable figuring this all out yourself. But we'll try to get you started in the right direction! Understanding your pump's full load current and overall electrical system is crucial for this process. For a 220V submersible deep well pump, you'll size the breaker by the pump's rated horsepower.
Choosing the appropriate breaker size depends on the water pump horsepower and voltage. A mismatch in circuit breaker size can cause tripping, a failure to protect the wiring, or a voltage drop. Refer to the chart below for guidance.
|
HP |
Volts |
Circuit Breaker Amps |
Standard Fuse Amps |
NM-B Wire Gauge Necessary |
|
½HP |
220V |
15 |
15 |
14ga |
|
¾HP |
20 |
20 |
12ga |
|
|
1HP |
25 |
25 |
10ga |
|
|
1.5HP |
30 |
30 |
10ga |
|
|
2HP |
30 |
30 |
10ga |
|
|
3HP |
45 |
40 |
8ga |
|
|
5HP |
70 |
60 |
4ga |
This chart is based on wire lengths up to 100 feet. If your setup exceeds that, use a thicker gauge to reduce voltage drop. The amp breaker should be rated high enough to support the pump’s electrical draw without exceeding 80% of its total capacity.
Always double-check your well pump specifications before selecting a breaker. Check that the breaker has sufficient amps to power residential water pumps. The breaker rating should be fine if you’re replacing an old pump with the same HP, but a higher horsepower rating may require a different size breaker.
The breaker panel should have a wiring assignment on the inside of the front door. Use this to identify which circuit is your well water pump and de-energize the circuit before installing. If the breaker takes up two adjacent slots in the panel, it's likely a double pole breaker, which is standard for 220V systems; a single-slot breaker typically indicates a 110V circuit.
UF-B direct burial or THHN/THWN wire pulled through conduit are suitable methods of wiring the starter box to the breaker. You must comply with local electrical codes and building ordinances when installing wire to the amp breaker.
For additional help ensuring a safe and properly sized install, use the freeWater Pump Sizing Calculator at RPS Water Pumps. It helps match pump systems with your exact water needs and power configuration, giving you clarity before installation even begins.
