Quick Answer
To determine the correct breaker size for a submersible pump, you'll need to calculate the total ampacity required, which includes the pump's motor rating, any additional components like a pressure switch, and the voltage drop allowance. Typically, the breaker size should be 125% of the pump's motor rating to account for inrush current and other factors.
Calculating Total Ampacity
When sizing a breaker for a submersible pump, start by identifying the pump’s motor rating in amperes. For example, let’s say a 1 HP (746 watts) submersible pump has a motor rating of 7.5 amps. Next, consider any additional components connected to the pump’s control circuit, such as a pressure switch, which might add 2-3 amps to the total load. Finally, add a 20-25% allowance to account for voltage drop and other losses.
Choosing the Correct Breaker
Based on the calculated total ampacity, select a breaker that matches or exceeds this value. For the example above, the total ampacity would be 9.375 amps (7.5 + 1.875 allowance). A 10-amp breaker would be a suitable selection, as it exceeds the calculated ampacity and provides some margin for safety. When selecting a breaker, ensure it’s rated for the same voltage as the pump’s motor and meets any local electrical codes or regulations.
Important Considerations
When sizing a breaker for a submersible pump, don’t forget to account for the inrush current, which can be 2-5 times the motor’s rated current. This is especially important for motors with high starting torque requirements. Additionally, consider the pump’s control circuit, including any potential ground faults, and ensure the breaker is compatible with the pump’s control system.
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