What’s the Difference: 2 Wire vs 3 Wire Submersible Well Pumps

Welcome back to another edition of Inspector Pumphead’s Quick Tips! In this space I, Inspector Pumphead, will be dispensing wisdom regarding your pump, whether it be about performance, maintenance, repair parts or navigating our site to find a new product, I’m here to help!

This week we’ll be talking about the difference between 2 and 3 wire submersible well pumps. Firstly, both types feature a ground wire which shouldn’t be counted. Two wire pumps will have 2 black wires and a green wire. Three wire pumps have a black, red, yellow, and green wire. Let’s dive in and figure out which one is right for your application!

Myers 2NFL52-12-P4-01 (2 Wire)

The main difference between 2 wire and 3 wire well pumps is characterized by where the starting components for the motor are located.

Three wire well pumps house the starting components (starting capacitors, running capacitors, relays, and thermal overloads) in a control box or panel. Control boxes are usually mounted on a wall above ground. Though the potential of failure for the parts is greater than a two wire system, the components can be easily accessed and cheaply repaired or replaced. For example, if a capacitor malfunctions on a three wire, just the capacitor itself will need to be replaced.

Two wire well pumps do not use a control box. All the elements already come built within the motor or pump house itself. This allows for easier installation. However, if any of the starting components fail, the pump will have to be pulled up and the whole motor will have to be replaced. The likelihood of component failure in a two wire system is much lower than a three wire, although it is a much more expensive and time consuming endeavor if a part does fail.

Berkeley 15P4JP05231-02 (3 Wire)

At the end of the day, it’s up to you to determine the more convenient approach for your application. Your circumstances may dictate one configuration over the other.  Keep in mind, motors that are more than 1.5 HP requires a three wire configuration and a control box to start the heavier motors.

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