How do I know if my submersible pump motor is a “2 wire” or a “3 wire”?

Franklin start box
Franklin start box

This terminology is used to describe the single phase motor that drives the submersible “wet-end” or pump. It is not used in reference to three phase submersible pumps. The difference between a “2 wire” and “3 wire” pump is based on the type of motor that is used. A “3 wire” single phase submersible pump motor requires a control box or start box that contains  a starting capacitor or start/run capacitor. This box is normally mounted near the power

Lowara bore start box
Lowara bore start box

source or buildings meter box. This has an on/off manual switch and motor running indicator. On installation an electrician puts a 24v relay in this to accept the signal from a reticulation controller if required, thereby automating the start box. Because of the method of starting, the motor requires three “hot” leads (plus a lead for the ground connection) to operate correctly. It is called a “3-wire” due to the three “hot” leads, though there are actually 4

individual wires when you count the earth (ground) wire. On the other hand a “2 wire” motor requires no control/start box because it does not use a starting capacitor.

Sumoto Submersible Start Box
Sumoto Submersible Start Box

Instead, a “2 wire” motor has a built-in electrical device that is used to start the motor. This only requires the pump to have 2 “hot” leads (plus earth), which is why it is called a “2 wire” pump.  But when counting the total number of wires coming to the surface we see a “2 wire” pump actually has 3 wires and a “3 wire” pump actually has 4  wires. Confused?  Fixing submersible bores and pumps is what we do every day.  Our experience is what sets us apart. Our service teams have the knowledge, experience and tools to get the job done right first time with a minimum of fuss. Call 1300 734 300 for any bore service needs Perth and surrounds.

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