2-Wire versus 3-wire Well Pump Motors Pros and cons

How do 2-Wire and 3-wire Well Pump Motors differ

In residential areas majority of the 4-inch submersible well pump motors are based on either 2-wire or 3- wire. In the naming of these wires, the numbers of wires mentioned are the ones excluding the ground wire.

2-wire motors comprise one green wire and two black wires whereas the 3-wire motors comprise one green, one yellow, one red, and one black wire.

In a 3-wire motor, the starting components are all within the control box located above the ground. These components include:

·         Start capacitors

·         Run capacitors

·         Relays, 

·         Thermal overloads

On the other hand, within 2-wire motors, these starting components are a part of the motor. This motor is placed on the pump that is located very deep into the well.

In larger submersible motors it is not practical to add starting components. That’s why 2-wire motors have a maximum horsepower of only 1.5. In comparison, the horsepower goes up to 15 horsepower in 3-wire single-phase motors.

You might wonder which one you should install.

2-Wire Advantages

• Installation is easier

• It is more cost-effective, and the submersible wire weighs lesser.

• Since the motor contains all internal components, they have less exposure to external elements. It means there are lesser chances of it becoming faulty or getting oxidized.

2-Wire Disadvantages

·         The whole motor has to be pulled out if any of the starting components fail for them to be replaced.

3-Wire Advantages

·         It is more convenient and cheap to replace the faulty starting components

·         Starting torque is higher

3-Wire Disadvantages

·         There are higher chances of damage and oxidization since starting components are in contact with external ground elements.

It is entirely on the installer or the homeowner whether they want to install a 2-wire motor or a 3-wire motor. Some installers might prefer a 2-wire motor with 1.5 horsepower due to the advantages it has. These include a more convenient installation, the longer useful life of starting components, cost-effectiveness, and lower maintenance costs.

Alternatively, some installers may prefer a 3-wire motor. One of the biggest reasons is that if a starting component fails and needs to be replaced or you need to replace the whole box of starting components, you can do it easily within 45 minutes.

You can choose one randomly yourself or either consult an installer. According to the information about the local area, the installer would be able to choose better amongst the 2-wire or 3-wire motor.