What is a Submersible Motor?

Lori Kilchermann

A submersible motor is an electric motor which can operate while being submerged in water. This sealed motor is typically found in use on pumps. Both sump pumps and water wells use a submersible motor to power the pumping mechanism used in the system. Due to the submersion in water, it is critical that all electrical connections be made watertight to prevent damage to the motor as well as to anyone working on the unit.

Submersible motors are used in sump pumps so they can operate while under water.
Submersible motors are used in sump pumps so they can operate while under water.

The typical water well relies on a submersible motor to pump the water out of the well. The motor is attached to a pump and lowered down through the well casing. Many well contractors attach a small cable to the pump unit to lower it down, while many simply lower the pump unit down by the electrical cord. In either case, the pump and the submersible motor rest at the bottom of the casing suspended in the water. A hose fitted to the nipple on the pump sends the water up and out of the well when the submersible motor turns on.

A submersible pump keeps its motor from getting wet.
A submersible pump keeps its motor from getting wet.

The typical sump pump found in a basement operates much like a toilet valve. The pump, connected to a submersible motor, is placed in a small pit in the lowest portion of the basement. As water fills the pit, a plastic float very similar to the toilet tank float rises with the deepening water and trips a switch on the pump. The pump sends the water into the building's plumbing and out into the sewer via a hose connected to the pump. In a larger building, there may be several sump pumps located throughout the basement.

This design is critical with an electric pump due to the advantage of pushing rather than pulling liquid. A pump is able to push a much greater amount of liquid than it is able to pull, thereby requiring the submersible motor to place the pump at the source of the liquid. Used in this manner, a pump is able to work effectively with a much smaller motor. This results in less electrical power used, a cooler running pump motor as well as a pump that is able to move a great quantity of liquid in a short time.

The typical submersible motor is contained within a rubber sock which maintains the pump's dryness. The sock is removed when servicing the pump or motor and replaced once the service is complete. This allows the pump to operate for a greater length of time without becoming damaged by the water. Many submersible motors offer years of uninterrupted use.

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What is a use of submersible motor other than submersible pumps?

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