Electrical Fundamentals

Published On: February 19, 2024By Categories: Features, Pumps and Water Systems

Having knowledge of basic electrical concepts can help ensure an optimal performance of well systems.

By Tom Stephan

Water well system installers encounter various challenges related to electrical basics in the installation, operation, and maintenance of their systems. Such challenges range from ensuring electrical safety and understanding wiring to preventing electrical failures and troubleshooting
control panels.

While many water professionals and contractors are familiar with hydraulic fundamentals, electrical basics are just as important for contractors and professionals to master to ensure efficiency, longevity, and reliability of water well systems.

Voltage, ohms, and amperage essentials

The most basic electrical concept for water well technologies is understanding Ohm’s law: V = I × R, where voltage (V) equals current (I) multiplied by resistance (R).

To help us grasp Ohm’s law, we use what we already know from hydraulics. Voltage is like pressure (psi) and is measured in volts. Current is like flow (gpm) and is measured in amps. Resistance is like friction loss and is measured in ohms.

Figure 1. Electrical involvement in water well systems.

Knowing the similarities between hydraulic and electrical systems can help contractors gain a deeper understanding of electrical involvement in water well technologies (Figure 1).

Motor nameplate information

Pertinent electrical information is located on the motor as well as in the technical documentation. It is critical to match the supply phase and voltage to that of the motor.

In Figure 2, the motor is single phase, 230 volts. Motors typically have a plus or minus 10% voltage tolerance from the nameplate value. In this case, the values are 207 to 253 volts. It is therefore critical to make sure the supply is within tolerance.

Since these motors are typically hundreds of feet down the well, wire size is also critical. Undersized wire generates higher resistance, leading to lower voltage at the motor, causing amperage to be higher.

Amperage is another critical piece of electrical data. In the figure example, amps and service factor max amps (SF max amps) are identified. Because there is a service factor, there are also SF max amps. This value must be looked up either in the technical manual or on the motor itself.

Figure 2. Amps and service factor max amps on nameplate.

Many 4-inch submersible motors are designed to operate into the service factor. This means when measuring amperage, we do not want to exceed the SF max amps, not the amps (often referred to as full load amps). Note that the use of SF max amps with submersible motors is somewhat unique and not likely to apply to other motors or applications.

Submersible motor considerations

In addition to identifying phase, voltage, and amperage, identifying the motor type is equally important for efficient operation. Factors like motor type (e.g., three-wire or two-wire) and elements like lightning surge protection and sacrificial anodes play a critical role in the operation of submersible motors. Ensuring proper cooling during motor startup is vital for preventing overheating.

Four (4)-inch single-phase submersible motor: three-wire vs. two-wire

The 4-inch single-phase submersible motor offers versatility with two primary types: the three-wire and two-wire configurations.


  • The three-wire submersible motor (Figure 3) involves three wires and a grounding wire, typically colored green. We call these three-wire even though they have a total of four wires.
  • Horsepower (hp) typically ranges from 0.5 to 5.0.
  • With a QD control box (quick disconnect), the motor is capacitor start/induction run. With a CSCR control box (capacitor start capacitor run) or a magnetic contactor control box, the motor is capacitor start/capacitor run.

    Figure 3. Three-wire submersible motor.

Control boxes with run capacitors have the advantage of lower amps compared to the QD control boxes

  • Advantages over two-wire include:
    o Higher starting torque
    o Troubleshooting ease due to the control box
    o Faster repair potential due to the control box.
  • Disadvantages from two-wire include:
    o Higher installation cost
    o May have slightly higher amps.


  • Two-wire submersible motors (Figure 4) consist of two wires and a grounding wire. These are called two-wire even though they have a total of three wires.
    • Two-wire motor designs vary. The CentriPro motor has a permanent split capacitor in the motor, meaning no additional components (e.g., control box) are necessary for the motor to operate
  • Advantages over three-wire:
    o Lower amps
    o Lower installation cost
    o Quicker installation.
  • Disadvantages from three-wire:
    o Lower starting torque
    o No control box for possible repair or replacement.

Four (4)-inch submersible motor design and accessories

Submersible motors typically feature built-in lightning/ surge protection and thermal overloads. These are designed to protect the motor from voltage surges and over-temperature conditions, respectively.

The lightning/surge devices cannot be replaced, but additional surge protection can always be added to the system, and this is replaceable. When the thermal overload is in the motor, it cannot be reset or replaced. When the thermal overload is in the control box, it can be tested, replaced, and reset.

Preventing motor overheating

With these considerations in mind, water well professionals also need to know how to proactively prevent overheating of the motor. The startup of a motor on a fixed-speed system triggers a rush of current, often reaching two to four times the full load amperage.

Figure 4. Two-wire submersible motor.

Given that amperage generates heat, this sudden heat increase requires an effective cooling mechanism. Submersible motors achieve this cooling through water flow past the motor, which dissipates the heat generated during startup. A general rule of thumb is to make sure the motor runs for at least a minute, particularly for pumps up to 1.5 hp, and two minutes for 2 hp and larger motors, to allow the motor to properly cool itself.

Since the tank is responsible for cycling the pump, sufficient cooling time is critical to size the tank properly. For example, a 1 hp pump with a flow rate of 10 gpm requires a tank with a drawdown of 10 gallons (minimum) to run the pump for one minute. A simple approach to achieve the minimum is matching the flow of the pump to the drawdown of the tank.

Optimizing longevity

Understanding basic electricity can help with optimizing water systems. Low voltage and undersized wire leads to lower voltage at the motor. This leads to a higher amperage and reduces the motor’s life. Undersized tanks increase the number of high amp starts as well as insufficient cool-down time, which also reduces the life of the motor.

Like other electrical motors, a submersible pump’s life is reduced by excessive amps or heat. There is no substitute for proper sizing and installation by professional contractors as they typically have decades of experience within a particular geographical area.

Ultimately, by mastering these electrical fundamentals, water well system installers can bring a holistic approach to their work, ensuring not only the reliability and efficiency of water well systems but also their own safety, and proficiency in troubleshooting and problem solving.

As technology and industry standards evolve, a solid understanding of these electrical principles will remain a cornerstone for professionals engaged in the installation and maintenance of water well systems.

Tom Stephan is the training manager for Goulds Water Technology Factory School. Stephan has decades of industry experience and received the 2023 NGWA Manufacturers Special Recognition Award. He can be reached at thomas.stephan@xylem.com.

Read the Current Issue

you might also like