Constant Pressure Systems / Variable Frequency Drives

Constant pressure systems are much like conventional systems in that they require a pump, a pressure tank and a pressure switch or sensor.  The pressure sensor monitors the system pressure and sends a signal to the control panel for the pump. The controller then signals the pump to perform at a rate required to maintain the desired system pressure and volume. Depending on the specific system, the pressure setting may be adjustable at either the pressure sensor or the motor controller.

Constant Pressure SystemPressure Tank
A pressure tank in a constant pressure system is usually much smaller than in a conventional system.  In a constant pressure system, the tank stores very little water acting primarily as a buffer to prevent pressure fluctuations.

constant pressure system

Pumps used in a constant pressure system are basically the same as those used in a conventional submersible system.  The difference being that the motor attached to the pump runs at variable speeds depending on the volume of water being demanded.  The motor speed is controlled by a variable frequency drive controller.  Depending on the specific system, the motor could be a single or three phase unit.

Benefits of a Constant Pressure System

  • The system maintains a steady pressure instead of cycling with a 20 pound differential.
  • Ideal for multiple uses, including sprinkler and drip irrigation systems.
  • Requires a much smaller pressure tank, saving precious space in what usually is a confined mechanical room, pump house or pit.
  • Soft starts and stops equates to less wear on the pump and motor.
  • On units operating with a three phase motor, wire size can be smaller which means less cost in some applications especially when the pump depth is deep.

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