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    Variable Frequency Drive (VFD)

    SubDrive Connect QD Pumptec
    SubDrive Connect QD Pumptec

    Variable Frequency Drive (VFD)

    A variable frequency drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage of its power supply. The VFD also has the capacity to control ramp-up and ramp-down of the motor during start or stop.

    This Grundfos system is a complete package designed to provide constant water pressure in any domestic and light commercial water supply, irrigation system, livestock watering or water transfer. It is comprised of systems based around an SP pump (2, 3 or 5 HP) and CU331SP Control Unit.

    The CU331SP is a constant pressure, variable frequency drive based on a proven product platform. CU331SP is a strong supplement to the Grundfos SmartFlo constant pressure program. This new product is designed to easily adapt to any combination of 2HP, 3HP or 5HP Grundfos SP pump systems using a 3-phase motor. This wall mounted system maintains a constant pressure within the maximum pump performance in spite of varying water consumption. The CU331SP is programmed with parameter settings optimized for submersible pump applications. An easy to follow Start-Up Guide walks the installer through a few screens and completes the set-up.


    Features & Benefits

    • Easy setup – simply run the Start-up Wizard and choose pressure set-point
    • The system determines the direction of rotation and sets the dry-run function, according to the pump
    • System design approach – the CU331SP works with any combination of matched pump and motor
    • CU331SP works with 2, 3 or 5Hp submersible pumps to fulfill your constant pressure requirements
    • Matched pump & motor – 2HP pump on 2HP motor, 3HP pump on 3HP motor, 5HP pump on 5HP motor
    • Built-in protection features – Soft start, dry run, overload, over/under voltage, sensor alarm, alarm relay and run relay
    • Wide voltage range – input: single phase 208 – 240VAC output: 3-phase 208-240VAC
    • Indoor (NEMA 12) or outdoor (NEMA 4X) enclosure options


    The user interface offers these possibilities:

    1. Local operation via a control panel with graphic display where the menu structure is based on the well-known system from Grundfos E-pumps
    2. Monitoring of operating status via indicator lights and signal relays
    3. Display of alarm or warning and logging of the last five alarms and warnings


    • Control mode – Constant pressure. The CU331SP has only one control mode, Constant pressure. The pressure is kept constant, independently of the flow rate.
    • Start-up guide – The CU331SP has a start-up guide, which is launched at the first power up. Parameters are set manually on the basis of the installation. The start-up guide can be repeated, if necessary. Thanks to the start-up guide, the installer can quickly set a few parameters and put the CU331SP into operation
    • Direction of rotation test. During start-up, the CU331SP automatically tests and sets the correct direction of rotation without changing the cable connections. The direction of rotation test can be performed manually if it fails for any reason
    • Dry-running protection. To protect the pump, the CU331SP will automatically set up dry-run protection so that water shortage can be detected. The dry-run alarm will automatically reset 30 minutes after the alarm is declared
    • Low-flow stop function. The low-flow stop function is used for changing between on/off operation at low flow rate and continuous operation at high flow rate. The low-flow stop function protects the pump and saves energy


    For 4″ or larger wells. Main applications:

    • Domestic and light commercial water supply
    • Irrigation
    • Livestock watering
    • Water transfer


    Grundfos CUE is the latest addition to the E-solutions program of speed-controlled pump systems for industry, building services, municipal water supply, municipal wastewater, and irrigation applications.

    Their new, comprehensive series of wall-mounted frequency converters with E-pump functionality and user interface is a complementary product to the Grundfos E-pumps featuring an integrated frequency converter.

    With a CUE solution, you can control the speed of most Grundfos pumps regardless of size, power range, and application area.

    The Grundfos CUE is suitable for most centrifugal pump types, all application areas, and all power ranges outside the E-pump range. The CUE can be used in connection with both new and existing Grundfos pumps and in installations where the integrated solution will not fit, is not wanted, or prohibited. Typical application areas include:

    • Submersible installations
    • Wastewater applications
    • Water supply and irrigation applications
    • Hazardous or explosive areas
    • Sanitary installations

    CUE Versions Available

    Power Supply HP
    1-phase x 200-240 V 1 ½ – 10
    3-phase x 200-240 V 1 – 60
    3-phase x 380-500 V ¾ – 300
    3-phase x 525-500 V 1 – 10
    3-phase x 525-690 V 10 – 300

    SubDrive Connect

    Constant Pressure Variable Frequency Drives (VFD)

    Franklin Electric’s SubDrive Connect Variable Frequency Drives provide an easy-to-install constant pressure solution and built-in protection for single-phase 3-wire and three-phase motors. Enhanced with advanced connectivity, they enable real-time local monitoring, quick setup and streamlined troubleshooting through the FE Connect mobile app.

    SubDrive Connect offers an array of compact NEMA 3R-rated drives to solve submersible and above ground pumping challenges with single-phase 3-wire or three-phase performance up to 5 horsepower using single-phase input.

    Pumptec Family

    QD Pumptec

    Exclusively designed for Franklin QD Relay Control Boxes, QD Pumptec is a solid state sensing device that monitors motor load and incoming power to automatically shut off a Franklin single-phase, 3-wire motor when related fault conditions are detected. QD Pumptec easily plugs into 3-wire Franklin QD Control Boxes with no additional wiring or tools required.

    • QD Pumptec allows the user to choose the standard factory calibration for underload or to calibrate to a particular system. Control knobs make it easy to adjust sensitivity and timeout sessions.
    • QD Pumptec easily plugs into 3-wire QD Relay Control Boxes in minutes, without additional wiring or tools.

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