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Emphasizes that installation, maintenance, and inspection must be done by trained personnel.
Outlines critical safety rules, including grounding and avoiding use of the On/Off button as a safety switch.
Lists general safety considerations for installation, including protection and cable selection.
Explains how low air pressure and long motor cables can affect performance.
Details necessary clearances for cooling and ambient temperature limits for installation.
Provides instructions on how to securely mount the CU331SP unit on a firm surface.
Covers essential electrical protection measures, including grounding and short-circuit protection.
Explains how to connect the power supply (mains) and the motor to the CU331SP.
Shows the basic wiring for signal terminals, including start/stop functionality.
Details how to configure the analog input (A54) for voltage or current signal type.
Provides guidelines for proper installation to ensure electromagnetic compatibility (EMC).
Describes the CU331SP's control panel, including buttons, indicator lights, and display elements.
Provides instructions on how to reset all CU331SP parameters to their factory default settings.
Details the process for automatically testing and setting the correct motor direction of rotation.
Explains how to set the desired discharge pressure (setpoint) using the feedback sensor.
Describes how the CU331SP indicates faults through alarms or warnings.
Configures how the CU331SP handles dry-run conditions (OFF, Warning, or Alarm).
Explains how the CU331SP detects and responds to low flow conditions to prevent pump damage.
Provides a list of error codes, their status (warning/alarm), operating mode, and reset method.
Details how to reset alarms, including manual, automatic, and locked alarm procedures.
The Grundfos CU331SP is a constant pressure variable frequency drive specifically engineered for submersible pumps. It is designed to maintain a constant discharge pressure across the pump's performance range, adapting the pump speed to actual demand. The device is suitable for use with Grundfos 2, 3, and 5 Hp 4" SP pumps.
The CU331SP features a user-friendly control panel for local settings and operation. The control panel includes navigating buttons (up, down, left, right, OK) to move through menus and adjust values. An On/Off button allows the user to make the pump ready for operation or stop it. Indicator lights on the control panel provide visual feedback on the pump's operating status: green for running or stopped by a stop function, flashing green for stopped by the user or external start/stop, orange for stopped by the On/Off button, and red for alarms or warnings. The display shows information such as the display name, value field, current display number, and menu name. The display contrast can be adjusted, and buttons can be locked to prevent accidental changes.
The device incorporates a start-up guide that facilitates quick parameter setting and commissioning. This guide is activated upon first power-up or can be restarted from the GENERAL menu, though restarting will erase previous settings. The start-up guide walks the installer through essential steps, including language selection, supply voltage setting, and priming/venting instructions. A key feature is the automatic setting of the direction of rotation, where the CU331SP tests and sets the correct rotation without requiring cable changes. If automatic setting fails or is unsuitable for certain pump types, a manual setting option is available, requiring the installer to observe the pump's head/flow rate for optimal performance. The start-up guide also automatically determines and sets the stop and dry-run functions based on the pump and motor combination, running the pump against closed valves to establish power settings.
The CU331SP offers various operating modes accessible via the OPERATION menu, including Normal, Max, Min, and Stop. These modes allow the user to control the pump's behavior, such as running at a constant pressure, maximum speed, minimum speed, or stopping the pump. The control mode is fixed as "Controlled operation (closed loop)" with a sensor connected, ensuring constant pressure independently of the flow rate.
For fault detection, the CU331SP provides both warning and alarm indications. A "warning" activates a warning indication but allows the pump to continue operating, while an "alarm" typically stops the pump or changes its operating mode to prevent damage. The device includes a log function for both fault types, storing the last five alarm and warning indications, including the alarm/warning code and the time elapsed since the event. Most alarms have an automatic reset function, with a 10-second reset time for most alarms and 30 minutes for the Dry-Run alarm. Locked alarms, however, require manual intervention to reset after the cause has been remedied.
The STATUS menu provides read-only displays of various operating parameters, such as actual setpoint, external setpoint, operating mode, actual value from sensor 1, pump speed, input power, motor current, operating hours, and power consumption. These displays offer a comprehensive overview of the CU331SP's real-time performance and historical data. The operating hours and power consumption are accumulated values that cannot be reset.
The INSTALLATION menu allows access to specific parameters for fine-tuning the system. This includes setting sensor 1 parameters (output signal, unit of measurement, measuring range), limiting the motor's maximum speed, and configuring the Dry Pump Function. The Dry Pump Function can be set to OFF, Warning, or Alarm, determining how the drive responds to dry-running conditions. The default "Alarm" setting stops the motor to protect the pump, while "Warning" provides an indication without stopping, and "OFF" disables the function entirely. The Power Correction Factor can be adjusted to fine-tune the Dry-Run function's sensitivity, though caution is advised as incorrect adjustments can risk pump damage. The protocol for the RS-485 port can also be selected, with GENIbus being the standard for Grundfos communication.
The CU331SP also incorporates low flow and stop functions. The low-flow detection periodically checks the flow by reducing pump speed and assessing pressure changes. If low flow is detected, the pump will increase speed to reach a stop pressure and then stop, restarting when pressure drops to a start pressure. The stop function requires a pressure sensor, a non-return valve, and a diaphragm tank for proper operation.
Maintenance features include guidelines for cleaning the CU331SP to ensure adequate cooling, particularly the cooling fins and fan blades. The manual also provides information on service parts and kits.
For electrical connections, the CU331SP emphasizes safety, requiring installation and operation to comply with local regulations and good practice. It features internal overcurrent protection for the motor output and protection against mains voltage transients. The device is designed for EMC-correct installation, with guidelines for using screened cables, proper grounding, and separation of main, motor, and signal cables to minimize noise and leakage currents. Built-in RFI filters are included to meet EMC requirements.
The CU331SP is designed for stationary, permanent installation and connection to the mains supply. It requires a reinforced ground connection due to leakage current exceeding 3.5 mA. The device and supply system must be protected against short-circuits using recommended back-up fuses. The motor requires no external protection as the CU331SP protects it against thermal overloading and blocking.
Overall, the Grundfos CU331SP is a robust and intelligent variable frequency drive designed for reliable constant pressure operation of submersible pumps, with comprehensive features for installation, control, monitoring, and fault management.
General| Type | CU331SP |
|---|---|
| Frequency | 50/60 Hz |
| Enclosure class | IP55 |
| Approvals | CE |
| Operating temperature | 50 °C |
| Relative humidity | Max. 95% RH |
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