VFD for Secondary Pump Applications
A Variable Frequency Drive, or VFD, is commonly used in secondary pump applications to control motor speed according to the actual flow, pressure or process demand. In HVAC and chilled-water systems, a secondary pump may not need to operate continuously at full speed. A correctly selected VFD can adjust pump motor speed according to the operating requirement.
Integrated Control Solutions provides VFD and industrial automation support for secondary pump applications, chilled-water circulation, HVAC pumping systems and industrial process pumping. Correct VFD selection depends on motor rating, supply voltage, pump characteristics, operating duty, control method, pressure or flow feedback, and installation environment.
What Is a VFD for Secondary Pump?
A VFD for secondary pump is an AC drive used to control the speed of an AC motor connected to a secondary circulation pump. By changing the motor frequency and voltage, the VFD can adjust pump speed according to the system demand.
Secondary pumps are often used in HVAC chilled-water systems, circulation loops and industrial process systems where variable flow may be required. When the system is designed for variable-speed operation, the pump can run at the speed needed for the current demand instead of remaining at full speed.
Where Are VFDs Used for Secondary Pumps?
- HVAC secondary chilled-water pumps
- Building circulation pumps
- Variable-flow chilled-water systems
- Industrial circulation pumps
- Process water systems
- Cooling-water circulation
- Pressure-controlled pumping systems
- Commercial HVAC plants
- Industrial utility systems
- Water distribution loops
Benefits of Using a VFD for Secondary Pump
Variable Pump Speed
A VFD allows the secondary pump motor speed to be adjusted according to actual system demand rather than operating continuously at full speed.
Pressure and Flow Control
When used with suitable sensors and a control system, pump speed can be adjusted according to pressure, differential pressure, flow or another process variable.
Smoother Motor Starting
A correctly selected VFD provides controlled acceleration and deceleration, reducing the sudden electrical and mechanical stress associated with direct-on-line starting.
Automation Integration
Industrial VFDs may provide analog inputs, digital inputs and communication interfaces for connection with PLCs, HVAC controllers or building automation systems.
Reduced Mechanical Stress
Controlled starting and stopping can reduce sudden loading on pump couplings, shafts, valves and connected piping components.
VFD for HVAC Secondary Pump
In many HVAC chilled-water systems, secondary pumps circulate chilled water from the plant to air handling units, fan coil units or other cooling loads. Demand may vary during the day depending on occupancy, temperature and process conditions.
Where the hydraulic system is designed for variable flow, the VFD can adjust pump speed according to the required operating condition. The control system may use differential pressure, flow or another suitable signal to determine the required speed.
VFD for Chilled-Water Secondary Pump
A chilled-water secondary pump VFD can be used to vary pump motor speed according to cooling demand. This can help the system respond to changes in load when the complete chilled-water system is designed for variable-speed operation.
The drive selection should consider motor current, pump operating curve, minimum speed requirement, system pressure, control signal and installation environment.
How to Select a VFD for Secondary Pump
VFD selection should not be based only on motor kW. The actual pump and system operating conditions should be checked before selecting the drive.
| Parameter | What to Check |
|---|---|
| Motor Power | Motor kW or HP rating |
| Motor Current | Rated current from the motor nameplate |
| Supply Voltage | Available input voltage and phase |
| Pump Type | Secondary chilled-water pump, circulation pump or process pump |
| Control Requirement | Pressure, differential pressure, flow or other process feedback |
| Operating Duty | Required flow range, duty cycle and minimum operating speed |
| Environment | Ambient temperature, humidity, dust and enclosure requirements |
Secondary Pump VFD Control Methods
Depending on the system design, the VFD may receive its speed reference from:
- Differential pressure sensor
- Pressure transmitter
- Flow transmitter
- 0–10 V analog signal
- 4–20 mA analog signal
- PLC
- HVAC controller
- Building automation system
- Supported communication network
Primary and Secondary Pump Systems
In a primary-secondary chilled-water system, the primary and secondary pumping circuits perform different functions. The secondary pump generally circulates chilled water through the distribution system according to building or process demand.
When applying a VFD to a secondary pump, the control strategy and system hydraulics should be reviewed to ensure the pump can operate safely across the required speed range.
Secondary Pump VFD Installation Considerations
The VFD should be installed according to the manufacturer’s instructions with suitable electrical protection, grounding, cable sizing, ventilation and motor connections.
Pump operating limits, minimum flow requirements, motor cooling and system pressure conditions should also be considered during commissioning.
Related Pump and HVAC VFD Solutions
- VFD for HVAC Applications
- VFD for AHU Applications
- AC Drives & VFD Solutions
- INVT GD200A Series Variable Frequency Drive
- Contact ICS for Pump VFD Selection
Frequently Asked Questions
What is a VFD for secondary pump?
A VFD for secondary pump is a variable frequency drive used to control the speed of a motor connected to a secondary circulation pump.
Can a VFD be used for a chilled-water secondary pump?
Yes. A VFD can be used for a suitable chilled-water secondary pump when the motor, pump and control system are correctly selected for variable-speed operation.
How do I select a VFD for a secondary pump?
Check motor power, rated current, supply voltage, pump type, operating duty, pressure or flow control requirement, and installation environment.
Can a VFD control pump pressure?
A VFD controls motor speed. When combined with a suitable pressure or differential-pressure sensor and controller, pump speed can be adjusted according to system pressure demand.
Can a secondary pump VFD connect to a building automation system?
Many industrial VFDs support analog, digital or communication interfaces. Compatibility should be checked for the selected drive and building automation system.
Where can I get a VFD quotation for a secondary pump?
Contact Integrated Control Solutions with the pump motor nameplate, supply voltage, pump application and control requirements for VFD selection and quotation support.
Request a VFD for Secondary Pump Quotation
For secondary pump VFD selection, pricing or technical assistance, share the motor rating, rated current, supply voltage, pump type and control requirement with Integrated Control Solutions.
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