Constant-Speed Constant-Volume Fan and Motor
Understand how the constant-speed constant-volume fan and motor works. Explore component overviews, measurements, and additional resources.
Overview
A constant-speed, constant-volume (CSCV) fan uses a power-driven rotating impeller to circulate air at a single speed. Fans can be either axial or centrifugal.
Types of Constant-Speed Constant-Volume Fans
Explore the types of CSCV fans used in various plants and system configurations. CSCV fans can go by many names depending on the plant and system the are in. Some of the most common types are:
Condenser Fan
Pulls outdoor air through the condenser coils to reject heat from the indoor space. The controlling variable is outdoor air temperature.
Found in the following plants and systems:
Cooling Tower Fan
Pulls or pushes large volumes of outside air through a cooling tower to facilitate evaporation. The controlling variable is Wet-bulb temperature
Found in the following plants and systems:
AHU Supply Fan
Pushes conditioned air into the building’s indoor spaces. The controlling variables can be motor schedule and/or Outdoor air temperature.
Found in the following plants and systems:
AHU Return Fan
Pulls stale air out of conditioned spaces and push it through the return ductwork. The controlling variables can be motor schedule and/or Outdoor air temperature.
Found in the following plants and systems:
Burner Fan
Pulls fresh oxygen into the combustion chamber for the gas burners and safely pushes exhaust gases and carbon monoxide to the outside. The controlling variables can be motor schedule and/or Outdoor air temperature.
Found in the following plants and systems:
- Hot-Water Heating Plant
- Steam Plant
- Domestic Hot Water Plant
How do I…
Quantify Electricity Usage (kWh) of AHU, Condenser and Burner Fans
Select a strategy depending on what can be measured:
Single Speed Fan Energy Using Motor kW
Measure the three-phase power of the fan motor.
How to Measure
Click any measurement below for detailed setup, data collection, and troubleshooting instructions.
Use this technique to measure the hourly three-phase power of the fan motor.
Borrow Equipment and Download Calculator
Reserve loggers, download the calculator, and enter your measured data.
This tool kit includes:
CSCV Fan Motor Energy (kW) Calculator
Provides estimated annual electricity consumption of a supply and return fan that operate at constant-speed, constant-volume using motor kW data.
For more details about the methodology behind this calculator, see Fan Motor Energy Consumption.
Download CalculatordownloadMeasurement Locations
Single Speed Fan Energy Using Motor Runtime
Measure the hourly average runtime of the fan motors and take spot measurements with a handheld power meter of true RMS power while the motors are running.
How to Measure
Click any measurement below for detailed setup, data collection, and troubleshooting instructions.
Use this technique to measure supply and return fan motor true RMS power with a handheld meter while the motor is running.
Use this technique to measure hourly motor runtime of supply and return fan motors.
Borrow Equipment and Download Calculator
Reserve loggers, download the calculator, and enter your measured data.
This tool kit includes:
CSCV Fan Motor Energy (Runtime) Calculator
Provides estimated annual electricity consumption of a single speed fan that operates at constant-speed, constant-volume using motor runtime data.
For more details about the methodology behind this calculator, see Fan Motor Energy Consumption.
Download CalculatordownloadMeasurement Locations
Two-speed Fans using Motor Current
Measure the average hourly current, take spot measurements of current and true RMS power at low and high speeds with a handheld power meter while the motors are running.
How to Measure
Click any measurement below for detailed setup, data collection, and troubleshooting instructions.
Use this technique to measure true RMS power, current, voltage and power factor of supply and return fan motors at high and low speeds.
Use this technique to measure hourly motor current draw of supply and return fan motors.
Borrow Equipment and Download Calculator
Reserve a kit, download the calculator, and enter your measured data.
CSCV Two-speed Fan Motor Energy (Current) Calculator
Provides estimated annual electricity consumption of supply and return fans that operate at constant-speed, constant-volume and have two operating speeds (high and low) using electrical current data.
For more details about the methodology behind this calculator, see Fan Motor Energy Consumption.
Download CalculatordownloadMeasurement Locations
Two-speed Fans using Motor Speed
Measure the hourly fan speed and take spot measurements of true RMS power while the motors are running at low and high speeds.
How to Measure
Click any measurement below for detailed setup, data collection, and troubleshooting instructions.
Use this technique to measure the fan motor true RMS power with a handheld meter.
Motor Speed data from the BAS
If the BAS can trend the motor speed data, download it and resample to hourly intervals.
Borrow Equipment and Download Calculator
Reserve a kit, download the calculator, and enter your measured data.
CSCV Two-speed Fan Motor Energy (Speed) Calculator
Provides estimated annual electricity consumption of constant-speed, constant-volume fans with two operating speeds (high and low) using electrical spot measurements and speed data.
For more details about the methodology behind this calculator, see Fan Motor Energy Consumption.
Download CalculatordownloadMeasurement Locations
Quantify Electricity Usage (kWh) of Cooling Tower (CT) Fans
Select a strategy depending on what can be measured:
Constant One or Two Speed CT Fan Energy using Motor kW
Measure the three-phase power of the fan motor and the outdoor air temperature. This data will be used to understand the relationship between outdoor temperature and fan motor operation.
How to Measure
Click any measurement below for detailed setup, data collection, and troubleshooting instructions.
Use this technique to measure the hourly three-phase power of the fan motor.
Use this technique to measure outdoor air temperature if the fan is weather dependent.
Borrow Equipment and Download Calculator
Reserve loggers, download the calculator, and enter your measured data.
This tool kit includes:
CSCV Fan Motor Energy (kW) Calculator
Provides estimated annual electricity consumption of a cooling tower fan that operates at constant-speed, constant-volume using motor power and OAT data.
For more details about the methodology behind this calculator, see Cooling Tower Fan Energy Consumption.
Download CalculatordownloadMeasurement Locations
Constant Speed CT Fan Energy using Electrical Current
Measure hourly electrical current supplied to the fan motor, instantaneous power, voltage and power factor, and outdoor air temperature with a weatherproof logger if the fan is weather dependent.
How to Measure
Click any measurement below for detailed setup, data collection, and troubleshooting instructions.
Use this technique to take spot measurements of power, voltage and power factor with a handheld power meter.
Use this technique to measure the amperage at one-hour intervals of the fan motor.
Use this technique to measure outdoor air temperature if the fan is weather dependent.
Borrow Equipment and Download Calculator
Reserve a kit, download the calculator, and enter your measured data.
Constant Speed CT Fan Energy (Current) Calculator
Provides estimated annual electricity consumption of a cooling tower fan that operates at constant-speed, constant-volume using electrical current data.
For more details about the methodology behind this calculator, see Cooling Tower Fan Energy Consumption.
Download CalculatordownloadMeasurement Locations
Constant Speed CT Fan Energy using Motor Runtime
Take spot measurement of true RMS power and long-term measurements of the operational schedule of the motor.
How to Measure
Click any measurement below for detailed setup, data collection, and troubleshooting instructions.
Use this technique to take spot measurements of power, voltage and power factor with a handheld power meter.
Use this technique to measure hourly CT fan motor runtime.
Use this technique to measure outdoor air temperature if the fan is weather dependent.
Borrow Equipment and Download Calculator
Reserve a kit, download the calculator, and enter your measured data.
This tool kit includes:
Constant Speed CT Fan Energy (Runtime) Calculator
Provides estimated annual electricity consumption of a cooling tower fan that operates at constant-speed, constant-volume using electrical current and runtime data.
For more details about the methodology behind this calculator, see Cooling Tower Fan Energy Consumption.
Download CalculatordownloadMeasurement Locations
Further Reading
Boyd, BK.; McMordie Stoughton, KL.; Lewis, T. (2017). “Cooling Tower (Evaporative Cooling System) Measurement and Verification Protocol.” Golden, CO: National Renewable Energy Laboratory. https://www.nrel.gov/docs/fy18osti/70219.pdf.
Crowther, H.; Furlong, J. (2004). “Optimizing Chillers and Towers.” ASHRAE Journal, Vol. 46, No. 7, July 2004; pp. 34-40.
Morrison, F. (2014). “Saving Energy with Cooling Towers.” ASHRAE Journal, Vol. 56, No. 2, February 2014; pp. 34-40.
Tom, S. (July 2017). Cat. No. 11-808-616-01. “CHILLED WATER SYSTEM OPTIMIZER.” Farmington, Connecticut: Carrier Corporation.