Case study 4: Variable speed drives on heating, ventilating, air conditioning {HVAC) system pumps
Case study summary
Large energy savings were achieved by fitting VFDs on pumps previously allowed to run uncontrolled at their maximum flow, saving pumping cost and heating energy.
Other potential applications
Heating and air conditioning systems which see varying heating load, i.e. almost all of them.
Savings achieved
Installation and operation details
Variable frequency drives have been fitted on the pumps for chilled, hot and condenser water and also medium pressure water for the boiler room. The installation was at a large, international private bank in London. One 4 kW, one 22 kW and two 75 kW drives were retrofitted.
Sensors in the pipework, connected to the drives, regulate the speed of the pumps to ensure optimum usage of the water’s energy content. The system is coordinated with the building management system, enabling easy control of the indoor climate.
The pumps are now running at the speed needed by the process. This is generally about 40% of the maximum speed, at which the pumps previously ran continuously. Before fitting the VFDs, water would be pumped out at 40°C and return with no temperature drop. Now the return is 32°C. The overall energy saving in gas and electricity in this case is reported to be 90%. The lower pump speed is also reducing pump maintenance cost.