Increasingly, golf courses are turning to pumps controlled by variable frequency drives (VFDs). Using drives, the system matches the pump flow and pressure to the requirements of the irrigation system by electronically changing the pump motor speed to regulate pressure precisely, reducing maintenance requirements and eliminating line surge created by "across the line" motor starts and cycling of pump motors, thereby reducing utility costs.
Golf courses can benefit from this technology, especially when energy costs are high and the course has varied irrigation needs. Irrigation systems equipped with VFDs can reduce energy costs by as much as 50% and substantially reduce maintenance costs. Take, for example, the ELKS Country Club located in Columbus, Nebraska, which until recently was suffering from high operating costs.
The club’s superintendent, John Keller, decided to install a VLT 8000 AQUA VFD pump control package after consulting with Dick Wright of The Sprinkler Company in Stanton, Nebraska.
Initially, the vertical turbine irrigation well pump with a 100 HP motor was started with an "across the line" magnetic starter. The motor then ran full speed, and the pressure was controlled by an expensive and complicated packaged mechanical controller. With widely varying flow rate demands from one zone to another, and water hammer created when switching from one zone to another, John found it difficult to accurately control the system pressure. Spikes in the pressure often caused damage to the piping system and sprinkler heads. Line surges in the system often exceeded 110 PSI, and operating pressures varied from as much as 5 to 10 PSI, resulting in water hammer.
After removing the existing packaged controller and installing a new VLT 8000 AQUA Series drive with an MBS 3000 pressure transducer in the pump discharge piping, things changed immediately. The operating pressure is now back to design and the system requires far less maintenance. Using a slow pressure ramp time after the system is filled has completely eliminated the water hammer. The operating system pressure is now held constant (within 1 PSI), independent of water usage. With the activation of the "Sleep Mode" feature in the VLT 8000 AQUA Series drive, the pump automatically shuts off when no water is used, and restarts automatically when water is required. Line pressure never exceeds the operating design pressure of the irrigation system, reducing the strain on all the components. The system responds to both fairway watering and hose usage with a single pump.
Another positive outcome became immediately evident. By matching the pump flow to the system demand and maintaining a constant pressure, the total energy consumption of the system has been reduced by nearly 50 percent.
The ELKS Country Club was able to reduce its electric bill from over $11,000 per year to less than $5,400, and typical annual piping system breaks from just under 30 down to 5 or 6. According to Dick Wright, if a golf course is billed by the utility using an "Electrical Demand Charge", converting to a VFD Controller will also eliminate the demand charge in most instances.