By Bob Lilland, Franklin Electric’s Field Service Engineer
As the importance of high efficiency operation continues to grow in the water well industry, so does the popularity of Variable Frequency Drives (VFDs). VFDs are often used in commercial, irrigation, agricultural, industrial, and municipal industries. Users of larger horsepower submersible pumping systems have switched from magnetic starters to VFDs due to better efficiency ratings, easier starts on the motor, and protection built into the drives. Yet, today’s VFDs are designed for more than just commercial applications; they can also provide incredible benefits for low-horsepower jobs, including those in residential or light commercial settings.
As Technology Advances, So Do VFDs
VFD technology continues to evolve to offer more functionality. There are options for adding devices to the drives that help the system’s overall operation. Multi-pump lead/lag and alternation, starting a magnetic starter for a smaller jockey pump, protection devices, and even offsite Programmable Logic Controllers (PLCs) or a Building Management System (BMS) can be operated by VFDs. These options can overcome unique challenges that owners and operators face.
For example, consider a golf course in the Tampa area with a pumping solution for their water delivery needs. Golf courses tend to use a lot of water, and this facility was close to the Gulf of Mexico, where water levels can rise and fall with the changing of the tides. To prevent damage to the system from overheating during run time in a low tide condition, we installed a 40hp VFD with a submersible pump. It included a flow switch and PT100 temperature sensor to protect the system in case of dry-run conditions.
VFDs in Agriculture
Some consider VFDs only when installing submersible pumps. However, VFDs can also be used on straight centrifugal pumps, vertical booster pumps and line shaft turbines. This usage is growing in popularity in agricultural settings due to the efficient operation VFDs provide. With line shaft turbines being the primary source of water production, farmers see the value of soft starts to help protect the pump and increase the system’s life. If the water demand declines from one zone to another, the pump’s speed is also reduced. The lower the RPM, the lower the power consumption required to operate the motor. And with built-in pump protection, the first time the drive goes into a fault condition due to an issue like underload or overvoltage, the upgrade to a VFD has paid for itself.
VFDs in Residential Applications
VFDs are gaining popularity in the residential market since they can be used with a jet pump or self-priming centrifugal pump – applications previously considered incompatible with VFDs. In these situations, homeowners get a high-performing solution to overcome water pressure issues.
Combining a jet pump with a VFD may seem like combining the old with the new. Many of us have moved away from installing jet pumps because submersible pumps can produce more water volume at higher pressures. Yet, when you pair a jet pump with a VFD, you can benefit from faster installation – and your customers get the constant water pressure they’re seeking.
A typical 1hp submersible pump replacement takes an average of two hours to complete. A 1hp shallow well jet pump can be changed in half that time. I’ve timed myself on wiring in a VFD to a jet pump and it took me only 15 minutes to have the system running. So, adding a VFD doesn’t require a lot more time – but it can increase your profits by adding a premium product to the system.
Recently I worked with a pump installer to add a popular, 2-wire VFD solution to a 1hp shallow well jet pump. I couldn’t get over how smoothly the pump motor ran. The noise level was lower than normal. The motor RPMs increased as demand went up and lowered as demand went down, just like a submersible pump. The homeowner couldn’t believe she hadn’t dealt with the low pressure from a 20/40 pressure setting. In fact, we set the pressure to 50 psi since a new pump was installed in place of the old worn-out jet pump. The pressure tank was also changed out. The price difference from a larger 44-gallon to a smaller 20-gallon tank helped offset some of the cost of the VFD as well. The contractor left the site maximizing his profit and quickly moving to the next job site.
A submersible pump usually feeds homes with cisterns or open-air aerator tanks, then a jet pump is installed to pump out of the tank and into the home. This is another excellent way to offer the homeowner a constant pressure system with built-in pump protection.
VFDs in Residential Irrigation
A self-priming centrifugal irrigation pump is another opportunity to offer a VFD. We have all been to a residence that utilizes a self-priming pump to irrigate the lawn. These pumps are started via a pump start relay and run continuously while the irrigation clock calls for water demand. Other times they are operated with a pressure tank. Either way, a VFD can offer great control. There are high-volume zones with rotor heads, medium-volume zones with pop-up sprayers, and low-volume zones with drip lines. These are all perfect scenarios for utilizing a VFD. Rapid cycling or heat is the number one cause of failure. Installing a VFD will fix the issue of rapid cycling, lower the speed of the motor, and allow the system to operate more efficiently – giving greater overall life to the pumping system.
Generate More Sales with VFDs
More manufacturers are delivering versatile, easy-to-use VFD platforms that help cover a wide array of applications for submersible and surface pumps. As technology continues to evolve, so do the capabilities of VFDs. Bluetooth, app connectivity and other features are all becoming available, creating more versatility with the units.
So put the jet and centrifugal pumps back in your line-up as an offering to your customers. It’s never been easier to convert an existing or new pumping system to constant pressure. It’s also never been a better time to offer your customers a premium product – and add to your bottom line.
As featured in the Florida Driller Article: Boost Your Bottom Line with the Versatility of VFDs: They’re not just for submersible commercial applications
Bob Lilland is a third generation, licensed water well drilling contractor. No stranger to the business, Bob's grandfather started a well drilling company in Florida in the early 1950's. This business is now owned by Bob's parents. Since the age of 18, Bob has worked full time in the family business, later branching off to start his own well drilling and pump company. Bob has been on the board of directors for a local well drilling association and currently sits on the board of directors for the Florida Groundwater Association.