One of the most significant changes is the use of advanced pump controllers that monitor the water pressure and adjust the pump speed to exactly match the water demand. While the pumps have changed very little, the pump controllers and control methodology has changed significantly. These new pump controllers are referred to as VFD’s (variable frequency drives) or constant pressure controllers.
In the traditional method of operation, pumps worked in conjunction with a large pressure tank and a pressure switch. The pressure tank held a significant volume of captive air and the pump is turned on forcing air into the tank. As air and water fill the tank, the pressure of both the air and water increase. When the pressure is high enough, the submersible well pump is turned off. As water is used the pressure decreases and the water is exhausted from the pressure tank with the compressed air forcing it out, when the pressure drops to a preset level in the pressure switch, power to the pump is turned on and it runs at full speed until the pressure tank is refilled and then the pump is turned off.
umps that operate in the traditional method require large pressure tanks or expensive valves to keep the pump from starting/running full speed and then shutting off in quick succession. Starting/stopping rapidly generates a lot of heat in the motor and too much of this can cause pump motor failure. This rapid cycling can also cause damage to piping and other equipment as pressures and water flow change very quickly. Because VFD’s carefully increase or decrease the pump speed to match your demand, rapid cycling is a thing of the past with a VFD controller. Because it is unlikely that you need all the water your submersible well pump can produce, using a VFD controller means that your well pump will NOT be running at full speed when you are using water. These slower speeds translate into less wear and tear on the pump and motor. Less wear and tear means longer pump/motor life!
VFD controllers are constantly monitoring the pressure and adjusting pump speed and only a small pressure tank to act as a buffer is needed. This means that the expense and space required for large pressure tanks is no longer required!
Using a VFD designed for a 3 phase pump motor means that smaller wire sizes are suitable for running the motor than an equivalent single phase pump motor. High quality copper wire is expensive and the savings in wire can add up quickly! 3 phase motors are typically considered by most industries to be simpler and more reliable than their single phase counterparts. At OPS we love solutions where installation cost savings and increases in reliability are both possible!
VFD’s designed for use with water pumps integrate advanced features. Automatic shutdown/feedback on dry well conditions, problems with the pressure tank, or pressure sensor are just a few of the standard features in today’s advanced pump controller. With the traditional pumping method, protection from rapid cycling or dry wells requires additional components and careful calibration.
One interesting advantage of constant pressure controllers/VFD’s is that they are solid state electrical devices. This means that they don’t have any open electrical contacts or switches. In the traditional system, the pressure switch is a key failure point. The electrical contacts corrode with moisture or are subject to insects crawling in them. Because the VFD systems don’t have this weak link, they are not prone to these failures!
Many customers in rural areas struggle with poor power quality with low voltages and other issues. Variable frequency drives/constant pressure controllers are essentially taking all the AC power from the utility, converting it to high voltage DC power and then re-inverting the power at the correct voltage/frequency the pump needs. What this means in layman’s terms is that your expensive pump deep in your well is going to see clean power, even if the utility is giving poor quality power. Keep in mind that VFD’s can correct minor power issues, but major power issues should be addressed by working with your utility.
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