Variable Frequency Drives or VFD's do not save energy!
It is a myth that VFD's save energy. The average person and even many "experts" may think it completely logical that reducing the RPM of a pump also reduces the amount of power used.This is Absolutely False!!
A VFD always causes more energy to be used per gallon produced.
The Cycle Stop Valve or CSV is the newest innovation in pump control technology. The CSV was designed to mimic the constant pressure performance of a Variable Frequency Drive or VFD, also sometimes called a constant pressure pump. The CSV is an upgrade for the problems and side effects associated with VFD controls. The CSV replaces VFD's. The CSV is a simple, inexpensive, long lasting device that provides constant pressure from any pump and saves just as much energy as a VFD, without needing to vary the RPM of the pump.
Even though it is also a myth, many people believe that controlling a pump with a valve is like "driving a car with one foot on the gas and the other on the brake". The average person and also many "experts", think it completely logical that restricting with a valve will make a pump work harder. This is not true. Restricting with a valve actually makes a pumps work easier, and reduces power consumption similar to varying the speed.
These things are counter intuitive. Being just opposite of what our brains want to believe makes it hard to grasp. The fact is that in most applications, there is very little if any difference in energy consumption between a CSV and VFD. A VFD is just trying to trick a pump into something a CSV can make it do naturally.
Does a VFD save energy? Does a CSV make a pump work harder? These questions should be your test to gauge the integrity or intelligence of the pump "expert" you are speaking with. They may not be as much of an "expert" as they think. Or maybe they are purposely using these myth-understandings, to con you into purchasing expensive and short lived VFD's.
Millions, maybe billions are being spent by companies claiming VFD's save energy and advertising VFD's as the greatest things since sliced bread. You should ask yourself, would companies who sell pumps, motors, controls, and energy spend so much advertising something that would make pumps last longer and reduce your electric bill?
I think not!
The CSV is simple, delivers constant pressure, makes pumps last longer, saves money, and saves as much energy as a VFD. There are many articles, curves, equations, pictures and testimonials in this web page that explains the advantages of CSV's over VFD's.