VFD's were causing me to lose customers. Commercial customers were specifying which VFD and pumps they wanted. I installed the pumps and VFD's as specified. Nuisance trips were a constant problem. Motor bearings would show vibration on the test meters when the VFD controlled the pump. Bearings, seals, and windings were being replaced much too often. Being the only person who qualified to work on VFD's in a company of 20 people, meant I was the one working nights and weekends on nuisance VFD calls. Weekends off became rare and several fishing trips were cancelled. The only time I tried to take a full week off, I had to cut it short and catch the next flight home to fix a *$%#@?x VFD.
Then I find out that as soon as the warranty was over, my customers were calling someone else. Even though the customers were specifying which VFD they wanted and exactly how they were to be installed and programmed, I was taking all the blame for the down time and problems. My customers thought the problems were my fault, because VFD's were the best thing since sliced bread. They went through several contractors after me, as they were all having the same problems. However, once the customer realized the VFD was to blame and not the contractor, they were too embarrassed to call me back and say I was right and they were wrong. Either way I lost a customer for life. It takes many years to gain the trust of customers. It only takes an instant to lose a customer because of the problems with VFD controls. Once you loose a customer they are gone for good.
Installing Across The Line starters and Valves as a backup for the VFD's, saved me many times. These Valves were the most reliable part of the system. I soon realized that the control valves were also reducing the power consumption as much as a VFD. Valves actually gave more precise control of the pressure, and did not have any of the negative side effects of a VFD. I began replacing VFD's with valves in 1993, and have been doing so ever since. Most of those first Valve systems I installed in 1993 and 94 are still running, and have had little to no maintenance to date. My reputation for installing dependable, long lasting pump systems has been restored, but I had to stop using VFD's altogether to accomplish this.
The next thing I have against VFD's is that companies are now using them to design in their "planned obsolescence". It took me several years to discover this. Several of the major pump manufacturers ask to test Cycle Stop Valves in 1993. I sent several CSV's to test, and even spent several days with company engineers around their test facilities. I answered their questions and they tested my theories about minimum cooling flows, recirculation, cavitation, radial deflection, friction loss, and many other things. I did not know all the answers back then, but they were still unable to stump me. However, I could never get them to purchase a valve or even give me an explanation as to why. Several years later an ex-employee of one of these companies contacted me. I was shocked when I found out why manufacturers had no interest in Cycle Stop Valves. The quote was; "This "company" has tested Cycle Stop Valves. Cycle Stop Valves make pumps and motors last longer, and use smaller pressure tanks. This company MAKES pumps and pressure tanks so, anyone who mentions a Cycle Stop Valve will be terminated immediately."
I have been angry about this since. I always thought that if you "have a better mousetrap, people would beat a path to your door." I never realized that if you have a mousetrap that will make mice extinct, people who sell mousetraps will do everything they can to discredit you. I always knew that it only took 5 cents extra to make a forever light bulb, and that light bulbs were purposely made to last a short time. I now realize that automobiles, appliances, electronics, and almost every other product produced, is being designed to fail in a short amount of time, when it would only cost a nickel more to make it last forever. "Planned obsolescence" is an enormous waste of energy, and a huge burden on the end user. Planned obsolescence" may well be the biggest cause of greenhouse warming and melting of the polar ice caps.
Pumping slurry, hot water, hydrocarbons, peanut butter, or just about anything except cool, clean, water, is usually a good place for a VFD. A Cycle Stop Valve is only superior to a VFD when pumping cool water at a constant pressure. However, there are millions of installations in this category, and that is why manufacturers are pushing VFD's, not because they are actually the best choice for the application.
VFD's are job security for those who work on them all the time, as well as for the manufacturer of VFD's, pumps, and motors. For the installer of fresh water pumps and controls, a VFD is a good way to lose customers and ruin his reputation. For the clueless end user, the "bait" of saving energy with a VFD is alluring. This will hook them into a repetitive cycle of spending their hard earned cash to replace expensive equipment on a regular basis. A CSV would have cost less and reduced energy consumption comparably. Cycle Stop Valves have been proven to make pump systems last many times longer, which can conserve more energy than making the electric meter spin a little slower.
There are many applications where a VFD is a good choice and really does save energy. However, there are just as many applications where the VFD causes more problems than it is worth.
There is a delicate balance between "Moore's Law", which is the advantages of computing power doubling every 18 months, and the principal of "Occam's Razor", which suggest that the simplest solution is the best solution. We need to take advantage of electronic technology when it is helpful, but not at the expense of eliminating simpler methods that would serve us better.