Water Well Journal
Issue link: https://read.dmtmag.com/i/557876
Although this explosion of electronics offers many advan- tages for us as consumers, I am not as convinced this carries over to their use in most water system applications. Think about it. Most water system control applications in- volve operating areas where the environment is either warm from ambient heat or the heat of motor control, moist from the same ambient conditions, or "varmitized" from the little crit- ters who like to live there. None of these locales is conducive to electronics and the problems that result from the use with these types of controls can often lead to downstream problems with the devices they are designed to control or protect. For that reason, I am careful with using these devices in ordinary water system applications. That's not to say there is never any place or environments in which to use electronic components or devices. I just recommend employing the proper level of caution and appropriate use. 2. Don't be afraid to try some of the new controls By now you probably think I've lost it. I no sooner suggest you keep your control logic and devices simple than I turn around and suggest you broaden your horizons and try out some of the new controls! There is a method to my madness. I'm not saying ignore my previous recommendations and implement the wholesale use of PLCs over conventional relay logic for all your water systems. But I am suggesting you recognize the overabun- dance of newer electronics available that will just about provide whatever logic you need in a compact, relatively low-cost, single device. Remember the old adage about "links in the chain." If you can provide a single device that will provide the same, or better, control than seven control relays, three timers, and the associated wiring, relay bases, and on and on—think how much simpler the revised controls could be. Don't immediately disconnect the simplistic float switches that have been reliably operating a sewage lift station for years and switch the controls over to an ultrasonic level de- vice. But do carefully research the many new and different kinds of electronic, conventional electrical, and even mechan- ical control devices introduced the past few years. One specific item you may consider in future projects is the use of "din-rail" relay mounting. This type of mounting arrangement allows you to pre-assemble a slide rail onto the panel or enclosure and then simply slide relay bases and other similar electrical equipment over the slide as needed. This avoids the need to mount each separate base onto the panel. This can save substantial labor and hassle. Regardless how attractive or cost competitive you may find this alternate method, you should never dive into a wholesale change-out of a control system until you and your customer are totally comfortable with the revisions and understand the advantages and limitations of the new system. You may be surprised. There may now be something available to provide the multiple control functions for that one system you've been waiting for! 3. Protect your submersible motors As I stated last month, in order to maximize their existing facilities and minimize cost, power utilities are finding more and more ways of extending the capability and capacity of their existing power supplies than ever before. This means higher voltage losses, lower power factors, and more voltage and current imbalance will usually occur. As we all know, voltage imbalance can have a significant impact on the performance and life of electric motors, particu- larly submersible motors, and the proper protection of these motors is critical. One of the methods I still use is using fuses over circuit breakers on many motor circuits. In this day and age, most power applications are equipped with circuit break- ers rather than fuses for motor and circuit protection, but I often select fuses over circuit breakers for several reasons. Although you must either keep spare fuses on hand or be able to get some in a hurry, the advantages gained in short- circuit protection can't be beat by using fuses. Many classes of fuses (FRN, FRS, Lo-Peak) are designed to blow quickly during a short-circuit event—preventing damaging levels of high current from passing through the fuse and potentially causing an explosion of the gases that can accumulate when that happens. This can prevent equipment damage, motor failure, and most important, personal harm in many cases. Certainly, I am not advocating using fuses on all applica- tions, but mainly in those installations with highly valued or high-horsepower motors or power supplies with high short- circuit capacity. This may also be a case where you will need to consult with an electrical engineer or the utility for the proper application and design. The second example of providing motor protection is through the use of phase-voltage monitors (PVMs). Loss of a phase on three-phase motors, low voltage, or phase reversal can have a devastating effect on all motors, but especially on three-phase submersible pump motors. All these potential "motor killers" can generally receive adequate protection through the use of a single device equipped with multiple levels of protection. The problems I cited earlier with stretching power supplies to the limit are causing more "single-phasing" and unbalanced power events on three-phase motors than ever before. Adding a PVM to a motor starter, even a retrofit to an existing instal- lation, is a simple and cost effective solution to this problem and one I wholeheartedly endorse as the use of an electronic device offers much more of a benefit than any potential disad- vantage in this case. 4. Protect against lowering or compromised water levels in wells At one time, an incident of a low water level in a well was fairly rare in most wells in our area. The added cost and com- plexity for adding a "low water level cutout" relay was gener- ally not worth the benefit gained or the money spent—not to mention the hassle often experienced from another "link in the chain" with the drop wires and probes. Times, though, have changed and we see more and more examples of pump and motor failure due to much more com- petition to a finite source of groundwater. This is leading to ENGINEERING continues on page 42 WWJ September 2015 41 Twitter @WaterWellJournl