Water Well Journal
Issue link: https://read.dmtmag.com/i/557876
in both small and large pump motors, your control systems should be tailored to provide the control functions unique to both classes. This means you should use full three-phase pro- tection for all three-phase motors, quick-trip thermal over- loads on all motor circuits (Class 10 for submersible motors), and the proper short-circuit protection, whether fuses or the appropriate circuit breakers. 8. Consider the use of backup controls or systems One thing I have learned over these past 40 years is no matter how precise and exacting you set out to design and construct a control system, someday something in that system will fail or malfunction. Depending on the system involved (and only the designer or owner can truly make this call), you either need to allow the overall system to safely shut down (sometimes progres- sively) until repaired or provide some method of backup (supplementary or second tier control system) to assume the control function from the primary control system until the problem has been corrected. Case in point: one water system I have been involved with since 1979 provides water to almost 40,000 people from a series of 15 wells and two booster pump stations. This water system operates through the use of a reliable and sophisticated supervisory control and data acquisition (SCADA) system. As the title implies, this SCADA system has two basic functions: (1) provide and receive supervisory control over the entire water system, and (2) transmit, receive, and process incoming data in the form of flow, pressure, and well and pump status points, both from and to each remote site, and then store this data for future reference. During the design of this system, the client, vendor, and I examined all the potential types of failure that could happen. The system has various ways of collecting, receiving, and in- terrogating the separate control and data points and then trans- mitting all of them from each remote site to the master panel where this information is then added to the information from the other sites and stored for future use. This is now the fourth generation of a SCADA system we have developed for this single client since the first one was activated in 1982, and each progressive system has been more reliable and with more capability and functions than the one it replaced. What we have never changed, though, was the need for an adequate type of system, a backup. For, no matter how reliable the systems were, in order to keep water flowing into homes, there had to be some method (sometimes more than one) of backup control. This doesn't mean the water system had to function in the same exact manner during a control sys- tem glitch, we just needed to keep the water flowing until a correction was made. As of today, there are two computers that provide the oper- ating parameters for the water system. One is the principal unit and the other unit serves as an online "hot" backup com- puter available to assume the functions of the primary unit should any problems occur. Behind the two computers the system is also designed to enable operation of each of the re- mote sites should failure happen with data transmission or a complete disruption of the main system. 9. Know and understand your codes Beyond all of these suggestions, new methods of control, or more refined data collection methods I discuss in this arti- cle, many of the local, state, or federal electrical codes may limit or ban the use of certain control devices or applications, particularly those used for power protection, monitoring, or control applications intended to protect or control motor cir- cuits. They may not be rated for the intended use, amperage, voltage, phase, wire size or type, or operating temperature you wish to apply the device for. It is important to always consider this aspect and verify any intended new device you wish to implement into an electrical system—whether as a new device or a retrofit—complies with the applicable codes before you install it. Beyond the applicable code considerations is the need to verify the way you wish to apply and install the component or system fully complies with the manufacturer's recommenda- tions and code limits. A second potential issue may necessitate assembly of con- trol panels only by shops with an industrial label. A third problem often seen involves the sole use of electrical equip- ment that has been examined and certified by an approved "testing laboratory." Typically, there are three testing labs rec- ognized throughout the United States: Underwriters Laborato- ries (UL), Electrical Testing Laboratories (ETL), and the Canadian Standards Association (CSA). Another concern you should always monitor is the applica- tion of conductors or devices to the proper operating tempera- ture. For example, the application of a 90ºC rated conductor must be limited to a 60ºC operating temperature when con- nected to a 60ºC terminal. This is a critical National Electrical Code limitation that is often ignored in practice, but is a favorite for inspectors to find. There are also numerous other trip-ups you must be wary of. Know the code. 10. Do things the way you should Each one of you has the ability to accept or deny any of my suggestions. It's up to you, but the process never starts if you don't start it. The next task each of you can also perform is the need to do things the way they should be done. This means to investi- gate the new and improved methods of motor and system control, protection, and data collection and to use these techniques for the ultimate betterment of your customer. You should perform this duty in a progressive and deliber- ate manner. Make sure all improvements or changes made to your control system are proper and justified. Don't make wholesale modifications simply because you'll make an extra dollar on the next installation. Verify all new methods and changes you enact are the right thing to do and will ultimately increase the life or reliability of a component or the entire water system. Lastly, much of the new technology in today's controls and systems is elaborate and complex, even for those who work with it daily. Don't get in over your head or be afraid to admit you may not understand the proper equipment to use or where ENGINEERING from page 42 waterwelljournal.com 44 September 2015 WWJ