Water Well Journal

March 2016

Water Well Journal

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No. 2. Improper wire sizing or bad splices You also need to make sure the proper voltage is reaching the motor through good connections, contacts, and proper wire sizing. Submersible motor manufacturers size wire per the recom- mended voltage loss in the U.S. National Electric Code. It's important to follow all state, local, and national electrical requirements and guidelines. For example, Franklin Electric has a 5% loss recommenda- tion in the United States and a 3% loss recommendation in Canada, but that can change based on location. Proper connections, or how the wires are spliced together, also matters to the life of a motor. "It needs to be a good mechanical and electrical connec- tion," Campbell points out. "That means inline connections should be done with proper tooling and proper connectors. Don't use copper tubing and a hammer. Even though it's done, it's not a good connection in all cases." In Smith's experience, wire sizing and connections don't seem to be a major killer of pumps in his area. "We typically take our wire sizing right out of the installa- tion manual, and if you go by those guidelines, you'll never have a problem," he assures. "We also traditionally hand wrap all of our splices, but the way most of the guys are splicing in our area is adequate for what they're doing." No. 3. Poor water flow over the motors Water must move over the entire length of the motor. Be- cause no motor is 100% efficient, it gives off heat. If water doesn't move around the motor, the water next to the motor gets warmer and ultimately cooks the motor. It is the top reason for mechanical failure. "We need to have a moving flow to dissipate the heat, similar to a car engine's radiator," Campbell here makes the comparison. "You've got to have air through a radiator or the car overheats even in the winter." If the water is coming in from the top of the well, it will come down past the pump into the screen. The intake screen of the pump is above the motor, so the water never passes the motor and overheats. The bigger the motor, the more critical this is. "With small motors—½ or ¾ horsepower motors—it seems like there's enough turbulence just from the water going into the intake screen that it keeps the motor cool," Smith says. "If you get into larger motors, it's important to keep the water moving past the motor." When constructing the well, see to it water enters only from below the motor. "You can also add a flow sleeve, which is essentially an upside down tin can if you will," Campbell suggests. "That goes over the motor and pump inlet and forces the water to come from below the motor to get to the intake of the pump." No. 4. Improperly programmed variable frequency drive The second major reason for a mechanical failure is a vari- able frequency drive not ramping the motor up fast enough. "Water-lubricated bearings such as the Mitchell and Kings- bury style the submersible industry uses requires water to be pulled into the bearings," Campbell notes. "So, you must have it at 30 hertz minimum speed within one second." An off-the-shelf aftermarket VFD must be configured to match the submersible application if it's not preprogrammed specifically for that purpose. If it's not up to speed quick enough, it damages the thrust bearings. "For some reason people think the longer the ramp time, the better off they are," Neubecker observes. "But we tell cus- tomers if they're going to provide the VFD, it has to be pro- grammed according to the motor manufacturer's parameters." No. 5. Inadequate tank size or a poorly maintained tank A tank too small for the system or one not properly main- tained will lead to rapid cycling and eventually wear out the motor. "We see systems a lot where the tank is too small," Smith says. "The larger the tank, the less the pump starts and stops. Starting and stopping is bad for every component of the system." In bladder or diaphragm tanks, a ruptured diaphragm or a hole in the bladder will lead to a waterlogged tank, causing rapid cycling. In galvanized tanks, a failure to keep the tank charged is often to blame. "It usually leads to stripping of the spline on the motor shaft from too many starts in the allowable period," is what Neubecker thinks. "Waterlogged tanks aren't as common anymore now that diaphragm tanks are popular, but it was common with old galvanized tanks." No. 6. Pumps set on polyethylene pipe It's a less common reason for failure, but pumps set on polyethylene pipe are a problem Smith encounters often in New Hampshire. The pipe, which doesn't come up in the well straight, ends up bouncing off the side of the well. "When the pump turns on and off, the pipe actually stretches, and when it stretches it bounces around," Smith says. "It takes the wire and rubs it against the well. The wire fails and the pump has to come out." It doesn't often directly lead to failure, but it causes pumps and motors to be replaced before they normally wear out. "If we pull a pump out and there are five or six bad spots in the wire, we don't want to make those repairs because it's bad 28 March 2016 WWJ waterwelljournal.com DACUM Codes To help meet your professional needs, this article covers skills and competencies found in DACUM charts for drillers and pump installers. PI refers to the pumps chart. The letter and number immediately following is the skill on the chart covered by the article. This article covers: PIB-4; PIC-6, 7, 8, 9; PIE-11; PIF-1, 2, 3, 4, 5, 6, 7 More information on DACUM and the charts are available at www.NGWA.org. SUBMERSIBLES from page 27

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