These old Fats Domino lyrics, written for a love song, are apropos for the groundwater industry, especially in this era of changing weather patterns and dropping water tables. A well that once produced 10 gpm on a continuous basis may now pump dry at that flow rate. What are you gonna do? The first thing you’re gonna do is to make sure the well pump is protected from damage that will occur if it runs dry. The protection method depends on whether you have a jet pump or submersible.
Jet pumps can be protected in several ways. A passive method is to install a 25-foot suction tube below the jet assembly. Since a jet pump cannot lift water that far, the pump produces water until the pumping level drops to the point where the weight of water in the suction tube exceeds the lifting capability of the pump and it simply circulates water through the jet assembly. This will heat up the water in the pump so it’s a good idea to put a max run timer that starts when the pump turns on and turns the pump off after so many minutes. This technique is limited to wells that are deep enough to accept a 25-foot suction tube.
A more active jet pump protection technique involves the use of probes down in the well that sense the level of the water. They turn the pump off when the pumping level drops to a minimum safe level and turn it back on when the well recovers to a high enough level to allow the pump to run for at least one minute. The one-minute minimum run time is to let the pump motor cool down between starts.
The use of probes in the well requires a special piece of electronics that measures the conductivity between the level sensing probe and the well casing, or reference probe in the case of plastic well casing. When the lower-level sensing probe is in the water, the liquid-level sensing device closes relay contacts that are wired in series with the pressure switch and, if the pressure switch is calling for water, the pump runs.
Once the pumping level drops below the lower probe, the contacts in the device open up and, regardless of the pressure switch condition, the pump shuts off. When the pumping level again reaches the upper probe, the liquid level control closes its contacts and, if the pressure switch is still calling for water, the pump turns back on.
There are two companies that make the liquid-level controls most commonly used in the groundwater industry in the U.S.—SymCom and Warrick. The devices are very similar in function and appearance. They both use an eight-pin octagonal socket and are pin-for-pin interchangeable. The SymCom unit is Model PC-200-LLC-GM where the Xs represent the operating voltage. They can be set for pump-down or pump-up applications, and the sensitivity is adjustable for varying well water conductivity, sort of a one-size-fits-all device. The only choice you have is the operating voltage.
The Warrick unit is model 16M and it comes in many different configurations, each one having a separate model number. For well applications, look for the direct or pump-down configuration with 10K sensitivity and whatever operating voltage you need.
With submersible pumps, you have more options. Liquid-level controls with probes can be used, but they require more maintenance than the newer load-monitoring dry well protection devices. The science behind these devices is that it takes more horsepower to spin an impeller that is pumping water than one that is not moving water. Here again, there are two dominant players in the field, Franklin Electric and SymCom.
Franklin Electric has a line of products for single-phase pump motors called Pumptec and for three-phase pump motors called Submonitor. Both monitor voltage and current, and use a power-factor algorithm to turn the pump off when it stops pumping water. The single-phase units are available in three sizes: Pumptec QD, which goes from 1⁄3 to 1 horsepower and fits inside of the control box; Pumptec, which goes from 1⁄3 to 1.5 horsepower and is in a 3R enclosure; and Pumptec Plus, which has a horsepower range from to 5 and is also in a 3R enclosure.
SymCom’s pump savers are called PumpSavers. They work on a similar principal to Franklin, but use horsepower verses power factor to determine when to turn to pump off. Their smallest single-phase unit is the 231 Insider which, like the QD, fits inside the control box and goes from 1⁄3 to 1 horsepower. Their next one is the 233P PumpSaver and it goes from 1⁄3 to 3 horsepower. It is available with or without a 3R enclosure. The largest single-phase unit is the 235P PumpSaver, which protects single-phase pump motors from 5 to 15 horsepower.
SymCom’s three-phase pump motor protectors are the PumpSaver 777-KW-HP-P2. The engineers obviously came up with that model number. It handles any motor up to 700 horsepower. They also make a model called MotorSaver 777-P2, which is similar to the KW-HP above but measures the load with amps instead of horsepower. Most contractors report that it works just fine on most pumping applications.
With either jet pumps or submersibles, it makes sense to throttle back the pump output as the well performance falls off to more closely match the performance of the pump with that of the well. This is done by restricting the outlet so that the system operates more toward the left side of the pump curve. Be mindful of not straying too far from the sweet spot of the pump where efficiency is highest.
Properly managed, low-yield wells can provide years of service to their owners.
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Protect Your Pump for When a Well Runs Dry
June 7, 2013