Most small pump motors now have a thermal overload built into the motor. These overloads will trip the motor off when it is pulling too many amps and overheats. Then after a few minutes for the motor to cool down, these overloads automatically reset themselves and try to start the pump again. Most people will notice that they are out of water for a few minutes then the water just magically comes on again. If something is not done to remedy the overload situation, the overload will continue to trip and reset itself until the motor is destroyed. When this happens the water no longer magically comes on again, and the motor must be replaced.
Overloads for larger motors are usually in the control panel, not the motor. These should be set for manual reset only. Many of these electronic overloads also protest against lose of phase. Any overload device will not trip off the motor until an overload condition exist, which is usually too late to prevent damage. Class 20 overloads are for above ground type motors, and will trip when an overload condition persist for 20 seconds. Class 10 overloads are for submersible motors, and will trip within 10 seconds.
Overloads are really to protect the electrical system from a shorted or overloaded motor. Thermal overloads are not good pump motor protection devices. By the time a thermal overload trips, damage has already occurred.
Lack of flow, rapid cycling, or voltage problems are usually the cause of pump failures. Shutting the pump off when one of these problems occur, will prevent the motor from ever seeing overheat or overload conditions.
The Cycle Sensor as seen above in Figure #1 was designed to look for reduced amperage that happens during a lack of flow condition. The Cycle Sensor will also look for length of time the pump runs each time it comes on. If the pump rapid doesn't run the prescribed length of time, of if the amperage is low enough to indicate a dry well condition, the Cycle Sensor will trip off the motor.
During normal operation, the Cycle Sensor displays the running amperage. If the Cycle Sensor trips off the motor for a rapid cycle condition, the Cycle Sensor will display the letters RCYC, which stands for Rapid Cycle. The pump will not restart until someone manually pushes the reset button or turns the power off and back on. This way the operator is made aware of the rapid cycle problem before damage occurs. The Cycle Sensor will not allow the pump to operate, until the problem that caused the rapid cycle condition is resolved.
If the Cycle Sensor trips off the motor because of low amperage, it will display DRY, which stands for Dry Run Condition. The Dry Run feature of the Cycle Sensor can be set for manual reset, or to restart automatically after a time delay of 1 to 300 minutes. If the pump is boosting city water pressure, pumping from a lake, stream, pond, or cistern, a manual reset is recommended. Water supply to the pump must be restored before the Cycle Sensor will allow the pump to operate. If the pump is in a well, then the timed automatic reset can be used. The Restart Delay needs to be set long enough to allow the well to recover. When there has been enough time for the water in the well to be restored, the Cycle Sensor will automatically restart the pump.
Most standard induction motors are fairly robust. Most motors will not be damaged with voltage fluctuations of plus or minus 10%. Even a considerable amount of phase unbalance will not harm a motor. If there is sufficient voltage to start the motor, the motor will usually continue to operate perfectly well. Many times it is better to let the motor run with slight discrepancies is these parameters, rather than shut the motor off and let the customer be out of water.
Overloads are already built into smaller motors. Larger motors have electronic overloads in the control that usually protect from phase loss as well. Dry running and rapid cycling will cause considerable damage to the pump or motor. Therefore, the Cycle Sensor protects from rapid cycle and dry run conditions, and will shut the pump down long before damage or an overload condition exist.
The Cycle Sensor will work with most any motor, above ground or submersible, single phase or three phase. However, the Cycle Sensor was specifically designed to work in concert with a Cycle Stop Valve or CSV. As the flow rate is reduced, and the CSV restricts the flow from the pump, the amperage can be reduced by as much as 50%. Many other pump and motor protectors see a slight drop in amps as a dry run condition. Others are preset to trip off the motor when there is a 25% decrease in amps. Many pump and motor protectors will see the amperage reducing ability of the CSV as a dry run condition, and shut the pump off. The Cycle Sensor allows you to see that the CSV causes the amperage to drop from 20 amps to 10 amps at low flow. The Dry Run feature can then be set to trip at 9 amps. This allows the Cycle Sensor to know the difference between a low flow and no flow condition.
Other Pump Motor Protection Devices
There are numerous pump motor protection devices on the market. Some of these devices are very simple and only look at one or two parameters. They may only look at under load, phase loss, or voltage problems. Other devices are very complicated and look at numerous parameters. These devices may look for under load, over load, under voltage, over voltage, false starts, unbalance phases, loss of phase, phase reversal, over heat, and many other things. Nuisance trips are common with complicated devices that look at multiple parameters. There can be a fine line between good pump protection and nuisance trips that make a customer angry.
Coyote or Pumptec
Pump Motor protection devices that do not have a fully adjustable under load, such as the Coyote or PumpTec will not work with a Cycle Stop Valve. The way some pump and motor devices handle a rapid cycle condition can also be detrimental.
Sym-Com Motor Saver
Some devices such as the Sym-Com 777 look at multiple parameters. Detecting a rapid cycle condition, these devices time out for a programmed amount of time, and restart the motor. After timing out, these devices will restart the motor and allow it to rapid cycle again. This process can continue until something is destroyed and an overload trips, before anyone is made aware of the problem.
Franklin Sub Monitor
Some devices such as the Franklin Sub Monitor also look at multiple parameters. I have found these devices are not fast enough to catch a chattering relay or rapid cycle condition. They are usually set to allow multiple rapid cycle events before they trip the motor off. When it takes multiple cycles before the Sub Monitor sees a rapid cycle event, after which it takes several of these rapid cycle events before the motor is tripped off, considerable damage to the pump and motor has already occurred. I have seen several instances where the pump came unscrewed and fell into the well, and the history in the Sub Monitor only showed 10 rapid cycle events. Apparently the Sub Monitor is not catching a chattering relay or bouncing pressure switch, as it takes many more than 10 rapid cycle events to unscrew a pump from the drop pipe.
The Cycle Sensor has a completely adjustable under load. It is fast enough to catch a chattering relay or bouncing pressure switch. Last of all it does not look at numerous other parameters that only cause nuisance trips. The Cycle Sensor protects the pump from what it really needs protection from, while not causing nuisance trips that irritate the installer and the customer.