Abstract:
Some embodiments of the invention provide a pumping system for at least one aquatic application. The pumping system includes a pump, a motor coupled to the pump, a user interface associated with the pump designed to receive input instructions from a user, and a controller in communication with the motor. The controller determines a power parameter associated with the motor and compares the power parameter to a predetermined threshold value. The controller triggers a safety vacuum release system based on the comparison of the power parameter and the threshold value.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 13/350,167 filed on Jan. 13, 2012, which is a divisional of U.S. application Ser. No. 12/572,774 filed on Oct. 2, 2009, which claims priority under 35 U.S.C. §119 to U.S. Provisional Patent Application No. 61/102,935 filed on Oct. 6, 2008, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Pool pumps are used to move water in one or more aquatic applications, such as pools, spas, and water features. The aquatic applications include one or more water inlets and one or more water outlets. The water outlets are connected to an inlet of the pool pump. The pool pump generally propels the water though a filter and back into the aquatic applications though the water inlets. For large pools, the pool pump must provide high flow rates in order to effectively filter the entire volume of pool water. These high flow rates can result in high velocities in the piping system connecting the water outlets and the pool pump. If a portion of the piping system is obstructed or blocked, this can result in a high suction force near the water outlets of the aquatic applications. As a result, foreign objects can be trapped against the water outlets, which are often covered by grates in the bottom or sides of the pool. Systems have been developed to try to quickly shut down the pool pump when a foreign object is obstructing the water outlets of the aquatic applications. However, these systems often result in nuisance tripping (i.e., the pool pump is shut down too often when there are no actual obstructions). 
       SUMMARY 
       [0003]    Some embodiments of the invention provide a pumping system for at least one aquatic application. The pumping system includes a pump, a motor coupled to the pump, a user interface associated with the pump designed to receive input instructions from a user, and a controller in communication with the motor. The controller determines a power parameter associated with the motor and compares the power parameter to a predetermined threshold value. The controller triggers a safety vacuum release system based on the comparison of the power parameter and the threshold value. 
         [0004]    Some embodiments of the invention provide a safety vacuum release system for at least one aquatic application. The safety vacuum release system includes a pump including an inlet, a motor coupled to the pump, and a controller in communication with the motor. The controller is designed to detect if an obstruction is present in the inlet based on at least one measurement related to the power consumption of the motor. 
         [0005]    Other embodiments of the invention provide a safety vacuum release system for at least one aquatic application. The safety vacuum release system comprises a pump including an inlet, a motor coupled to the pump, a detached controller designed to operate the pump, and an on-board controller in communication with the motor. The on-board controller is designed to detect if an obstruction is present in the inlet based only on at least one measurement related to the power consumption of the motor defining a power consumption value. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view of a pool pump according to one embodiment of the invention; 
           [0007]      FIG. 2  is an exploded perspective view of the pool pump of  FIG. 1 ; 
           [0008]      FIG. 3A  is a front view of an on-board controller according to one embodiment of the invention; 
           [0009]      FIG. 3B  is a perspective view of an external controller according to one embodiment, of the invention; 
           [0010]      FIG. 4  is a flow chart of settings of the on-board controller of  FIG. 3A  and/or the external controller of  FIG. 3B  according to one embodiment of the invention; 
           [0011]      FIG. 5A  is a graph of an absolute power variation of the pool pump when a clogged suction pipe occurs at a certain time; 
           [0012]      FIG. 5B  is a graph of a relative power variation of the pool pump when a clogged suction pipe or water outlet occurs at a certain time; 
           [0013]      FIG. 5C  is a graph of a relative counter for the relative power variation of  FIG. 5B ; 
           [0014]      FIG. 6  is a graph of a power consumption versus the speed of the pool pump according to one embodiment of the invention; and 
           [0015]      FIG. 7  is a schematic illustration of a pool system with a person blocking a water outlet of the pool. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
         [0017]    The following discussion is presented to enable a person skilled in the art to make and use embodiments of the invention. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein can be applied to other embodiments and applications without departing from embodiments of the invention. Thus, embodiments of the invention are not intended to be limited to embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the invention. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of embodiments of the invention. 
         [0018]      FIG. 1  illustrates a pool pump  10  according to one embodiment of the invention. The pool pump  10  can be used for any suitable aquatic application, such as pools, spas, and water features. The pool pump  10  can include a housing  12 , a motor  14 , and an on-board controller  16 . In some embodiments, the motor  14  can be a variable speed motor. In one embodiment, the motor  14  can be driven at four or more different speeds. The housing  12  can include an inlet  18 , an outlet  20 , a basket  22 , a lid  24 , and a stand  26 . The stand  26  can support the motor  14  and can be used to mount the pool pump  10  on a suitable surface (not shown). 
         [0019]    In some embodiments, the on-board controller  16  can be enclosed in a case  28 . The case  28  can include a field wiring compartment  30  and a cover  32 . The cover  32  can be opened and closed to allow access to the on-board controller  16  and protect it from moisture, dust, and other environmental influences. The case  28  can be mounted on the motor  14 . In some embodiments, the field wiring compartment  30  can include a power supply to provide power to the motor  14  and the on-board controller  16 . 
         [0020]      FIG. 2  illustrates the internal components of the pool pump  10  according to one embodiment of the invention. The pool pump  10  can include seal plate  34 , an impeller  36 , a gasket  38 , a diffuser  40 , and a strainer  42 . The strainer  42  can be inserted into the basket  22  and can be secured by the lid  24 . In some embodiments, the lid  24  can include a cap  44 , an O-ring  46 , and a nut  48 . The cap  44  and the O-ring  46  can be coupled to the basket  22  by screwing the nut  48  onto the basket  22 . The O-ring  46  can seal the connection between the basket  22  and the lid  24 . An inlet  52  of the diffuser  40  can be fluidly sealed to the basket  22  with a seal  50 . In some embodiments, the diffuser  40  can enclose the impeller  36 . An outlet  54  of the diffuser  40  can be fluidly sealed to the seal plate  34 . The seal plate  34  can be sealed to the housing  12  with the gasket  38 . The motor  14  can include a shaft  56 , which can be coupled to the impeller  36 . The motor  14  can rotate the impeller  36 , drawing fluid from the inlet  18  through the strainer  42  and the diffuser  40  to the outlet  20 . 
         [0021]    In some embodiments, the motor  14  can include a coupling  58  to connect to the on-board controller  16 . In some embodiments, the on-board controller  16  can automatically operate the pool pump  10  according to at least one schedule. If two or more schedules are programmed into the on-board controller  16 , the schedule running the pool pump  10  at the highest speed can have priority over the remaining schedules. In some embodiments, the on-board controller  16  can allow a manual operation of the pool pump  10 . If the pool pump  10  is manually operated and is overlapping a scheduled run, the scheduled run can have priority over the manual operation independent of the speed of the pool pump  10 . In some embodiments, the on-board controller  16  can include a manual override. The manual override can interrupt the scheduled and/or manual operation of the pool pump  10  to allow for, e.g., cleaning and maintenance procedures. In some embodiments, the on-board controller  16  can monitor the operation of the pool pump  10  and can indicate abnormal conditions of the pool pump  10 . 
         [0022]      FIG. 3A  illustrates a user interface  60  for the on-board controller  16  according to one embodiment of the invention. The user interface  60  can include a display  62 , at least one speed button  64 , navigation buttons  66 , a start-stop button  68 , a reset button  70 , a manual override button  72 , and a “quick clean” button  74 . The manual override button  72  can also be called “time out” button. In some embodiments, the navigation buttons  66  can include a menu button  76 , a select button  78 , an escape button  80 , an up-arrow button  82 , a down-arrow button  84 , a left-arrow button  86 , a right-arrow button  88 , and an enter button  90 . The navigation buttons  66  and the speed buttons  64  can be used to program a schedule into the on-board controller  16 . In some embodiments, the display  62  can include a lower section  92  to display information about a parameter and an upper section  94  to display a value associated with that parameter. In some embodiments, the user interface  60  can include light emitting diodes (LEDs)  96  to indicate normal operation and/or a detected error of the pool pump  10 . 
         [0023]    The on-board controller  16  operates the motor  14  to provide a safety vacuum release system (SVRS) for the aquatic applications. If the on-board controller  16  detects an obstructed inlet  18 , the on-board controller  16  can quickly shutdown the pool pump  10 . In some embodiments, the on-board controller  16  can detect the obstructed inlet  18  based only on measurements and calculations related to the power consumption of the motor  14  (e.g., the power needed to rotate the motor shaft  56 ). In some embodiments, the on-board controller  16  can detect the obstructed inlet  18  without any additional inputs (e.g., without pressure, flow rate of the pumped fluid, speed or torque of the motor  14 ). 
         [0024]      FIG. 3B  illustrates an external controller  98  for the pool pump  10  according to one embodiment of the invention. The external controller  98  can communicate with the on-board controller  16 . The external controller  98  can control the pool pump  10  in substantially the same way as the on-board controller  16 . The external controller  98  can be used to operate the pool pump  10  and/or program the on-board controller  16 , if the pool pump  10  is installed in a location where the user interface  60  is not conveniently accessible. 
         [0025]      FIG. 4  illustrates a menu  100  for the on-board controller  16  according to one embodiment of the invention. In some embodiments, the menu  100  can be used to program various features of the on-board controller  16 . In some embodiments, the menu  100  can include a hierarchy of categories  102 , parameters  104 , and values  106 . From a main screen  108 , an operator can, in some embodiments, enter the menu  100  by pressing the menu button  76 . The operator can scroll through the categories  102  using the up-arrow button  82  and the down-arrow button  84 . In some embodiments, the categories  102  can include settings  110 , speed  112 , external control  114 , features  116 , priming  118 , and anti freeze  120 . In some embodiments, the operator can enter a category  102  by pressing the select button  78 . The operator can scroll through the parameters  104  within a specific category  102  using the up-arrow button  82  and the down-arrow button  84 . The operator can select a parameter  104  by pressing the select button  78  and can adjust the value  106  of the parameter  104  with the up-arrow button  82  and the down-arrow button  84 . In some embodiments, the value  106  can be adjusted by a specific increment or the user can select from a list of options. The user can save the value  106  by pressing the enter button  90 . By pressing the escape button  80 , the user can exit the menu  100  without saving any changes. 
         [0026]    In some embodiments, the settings category  110  can include a time setting  122 , a minimum speed setting  124 , a maximum speed setting  126 , and a SVRS automatic restart setting  128 . The time setting  122  can be used to run the pool pump  10  on a particular schedule. The minimum speed setting  124  and the maximum speed setting  126  can be adjusted according to the volume of the aquatic applications. An installer of the pool pump  10  can provide the minimum speed setting  124  and the maximum speed setting  126 . The on-board controller  16  can automatically prevent the minimum speed setting  124  from being higher than the maximum speed setting  126 . The pool pump  10  will not operate outside of these speeds in order to protect flow-dependent devices with minimum speeds and pressure-sensitive devices (e.g., filters) with maximum speeds. The SVRS automatic restart setting  128  can provide a time period before the on-board controller  16  will resume normal operation of the pool pump  10  after an obstructed inlet  18  has been detected and the pool pump  10  has been stopped. In some embodiments, there can be two minimum speed settings—one for dead head detection (higher speed) and one for dynamic detection (lower speed). 
         [0027]    In some embodiments, the speed category  112  can be used to input data for running the pool pump  10  manually and/or automatically. In some embodiments, the on-board controller  16  can store a number of manual speeds  130  and a number of scheduled runs  132 . In some embodiments, the manual speeds  130  can be programmed into the on-board controller  16  using the up-arrow button  82 , the down-arrow button  84  and the enter button  90 . Once programmed, the manual speeds  130  can be accessed by pressing one of the speed buttons  64  on the user interface  60 . The scheduled runs  132  can be programmed into the on-board controller  16  using the up-arrow button  82 , the down-arrow button  84 , and the enter button  90 . For the scheduled runs  132 , a speed, a start time, and a stop time can be programmed. In some embodiments, the scheduled runs  132  can be programmed using a speed, a start time, and a duration. In some embodiments, the pool pump  10  can be programmed to run continuously. 
         [0028]    The external control category  114  can include various programs  134 . The programs  134  can be accessed by the external controller  98 . The quantity of programs  134  can be equal to the number of scheduled runs  132 . 
         [0029]    The features category  116  can be used to program a manual override. In some embodiments, the parameters can include a “quick clean” program  136  and a “time out” program  138 . The “quick clean” program  136  can include a speed setting  140  and a duration setting  142 . The “quick clean” program  136  can be selected by pressing the “quick clean” button  74  located on the user interface  60 . When pressed, the “quick clean” program  136  can have priority over the scheduled and/or manual operation of the pool pump  10 . After the pool pump  10  has been operated for the time period of the duration setting  142 , the pool pump  10  can resume to the scheduled and/or manual operation. If the SVRS has been previously triggered and the time period for the SVRS automatic restart  128  has not yet elapsed, the “quick clean” program  136  may not be initiated by the on-board controller  16 . The “time out” program  138  can interrupt the operation of the pool pump  10  for a certain amount of time, which can be programmed into the on-board controller  16 . The “time out” program  138  can be selected by pressing the “time out” button  72  on the user interface  60 . The “time out” program  138  can be used to clean the aquatic application and/or to perform maintenance procedures. 
         [0030]    In the priming category  118 , the priming of the pool pump  10  can be enabled or disabled. If the priming is enabled, a duration for the priming sequence can be programmed into the on-board controller  16 . In some embodiments, the priming sequence can be run at the maximum speed  126 . The priming sequence can remove substantially all air in order to allow water to flow through the pool pump  10  and/or connected piping systems. 
         [0031]    In some embodiments, a temperature sensor (not shown) can be connected to the on-board controller  16  in order to provide an anti-freeze operation for the pumping system and the pool pump  10 . In the anti-freeze category  120 , a speed setting  144  and a temperature setting  146  at which the pool pump  10  can be activated to prevent water from freezing in the pumping system can be programmed into the on-board controller  16 . If the temperature sensor detects a temperature lower than the temperature setting  146 , the pool pump  10  can be operated according to the speed setting  144 . However, the anti-freeze operation can also be disabled. 
         [0032]      FIG. 5A-5C  illustrate power consumption curves associated with the motor shaft  56  of the pool pump  10 . The power consumption of the motor that is necessary to pump water and overcome losses will be referred to herein and in the appended claims as any one of “power consumption curves,” “power consumption values,” or simply “power consumption.”  FIG. 5A  illustrates power consumption curves for the motor shaft  56  when the inlet  18  is obstructed at a particular time  200 .  FIG. 5A  illustrates an actual power consumption curve  202 , a current power consumption curve  204 , and a lagged power consumption curve  206 . The actual power consumption  202  can be evaluated by the on-board controller  16  during a certain time interval (e.g., about 20 milliseconds). 
         [0033]    In some embodiments, the on-board controller  16  can filter the actual power consumption  202  using a fast low-pass filter to obtain the current power consumption  204 . The current power consumption  204  can represent the actual power consumption  202 ; however, the current power consumption  204  can be substantially smoother than the actual power consumption  202 . This type of signal filtering can result in “fast detection” (also referred to as “dynamic detection”) of any obstructions in the pumping system (e.g., based on dynamic behavior of the shaft power when the inlet  18  is blocked suddenly). In some embodiments, the fast low-pass filter can have a time constant of about 200 milliseconds. 
         [0034]    In some embodiments, the on-board controller  16  can filter the signal for the actual power consumption  202  using a slow low-pass filter to obtain the lagged power consumption  206 . The lagged power consumption  206  can represent the actual power consumption from an earlier time period. If the inlet  18  is obstructed at the time instance  200 , the actual power consumption  202  will rapidly drop. The current power consumption  204  can substantially follow the drop of the actual power consumption  202 . However, the lagged power consumption  206  will drop substantially slower than the actual power consumption  202 . As a result, the lagged power consumption  206  will generally be higher than the actual power consumption  202 . This type of signal filtering can result in “slow detection” (also referred to as “dead head detection” or “static detection”) of any obstructions in the pumping system (e.g., when there is an obstruction in the pumping system and the pool pump  10  runs dry for a few seconds). In some embodiments, the slow low-pass filter can have a time constant of about 1400 milliseconds. 
         [0035]    The signal filtering of the actual power consumption  202  can be performed over a time interval of about 2.5 seconds, resulting in a reaction time between about 2.5 seconds and about 5 seconds, depending on when the dead head condition occurs during the signal filtering cycle. In some embodiments, the static detection can have a 50% sensitivity which can be defined as the power consumption curve calculated from a minimum measured power plus a 5% power offset at all speeds from about 1500 RPM to about 3450 RPM. When the sensitivity is set to 0%, the static detection can be disabled. 
         [0036]      FIG. 5B  illustrates a relative power consumption curve  208  of the pool pump  10  for the same scenario of  FIG. 5A . In some embodiments, the relative power consumption can be computed by calculating the difference between the current power consumption  204  and the lagged power consumption  206  (i.e., the “absolute power variation”) divided by the current power consumption  204 . The greater the difference between the time constants of the fast and slow filters, the higher the time frame for which absolute power variation can be calculated. In some embodiments, the absolute power variation can be updated about every 20 milliseconds for dynamic detection of obstructions in the pumping system. Due to the lagged power consumption  206  being higher than the current power consumption  204 , a negative relative power consumption  208  can be used by the SVRS of the on-board controller  16  to identify an obstructed inlet  18 . 
         [0037]    The relative power consumption  208  can also be used to determine a “relative power variation” (also referred to as a “power variation percentage”). The relative power variation can be calculated by subtracting the lagged power consumption  206  from the current power consumption  204  and dividing by the lagged power consumption  206 . When the inlet  18  is blocked, the relative power variation will be negative as shaft power decreases rapidly in time. A negative threshold can be set for the relative power variation. If the relative power variation exceeds the negative threshold, the SVRS can identify an obstructed inlet  18  and shut down the pool pump  10  substantially immediately. In one embodiment, the negative threshold for the relative power variation can be provided for a speed of about 2200 RPM and can be provided as a percentage multiplied by ten for increased resolution. The negative threshold for other speeds can be calculated by assuming a second order curve variation and by multiplying the percentage at 800 RPM by six and by multiplying the percentage at 3450 RPM by two. In some embodiments, the sensitivity of the SVRS can be altered by changing the percentages or the multiplication factors. 
         [0038]    In some embodiments, the on-board controller  16  can include a dynamic counter. In one embodiment, a dynamic counter value  210  can be increased by one value if the absolute power variation is negative. The dynamic counter value  210  can be decreased by one value if the absolute power variation is positive. In some embodiments, if the dynamic counter value  210  is higher than a threshold (e.g., a value of about 15 so that the counter needs to exceed 15 to trigger an obstructed inlet alarm), a dynamic suction blockage is detected and the pool pump  10  is shut down substantially immediately. The dynamic counter value  210  can be any number equal to or greater than zero. For example, the dynamic counter value  210  may remain at zero indefinitely if the shaft power continues to increase for an extended time period. However, in the case of a sudden inlet blockage, the dynamic counter value  210  will rapidly increase, and once it increases beyond the threshold value of 15, the pool pump  10  will be shut down substantially immediately. In some embodiments, the threshold for the dynamic counter value  210  can depend on the speed of the motor  14  (i.e., the thresholds will follow a curve of threshold versus motor speed). In one embodiment, the dynamic detection can monitor shaft power variation over about one second at a 20 millisecond sampling time to provide fast control and monitoring.  FIG. 5C  illustrates the dynamic counter value  210  of the dynamic counter for the relative power consumption  208  of  FIG. 5B . 
         [0039]    In one embodiment, the SVRS can determine that there is an obstructed inlet  18  when both of the following events occur: (1) the relative power variation exceeds a negative threshold; and (2) the dynamic counter value  210  exceeds a positive threshold (e.g., a value of 15). When both of these events occur, the on-board controller  16  can shut down the pool pump  10  substantially immediately. However, in some embodiments, one of these thresholds can be disabled. The relative power variation threshold can be disabled if the relative power variation threshold needs only to be negative to trigger the obstructed inlet alarm. Conversely, the dynamic counter can be disabled if the dynamic counter value needs only to be positive to trigger the obstructed inlet alarm. 
         [0040]    The on-board controller  16  can evaluate the relative power consumption  208  in a certain time interval. The on-board controller  16  can adjust the dynamic counter value  210  of the dynamic counter for each time interval. In some embodiments, the time interval can be about 20 milliseconds. In some embodiments, the on-board controller  16  can trigger the SVRS based on one or both of the relative power consumption  208  and the dynamic counter value  210  of the relative counter. The values for the relative power consumption  208  and the dynamic counter value  210  when the on-board controller  16  triggers the SVRS can be programmed into the on-board controller  16 . 
         [0041]      FIG. 6  illustrates a maximum power consumption curve  212  and a minimum power consumption curve  214  versus the speed of the pool pump  10  according to one embodiment of the invention. In some embodiments, the maximum power consumption curve  212  and/or the minimum power consumption curve  214  can be empirically determined and programmed into the on-board controller  16 . The maximum power consumption curve  212  and the minimum power consumption curve  214  can vary depending on the size of the piping system coupled to the pool pump  10  and/or the size of the aquatic applications. In some embodiments, the minimum power consumption curve  214  can be defined as about half the maximum power consumption curve  212 . 
         [0042]      FIG. 6  also illustrates several intermediate power curves  216 . The maximum power consumption curve  212  can be scaled with different factors to generate the intermediate power curves  216 . The intermediate power curve  216  resulting from dividing the maximum power consumption curve  212  in half can be substantially the same as the minimum power consumption curve  214 . The scaling factor for the maximum power consumption  212  can be programmed into the on-board controller  16 . One or more of the maximum power consumption  212  and the intermediate power curves  216  can be used as a threshold value to detect an obstructed inlet  18 . In some embodiments, the on-board controller  16  can trigger the SVRS if one or both of the actual power consumption  202  and the current power consumption  204  are below the threshold value. 
         [0043]    In some embodiments, the on-board controller  16  can include an absolute counter. If the actual power consumption  202  and/or the current power consumption  204  is below the threshold value, a value of the absolute counter can be increased. A lower limit for the absolute counter can be set to zero. In some embodiments, the absolute counter can be used to trigger the SVRS. The threshold value for the absolute counter before the SVRS is activated can be programmed into the on-board controller  16 . In some embodiments, if the absolute counter value is higher than a threshold (e.g., a value of about 10 so that the counter needs to exceed 10 to trigger an obstructed inlet alarm), a dead head obstruction is detected and the pool pump  10  is shut down substantially immediately. In other words, if the actual power consumption  202  stays below a threshold power curve (as described below) for 10 times in a row, the absolute counter will reach the threshold value of 10 and the obstructed inlet alarm can be triggered for a dead head condition. 
         [0044]    For use with the absolute counter, the threshold value for the actual power consumption  202  can be a threshold power curve with a sensitivity having a percentage multiplied by ten. For example, a value of 500 can mean 50% sensitivity and can correspond to the measured minimum power curve calculated using second order approximation. A value of 1000 can mean 100% sensitivity and can correspond to doubling the minimum power curve. In some embodiments, the absolute counter can be disabled by setting the threshold value for the actual power consumption  202  to zero. The sensitivity in most applications can be above 50% in order to detect a dead head obstruction within an acceptable time period. The sensitivity in typical pool and spa applications can be about 65%. 
         [0045]    In some embodiments, the SVRS based on the absolute counter can detect an obstructed inlet  18  when the pool pump  10  is being started against an already blocked inlet  18  or in the event of a slow clogging of the inlet  18 . The sensitivity of the SVRS can be adjusted by the scaling factor for the maximum power consumption  212  and/or the value of the absolute counter. In some embodiments, the absolute counter can be used as an indicator for replacing and/or cleaning the strainer  42  and/or other filters installed in the piping system of the aquatic applications. 
         [0046]    In some embodiments, the dynamic counter and/or the absolute counter can reduce the number of nuisance trips of the SVRS. The dynamic counter and/or the absolute counter can reduce the number of times the SVRS accidently shuts down the pool pump  10  without the inlet  18  actually being obstructed. A change in flow rate through the pool pump  10  can result in variations in the absolute power consumption  202  and/or the relative power consumption  208  that can be high enough to trigger the SVRS. For example, if a swimmer jumps into the pool, waves can change the flow rate through the pool pump  10  which can trigger the SVRS, although no blockage actually occurs. In some embodiments, the relative counter and/or the absolute counter can prevent the on-board controller  16  from triggering the SVRS if the on-board controller  16  changes the speed of the motor  14 . In some embodiments, the controller  16  can store whether the type of obstructed inlet was a dynamic blocked inlet or a dead head obstructed inlet. 
         [0047]    The actual power consumption  202  varies with the speed of the motor  14 . However, the relative power consumption  208  can be substantially independent of the actual power consumption  202 . As a result, the power consumption parameter of the motor shaft  56  by itself can be sufficient for the SVRS to detect an obstructed inlet  18  over a wide range of speeds of the motor  14 . In some embodiments, the power consumption parameter can be used for all speeds of the motor  14  between the minimum speed setting  124  and the maximum speed setting  126 . In some embodiments, the power consumption values can be scaled by a factor to adjust a sensitivity of the SVRS. A technician can program the power consumption parameter and the scaling factor into the on-board controller  16 . 
         [0048]      FIG. 7  illustrates a pool or spa  300  with a vessel  302 , an outlet pipe  304 , an inlet pipe  306 , and a filter system  308  coupled to the pool pump  10 . The vessel  302  can include an outlet  310  and an inlet  312 . The outlet pipe  304  can couple the outlet  310  with the inlet  18  of the pool pump  10 . The inlet pipe  306  can couple the outlet  20  of the pool pump  10  with the inlet  312  of the vessel  302 . The inlet pipe  306  can be coupled to the filter system  308 . 
         [0049]    An object in the vessel  302 , for example a person  314  or a foreign object, may accidently obstruct the outlet  310  or the inlet  18  may become obstructed over time. The on-board controller  16  can detect the blocked inlet  18  of the pool pump  10  based on one or more of the actual power consumption  202 , the current power consumption  204 , the relative power consumption  208 , the dynamic counter, and the absolute counter. In some embodiments, the on-board controller  16  can trigger the SVRS based on the most sensitive (e.g., the earliest detected) parameter. Once an obstructed inlet  18  has been detected, the SVRS can shut down the pool pump  10  substantially immediately. The on-board controller  16  can illuminate an LED  96  on the user interface  60  and/or can activate an audible alarm. In some embodiments, the on-board controller  16  can restart the pool pump  10  automatically after the time period for the SVRS automatic restart  128  has elapsed. In some embodiments, the on-board controller  16  can delay the activation of the SVRS during start up of the pool pump  10 . In some embodiments, the delay can be about two seconds. 
         [0050]    If the inlet  18  is still obstructed when the pool pump  10  is restarted, the SVRS will be triggered again. Due to the pool pump  10  being started against an obstructed inlet  18 , the relative power consumption  208  may be inconclusive to trigger the SVRS. However, the on-board controller  16  can use the actual power consumption  202  and/or the current power consumption  204  to trigger the SVRS. In some embodiments, the SVRS can be triggered based on both the relative power consumption  208  and the actual power consumption  202 . 
         [0051]    In some embodiments, the SVRS can be triggered for reasons other than the inlet  18  of the pool pump  10  being obstructed. For example, the on-board controller  16  can activate the SVRS if one or more of the actual power consumption  202 , the current power consumption  204 , and the relative power consumption  208  of the pool pump  10  varies beyond an acceptable range for any reason. In some embodiments, an obstructed outlet  20  of the pool pump  10  can trigger the SVRS. In some embodiments, the outlet  20  may be obstructed anywhere along the inlet pipe  306  and/or in the inlet  312  of the pool or spa  300 . For example, the outlet  20  could be obstructed by an increasingly-clogged strainer  42  and/or filter system  308 . 
         [0052]    In some embodiments, the number of restarts of the pool pump  10  after time period for the SVRS automatic restart  128  has been elapsed can be limited in order to prevent excessive cycling of the pool pump  10 . For example, if the filter system  308  is clogged, the clogged filter system  308  may trigger the SVRS every time the pool pump  10  is restarted by the on-board controller  16 . After a certain amount of failed restarts, the on-board controller  16  can be programmed to stop restarting the pool pump  10 . The user interface  60  can also indicate the error on the display  62 . In some embodiments, the user interface  60  can display a suggestion to replace and/or check the strainer  42  and/or the filter system  308  on the display  62 . 
         [0053]    It will be appreciated by those skilled in the art that while the invention has been described above in connection with particular embodiments and examples, the invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications and departures from the embodiments, examples and uses are intended to be encompassed by the claims attached hereto. The entire disclosure of each patent and publication cited herein is incorporated by reference, as if each such patent or publication were individually incorporated by reference herein. Various features and advantages of the invention are set forth in the following claims.