Pumping apparatus and method of detecting an entrapment in a pumping apparatus

BACKGROUND

0001The invention relates to a pumping apparatus having a motor and a controller for the motor as defined in the preamble of Claim 1.It also relates to a method of detecting an entrapment event in a jetted-fluid system comprising inter alia a pumping apparatus as mentioned above. Occasionally on a swimming pool, spa, or similar jetted fluid application, the main drain can become obstructed with an object, such as a towel or pool toy. When this happens, the suction force of the pump is applied to the obstruction and the object sticks to the drain. This is called suction entrapment. If the object substantially covers the drain (such as a towel covering the drain), water is pumped out of the drain side of the pump. Eventually the pump runs dry, the seal burns out, and the pump can be damaged.

0002Another type of entrapment is referred to as a mechanical entrapment. Mechanical entrapment occurs when an object, such as a towel or pool toy, gets tangled in the drain cover. Mechanical entrapment may also effect the operation of the pump.

0003Several solutions have been proposed for suction and mechanical entrapment. For example, new pool construction is required to have two drains, so that if one drain becomes plugged, the other can still flow freely and no vacuum entrapment can take place. This does not help existing pools, however, as adding a second drain to an in-ground, one-drain pool is very difficult and expensive. Modern pool drain covers are also designed such that items cannot become entwined with the cover.

0004As another example, several manufacturers offer systems known as Safety Vacuum Release Systems (SVRS). SVRS often contain several layers of protection to help prevent both mechanical and suction entrapment. Most SVRS use hydraulic release valves that are plumbed into the suction side of the pump. The valve is designed to release (open to the atmosphere) if the vacuum (or pressure) inside the drain pipe exceeds a set threshold, thus releasing the obstruction. These valves can be very effective at releasing the suction developed under these circumstances. Unfortunately, they have several technical problems that have limited their use. The first problem is that when the valves are released, the pump loses its water supply and the pump can still be damaged. The second problem is that the release valve typically needs to be mechanically adjusted for each pool. Even if properly adjusted, the valve can be prone to nuisance trips. The third problem is that the valve needs to be plumbed properly into the suction side of the pump. This makes installation difficult for the average homeowner.

0005<patcit id="pcit0001" dnum="US4703387A"><text>US 4703387</text></patcit> and <patcit id="pcit0002" dnum="US5577890A"><text>US 5577890</text></patcit> disclose pumps having pump protection systems including voltage sensing circuits and current sensing circuits.

SUMMARY

0006In one embodiment, the invention provides a pumping apparatus for a jetted fluid system and a method for detecting an entrapment event in a jetted-fluid vessel according to the claims. The pumping apparatus comprises a controller for a motor that monitors motor input power. The controller may additionally monitor pump inlet side pressure (also referred to as pump inlet side vacuum). This monitoring helps to determine if a drain obstruction has taken place. If the drain or plumbing is substantially restricted on the suction side of the pump, the pressure on that side of the pump increases. At the same time, because the pump is no longer pumping fluid, input power to the motor drops. Either of these conditions may be considered a fault and the motor is powered down. It is also envisioned that should the pool filter become plugged, the pump input power also drops and the motor is powered down as well.

0007Other features and aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

0008<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> is a schematic representation of a jetted-spa incorporating the invention.</li><li><figref idref="f0002">Fig. 2</figref> is a block diagram of a first controller capable of being used in the jetted-spa shown in <figref idref="f0001">Fig. 1</figref>.</li><li><figref idref="f0003">Figs. 3A</figref> and <figref idref="f0004">3B</figref> are electrical schematics of the first controller shown in <figref idref="f0002">Fig. 2</figref>.</li><li><figref idref="f0005">Fig. 4</figref> is a block diagram of a second controller capable of being used in the jetted-spa shown in <figref idref="f0001">Fig. 1</figref>.</li><li><figref idref="f0006">Figs. 5A</figref> and <figref idref="f0007">5B</figref> are electrical schematics of the second controller shown in <figref idref="f0005">Fig. 4</figref>.</li><li><figref idref="f0008">Fig. 6</figref> is a block diagram of a third controller capable of being used in the jetted-spa shown in <figref idref="f0001">Fig. 1</figref>.</li></ul>

DETAILED DESCRIPTION

0009<figref idref="f0001">Fig. 1</figref> schematically represents a jetted-spa 100 incorporating the invention. However, the invention is not limited to the jetted-spa 100 and can be used in other jetted-fluid systems (e.g., pools, whirlpools, jetted-tubs, etc.). It is also envisioned that the invention can be used in other applications (e.g., fluid-pumping applications).

0010As shown in <figref idref="f0001">Fig. 1</figref>, the spa 100 includes a vessel 105. As used herein, the vessel 105 is a hollow container such as a tub, pool, tank, or vat that holds a load. The load includes a fluid, such as chlorinated water, and may include one or more occupants or items. The spa further includes a fluid-movement system 110 coupled to the vessel 105. The fluid-movement system 110 includes a drain 115, a pumping apparatus 120 having an inlet 125 coupled to the drain and an outlet 130, and a return 135 coupled to the outlet 130 of the pumping apparatus 120. The pumping apparatus 120 includes a pump 140, a motor 145 coupled to the pump 140, and a controller 150 for controlling the motor 145. For the constructions described herein, the pump 140 is a centrifugal pump and the motor 145 is an induction motor (e.g., capacitor-start, capacitor-run induction motor; split-phase induction motor; three-phase induction motor; etc.). However, the invention is not limited to this type of pump or motor. For example, a brushless, direct current (DC) motor may be used in a different pumping application. For other constructions, a jetted-fluid system can include multiple drains, multiple returns, or even multiple fluid movement systems.

0011Referring back to <figref idref="f0001">Fig. 1</figref>, the vessel 105 holds a fluid. When the fluid movement system 110 is active, the pump 140 causes the fluid to move from the drain 115, through the pump 140, and jet into the vessel 105. This pumping operation occurs when the controller 150 controllably provides a power to the motor 145, resulting in a mechanical movement by the motor 145. The coupling of the motor 145 (e.g., a direct coupling or an indirect coupling via a linkage system) to the pump 140 results in the motor 145 mechanically operating the pump 140 to move the fluid. The operation of the controller 150 can be via an operator interface, which may be as simple as an ON switch.

0012<figref idref="f0002">Fig. 2</figref> is a block diagram of a first construction of the controller 150, and <figref idref="f0003">Figs. 3A</figref> and <figref idref="f0004">3B</figref> are electrical schematics of the controller 150. As shown in <figref idref="f0002">Fig. 2</figref>, the controller 150 is electrically connected to a power source 155 and the motor 145.

0013With reference to <figref idref="f0002">Fig. 2</figref> and <figref idref="f0004">Fig. 3B</figref>, the controller 150 includes a power supply 160. The power supply 160 includes resistors R46 and R56; capacitors C13, C14, C16, C18, C19, and C20; diodes D10 and D11; zener diodes D12 and D13; power supply controller U7; regulator U6; and optical switch U8. The power supply 160 receives power from the power source 155 and provides the proper DC voltage (e.g., -5 VDC and -12 VDC) for operating the controller 150.

0014For the controller 150 shown in <figref idref="f0002">Figs. 2</figref> and <figref idref="f0003">3A</figref>, the controller 150 monitors motor input power to determine if a drain obstruction has taken place. In an example, outside the scope of the claims, the controller 150 may also monitor pump inlet side pressure. If the drain 115 or plumbing is plugged on the suction side of the pump 140, the pressure on that side of the pump 140 increases. At the same time, because the pump 140 is no longer pumping water, input power to the motor 145 drops. If either of these conditions occur, the controller 150 declares a fault, the motor 145 powers down, and a fault indicator lights.

0015A voltage sense and average circuit 165, a current sense and average circuit 170, a line voltage sense circuit 175, a triac voltage sense circuit 180, and the microcontroller 185 perform the monitoring of the input power. One example voltage sense and average circuit 165 is shown in and average circuit rectifies the voltage from the power source 155 and then performs a DC average of the rectified voltage. The DC average is then fed to the microcontroller 185.

0016One example current sense and average circuit 170 is shown in <figref idref="f0003">Fig. 3A</figref>. The current sense and average circuit 170 includes transformer T1 and resistor R45, which act as a current sensor that senses the current applied to the motor. The current sense and average circuit also includes resistors R25, R26, R27, R28, and R33; diodes D7 and D8; capacitor C9; and operational amplifiers U4C and U4D, which rectify and average the value representing the sensed current. For example, the resultant scaling of the current sense and average circuit 170 can be a negative five to zero volt value corresponding to a zero to twenty-five amp RMS value. The resulting DC average is then fed to the microcontroller 185.

0017One example line voltage sense circuit 175 is shown in <figref idref="f0003">Fig. 3A</figref>. The line voltage sense circuit 175 includes resistors R23, R24, and R32; diode D5; zener diode D6; transistor Q6; and NAND gate U2B. The line voltage sense circuit 175 includes a zero-crossing detector that generates a pulse signal. The pulse signal includes pulses that are generated each time the line voltage crosses zero volts.

0018One example triac voltage sense circuit 180 is shown in <figref idref="f0003">Fig. 3A</figref>. The triac voltage sense circuit 180 includes resistors R1, R5, and R6; diode D2; zener diode D1; transistor Q1; and NAND gate U2A. The triac voltage sense circuit includes a zero-crossing detector that generates a pulse signal. The pulse signal includes pulses that are generated each time the motor current crosses zero.

0019One example microcontroller 185 that can be used with the invention is a Motorola brand microcontroller, model no. MC68HC908QY4CP. The microcontroller 185 includes a processor and a memory. The memory includes software instructions that are read, interpreted, and executed by the processor to manipulate data or signals. The memory also includes data storage memory. The microcontroller 185 can include other circuitry (e.g., an analog-to-digital converter) necessary for operating the microcontroller 185. In general, the microcontroller 185 receives inputs (signals or data), executes software instructions to analyze the inputs, and generates outputs (signals or data) based on the analyses. Although the microcontroller 185 is shown and described, the invention can be implemented with other devices, including a variety of integrated circuits (e.g., an application-specific-integrated circuit), programmable devices, and/or discrete devices, as would be apparent to one of ordinary skill in the art. Additionally, it is envisioned that the microcontroller 185 or similar circuitry can be distributed among multiple microcontrollers 185 or similar circuitry. It is also envisioned that the microcontroller 185 or similar circuitry can perform the function of some of the other circuitry described (e.g., circuitry 165-180) above for the controller 150. For example, the microcontroller 185, in some constructions, can receive a sensed voltage and/or sensed current and determine an averaged voltage, an averaged current, the zero-crossings of the sensed voltage, and/or the zero crossings of the sensed current.

0020The microcontroller 185 receives the signals representing the average voltage applied to the motor 145, the average current through the motor 145, the zero crossings of the motor voltage, and the zero crossings of the motor current. Based on the zero crossings, the microcontroller 185 can determine a power factor. The power factor can be calculated using known mathematical equations or by using a lookup table based on the mathematical equations. The microcontroller 185 can then calculate an input power with the averaged voltage, the averaged current, and the power factor as is known. As will be discussed later, the microcontroller 185 compares the calculated input power with a power calibration value to determine whether a fault condition (e.g., due to an obstruction) is present.

0021Referring again to <figref idref="f0002">Figs. 2</figref> and <figref idref="f0003">3A</figref>, a pressure (or vacuum) sensor circuit 190 and the microcontroller 185 monitor the pump inlet side pressure. One example pressure sensor circuit 190 is shown in <figref idref="f0003">Fig. 3A</figref>. The pressure sensor circuit 190 includes resistors R16, R43, R44, R47, and R48; capacitors C8, C12, C15, and C17; zener diode D4, piezoresistive sensor U9, and operational amplifier U4-B. The piezoresistive sensor U9 is plumbed into the suction side of the pump 140. The pressure sensor circuit 190 and microcontroller 185 translate and amplify the signal generated by the piezoresistive sensor U9 into a value representing inlet pressure. As will be discussed later, the microcontroller 185 compares the resulting pressure value with a pressure calibration value to determine whether a fault condition (e.g., due to an obstruction) is present.

0022The calibrating of the controller 150 occurs when the user activates a calibrate switch 195. One example calibrate switch 195 is shown in <figref idref="f0003">Fig. 3A</figref>. The calibrate switch 195 includes resistor R18 and Hall effect switch U10. When a magnet passes Hall effect switch U10, the switch 195 generates a signal provided to the microcontroller 185. Upon receiving the signal, the microcontroller 185 stores a pressure calibration value for the pressure sensor by acquiring the current pressure and stores a power calibration value for the motor by calculating the present power.

0023As stated earlier, the controller 150 controllably provides power to the motor 145. With references to <figref idref="f0002">Fig. 2</figref> and <figref idref="f0003">3A</figref>, the controller 150 includes a retriggerable pulse generator circuit 200. The retriggerable pulse generator circuit 200 includes resistor R7, capacitor C1, and pulse generator U1A, and outputs a value to NAND gate U2D if the retriggerable pulse generator circuit 200 receives a signal having a pulse frequency greater than a set frequency determined by resistor R7 and capacitor C1. The NAND gate U2D also receives a signal from power-up delay circuit 205, which prevents nuisance triggering of the relay on startup. The output of the NAND gate U2D is provided to relay driver circuit 210. The relay driver circuit 210 shown in <figref idref="f0003">Fig. 3A</figref> includes resistors R19, R20, R21, and R22; capacitor C7; diode D3; and switches Q5 and Q4. The relay driver circuit 210 controls relay K1.

0024The microcontroller 185 also provides an output to triac driver circuit 215, which controls triac Q2. As shown in <figref idref="f0003">Fig. 3A</figref>, the triac driver circuit 215 includes resistors R12, R13, and R14; capacitor C11; and switch Q3. In order for current to flow to the motor, relay K1 needs to close and triac Q2 needs to be triggered on.

0025The controller 150 also includes a thermoswitch S1 for monitoring the triac heat sink, a power supply monitor 220 for monitoring the voltages produced by the power supply 160, and a plurality of LEDs DS1, DS2, and DS3 for providing information to the user. In the construction shown, a green LED DS1 indicates power is applied to the controller 150, a red LED DS2 indicates a fault has occurred, and a third LED DS3 is a heartbeat LED to indicate the microcontroller 185 is functioning. Of course, other interfaces can be used for providing information to the operator.

0026The following describes the normal sequence of events for one method of operation of the controller 150. When the fluid movement system 110 is initially activated, the system 110 may have to draw air out of the suction side plumbing and get the fluid flowing smoothly. This "priming" period usually lasts only a few seconds, but could last a minute or more if there is a lot of air in the system. After priming, the water flow, suction side pressure, and motor input power remain relatively constant. It is during this normal running period that the circuit is effective at detecting an abnormal event. The microcontroller 185 includes a startup-lockout feature that keeps the monitor from detecting the abnormal conditions during the priming period.

0027After the system 110 is running smoothly, the spa operator can calibrate the controller 150 to the current spa running conditions. The calibration values are stored in the microcontroller 185 memory, and will be used as the basis for monitoring the spa 100. If for some reason the operating conditions of the spa change, the controller 150 can be re-calibrated by the operator. If at any time during normal operations, however, the suction side pressure increases substantially (e.g., 12%) over the pressure calibration value, or the motor input power drops (e.g., 12%) under the power calibration value, the pump will be powered down and a fault indicator is lit.

0028As discussed earlier, the controller 150 measures motor input power, and not just motor power factor or input current. Some motors have electrical characteristics such that power factor remains constant while the motor is unloaded. Other motors have an electrical characteristic such that current remains relatively constant when the pump is unloaded. However, the input power drops on pump systems when the drain is plugged, and water flow is impeded.

0029The voltage sense and average circuit 165 generates a value representing the average power line voltage and the current sense and average circuit 170 generates a value representing the average motor current. Motor power factor is derived from the difference between power line zero crossing events and triac zero crossing events. The line voltage sense circuit 175 provides a signal representing the power line zero crossings. The triac zero crossings occur at the zero crossings of the motor current. The triac voltage sense circuit 180 provides a signal representing the triac zero crossings. The time difference from the zero crossing events is used to look up the motor power factor from a table stored in the microcontroller 185. This data is then used to calculate the motor input power using equation e1. <maths id="math0001" num="[e1]"><math display="block"><mrow><msub><mi>V</mi><mi mathvariant="italic">avg</mi></msub><mo>∗</mo><msub><mi>I</mi><mi mathvariant="italic">avg</mi></msub><mo>∗</mo><mi mathvariant="italic">PF</mi><mo>=</mo><mi mathvariant="italic">Motor_Input_Power</mi></mrow></math><img file="EP1585205B1_D0001.tif" /></maths>

0030The calculated motor_input_power is then compared to the calibrated value to determine whether a fault has occurred. If a fault has occurred, the motor is powered down and the fault is lit.

0031Another aspect of the controller 150 is a "soft-start" feature. When a typical pump motor 145 is switched on, it quickly accelerates up to full speed. The sudden acceleration creates a vacuum surge on the inlet side of the pump 140, and a pressure surge on the discharge side of the pump 140. The vacuum surge can nuisance trip the hydraulic release valves of the spa 100. The pressure surge on the outlet can also create a water hammer that is hard on the plumbing and especially hard on the filter (if present). The soft-start feature slowly increases the voltage applied to the motor over a time period (e.g., two seconds). By gradually increasing the voltage, the motor accelerates more smoothly, and the pressure/vacuum spike in the plumbing is avoided.

0032Another aspect of the controller 150 is the use of redundant sensing systems. By looking at both pump inlet side pressure and motor input power, if a failure were to occur in either one, the remaining sensor would still shut down the system 110.

0033Redundancy is also used for the power switches that switch power to the motor. Both a relay and a triac are used in series to do this function. This way, a failure of either component will still leave one switch to turn off the motor 145. As an additional safety feature, the proper operation of both switches is checked by the microcontroller 185 every time the motor is powered on.

0034One benefit of using a triac Q2 in series with the relay K1 is that the triac Q2 can be used as the primary switching element, thus avoiding a lot of wear and tear on the relay contacts. When relay contacts open or close with an inductive motor or inductive load, arcing may occur, which eventually erodes the contact surfaces of the relay K1. Eventually the relay K1 will no longer make reliable contact or even stick in a closed position. By using the triac Q2 as the primary switch, the relay contacts can be closed before the triac completes the circuit to the motor 145. Likewise, when powering down, the triac Q2 can terminate conduction of current before the relay opens. This way there is no arcing of the relay contacts. The triac Q2 has no wear-out mechanism, so it can do this switching function repeatedly.

0035Another aspect of the controller 150 is the use of several monitoring functions to verify that all the circuits are working as intended. These functions can include verifying whether input voltage is in a reasonable range, verifying whether motor current is in a reasonable range, and verifying whether suction side pressure is in a reasonable range. For example, if motor current exceeds 135% of its calibrated value, the motor may be considered over-loaded and is powered down.

0036As discussed earlier, the controller 150 also monitors the power supply 160 and the temperature of the triac heat sink. If either is out of proper range, the controller 185 can power down the motor 145 and declare a fault. The controller 150 also monitors the line voltage sense and triac voltage sense circuits 175 and 180, respectively. If zero crossing pulses are received from either of these circuits at a frequency less than a defined time (e.g., every 80 milliseconds), the motor powers down.

0037Another aspect of the controller 150 is that the microcontroller 185 must provide pulses at a frequency greater than a set frequency (determined by the time constant of resistor R7 and C1) to close the relay K1. If the pulse generator U1A is not triggered at the proper frequency, the relay K1 opens and the motor powers down.

0038While numerous aspects of the controller 150 were discussed above, not all of the aspects and features discussed above are required for the invention if compatible with what is defined by the appended claims. Additionally, other aspects and features can be added to the controller 150 shown in the figures. For example, some of the features discussed below for controller 150a can be added to the controller 150.

0039<figref idref="f0005">Fig. 4</figref> is a block diagram of a second construction of the controller 150a, and <figref idref="f0006">Figs. 5A</figref> and <figref idref="f0007">5B</figref> are an electrical schematic of the controller 150a. As shown in <figref idref="f0005">Fig. 4</figref>, the controller 150a is electrically connected to a power source 155 and the motor 145.

0040With reference to <figref idref="f0005">Fig. 4</figref> and <figref idref="f0007">Fig. 5B</figref>, the controller 150a includes a power supply 160a. The power supply 160a includes resistors R54, R56 and R76; capacitors C16, C18, C20, C21, C22, C23 and C25; diodes D8, D10 and D11; zener diodes D6, D7 and D9; power supply controller U11; regulator U9; inductors L1 and L2, surge suppressors MOV1 and MOV2, and optical switch U10. The power supply 160a receives power from the power source 155 and provides the proper DC voltage (e.g., +5 VDC and +12 VDC) for operating the controller 150a.

0041For the controller 150a shown in <figref idref="f0005">Fig. 4</figref>, <figref idref="f0006">Fig 5A</figref>, and <figref idref="f0007">Fig. 5B</figref>, the controller 150a monitors motor input power to determine if a drain obstruction has taken place. Similar to the earlier disclosed construction, if the drain 115 or plumbing is plugged on the suction side of the pump 140, the pump 140 will no longer be pumping water, and input power to the motor 145 drops. If this condition occurs, the controller 150a declares a fault, the motor 145 powers down, and a fault indicator lights.

0042A voltage sense and average circuit 165a, a current sense and average circuit 170a, and the microcontroller 185a perform the monitoring of the input power. One example voltage sense and average circuit 165a is shown in <figref idref="f0006">Fig. 5A</figref>. The voltage sense and average circuit 165a includes resistors R2, R31, R34, R35, R39, R59, R62, and R63; diodes D2 and D12; capacitor C14; and operational amplifiers U5C and U5D. The voltage sense and average circuit 165a rectifies the voltage from the power source 155 and then performs a DC average of the rectified voltage. The DC average is then fed to the microcontroller 185a. The voltage sense and average circuit 165a further includes resistors R22, R23, R27, R28, R30, and R36; capacitor C27; and comparator U7A; which provide the sign of the voltage waveform (i.e., acts as a zero-crossing detector) to the microcontroller 185a.

0043One example current sense and average circuit 170a is shown in <figref idref="f0007">Fig. 5B</figref>. The current sense and average circuit 170a includes transformer T1 and resistor R53, which act as a current sensor that senses the current applied to the motor 145. The current sense and average circuit 170a also includes resistors R18, R20, R21, R40, R43, and R57; diodes D3 and D4; capacitor C8; and operational amplifiers U5A and U5B, which rectify and average the value representing the sensed current. For example, the resultant scaling of the current sense and average circuit 170a can be a positive five to zero volt value corresponding to a zero to twenty-five amp RMS value. The resulting DC average is then fed to the microcontroller 185a. The current sense and average circuit 170a further includes resistors R24, R25, R26, R29, R41, and R44; capacitor C11; and comparator U7B; which provide the sign of the current waveform (i.e., acts as a zero-crossing detector) to microcontroller 185a.

0044One example microcontroller 185a that can be used with the invention is a Motorola brand microcontroller, model no. MC68HC908QY4CP. Similar to what was discussed for the earlier construction, the microcontroller 185a includes a processor and a memory. The memory includes software instructions that are read, interpreted, and executed by the processor to manipulate data or signals. The memory also includes data storage memory. The microcontroller 185a can include other circuitry (e.g., an analog-to-digital converter) necessary for operating the microcontroller 185a and/or can perform the function of some of the other circuitry described above for the controller 150a. In general, the microcontroller 185a receives inputs (signals or data), executes software instructions to analyze the inputs, and generates outputs (signals or data) based on the analyses.

0045The microcontroller 185a receives the signals representing the average voltage applied to the motor 145, the average current through the motor 145, the zero crossings of the motor voltage, and the zero crossings of the motor current, Based on the zero crossings, the microcontroller 185a can determine a power factor and an input power as was described earlier. The microcontroller 185a can then compare the calculated input power with a power calibration value to determine whether a fault condition (e.g., due to an obstruction) is present.

0046The calibrating of the controller 150a occurs when the user activates a calibrate switch 195a. One example calibrate switch 195a is shown in <figref idref="f0006">Fig. 5A</figref>, which is similar to the calibrate switch 195 shown in <figref idref="f0003">Fig. 3A</figref>. Of course, other calibrate switches are possible. In one method of operation for the calibrate switch 195a, a calibration fob needs to be held near the switch 195a when the controller 150a receives an initial power. After removing the magnet and cycling power, the controller 150a goes through priming and enters an automatic calibration mode (discussed below).

0047The controller 150a controllably provides power to the motor 145. With references to <figref idref="f0005">Fig. 4</figref> and <figref idref="f0006">5A</figref>, the controller 150a includes a retriggerable pulse generator circuit 200a. The retriggerable pulse generator circuit 200a includes resistors R15 and R16, capacitors C2 and C6, and pulse generators U3A and U3B, and outputs a value to the relay driver circuit 210a if the retriggerable pulse generator circuit 200a receives a signal having a pulse frequency greater than a set frequency determined by resistors R15 and R16, and capacitors C2 and C6. The retriggerable pulse generators U3A and U3B also receive a signal from power-up delay circuit 205a, which prevents nuisance triggering of the relays on startup. The relay driver circuits 210a shown in <figref idref="f0006">Fig. 5A</figref> includes resistors R1, R3, R47, and R52; diodes D1 and D5; and switches Q1 and Q2. The relay driver circuits 210a control relays K1 and K2. In order for current to flow to the motor, both relays K1 and K2 need to "close".

0048The controller 150a further includes two voltage detectors 212a and 214a. The first voltage detector 212a includes resistors R71, R72, and R73; capacitor C26; diode D14; and switch Q4. The first voltage detector 212a detects when voltage is present across relay K1, and verifies that the relays are functioning properly before allowing the motor to be energized. The second voltage detector 214a includes resistors R66, R69, and R70; capacitor C9; diode D 13; and switch Q3. The second voltage detector 214a senses if a two speed motor is being operated in high or low speed mode. The motor input power trip values are set according to what speed the motor is being operated. It is also envisioned that the controller 150a can be used with a single speed motor without the second voltage detector 214a (e.g., controller 150b is shown in <figref idref="f0008">Fig. 6</figref>).

0049The controller 150a also includes an ambient thermal sensor circuit 216a for monitoring the operating temperature of the controller 150a, a power supply monitor 220a for monitoring the voltages produced by the power supply 160a, and a plurality of LEDs DS1 and DS3 for providing information to the user. In the construction shown, a green LED DS2 indicates power is applied to the controller 150a, and a red LED DS3 indicates a fault has occurred. Of course, other interfaces can be used for providing information to the operator.

0050The controller 150a further includes a clean mode switch 218a, which includes switch U4 and resistor R10. The clean mode switch can be depressed by an operator (e.g., a maintenance person) to deactivate the power monitoring function described herein for a time period (e.g., 30 minutes so that maintenance person can clean the vessel 105). After the time period, the controller 150a returns to normal operation.

0051The following describes the normal sequence of events for one method of operation of the controller 150a, some of which may be similar to the method of operation of the controller 150. When the fluid movement system 110 is initially activated, the system 110 may have to prime (discussed above) the suction side plumbing and get the fluid flowing smoothly (referred to as "the normal running period"). It is during the normal running period that the circuit is most effective at detecting an abnormal event.

0052After the system 110 enters the normal running period, the controller 150a can include instructions to perform an automatic calibration after priming upon a system power-up. The calibration values are stored in the microcontroller 185 memory, and will be used as the basis for monitoring the spa 100. If for some reason the operating conditions of the spa change, the controller 150a can be re-calibrated by the operator. If at any time during normal operation, however, the motor input power varies from the power calibration value (e.g., varies from a 12.5% window around the power calibration value), the pump motor 145 will be powered down and a fault indicator is lit.

0053Similar to controller 150, the controller 150a measures motor input power, and not just motor power factor or input current.

0054However, it is envisioned that, as an example and outside the scope of the claims, the controllers 150 or 150a can be modified to monitor other motor parameters (e.g., only motor current, only motor power factor, or motor speed). But motor input power is the claimed motor parameter for controller 150a for determining whether the water is impeded. Also, it is envisioned that, as an example and outside the scope of the claims, the controller 150a can be modified to monitor other parameters (e.g., suction side pressure) of the system 110.

0055For some constructions of the controller 150a, the microcontroller 185a monitors the motor input power for an over power condition in addition to an under power condition. The monitoring of an over power condition helps reduce the chance that controller 150a was incorrectly calibrated, and/or also helps detect when the pump is over loaded (e.g., the pump is moving too much fluid). The voltage sense and average circuit 165a generates a value representing the averaged power line voltage and the current sense and average circuit 170a generates a value representing the averaged motor current. Motor power factor is derived from the timing difference between the sign of the voltage signal and the sign of the current signal. This time difference is used to look up the motor power factor from a table stored in the microcontroller 185a. The averaged power line voltage, the averaged motor current, and the motor power factor are then used to calculate the motor input power using equation e1 as was discussed earlier. The calculated motor input power is then compared to the calibrated value to determine whether a fault has occurred. If a fault has occurred, the motor is powered down and the fault indicator is lit. Redundancy is also used for the power switches of the controller 150a. Two relays K1 and K2 are used in series to do this function. This way, a failure of either component will still leave one switch to turn off the motor 145. As an additional safety feature, the proper operation of both relays is checked by the microcontroller 185a every time the motor 145 is powered on via the relay voltage detector circuit 212a.

0056Another aspect of the controller 150a is the use of several monitoring functions to verify that all the circuits are working as intended. These functions can include verifying whether input voltage is in a reasonable range (i.e. 85 to 135 VAC, or 175 to 255 VAC), and verifying whether motor current is in a reasonable range (5% to 95% of range). Also, if motor current exceeds 135% of its calibrated value, the motor may be considered over-loaded and is powered down.

0057The controller 150a also monitors the power supply 160a and the ambient temperature of the circuitry of the controller 150a. If either is out of proper range, the controller 150a will power down the motor 145 and declare a fault. The controller 150a also monitors the sign of the power line voltage and the sign of the motor current. If the zero crossing pulses resulting from this monitoring is at a frequency less than a defined time (e.g., every 30 milliseconds), then the motor powers down.

0058Another aspect of the controller 150a is that the microcontroller 185a provides pulses at a frequency greater than a set frequency (determined by the retriggerable pulse generator circuits) to close the relays K1 and K2. If the pulse generators U3A and U3B are not triggered at the proper frequency, the relays K1 and K2 open and the motor powers down.

0059Another aspect of some constructions of the controller 150a is that the microcontroller 185a includes an automatic reset feature, which may help to recognize a nuisance trip (e.g., due to an air bubble in the fluid-movement system 110). For this aspect, the microcontroller 185a, after detecting a fault and powering down the motor, waits a time period (e.g., a minute), resets, and attempts to start the pump. If the controller 150a cannot successfully start the pump after a defined number of tries (e.g., five), the microcontroller 185a locks until powered down and restarted. The microcontroller 185a can further be programmed to clear the fault history if the pump runs normally for a time period.

0060The microcontroller 185a can include a startup-lockout feature that keeps the monitor from indicating abnormal conditions during a priming period, thereby preventing unnecessary nuisance trips. In one specific method of operation, the microcontroller 185a initiates a lockout-condition upon startup, but monitors motor input power upon startup. If the pump 140 is priming, the input is typically low. Once the input power enters a monitoring window (e.g., within 12.5% above or below the power calibration value) and stays there for a time period (e.g., two seconds), the microcontroller 185 ceases the lockout condition and enters (e.g., two seconds), the microcontroller 185 ceases the lockout condition and enters normal operation even though the pump may not be fully primed. This feature allows the controller 150a to perform normal monitoring as soon as possible, while reducing the likelihood of nuisance tripping during the priming period. For example, a complete priming event may last two-to-three minutes after the controller 150a is powered up. However, when the motor input power has entered the monitoring window, the suction force on the inlet 115 is sufficient for entrapment. By allowing the controller to enter run mode at this point, the likelihood of a suction event is greatly reduced through the remaining portion of the priming period. Therefore, the just-described method of operation for ceasing the lockout condition provides a greater efficiency of protection than a timed, startup lockout.

0061While numerous aspects of the controller 150a were discussed above, not all of the aspects and features discussed above are required for the invention if within the scope of the appended claims. Additionally, other aspects and features can be added to the controller 150a shown in the figures.