Icemaker control system

Abstract

A control system for an icemaker utilizes a control scheme in which various operating conditions of the icemaker are monitored sand the icemaker is shut down if a fault condition is sensed. In response to detection of the fault condition, steps are taken to actively remove the fault. Restarting of the icemaker is then attempted if sensors indicate that normal continued operation should be possible. The operating conditions sensed include the temperature of refrigerant at an outlet from a condenser, the rate at which a water pan fills with water while water is delivered to it for subsequent delivery to and over an evaporator to freeze the water into ice on the evaporator. and the time required to harvest ice from the evaporator.

Description

FIELD OF THE INVENTION

The present invention relates to commercial icemakers, and in particular to control systems therefore.

BACKGROUND OF THE INVENTION

Commercial ice making machines are well known in the art and provide for the manufacture of ice in various forms, such as cubed and flaked. Cube type icemakers typically make ice by running a flow of water over a vertically oriented evaporator until ice of a sufficient thickness has formed thereon. When the ice is of harvest size, a hot gas defrosting procedure is typically used to remove the ice from the evaporator. It has long been recognized that icemakers are prone to a variety of malfunction events. In response thereto icemakers were first designed to include different control systems that shut down the icemaker in response to a sensor indicating that a problem exists. Examples of such malfunctions include the condenser being too cold or too hot, ice not being successfully harvested from the evaporator, or insufficient water in the water pan. It is also well understood that certain of the malfunctions can be due to causes that are transient in nature. Thus, control strategies have been proposed that allow the ice machine to shut down if a problem is sensed and then to restart and attempt to again make ice. In case the malfunction is not due to a transient problem, these restarts are usually limited to some predetermined number so that the icemaker does not vainly attempt an unlimited number of restarts. It is also well known to add a time delay between each restart in order to increase the total time period over which the limited number of restarts is attempted. This approach can provide more time for the transient problem to go away, while not increasing the number of restarts. At the end of the number of predetermined restart attempts after which a normal cycle of functioning is not restored, it is known to put the machine into a permanent shut-down and activate an indicator light to summon a service technician. Likewise, it is known to reset the counting of restarts to zero if a full ice making cycle results and is followed by a successful harvest.

A problem with the foregoing control approaches is that the restarts simply occur right after the error is sensed or after the predetermined time delays. In either case, the restart is essentially “mechanical”, that is, without any regard to the actual conditions of the machine. Thus, as long as the particular problem that initiated the shut down continues to exist, each restart attempt during that time is futile and can result in a needless waste of water and/or energy. Efficiency of energy and water use is of critical concern to owners and operators of ice making machines. Accordingly, it would be very desirable to have a control system that is better responsive to the actual operating condition of the ice maker so that restart attempts are minimized and are only initiated when there is a greater chance of a successful ice making cycle occurring. A further problem with the prior art controls concerns the fact that nothing is done in an attempt to actively remove or clear the problem causing the fault condition. Restart attempts are simply repeated in hopes that the error condition goes away or is somehow eliminated by the restart process itself Thus, it would also be desirable to have a more active control strategy that can take specific and more positive steps to eliminate an error condition.

SUMMARY OF THE INVENTION

The present invention concerns a control system for an ice maker wherein various operating condition thereof are continually monitored and where the ice maker is shut-down if a fault condition is sensed. A restart is attempted if sensors indicate that normal continued operation should be possible. Also, certain control steps are taken to actively remove the error condition.

A condenser routine is shown wherein operation of the ice maker is discontinued if a predetermined high temperature thereof is sensed. The ice maker is only restarted when a suitably low condenser temperature is sensed indicating that a subsequent full cycle ice making operation is attainable. If the predetermined high temperature is nevertheless again encountered, the control will again shut-down the ice maker and wait again for the desired low temperature to be sensed. A predetermined number of theses restarts will result in a permanent shut down condition being instructed. Thus, the control of the present invention does not attempt a restart unless and until the condenser temperature has come down to a predetermined low temperature. Thus, the restart has a much greater likelihood of leading to a successful completion of an ice making cycle.

A water fill rate routine is shown wherein a sensor monitors the rate of filling of a water pan below the evaporator. If the fill rate falls below a predetermined rate, the ice maker shuts off the compressor and the fill valve remains on. Once the rate increases above the predetermined rate or the high level is obtained, the compressor turns on, and the ice maker resumes a normal ice making cycle. If the water fill rate goes below a predetermined low fill rate the ice maker is shut off and water filling is discontinued. In this manner the control of the present invention conserves energy by turning off the compressor if the water fill rate is low but otherwise acceptable. The compressor is then restarted when the water does eventually reach the desired full level.

A failed harvest routine is shown and requires the monitoring of one or more proximity switches associated with a curtain that is pivotally positioned adjacent the evaporator. If ice is successfully harvested from the evaporator, it will fall there from into an ice bin there below, and in doing so, will contact and move the curtain to an open position. If the one or more curtain proximity switches do not all open in 4 minutes, thereby indicating a failed harvest, the compressor and hot gas valve shut off. The fill valve opens, allowing new warm water to enter the system and the circulating pump then runs for 10 minutes circulating that water over the evaporator. The control then causes the ice maker to enter into a hot gas cycle wherein hot gas from the compressor is sent through the evaporator. The control keeps track of the repeated failed harvests until a predetermined maximum value is reached and then stops any further restart attempts. Therefore, the control of the present invention includes the further and more aggressive steps of circulating warm water over the evaporator in order to more effectively dislodge ice that is resistant to being successfully harvested from the evaporator.

DESCRIPTION OF THE DRAWINGS

A better understanding of the construction and operation of the present invention as well as the objects and advantages thereof can be had by reference to the following detailed description which refers to the following figures, wherein:

FIG. 1 shows a perspective view of an ice maker mounted atop an ice storage bin.

FIG. 2 shows a partial cross-sectional view of the interior of the ice maker.

FIG. 3 shows a schematic representation of the ice maker.

FIG. 4 shows an enlarged view of the ice maker control board.

FIG. 5 shows an enlarged partial cross-sectional view of the water pan and pressure fitting.

FIGS. 6A and 6B show a flow diagram of the general control strategy of the present invention.

FIG. 7 shows a flow diagram of the condenser control routine of the present invention.

FIG. 8 shows a flow diagram of the water fill control routine of the present invention.

FIG. 9 shows a flow diagram of the failed harvest control routine of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The ice maker of the present invention is seen in FIG. 1, and referred to generally by the numeral 10. Ice maker 10 includes an exterior housing 12 and is positioned atop an insulated ice retaining bin 14. As is further understood by referring to FIGS. 2 and 3, and as is conventional in the art, ice maker 10 includes a vertical ice forming evaporator plate 16, a condenser and fan 18 and a compressor 20 connected by high pressure refrigerant lines 21a and low pressure line 21b. As is also well understood, the refrigeration system herein includes an expansion valve 22 and a hot gas valve 24. A water catching pan 26 is positioned below evaporator 16 and includes a partial cover 27. A water distribution tube 28 having a water inlet 29 extends along and above evaporator 16. A water supply solenoid valve 30 has an inlet connected to a source of potable water, not shown, and an outlet line 31 supplying water to pan 26. A water pump 32 provides for circulating water from outlet 32b thereof to inlet 29 of distribution tube 28 along a water line 34.

A solenoid operated dump valve 36 is fluidly connected to line 34 and serves, when open, to direct water pumped thereto to a drain, not shown. An evaporator curtain 37 is pivotally positioned closely adjacent evaporator 16 and includes a magnetic switch 38 for indication when it has moved away from evaporator 16 to an open position indicated by the dashed line representation thereof. For purposes of clarity of the view of FIG. 2, the various fluid connections of pump 32, dump valve 36 and water supply valve 30 are not shown, such being represented in schematic form in FIG. 3.

As particularly seen in FIG. 4, and also by referring to FIG. 2, an electronic control board 40 is located within a separate housing 41 at a position remote and physically isolated from pan 26 and evaporator 16. Control board 40 includes a microprocessor 42 for controlling the operation of ice maker 10. Board 40 includes a pressure sensor 44, such as manufactured and sold by Motorola, Inc. of Phoenix, Ariz., and identified as model MPXV5004G. As understood by also viewing FIG. 5, a plastic pneumatic tube 46, shown in dashed outline, is connected to sensor 44 and on its opposite end to a cylindrical air cup or fitting 48. Those of skill will understand that housing 41 includes a cover, not shown, that provides for the enclosing and protection of control 40 and sensor 44 therein and through which tube 46 passes prior to connecting to sensor 44. A temperature sensor 47 is positioned on the outlet refrigerant line of condenser 18 and is connected to control 40.

Fitting 48 resides in pan 26 at the bottom thereof and is press fit within a circular ridge 49 that is formed as an integral molded portion of the bottom surface of pan 26. Fitting 48 includes an outer housing 48a defining an inner air trapping area 48b and a tube connecting portion 48c. Four water flow openings 50 exist around a bottom perimeter of housing 48a.

The operation of the present invention can be better understood by referring to the flow diagram of FIGS. 6A and 6B wherein the basic operation of the present invention is shown. At start block 51 power is provided to control 40. At block 52 compressor 20 is turned on and substantially simultaneously at block 54 fill valve 30 and dump valve 36 are opened. Thus, cooling of evaporator 18 begins and water flows into pan 26. At decision block 56, once a predetermined pump-on water level is reached in pan 26, as indicated by the level line represented by the letter P in FIG. 5, circulatory water pump 32 is turned on at block 58. The pump-on point is sensed by sensor 44. In particular, as water fills pan 26, water flows through holes 50 of fitting 48. As that occurs, air trapped in area 48b is slightly compressed and forced into tube 46 which communicates such pressure increase to sensor 44. That pressure is then input as a voltage to microprocessor 42 which assigns a numerical value thereto corresponding to a pressure scale. Therefore, when the predetermined pressure value is sensed that corresponds to the pressure at level P, pump 32 is turned on. Because of the fluid connections of pump 32 and dump valve 36, the action of pump 32 serves to move any water in pan 26 to valve 36 causing the draining away thereof. Thus, a minimum water level, indicated by the level line represented by the letter M in FIG. 5, is sensed in the same manner as described above for level P. When that predetermined volume of the water has been removed from pan 26, pump 32 is stopped at block 62. As the water supply valve remains on, the level in pan 26 begins to rise and when the P level is again sensed at block 64, then at block 66, pump 32 is re-started and fill valve 30 closed. As dump valve 34 remains open, water will again be pumped from pan 26. At block 68 control 40 again senses for the attainment of the M level. When that occurs, then, at block 70, water pump 32 is stopped, dump valve 34 is closed and fill valve 30 is opened. It can be appreciated that blocks 52-68 serve as a dump cycle whereby any contaminants that have accumulated in pan 26 are agitated by the action of pump 32 and the inflow of water and are twice flushed in this manner and removed from the system.

At block 72 control 40 monitors for the attainment of a maximum fill level for pan 26 indicated by the level line denoted by letters MX. When this highest pressure level is sensed, then at block 74 fill valve 30 is closed. At block 76, a 45 second clock is initiated to provide for some pre-cooling of the water delivered to pan 26 through flow over evaporator 16. At block 78 pump 32 is again turned on. A further 45 second clock is set at block 80, and when that has timed out, fill valve 30 is opened. It will be understood by those of skill that action of pump 32 will serve to fill fluid line 34 and distribution tube 28 which will slightly lower the level of water in pan 26 below that of the desired maximum water volume indicated by level MX. Thus, fill valve 30 is opened at block 82, to replenish that volume as is determined at block 84. At block 86, fill valve 30 is closed when the desired starting maximum level MX is again attained.

At this point pump 32 is operating to flow water over evaporator 16 as such is being cooled by the action of compressor 20, condenser and fan 18 and expansion valve 22, all as operated by control 40. As ice forms on evaporator 16, the water level in pan 26 goes down as does the pressure sensed by sensor 44. When a predetermined harvest water level is reached, as indicated by the level line denoted H, a corresponding predetermined pressure value is sensed by control 40 at block 88. When the harvest point is indicated, pump 32 is stopped and hot gas valve 24 is opened at block 90, causing evaporator 16 to warm resulting in the release of the ice slab formed thereon. Of course, those of skill will understand that other heating means known in the art could be employed, such as, an electrical heater integral with the ice forming evaporator. As is well understood, when the slab of ice falls from evaporator 16, curtain 37 is opened and switch 38 is closed, signaling to the control 40 the release of the ice slab from evaporator 16. As is also known, to insure that the slab of ice has fallen into bin 12 and is no longer in the vicinity of evaporator 16, at block 96, the control herein awaits the remaking of switch 38 which occurs when curtain 36 is free to swing back to its normal closed position unobstructed by any ice. At block 98 the control returns to start and initiates a further ice making cycle.

It was found that the pressure-based water level sensing as described herein provides for very accurate and repeatable determination and control thereof, and hence, for very reliable control of the harvest cycle of an ice maker. In particular, the physical isolation of the pressure sensor 44 from pan 26 contributes to this improved performance by serving to prevent any degradation of the sensor due to the presence of water and/or the corrosive impact thereof.

The operation of the high condenser temperature error control can best be understood by reference to FIG. 7. As seen therein at block 100, ice maker 10 is in an ice making cycle where upon at block 102 the temperature of condenser 18 is sensed by temperature sensor 47. If at block 104 the temperature is determined to be greater than 160 degrees Fahrenheit (F.) at block 106 a time period “C” is started. At block 108 the condenser temperature is read again, and if at block 110 the temperature of the condenser has gone below 160 Degrees F. normal ice making is continued after stopping the timing of period C at block 112 and resetting the time C timer at block 114. If however, at block 116 time C has timed out, in the present case at 2 seconds, a counter is incremented once at block 118. At block 120 it is determined if the counter equals three, i.e. that three successive time periods C have timed out without a successful return to an ice making cycle and the full completion thereof through harvest. If the C count is equal to 3, then at block 122 a high temp shut down code is flashed. All outputs are then turned off at block 124 which then requires that ice maker 10 be restarted by a manual restart at block 126 in order to re-enter the ice maker start-up or ice making routine at block 128. If at block 120 the count is less than three, then at block 130 a high temperature waning code is flashed and all outputs are turned off at block 132. The temperature of the condenser is monitored at block 134 and if at block 136 the temperature of the condenser goes to a predetermined low temperature, e.g. 100 degrees F., the ice malting start-up sequence is reinitiated at block 138. It can be understood that the condenser temperature error control of the present invention only reinitiates if the condenser temperature is deemed to have gone to a suitably low temperature that restart makes sense, i.e. there is a greater likelihood that a successful ice making cycle will ensue.

The water fill cycle control of the present invention is best understood by referring to the flow diagram of FIG. 8. At block 200 an ice making cycle is initiated and the control first determines at block 202 if water is at the maximum MX level. If it is, then at block 204 it is first determined that the hot gas valve 24 is closed and then at block 206 the ice making cycle is entered. If at block 202 the water level is not at the maximum, then a water fill timer is started at block 208 after which valve 30 is opened at block 210. At block 212 the rate of flow in terms of inches of water depth increase in water pan 26 is determined by processor 42 as a function of the input of pressure communicated to sensor 44. If, at block 212 it is determined that the water flow rate is increasing at a rate equal to or greater than 0.1 inch per 10 seconds it is then determined at block 214 if the MX water level has been reached. If that MX level has been achieved at block 214 then valve 30 is closed at block 216 and the hot gas valve 24 is checked at block 218. If valve 24 is off, then an ice making cycle is entered at block 220. Thus, as long as the flow rate of the water entering pan 26 correlates to a rate of fill of greater than or equal to 0.1 inch per 10 seconds of water level increase in pan 26, ice maling proceeds once the MX level is reached. However, if at block 222 it is determined that the water level in pan 26 is less than one quarter of an inch, then at block 224 a failed water system shut down code is flashed and all outputs are turned off at block 226. A manual restart at block 228 is then required to re-enter the ice making routine start-up at block 230. If at block 212 it is determined that the pressure increase corresponds to a fill rate of pan 26 per 10 seconds as being less that 0.1 inch at block 232 the compressor is turned off and at block 234 an inlet water warning is flashed.

It can now be understood that the water safety control of the present invention actively looks at the fill rate of pan 26 and has a built in tolerance for that fill rate. If the fill rate is above a certain predetermined rate, the compressor is left on. If the fill rate is low but otherwise acceptable, i.e. the filling of the pan will occur in a slower but nevertheless reasonable period of time, then that filling is allowed to continue. However, the compressor is turned off so as not to waste energy during the longer fill cycle. The water fill routine of the present invention is also an improvement over the prior art wherein a simple timer is used without regard to the actual fill rate. Thus, the water fill routine herein will not recognize as a “fault” what other systems may otherwise determine as such based upon the simple timing out of a timer. A threshold low or no fill rate is also determined below which the filling of pan 26 is exceedingly slow or not occurring at all, whereupon a manual restart should be required. If less than one quarter of an inch of water is seen in pan 26, that would indicate that no water is flowing or that, for example, pan 28 is leaking water and not filling.

The improved harvest cycle control of the present invention can best be understood in view of FIG. 9. At block 300, a harvest cycle is signaled to begin and at block 302 hot gas valve 24 is opened. A harvest timer is then started at block 304. If, at block 306 the harvest time is less than four minutes and at block 308 all the proximity switches 38 are open, indicating a successful harvest, then at block 310 a subsequent ice maling cycle is entered. If at block 306 the harvest time exceeds 4 minutes, then a harvest timer counter is reviewed at block 312 and if the count thereof equals 5, then a harvest time out shut down code is flashed at block 314. At block 316 all outputs are turned off such that a manual restart is required at block 318 in order to re-enter an ice making cycle at block 320. If at block 312 the count is less than 5, the counter is incremented at block 322 the compressor is turned off at block 324, and a harvest time out warning code is flashed at block 326. At block 328 a water fill timer is started and valve 30 is opened at block 330 letting warm water fill pan 26. If at blocks 332 and 334 either the water fill timer equals 4 minutes or the water MX level is reached, then a water pump timer is started at block 336. Water pump 32 is then started at block 338 and circulates the warm replacement water over the evaporator 16. When the water pump timer reaches 10 minutes at block 340, then the ice making restart cycle is entered at block 342.

It can be appreciated that the harvest control of the present invention uses a novel approach to circulate warm water over the evaporator for a predetermined period of time in order to melt and remove any recalcitrant ice from the evaporator. Thus, the control herein takes active measures to eliminate a fault resulting from a failed harvest, wherein ice is not seen to have fallen from the evaporator.

While embodiments of the invention have been described in detail, one skilled in the art can devise various modifications and other embodiments without departing from the spirit and scope of the invention, as defined in the accompanying claims.

Claims

1. A control system for an icemaker of a type having a compressor for delivering refrigerant to and though a condenser to an evaporator, a water pan, means for delivering water to said water pan and a pump for delivering water from said water pan to and across said evaporator to freeze the water into ice on said evaporator for subsequent harvesting of the ice, said control system comprising: means responsive to the temperature of refrigerant at an outlet from said condenser being greater than a predetermined high temperature to interrupt operation of said icemaker; means responsive to a level of water in said water pan that is less than a selected high level and to delivery of water to said water pan at a rate less than a predetermined rate to inhibit operation of said compressor; and means responsive during an ice harvesting cycle of said icemaker to a failure to complete harvesting of ice from said evaporator within a selected period of time to interrupt operation of said icemaker.

2. A control system as in claim 1, wherein said means responsive to the temperature of refrigerant at said condenser outlet is responsive to the temperature being greater than said predetermined high temperature for a selected time to interrupt operation of said icemaker.

3. A control system as in claim 1, wherein said means responsive to the temperature of refrigerant at said condenser outlet includes timer means responsive to the temperature being greater than said predetermined high temperature to begin timing a selected period of time, means for resetting said timer means upon occurrence of a the temperature being no greater than said predetermined high temperature, and means responsive to timing out of said timer means at the end said selected time period to interrupt operation of said icemaker.

4. A control system as in claim 3, wherein said means responsive to the temperature of refrigerant at said condenser outlet further includes means, operative following interruption of operation of said icemaker upon timing out of said timer means at the end of said selected time period, for enabling continued operation of said icemaker upon the temperature of refrigerant at said condenser outlet decreasing to a predetermined low temperature.

5. A control system as in claim 4, wherein said means responsive to the temperature of refrigerant at said condenser outlet further includes counter means for storing a count of the number of times said timer means times out by reaches the end of said selected time period, means responsive to said stored count being less than a selected number for enabling operation of said icemaker upon the temperature of refrigerant at said condenser outlet decreasing to said predetermined low temperature, and means responsive to said stored count reaching said selected number for interrupting operation of said icemaker and generating a signal that manual intervention is required to enable continued operation of said icemaker.

6. A control system as in claim 1, including means for sensing the level of water in said water pan, and means responsive to the sensed level of water being at said selected high level to prevent delivery of water to said water pan and to enable operation of said icemaker, and responsive to the sensed level of water being less than a selected low level for inhibiting operation of said icemaker and for generating an indication that manual intervention is required to enable continued operation of said icemaker.

7. A control system as in claim 6, including means for sensing, upon delivery of water to said water pan, the rate of filling of said water pan with water, and means responsive to the sensed water fill rate being at least equal to a selected rate and to the sensed water level being intermediate said selected low and high levels for enabling operation of said compressor while the sensed water level is less than said selected high level, and for interrupting delivery of water to said water pan and enabling operation of said icemaker when the sensed water level reaches said selected high level.

8. A control system as in claim 7, wherein said means for sensing the rate of filling of said water pan water includes means responsive to changes in the sensed level of water in the water pan with respect to time to determine the rate of filling.

9. A control system as in claim 1, including means for delivering hot refrigerant from said condenser to said evaporator to heat said evaporator to cause release of ice formed on said evaporator in order to harvest the ice, and wherein said means responsive to a failure to complete harvesting of ice from said evaporator within said selected period of time includes timer means responsive to delivery of hot refrigerant to said evaporator to beg timing said selected time period, means for sensing release of ice from said evaporator, and means responsive to said sensing means sensing release of ice from said evaporator before said timer means reaches the end of said selected time period to enable continued operation of said icemaker.

10. A control system as in claim 9, wherein said means responsive to a failure to complete harvesting of ice from said evaporator within said selected time period includes means responsive to failure of said sensing means to sense release of ice from said evaporator before said timer means times out at the end of said selected time period to disable operation of said compressor.

11. A control system as in claim 10, wherein said means responsive to failure to complete harvesting of ice from said evaporator within said selected time period includes means for delivering water to said water pan and for operating said pump to flow the water from the water pan over said evaporator to warm and release ice remaining on said evaporator, and for then enabling operation of said icemaker.

12. A control system as in claim 9, including counter means for storing a count of the number of failures of said sensing means to sense release of ice from said evaporator before said tier means times out at the end of said selected time period, and means responsive to said counter means stored count being equal to a selected count to interrupt operation of said icemaker and to generate a signal indicating that manual intervention is required to enable continued operation of said icemaker.

13. A control system for an icemaker of a type having a compressor for delivering refrigerant to and though a condenser to an evaporator, a water pan, means for delivering water to said water pan and a pump for delivering water from said water pan to and across said evaporator to freeze the water into ice on said evaporator for subsequent harvesting, said control system comprising: means for sensing the temperature of refrigerant at an outlet from said condenser; and means responsive to said sensed refrigerant temperature being no greater than a predetermined high temperature or greater than said predetermined high temperature for less than a selected period of time for enabling continued operation of said icemaker.

14. A control system as in claim 13, including timer means responsive to said sensed refrigerant temperature being greater than said predetermined high temperature to begin timing said selected time period; means for resetting said timer means in response to sensing a refrigerant temperature no greater than said predetermined high temperature before said timer means times out at the end of said selected time period; means responsive to said timer means timing out at the end of said selected time period to interrupt operation of said icemaker; and means responsive to said sensing means sensing a subsequent decrease in refrigerant temperature to a predetermined low temperature to enable continued operation of said icemaker.

15. A control system as in claim 13, including counter means responsive to each occurrence of said timer means timing out at the end of said selected time period to advance by one a count stored therein; and means responsive to said counter means reaching a selected stored count to inhibit operation of said icemaker and to generate a signal indicating that manual intervention is required to enable continued operation of said icemaker.

16. A control system for an icemaker of a type having a compressor for delivering refrigerant to and though a condenser to an evaporator, a water pan for being filled with water, means for delivering water to said water pan, and a pump for delivering water from said water pan to and across said evaporator to freeze the water into ice on said evaporator for subsequent harvesting of the ice, said control system comprising: means for operating said compressor to deliver cold refrigerant to said evaporator; means for sensing the level of water in said water pan; means responsive to a selected maximum level of water in said water pan to enable operation of said icemaker; means responsive to less than said selected maximum level of water in said water pan to initiate delivery of water to said water pan; means for sensing the rate of filling of said water pan with water during delivery of water; means responsive to said sensed water fill rate being at least equal to a selected rate to continue operation of said compressor; and means responsive to said water level sensing means sensing said selected maximum level of water in said water pan to interrupt delivery of water and enable operation of said icemaker.

17. A control system as in claim 16, including means responsive to said sensed water fill rate being less than said selected rate to interrupt operation of said compressor until said water level sensing means senses said selected maximum level of water in said water pan, and for then enabling operation of said compressor and said icemaker.

18. A control system as in claim 16, including means responsive to said water level sensing means sensing a selected minimum level of water in said water pan to inhibit operation of said compressor and icemaker and to generate a signal indicating that manual intervention is required to enable continued operation of said icemaker.

19. A control system for an icemaker of a type having a compressor for delivering refrigerant to and though a condenser to an evaporator, a water pan for being filled with water, means for delivering water to said water pan, and a pump for delivering water from said water pan to and across said evaporator to freeze the water into ice on said evaporator for subsequent harvesting of the ice, said control system comprising: means for delivering hot refrigerant from said condenser to said evaporator to heat said evaporator to release ice formed on said evaporator in order to harvest the ice; timer means responsive to delivery of hot refrigerant to said evaporator to begin timing a selected period of time; means for sensing release of ice from said evaporator; means responsive to sensing release of ice from said evaporator before said timer means times out at the end of said selected time period for enabling continued operation of said icemaker; means responsive to a failure to sense release of ice from said evaporator before said timer means times out at the end of said selected time period for turning off said compressor, causing delivery of water to said water pan, operating said pump to flow water across said evaporator to release ice remaining said evaporator, and then enabling continued operation of said icemaker.

20. A control system as in claim 19, said control system including a water pump timer for controlling the time for which said pump is operated to flow water from said water pan over said evaporator to warm and release ice from said evaporator before continued operation of said icemaker is enabled.

21. A control system as in claim 19, including counter means for storing a count of the number of failures to sense release of ice from said evaporator before said timer means times out at the end of said selected time period, and means responsive to said counter means stored count equaling a selected count to inhibit further operation of said icemaker and to generate a signal indicating that manual intervention is required to enable continued operation of said icemaker.

22. A method of controlling an icemaker of a type having a compressor for delivering refrigerant to and though a condenser to an evaporator, a water pan, a supply line for delivering water to the water pan and a pump for delivering water from the water pan to and across the evaporator to freeze the water into ice on the evaporator for subsequent harvesting of the ice, said method comprising the steps of: controlling the temperature of refrigerant at an outlet from the condenser to be no greater than a predetermined high temperature by sensing the temperature of refrigerant at the condenser outlet and, in response to the sensed temperature being greater than a predetermined high temperature, interrupting operation of the icemaker; ensuring the availability of sufficient water in the water pan for delivery to the evaporator during an ice freezing cycle by delivering water to the water pan while sensing both the level of water in the water pan and the rate at which the water pan is being filled with water and, in response to a sensed level of water in the water pan that is less than a selected high level and to a sensed water fill rate that less than a selected rate, inhibiting operation of the compressor; and after water has been frozen into ice on the evaporator, monitoring completion of a cycle of harvesting ice from the evaporator upon delivery of hot refrigerant from the condenser to the evaporator to warm the evaporator to release the ice from its bond to the evaporator, by sensing release of the ice from the evaporator and, if release of the ice from the evaporator is not sensed within a selected period of time, interrupting operation of the icemaker.

23. A method as in claim 22, wherein controlling the temperature of refrigerant at the condenser outlet includes the step of measuring the time for which the sensed refrigerant temperature is greater than the predetermined high temperature, said interrupting step being responsive to the sensed temperature being continuously greater than the predetermined high temperature for a selected time to interrupt operation of the icemaker.

24. A method as in claim 23, wherein controlling the temperature of refrigerant at the condenser outlet includes the further steps, following performance of said interrupting step, of sensing a decrease in the temperature of refrigerant at the condenser outlet to a predetermined low temperature and, in response thereto, enabling continued operation of the icemaker.

25. A method as in claim 24, wherein controlling the temperature of refrigerant at the condenser outlet includes the further steps of storing a count of the number of times said icemaker operation interrupting step is performed and, upon the stored count equaling a selected number, interrupting operation of the icemaker and generating a signal indicating that manual intervention is required to enable continued operation of the icemaker.

26. A method as in claim 22, wherein ensuring the availability of sufficient water in the water pan for delivery to the evaporator during an ice freezing cycle includes the steps, performed in response to said sensing step sensing that the level of water in the water pan is at a selected high level, of interrupting delivery of water to the water pan, and enabling operation of the icemaker, as well as the steps, performed in response to said sensing step sensing that the level of water in the water pan is less than a selected low level, of inhibiting operation of the icemaker and generating an indication that manual intervention is required.

27. A method as in claim 22, wherein ensuring the availability of sufficient water in the water pan for delivery to the evaporator during an ice freezing cycle includes the further steps, performed in response to said sensing step sensing that the rate at which the water pan is being filled with water is at least the selected rate and that the level of water in the water pan is intermediate a selected low level and the selected high level, of enabling operation of the compressor and continuing to deliver water to the water pan, and interrupting delivery of water to the water pan and enabling operation of the icemaker when the sensed water level reaches the selected high level.

28. A method as in claim 22, wherein monitoring completion of a cycle of harvesting ice from the evaporator includes the further steps, in response to a failure to sense release of the ice from the evaporator within the selected time period, of delivering water to the water pan, operating the pump to flow the water from the water pan over the evaporator to warm and release ice remaining on the evaporator, and then enabling operation of the icemaker.

29. A method as in claim 28, wherein monitoring completion of a cycle of harvesting ice from the evaporator includes the further steps of storing a count of the number of times failures to sense release of the ice from the evaporator within the selected time period during ice harvesting and, in response to the stored count reaching a selected count, interrupting operation of the icemaker and generating an indication that manual intervention is required to enable continued operation of the icemaker.

29. A method of controlling an icemaker of a type having a compressor for delivering refrigerant to and though a condenser to an evaporator, a water pan, a supply line for delivering water to the water pan and a pump for delivering water from the water pan to and across the evaporator to freeze the water into ice on the evaporator for subsequent harvesting, said method comprising the steps of: sensing the temperature of refrigerant at an outlet from the condenser; and enabling operation of the icemaker in response to a sensed temperature of refrigerant that is no greater than a predetermined high temperature or that is greater than the predetermined high temperature for less than a selected time.

30. A method as in claim 29, including the further steps of: interrupting operation of the icemaker in response to a sensed refrigerant temperature that is greater than the predetermined high temperature continuously for a selected time; and enabling continued operation of the icemaker, following performance of said interrupting step, in response to a sensed decrease in refrigerant temperature to a predetermined low temperature.

31. A method as in claim 29, including the further steps of: storing a count of each occurrence of a sensed refrigerant temperature that is greater than the predetermined high temperature continuously for the selected time; and in response to the stored count reaching a selected count, inhibiting operation of the icemaker and generating an indication that manual intervention is required to enable continued operation of the icemaker.

32. A method of controlling an icemaker of a type having a compressor for delivering refrigerant to and though a condenser to an evaporator, a water pan, a supply line for delivering water to the water pan and a pump for delivering water from the water pan to and across the evaporator to freeze the water into ice on the evaporator for subsequent harvesting of the ice on the evaporator, said method comprising the steps of: operating the compressor to deliver cold refrigerant to the evaporator; sensing the level of water in the water pan; enabling operation of the icemaker in response to a sensed maximum level of water in the water pan; delivering water to the water pan in response to a sensing less than the maximum level of water in the water pan; sensing the rate of filling of the water pan with water during deliver of water to the water pan; continuing operation of the compressor in response to the sensed water fill rate being at least equal to a selected water fill rate; and interrupting delivery of water to the water pan and enabling operation of the icemaker in response to sensing the maximum level of water in the water pan.

32. A method as in claim 32, including the further steps of; interrupting operation of the compressor upon the sensed water fill rate being less than the selected fill rate while continuing to deliver water to the water pan; and enabling operation of the icemaker upon the sensed level of water in the water pan reaching the selected maximum level.

34. A method as in claim 32, including the steps of inhibiting operation of the icemaker and, in response to sensing a selected minimum level of water in the ice pan, generating an indication that manual intervention is required to enable continued operation of the icemaker.

35. A method of controlling an icemaker of a type having a compressor for delivering refrigerant to and though a condenser to an evaporator, a water pan, a supply line for delivering water to the water pan and a pump for delivering water from the water pan to and across the evaporator to freeze the water into ice on the evaporator for subsequent harvesting of the ice on the evaporator, said method comprising the steps, at the end of an icemaking cycle when water has been frozen into ice on the evaporator, of: delivering hot refrigerant from the condenser to the evaporator to heat the evaporator to release the ice from the evaporator; sensing release of the ice from the evaporator; enabling continued operation of the icemaker in response to sensing release of the ice from the evaporator within less than a selected time following delivery of hot refrigerant to the evaporator; and in response to failing to sense release of the ice from the evaporator within the selected time, performing the steps of turning off the compressor, delivering water to the water pan, operating the pump to flow water from the water pan to and across the evaporator to warm and release ice remaining on the evaporator, and then enabling operation of the icemaker.

36. A method as in claim 35, wherein the step of flowing water across the evaporator to release ice from the evaporator flows the water across the evaporator for a selected time.

37. A method as in claim 35, including the steps of storing a count of the number of failures to sense release of the ice from the evaporator within the selected time following delivery of hot refrigerant to the evaporator and inhibiting further operation of the icemaker and, in response the stored count reaching a selected count, generating an indication that manual intervention is required to enable continued operation of the icemaker.