Abstract:
Methods and apparatus that manage electric power consumed by an appliance are disclosed. The appliance has an interior accessible by consumers through a door having an open state and a closed state. The appliance includes a cooling system having at least a first mode of operation and a second mode of operation for cooling the interior of the appliance. Power consumption is managed by monitoring the appliance to identify the open state of the door and transitioning the cooling system of the appliance from the first mode of operation to the second mode of operation responsive at least in part to identification of the open state of the door.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part of U.S. patent application Ser. No. 10/291,066 filed Nov. 8, 2002, now U.S. Pat. No. 6,975,926 the contents of which are incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to cooling systems and, more particularly, to methods and apparatus for reducing refrigerated appliance power consumption. 
   BACKGROUND OF THE INVENTION 
   Consumer accessible refrigerated appliances include cooling systems to refrigerate products such as canned or bottled beverages for purchase by consumers. The cooling systems are designed to maintain the interior of these appliances (and the products therein) within a predefined temperature range. Typically, a consumer accessible refrigerated appliance (herein appliance) has a door (generally glass) that is opened by either sliding the door to a side of the appliance or rotating the door about a hinged axis to gain access to the products therein. Such appliances are commonly referred to in the industry as reach-in coolers, slide coolers, or visi-coolers, for example. 
   It is not uncommon for the door of an appliance to remain ajar after it has been opened. When this occurs, the temperature within the appliance rises and often, even though running continuously, the cooling system is unable to cool the interior of the appliance much below the ambient temperature of the air surrounding the appliance. Thus, the cooling system wastes a large amount of power in attempting to cool the interior of the appliance with the interior of the appliance having essentially the same temperature as it would have if the cooling system were off. In addition, continuously running the cooling system may result in condensation freezing on the evaporator coils of the cooling system, thereby further reducing the efficiency of the cooling system. 
   Additionally, the cooling system of an appliance typically maintains the interior of the appliance within the predefined temperature range regardless of usage. Thus, the refrigerated appliance may consume a great deal of power/energy maintaining products therein at a low temperature even when there is no demand for the product. For example, if the appliance is located in a grocery store that is closed at night, the appliance will consume power to keep the product cool even though no one will be purchasing the product at those times. 
   Further, the cooling system of the appliance typically transitions the cooling system between two modes based on one or more absolute temperature set points. In a first mode of operation (e.g., a cooling needed mode), a compressor and an evaporator fan are both ON to lower the temperature to a predetermined low set point. In a second mode of operation (e.g., a no cooling needed mode), the compressor is OFF and the evaporator fan remains ON while the temperature is allowed to raise to a predetermined high set point. Thus, the evaporator fan is always ON to circulate air within the appliance. In addition to circulating air, however, the evaporator fan introduces heat, which must then be removed through operation of the compressor. 
   SUMMARY OF THE INVENTION 
   The present invention is embodied in methods and apparatus that manage electric power consumed by an appliance. The appliance has an interior accessible by consumers through a door having an open state and a closed state. The appliance includes a cooling system having at least a first mode of operation and a second mode of operation for cooling the interior of the appliance. Power consumption is managed by monitoring the appliance to identify the open state of the door and transitioning the cooling system of the appliance from the first mode of operation to the second mode of operation responsive at least in part to identification of the open state of the door. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is best understood from the following detailed description when read in connection with the accompanying drawings, with like elements having the same reference numerals. When a plurality of similar elements are present, a single reference numeral may be assigned to the plurality of similar elements with a small letter designation referring to specific elements. When referring to the elements collectively or to a non-specific one or more of the elements, the small letter designation may be dropped. The letter “n” may represent a non-specific number of elements. This emphasizes that according to common practice, the various features of the drawings are not drawn to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following figures: 
       FIG. 1  is a schematic diagram of a refrigerated appliance with a cooling system in accordance with an exemplary embodiment of the present invention; 
       FIG. 2  is a block diagram of exemplary cooling modes implemented by the cooling system of  FIG. 1  in accordance with various aspects of the present invention; 
       FIG. 3  is a flow chart of exemplary steps for identifying a door open state of the appliance of  FIG. 1  in accordance with an exemplary embodiment of the present invention; 
       FIG. 4  is a flow chart of exemplary steps for monitoring and controlling the cooling system in an initialization mode in accordance with an exemplary embodiment of the present invention; 
       FIG. 5  is a flow chart of exemplary steps for monitoring and controlling the cooling system in an normal off mode in accordance with an exemplary embodiment of the present invention; 
       FIG. 6A  is a flow chart of exemplary steps for monitoring and controlling the cooling system in a normal cooling mode in accordance with an exemplary embodiment of the present invention; 
       FIG. 6B  is a continuation of the flow chart of  FIG. 6A ; 
       FIG. 7  is a flow chart of exemplary steps for monitoring and controlling the cooling system in a recovery mode in accordance with an exemplary embodiment of the present invention; 
       FIG. 8  is a flow chart of exemplary steps for monitoring and controlling the cooling system in a savings maximum mode in accordance with an exemplary embodiment of the present invention; and 
       FIG. 9  is a flow chart of exemplary steps for monitoring and controlling the cooling system in a savings minimum mode in accordance with an exemplary embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  depicts an exemplary appliance  100 . Illustrated appliance  100  includes a housing  101  having a product display area  102  with an interior  104 . Appliance  100  is depicted with a plurality of products within product display area  102  (represented by products  108   a–o  positioned on shelves  110   a–d ). Exemplary products, by non-limiting example, include canned or bottled beverages, other ingestible items, or essentially any item that would benefit from refrigeration. 
   Interior  104  of appliance  100  (and, thus, products  108 ) may be accessed through one or more doors coupled to the housing  101  (represented by a first door  112  and a second door  114  in the illustrated embodiment), each door having an open state and a closed state. Doors  112 / 114  are illustrated in their closed state. In an exemplary embodiment, doors  112 / 114  are positioned within a track defined by a lower track  116  and an upper track  118 . Doors  112 / 114  may be opened/closed by sliding doors  112 / 114  within the track from one side of appliance  100  toward the other. For example, first door  112  may be opened by sliding it to the left and second door  114  may be opened by sliding it to the right. In an alternative exemplary embodiment, doors  112 / 114  may be opened by pivoting doors  112 / 114  about hinges (not shown) on a side of doors  112 / 114 . Various alternative methods for enabling access to interior  104  of appliance  100  will be understood by one of skill in the art from the description herein. For ease of description, the invention is described below in terms of a single door  112  that may be opened by sliding it to the left and closed by sliding it to the right. 
   A cooling system  120  controls the temperature of interior  104  of appliance  100 . Power for the cooling system  120  may be provided by a conventional power outlet  122  via a power cord  124 . Power from power outlet  122  is received by a power supply  126  within cooling system  120 . Power supply  126  supplies power to a compressor  128  and an evaporator fan  130  via a first switch  132  and a second switch  134 , respectively, that are controlled by control signals received from a processor  136  (described in further detail below). Evaporator fan  130  is typically located within interior  104  of appliance  100  to remove heat from interior  104 , but is illustrated in  FIG. 1  outside interior  104  for the sake of clarity in the figure. In addition, power supply  126  may further supply power to a condenser fan (not shown), which may receive power via first switch  132 , may be controlled separately, or may be configured to receive power continuously (i.e., always ON). It is contemplated that power supply  126  may be eliminated—with power from outlet  122  being supplied directly to at least one of switches  132 / 134 . The cooling system  120  may further include one or more visual indicators (such as optional LED  138 ) that are under control of processor  136 . Suitable components for use within cooling system  120  will be understood by one of skill in the art from the description herein. 
   Processor  136  configures cooling system  120  by controlling the flow of power to compressor  128  and evaporator fan  130  of cooling system  120  in accordance with cooling modes (described below) based at least in part on temperature feedback received from interior  104  of appliance  100 . Processor  136  may work together with other known cooling controls (e.g., mechanical cold controls) in appliance  100  or may perform all cooling operations. In an exemplary embodiment, temperature feedback is received from a temperature sensor  140  (e.g., a thermister) positioned within interior  104  of appliance  100 . Additionally, processor  136  may receive an actuated signal from an optional proximity sensor  142  and/or an occupancy signal from an optional occupancy sensor  144 . Processor  136  may include an internal timer(s) or an external timer(s)  146  (as illustrated). Processor  136  may control the flow of power to compressor  128  and evaporator fan  130  based further on the actuated signal, occupancy sensor, and/or timer values. Suitable temperature sensors, proximity sensors, occupancy sensors, and timers for use with the present invention will be understood by one of skill in the art from the description herein. 
   In exemplary embodiments including proximity sensor  142 , proximity sensor  142  is positioned such that a signal is generated when door  112  of appliance  100  is opened. In exemplary embodiments including occupancy sensor  144 , occupancy sensor  144  may be an infrared (IR) sensor, for example, that monitors the IR spectrum within interior  104  of appliance  100 . The IR sensor senses when door  112  is open by sensing a change in IR spectrum. In accordance with this embodiment, door  112  of appliance  100  is preferably opaque to IR light and, thus, general pedestrian traffic passing by appliance  100  does not result in a false indication that door  112  is open. 
     FIG. 2  depicts exemplary cooling modes of operation  200  that processor  100  ( FIG. 1 ) implements to control cooling system  120 . Cooling modes of operation  200  include a normal mode of operation  202  and an energy savings mode of operation  204 , which consumes less power than normal mode of operation  202 . In an exemplary embodiment, normal mode of operation  202  includes four different modes and energy savings mode of operation  204  includes two different modes. Illustrated normal mode of operation  202  includes an initialization mode  206 , a normal off mode  208 , a normal cooling mode  210 , and a recovery mode  212 . Illustrated energy savings mode of operation  204  includes a savings maximum (max) mode  214  and a savings minimum (min) mode  216 . In an exemplary embodiment, processor  136  implements these modes through separate control of evaporator fan  130  and compressor  128 . Processor  136  may also control a condenser fan (not shown) in conjunction with compressor  128  to implement the modes, resulting in further energy savings. In the description below it will be understood that the condenser fan may be transitioned between ON and OFF essentially simultaneously with compressor  128  to implement the modes in accordance with exemplary embodiments of the present invention. These modes will be described in detail below. 
   In an exemplary embodiment, processor  136  transitions cooling system  120  from an energy savings mode of operation  204  (such as the savings max mode  214  or the savings min mode  216 ) to another mode such as one of the normal modes  202  in response to door  112  ( FIG. 1 ) being detected as open. In addition, processor  136  may be configured to maintain one or more modes for at least a minimum period time, e.g., 30 seconds to 2 minutes, before transitioning to another mode. The modes may have the same minimum period of time or different minimum periods of time. 
   In an exemplary embodiment, an open door  112  is detected by processor  136  based on temperature readings within interior  104  of appliance  110 .  FIG. 3  depicts a flow chart  300  of exemplary steps for use by processor  136  of cooling system  120  in detecting if door  112  is open based on temperature readings within interior  104  of appliance  100 , e.g., obtained through temperature sensor  140 . 
   At block  302 , a door open detection loop is entered. At block  304 , a current sample temperature (CTMP) within interior  104  of appliance  100  and a previous sample temperature (PTMP) within interior  104  of appliance  100  are determined. The difference in time between CTMP and PTMP may be a relatively short period of time, e.g., 2, 5, or 10 seconds. In an exemplary embodiment, processor  136  determines CTMP and PTMP by taking numerous temperature samples per second (e.g., obtained from temperature sensor  140 ) and averaging them to remove noise from the samples. Processor  136  may obtain and store PTMP in a memory (not shown). In addition, processor  136  may obtain and store CTMP in the memory. 
   At block  306 , a decision is made regarding the difference between CTMP and PTMP compared to a minimum rise temperature to detect a door open event (DLT 1 ). If CTMP minus PTMP is greater than DLT 1 , processor  136  identifies door  112  as open and processing proceeds at block  308 . Otherwise, processing proceeds at block  310 . In an exemplary embodiment, the decision of block  306  is performed several times per minute, e.g., once every five or ten seconds. 
   At block  308 , a door open timer (DOORTMR) is reset. In an exemplary embodiment, the DOORTMR increments once per minute and is reset when the difference between CTMP and PTMP exceeds a certain level. Thus, DOORTMR represents the elapsed time in minutes since the door was last open, i.e., how long the door has been closed. Since CTMP and PTMP are separated by a period of time, the difference between them represents a rate of change within the interior  104  of the appliance  100 . Accordingly, if the rate of change exceeds a certain level, e.g., 0.2–0.4 degrees per sample, the door is detected as open. 
   At block  310 , the end of the door open detection loop is reached and processing returns to block  302 . In an exemplary embodiment, the door open detection loop runs continuously in the background as long as appliance  100  is receiving power. The door open detection loop may be configured to run on a faster clock than normal and energy savings modes  202 / 204 . In addition, cooling system  120  may be configured to change states based on detection of an open door. The door open detection loop may include a roll over timer that prevents an open door condition from being communicated more frequently than a predefined period of time, e.g., once a minute. 
   In alternative exemplary embodiments, door  112  may be identified as open via proximity switch  142  and/or occupancy sensor  144  ( FIG. 1 ). For example, as door  112  is moved to the left, a lever  143  on proximity switch  142  is actuated by the door  112 , causing proximity switch  142  to identify to processor  136  that door  112  is open. In another example, opening door  112  or the insertion of a user&#39;s hand into interior  104  of appliance  100  may cause occupancy sensor  144  to identify to processor  136  that door  112  is open. 
     FIG. 4  depicts a flow chart  400  of exemplary steps for initialization mode  206  ( FIG. 2 ). At block  402 , initialization mode  206  is entered. In an exemplary embodiment, initialization mode  206  is entered only from initial “power on” of appliance  100  and, thus, compressor  128  ( FIG. 1 ) is OFF and evaporator fan  130  is OFF at the start of initialization mode  206 . 
   At block  404 , timers and variables for the normal and energy savings modes  202 / 204  are initialized (reset). In an exemplary embodiment, the timers set forth below in Table 1 and the variable set forth below in Table 2 are reset. Timers listed in Table 1 may be configured to either increment or decrement at a predetermined rate, e.g., once per minute. Predefined variable values will be understood by one of skill in the art from the description herein. 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 1 
             
             
                 
             
             
               Timers (Minutes) 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                 
               DOORTMR 
               Door Open Timer 
             
             
                 
               FR1TMR 
               Freeze 1 Timer 
             
             
                 
               FR2TMR 
               Freeze 2 Timer 
             
             
                 
               CRUNTMR 
               Compressor Run Timer 
             
             
                 
               ICETMR 
               Cooling Timer 
             
             
                 
               COFFTMR 
               Compressor Off Timer 
             
             
                 
               RECTMR 
               Recovery Timer 
             
             
                 
               SAVETMR 
               Time in Saving Min/Max Timer 
             
             
                 
               FOFFTMR 
               Evaporator Fan Off Timer 
             
             
                 
               COOLTMR 
               Comp. Run Timer after HitTMP5 set 
             
             
                 
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
           
         
             
               TABLE 2 
             
             
                 
             
             
               Timer Variables (Minutes) 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                 
               T1 
               Minimum time since a door open event was detected. 
             
             
                 
               T2 
               Maximum time since entering Savings Min/Max. 
             
             
                 
               T3 
               Minimum time since evaporator fan turned OFF. 
             
             
                 
               T4 
               Value of CRUNTMR when HitTMP5 flag set. 
             
             
                 
               T5 
               Maximum time since Freeze 1 timer last reset. 
             
             
                 
               T6 
               Maximum time since Freeze 2 timer last reset. 
             
             
                 
               T7 
               Maximum time for COOLTMR, set to 2 × T4 once 
             
             
                 
                 
               HitTMP5 flag set. 
             
             
                 
               T8 
               Maximum time since ICETMR reset. 
             
             
                 
               T9 
               Minimum time since entering recovery. 
             
             
                 
               T10 
               Minimum time compressor must be turned OFF. 
             
             
                 
                 
             
           
        
       
     
   
   At block  406 , a decision is made regarding CTMP. If CTMP is within a normal operation temperature range, e.g., less than a high level operation temperature (TMP 1 ) and greater than a low level operation temperature (TMP 7 ), processing proceeds at block  410 . Otherwise, processing proceeds at block  408 . 
   A block  408 , one or more diagnostic self-tests are performed. After the diagnostic self-tests are performed, processing proceeds at block  406  with the determination of whether CTMP is within the normal operation temperature range. Suitable diagnostic self-tests for use with the present invention will be understood by one of skill in the art from the description herein. 
   At block  410 , DOORTMR and an off timer for compressor  128  (COFFTMR) are reset. COFFTMR represents the elapsed time compressor  128  has been OFF. Cooling system  120  then enters normal off mode  208  ( FIG. 2 ) at block  412 . When transitioning from initialization mode  402  to normal off mode  208 , compressor  128  remains OFF and evaporator fan  130  is transitioned from OFF to ON. 
     FIG. 5  depicts a flow chart  500  of exemplary steps for normal off mode  208  ( FIG. 2 ). At block  502 , normal off mode  208  is entered. In an exemplary embodiment, normal off mode  208  is the first mode entered after initialization mode  206  described above and can be entered from any other mode. In normal off mode  208 , compressor  128  of cooling system  120  is OFF and evaporator fan  128  is ON. 
   At block  504 , a decision is made regarding COFFTMR. If COFFTMR is less than a predefined minimum time compressor  128  must be turned OFF (T 10 ), e.g., 30 second to 2 minutes, processing proceeds at block  502  with cooling system  120  in normal off mode  208 . Otherwise, processing proceeds at block  506 . 
   At block  506 , a decision is made regarding DOORTMR. If DOORTMR is greater than a predefined minimum time since door  112  was detected open (T 1 ), processing proceeds at block  508 . Otherwise, processing proceeds at block  512 . 
   At block  508 , an off timer for evaporator  130  (FOFFTMR) and a timer representing the elapsed time in savings minimum and/or savings maximum mode (SAVETMR) are reset. Processing then proceeds to block  510  with cooling system  120  transitioning to energy savings max mode  214 . When transitioning from normal off mode  208  to energy savings max mode  214 , compressor  128  remains OFF and evaporator fan  130  is transitioned from ON to OFF. 
   At block  512 , which is reached if DOORTMR is found to be less than or equal to T 1  at block  506 , a decision is made regarding CTMP. If CTMP is less than a predefined high set point for normal mode  202  (TMP 3 ), processing proceeds at block  502  with cooling system  120  in normal off mode  208 . Otherwise, processing proceeds at block  514 . 
   At block  514 , a decision is made regarding power source  122 . If the power source  122  has a voltage level that is too low or too high, which may damage cooling system  120 , processing proceeds at block  502  with cooling system  120  in normal off mode  208 . Otherwise, processing proceeds at block  516 . 
   At blocks  516  and  518 , a cooling timer (ICETMR), a first freezer timer (FR 1 TMR), and a second freezer timer (FR 2 TMR) are reset; a temperature when ICETMR is reset (ICETMP), a temperature when FR 1 TMR is reset (FR 1 TMP), and a temperature when FR 2 TMR is reset (FR 2 TMP) are set; and a reached TMP 3  flag (HitTMP 3 ), a reached TMP 5  flag (HitTMP 5 ), and a time flag are cleared. TMP 5  represents a first predefined low set point. 
   At block  520 , cooling system  120  enters normal cooling mode  210  with evaporator fan  130  remaining ON and compressor  128  transitioning from OFF to ON. The voltage check at block  514  guards against turning compressor  1280 N when voltage levels that are potentially damaging to compressor  128  are being supplied by the power source  122 . 
     FIGS. 6A and 6B  depict a flow chart  600  of exemplary steps for normal cooling mode  210  ( FIG. 2 ). At block  602 , normal cooling mode  210  is entered. In an exemplary embodiment, normal cooling mode  210  is entered from normal off mode  208 . In normal cooling mode  210 , compressor  128  is ON and evaporator fan  130  is OFF. 
   At block  603 , a decision is made regarding power source  122 . If the power source  122  has a voltage level that is too low or too high, which may damage cooling system  120 , processing proceeds at block  628  with the cooling system  120  entering normal off mode  208 . Otherwise, processing proceeds at block  604 . 
   At block  604 , a decision is made regarding FR 2 TMR. If FR 2 TMR is greater than a maximum predefined time since FR 2 TMR was last reset (T 6 ), processing proceeds at block  606  with a recovery timer (RECTMR) and COFFTMR being reset. Recovery mode  212  is then entered at block  608  with compressor  128  transitioning from ON to OFF and evaporator fan  130  remaining ON. Otherwise, processing proceeds at block  610 . 
   At block  610 , a decision is made regarding FR 1 TMP and CTMP. If FR 2 TMP minus CTMP is greater than a predefined minimum temperature change to reset FR 1 TMR (DLT 5 ), processing proceeds at block  612  with FR 2 TMR being reset and FR 2 TMP being set. Otherwise, processing proceeds at block  614 . 
   At block  614 , a decision is made regarding HitTMP 3 . If HitTMP 3  is not set, processing proceeds at block  616  with the reset of a run timer for compressor  128  (CRUNTMR). Otherwise, processing proceeds at block  622 . 
   At block  618 , a decision is made regarding CTMP. If CTMP is not greater than TMP 3 , processing proceeds at block  620  with HitTMP 3  flag being set. Otherwise, processing proceeds at block  640  (see  FIG. 6B ). 
   At block  622 , a decision is made regarding HitTMP 5  flag. If HitTMP flag is set, processing proceeds at block  624 . Otherwise, processing proceeds at block  627 . 
   At block  624 , a decision is made regarding the elapsed running time of compressor  128  since the HitTMP 5  flag was set (COOLTMR). If COOLTMR is greater than a maximum time set for COOLTMR (T 7 ), e.g., a predefined maximum or twice the value of CRUNTMR once HitTMP 5  flag is set, processing proceeds at block  626  with COFFTMR being reset and cooling system  120  reentering normal off mode  208  at block  628 . Otherwise, processing proceeds at block  636 . When transitioning from normal cooling mode  210  to normal off mode  208 , evaporator fan  130  remains ON and compressor  128  is transitioned from ON to OFF. 
   At block  627 , a decision is made regarding CTMP. If CTMP is greater than TMP 5 , processing proceeds at block  640  (see  FIG. 6B ). Otherwise, processing proceeds at block  632  with HitTMP 5  being set, T 4  being set to CRUNTMR, and CRUNTMR being stopped. At block  634 , COOLTMR is reset and T 7  is set to twice T 4 . 
   At block  636 , a decision is made regarding CTMP. If CTMP is less than a second predefined cooling mode low set point (TMP 6 ), processing proceeds at block  626  with COFFTMR being reset and cooling system  120  reentering the normal off mode  208  at block  628 . Otherwise, processing proceeds at block  640  (see  FIG. 6B ). 
   At block  640  (see  FIG. 6B ), which is reached if CTMP is greater than TMP 3  at block  618  or CTMP is greater than TMP 5  at block  627  or CTMP is not less than TMP 6  at block  636 , a decision is made regarding CTMP. If CTMP is greater than TMP 3 , ICETMR and FR 1 TMR are reset, ICETMP and FR 1 TMP are set at block  642 , and cooling system  120  remains in normal cooling mode  210  at block  602 . Otherwise, processing proceeds at block  644 . 
   At block  644 , a decision is made regarding the temperature when FR 1 TMR was reset (FR 1 TMP) and CTMP. If CTMP is less than FR 1 TMP by at least a predefined minimum drop to reset FR 1 TMR, processing proceeds at block  642 . Otherwise, processing proceeds at block  646 . 
   At block  646 , a decision is made regarding FR 1 TMR. IF FR 1 TMR is greater than a predefined maximum time since FR 1 TMR was reset (T 5 ), FR 1 TMR is reset and FR 1 TMP is set at block  648 . Otherwise, processing proceeds at block  650 . 
   At blocks  650  and  652 , decisions are made regarding ICETMP and CTMP. If ICETEMP minus CTMP is greater than a predefined minimum drop in temperature to reset ICETMR (DLT 6 ) or CTMP minus ICETMP is greater than a predefined minimum rise in temperature to reset ICETMR (DLT 7 ), processing proceeds at block  642  (described above) and cooling system  120  remains in normal cooling mode  210  at block  602 . Otherwise, processing proceeds at block  654 . 
   At block  654 , a decision is made regarding ICETMR. If ICETMR is greater than T 6 , processing proceeds at block  656  where RECTMR and COFFTMR are reset, and cooling system  120  enters recover mode  212  at block  658 . Otherwise, cooling system  120  remains in normal cooling mode  212  at block  602 . When transitioning from normal cooling mode  210  to recovery mode  212 , the evaporator fan  130  remains ON and compressor  128  is transitioned from ON to OFF. 
     FIG. 7  depicts a flow chart  700  of exemplary steps for recovery mode  212  ( FIG. 2 ). At block  702 , recovery mode  212  is entered. In an exemplary embodiment, recovery mode  212  is entered when cooling system  120  detects a possible frozen evaporator coil condition (e.g., based on temperature readings and timer values processed in accordance with the steps of flow chart  600 ). Recovery mode  212  is entered from normal cooling mode  210  and exits to normal off mode  208 . In recovery mode  212 , compressor  128  is OFF and evaporator fan  130  is ON. When entering recovery mode  212  from normal cooling mode  210 , evaporator fan  130  remains ON and compressor  128  is transitioned from ON to OFF. Turning compressor  128  OFF prevents condensation on the evaporator coils (not shown) of cooling system  120  from freezing and leaving evaporator fan  130  ON reduces condensation on the evaporator coils. This prevents the evaporator coils from freezing up, thereby improving the efficiency of cooling system  120 . 
   At block  704 , a decision is made regarding RECTMR. If RECTMR is not less than T 7 , processing proceeds to block  706 . Otherwise, processing proceeds at block  702  with cooling system  120  remaining in recovery mode  212 . In an exemplary embodiment, T 7  is between about 5 and 60 minutes, e.g., 30 minutes. 
   At block  706 , a decision is made regarding CTMP. If CTMP is not less than a predefined recovery high set point (TMP 4 ), processing proceeds at block  708  with cooling system  120  transitioning from recovery mode  212  to normal off mode  208  at block  708 . Otherwise, processing proceeds at block  702  with cooling system  120  remaining in recovery mode  212 . When transitioning from recovery mode  212  to normal off mode  208 , compressor  128  remains OFF and evaporator fan  130  remains ON. 
     FIG. 8  depicts a flow chart  800  of exemplary steps for energy savings max mode  214  ( FIG. 2 ). At block  802 , energy savings max mode  214  is entered. In an exemplary embodiment, energy savings max mode  214  is entered from normal off mode  208  and exits to either normal off mode  208  or energy savings min mode  216 . In energy savings max mode  214 , compressor  128  of cooling system  120  is OFF and evaporator fan  130  is OFF. 
   At block  804 , a decision is made regarding DOORTMR. If DOORTMR is less than a predefined minimum time since door  112  was detected open (T 1 ), processing proceeds at block  806  with the reset of DOORTMR and cooling system  120  enters normal off mode  208  at block  808 . Otherwise processing proceeds at block  810 . 
   At block  810 , a decision is made regarding SAVETMR. If SAVETMR is greater than a predefined maximum time since entering the savings minimum or maximum mode (T 2 ), processing proceeds at block  806  with the reset of DOORTMR and cooling system  120  enters normal off mode  208  at block  808 . Otherwise, processing proceeds at block  812 . When transitioning from savings max mode  214  to normal off mode  208 , compressor  128  remains OFF and evaporator fan  130  is transitioned from OFF to ON. 
   At block  812 , a decision is made regarding CTMP. If CTMP is less than a predefined high set point for energy savings mode  204  (TMP 2 ), cooling system  120  remains in energy savings max mode  214  at block  802 . Otherwise, processing proceeds at block  814 . 
   At block  814 , a decision is made regarding FOFFTMR. If FOFFTMR is less than a predefined minimum time since evaporator fan  130  was turned OFF (T 3 ), processing proceeds at block  806  with the reset of DOORTMR and cooling system  120  enters normal off mode  208  at block  808 . Otherwise, processing proceeds at block  816  where a temperature when savings min mode  216  was entered (STMP) is set and cooling system  120  enters energy savings min mode  216  at block  818 . When transitioning from savings max mode  214  to savings min mode  216 , compressor  128  remains OFF and evaporator fan  130  is transitioned from OFF to ON. 
     FIG. 9  depicts a flow chart  900  of exemplary steps for energy savings min mode  216  ( FIG. 2 ). At block  902 , energy savings min mode  216  is entered. In an exemplary embodiment, energy savings min mode  216  is entered from energy savings max mode  214  and exits to either normal off mode  208  or energy savings max mode  214 . In energy savings min mode  216 , compressor  128  of cooling system  120  is OFF and evaporator fan  130  is ON. 
   At block  904 , a decision is made regarding DOORTMR. If DOORTMR is less than T 1 , processing proceeds at block  906  with the reset of DOORTMR and cooling system  120  entering normal off mode  208  at block  908 . Otherwise, processing proceeds at block  910 . When transitioning from energy savings min mode  216  to normal off mode  208 , compressor  128  remains OFF and evaporator fan  130  remains ON. 
   At block  910 , a decision is made regarding SAVETMR. If SAVETMR is greater than T 2 , processing proceeds at block  906  with the reset of DOORTMR and cooling system  120  entering normal off mode  208  at block  908 . Otherwise, processing proceeds at block  912 . 
   At block  912 , a decision is made regarding PTMP and CTMP. If PTMP minus CTMP is not less than a predefined minimum temperature drop per minute to stay in energy savings min mode (DLT 2 ), processing proceeds at block  914 . Otherwise, processing proceeds at block  902  with cooling system  120  remaining in energy savings min mode  216 . 
   At block  914 , a decision is made regarding CTMP. If CTMP is greater than TMP 2 , processing proceeds at block  906  with the reset of DOORTMR and cooling system  120  entering normal off mode  208  at block  908 . Otherwise, processing proceeds at block  916 . 
   At block  916 , a decision is made regarding STMP and CTMP. If STMP minus CTMP is less than a predefined minimum temperature drop since entering energy savings min mode  216  (DLT 3 ), processing proceeds at block  906  with the reset of DOORTMR and cooling system  120  entering normal off mode  208  at block  908 . Otherwise, processing proceeds at block  918  with the reset of FOFFTMR and cooling system  120  entering energy savings max mode  214  at block  920 . When transitioning from energy savings min mode  216  to energy savings max mode  214 , compressor  128  remains OFF and evaporator fan  130  transitions from ON to OFF. 
   In an exemplary embodiment, processor  136  further controls LED  138 . In accordance with this embodiment, processor  136  selectively sets LED  138  in one of a plurality of states corresponding to the current mode of cooling system  120 . Exemplary cycle times for all LED states except a door open condition are 1 second, for example. For a door open condition, the LED may have a 50% duty cycle with 0.2 second cycle time for 5 seconds. In initialization mode, LED  138  may flash twice to indicate processor  136  and temperature sensor  140  are operational at power-up. In normal off mode  208 , LED  138  may remain ON continuously. In normal cooling mode  210  with a door open detection within a predefined number of minutes, e.g., 15 minutes, LED  138  may have a 90% duty cycle. In normal cooling mode  210  without a door open detection within a predefined number of minutes, e.g., 15 minutes, LED  138  may have a 50% duty cycle. In energy savings modes  214 / 216 , LED  138  may have a 10% duty cycle. In recovery mode  212 , LED  138  may be OFF. Thus, LED  138  provides information indicative of the operation of cooling system  120 , which may be useful for servicing cooling system  120 . 
   In accordance with aspects of the present invention, one or more energy savings modes are added to the normal modes of operation (e.g., a cooling needed mode and a no cooling needed mode) typically found in conventional cooling systems. In exemplary embodiments, evaporator fan  130  is OFF during at least one energy savings mode (e.g., energy savings max mode  214 ) while compressor  128  is OFF. By turning evaporator fan  130  OFF, energy required to run evaporator fan  130  is no longer introduced to interior  104  of appliance  130  and, thus, does not need to be removed, e.g., through operation of compressor  128 . Thus, energy savings may be realized through the decreased operation of both compressor  128  and evaporator fan  130 . 
   Additionally, exemplary embodiments of the present invention look at the rate of temperature change within interior  104  of appliance  100  to determine if door  112  is open and to identify possible freeze-up conditions of evaporator fan  130  in addition to (or instead of) looking solely at the absolute temperature within the interior  104  of appliance  100  to determine if it is above or below high and low set points as in conventional systems. By looking at the rate of temperature change, cooling system  120  can determine whether compressor  128  is decreasing the temperature and, depending on the times and temperatures involved, cooling system  120  can transition compressor  128  OFF and enter another mode of operation such as recovery mode  212  to clear frozen compressor coils or normal off mode  208 . 
   Cooling system  120  may look at multiple rates of change timers and temperatures, e.g., to determine particular door open events or frozen compressor coils. For example, cooling system  120  may operate normally and yet never reach a low set point due to appliance  100  having very high sales activity and/or being frequently reloaded with product. In this case, a long term rate of change may not be reached, but the short term rates of change may be reached several times (e.g., a long term timer may look for a 6 degree drop in temperature over the course of an hour and a short term timer may look for a 1 degree drop in ten minutes). If door  112  is opened every 5 to 10 minutes, the short term rate of change may be satisfied, but the temperature never drops by more than the couple of degrees needed to satisfy the long term rate of change. This indicates that compressor  120  is cooling interior  104  of appliance  100  and, thus, that the compressor coils are not frozen-up. In another example, cooling system  120  may not satisfy either the short term or the long term rates of change, thereby indicating frozen compressor coils. Accordingly, cooling system  120  may transition to recovery mode  212 . 
   Various aspects of the invention may be implemented in software that configures a computer (not shown) such as a microcontroller. In accordance with this embodiment, one or more of the functions of processor  136  and timer  146  may be implemented in software. Firmware may be employed to monitor inputs (e.g., inputs from temperature sensor  140 , occupancy sensor  144 , and/or proximity sensor  142 ). Software may be embodied in a computer readable carrier, for example, a magnetic or optical disk, a memory-card or an audio frequency, radio-frequency, or optical carrier wave. 
   Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.