Abstract:
A method and system provide for the cooperative powering of unitary air conditioners. The method and system includes coordinating powering of unitary air conditioners in a multiunit building or other low level of aggregation in a power grid. Multiple unitary air conditioners can use a power line communication (PLC) communication module for communicating with other air conditioners that are within the same multiunit building. According to one aspect of the method and system, by using power line communications, multiple unitary air conditioners within a single building can form self-contained local area networks. The LAN can also support a token ring network. According to this token ring network, a predetermined number of tokens can be assigned within the token ring network.

Description:
PRIORITY AND RELATED APPLICATIONS STATEMENT 
     This application claims priority under 35 U.S.C. §120 and is a continuation of U.S. patent application Ser. No. 12/492,211, filed on Jun. 26, 2009 now U.S. Pat. No. 8,239,068 and entitled, “METHOD AND SYSTEM FOR COOPERATIVE POWERING OF UNITARY AIR CONDITIONERS,” the entire contents of which are hereby incorporated by reference. 
    
    
     FIELD OF INVENTION 
     The invention is generally directed to unitary or “room” air conditioners. The technology relates more particularly to cooperative powering of unitary air conditioners. 
     BACKGROUND OF THE INVENTION 
     Unitary air conditioners, also known as room air conditioners, have all of the components of a central air conditioning system but all of the components are contained within a single housing. This means that the condenser, evaporator, expansion valve, compressor, exterior fan, and interior fan are generally contained within a single housing. 
     Unitary air conditioners are often used in buildings where there are multiple individual living spaces, such as in apartment buildings and office buildings. Within each living space, an occupant may have individual control over each respective unitary air conditioner that is supplied to cool a particular living space. In warm weather months or in warm weather climates, multiple unitary air conditioners operating at the same time or in unison can create tremendous loads on electric power grids. Also, the building electrical bill may depend on the peak amount of energy used in any one interval (often 15 or 30 minutes) in a billing period as well as on the total energy used in the billing period. This peak interval usage is referred to as a demand charge. Multiple air conditioners on at the same time can cause a demand peak for the building. 
     In addition to the problems caused by multiple unitary air conditioners operating at the same time within multiunit buildings, it is understood that each living space within a multiunit building may have a unique cooling load. In other words, each living space may require a different level of energy to cool the living space to a temperature desired by an occupant. For example, a south facing side living space which receives a significant amount of sunlight during daylight hours will generally need more energy to cool its living space compared to a north facing side living space which is generally in the shade caused by the shadow of the building during daylight hours. 
     Accordingly, there is a need in the art for a method and system for the cooperative powering of unitary air conditioners which takes into account the unique cooling loads of different living spaces caused by the position of each living space relative to sunlight it may receive or other external environmental elements which may impact a cooling load on a given living space. There is a further need in the art for a method and system for cooperative powering of unitary air conditioners in order to reduce the load or strain on an electric power grid, while also allowing each unitary air conditioner to achieve a temperature of a living space desired by an occupant. 
     SUMMARY OF THE INVENTION 
     A method and system provide for the cooperative powering of unitary air conditioners. The method and system includes coordinating powering of unitary air conditioners in a multiunit building or other low level of aggregation in a power grid. 
     Multiple unitary air conditioners can use a power line communication (PLC) communication module for communicating with other air conditioners that are within the same multiunit building. According to one aspect of the method and system, by using power line communications, multiple unitary air conditioners within a single building can form self-contained local area networks. 
     According to the method and system, after the unitary air conditioners are coupled to one another through power line communications, they can form a communication network, such as a local area network (LAN). The LAN can also support a token ring network. According to this token ring network, a predetermined number of tokens can be assigned within the token ring network. In one exemplary embodiment, one token may be assigned to a single unitary air conditioner out of a group of unitary air conditioners which are part of the token ring network. But more than one token may be provided, such as a plurality of tokens within a given token ring network, and is within the scope of the invention. 
     Only unitary air conditioners with a token may receive energy or be permitted to turn “on.” In this way, a power grid servicing a multiunit building is reduced. In this way, overloading and possible failure of a power grid may be avoided and peak billing demand may be reduced. 
     Alternatively, the token passing system could be used to implement a token that acts in the opposite sense, that is, if a unit receives a token, it turns off and then follows a preset procedure to determine when to pass on the token. After passing the token, the unit would then be enabled to turn on. This alternate arrangement would be more efficient in a situation where the majority of air conditioners would be allowed to run. Hence, fewer tokens would be required. 
     During formation of a token ring network, a list can be generated to enumerate the unitary air conditioners who are part of the network. This list can be stored in each air conditioner&#39;s memory. Next, the first token or first set of tokens can be assigned to one or more unitary air conditioners within the network. The assignment of the first token or tokens can be made according to predetermined criteria. For example, such predetermined criteria can include an assessment of the permanent serial numbers that may be assigned to each unitary air conditioner. A unitary air conditioner with the highest or lowest serial number may be assigned to the first token. Other criteria beyond serial identification numbers of unitary air conditioners for assigning the first token or first set of tokens is within the scope of the invention. 
     The unitary air conditioner assigned with the first token then can determine the priority of the token distribution within the token ring network. The unitary air conditioner assigned with the token can assess many variables associated with cooling a multiunit building in order to determine the order in which unitary air conditioners should receive the token. For example, variables such as desired temperatures of a living space, and the amount of time available compared to the amount of power needed to cool each living space to a desired temperature can be assessed. 
     Once the unitary air conditioner with the first token determines the priority or order in which the token should be passed from one unitary air conditioner to the next, the token is passed to the unitary air conditioner with the highest priority. Next, the unitary air conditioner with the token is able to start cooling its assigned living space. While the unitary air conditioner with the token is cooling its assigned living space, the unitary air conditioner can also monitor the status of the other unitary air conditioners who are members of the token ring network. The unitary air conditioner assigned with the token can also monitor other variables in the token ring network. 
     For example, other variables which can be monitored by the unitary air conditioner assigned with the token ring can include, but are not limited to, monitoring the time of day; determining if there is enough time to cool remaining living spaces within the time allotted by each living space occupant; checking to see if other new unitary air conditioners have entered into the local network; and determining if there have been updates by occupants for desired temperatures of a living space. 
     According to another exemplary aspect, a method and system assigns living spaces of a multiunit building to predetermined groups. Each predetermined group may include living spaces that have similar cooling loads, such as those living spaces which are directly impacted by sunlight or shade. With these groupings, the living spaces can be cooled by taking into account the extra energy or power that may be needed by some higher cooling load living spaces relative to other lower cooling load living spaces which have a reduced cooling load due to environmental factors such as shade. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a functional block diagram of a unitary air conditioner according to one exemplary embodiment of the invention. 
         FIG. 2A  is a functional block diagram illustrating an exemplary token ring network formed by unitary air conditioners of a multiunit building according to one exemplary embodiment of the invention. 
         FIG. 2B  is a functional block diagram illustrating an exemplary token ring network in which a first token has been assigned to a unitary air conditioner according to one exemplary embodiment of the invention. 
         FIG. 2C  is a functional block diagram illustrating the second token assigned to a second unitary air conditioner of a token ring network according to one exemplary embodiment of the invention. 
         FIG. 3  is a logic flow diagram illustrating an exemplary method for managing unitary air conditioners of a multiunit building according to one exemplary embodiment of the invention. 
         FIG. 4  is a diagram illustrating exemplary different cooling loads of a multiunit building which may be caused by external environmental elements such as sunlight according to one exemplary embodiment of the invention. 
         FIG. 5  is a logic flow diagram illustrating an exemplary method for controlling unitary air conditioners in a multiunit building by assigning each unitary air conditioner to predetermined groups based on environmental factors which may impact cooling loads according to one exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Turning now to the drawings, in which like reference numerals refer to like elements,  FIG. 1  is a functional block diagram of a unitary air conditioner  100  according to one exemplary embodiment of the invention. The unitary air conditioner  100  can comprise a housing  102  that contains a communications transceiver  107  coupled to a relays or switches  165 A,  165 B. The relays or switches  165  may control power to a compressor  115  and the exterior vent fan/condenser fan  120 . 
     The communications transceiver  107  may comprise a packet radio in which the transceiver  107  is coupled to an antenna  104 . The communications transceiver  107  can support wireless communications protocols, such as the Zigbee wireless communication protocol. For the Zigbee wireless communication protocol, the transceiver  107  may comprise a low-powered digital radio which employs the IEEE802.15.4-2006 standard for wireless personal area networks. However, other communication protocols and standards for radio frequency communications are not beyond the scope of the invention. For example, other communication protocols can include, but are not limited to IEEE802.11, Bluetooth IEEE802.16 (wireless LAN), WAN, and other like wireless communication protocols. The section below describes how a token ring network is formed in a power line communication (PLC) environment. A technique similar to the PLC embodiment can be employed in an RF environment where the range limitations of the wireless technology is exploited to limit the potential participants in the token ring network. This is similar to how the PLC embodiment uses the natural attenuation properties of a wired network to limit its participants, 
     Specifically, in a wired embodiment, the transceiver  107  could also support power line communications (PLCs). PLCs referred to in this description include systems for carrying data on conductors  106  that may also be used for electric power transmission. Electrical power is typically transmitted over high voltage transmission lines, distributed over medium voltage, and used inside buildings at lower voltages. It is well understood to one of ordinary skill in the art that power line communications can be applied at each stage. 
     Many PLC technologies may limit themselves to one set of wires such as in the case of wires within a single structure, but some PLC can cross between two levels. For examples, some PLC can cross between a distribution network and premises wiring. The power line communications systems used herein may operate by impressing a modulated carrier signal on the wiring system  106 . Different types of power line communications can use different frequency bands, depending on the signal transmission characteristics of the power wiring used. 
     Since many power wiring systems are usually intended for only transmission of alternating current power, many power wire circuits usually have a limited ability to carry higher frequencies. This propagation problem can be a limiting factor for power line communications, however, this propagation problem is used advantageously by the unitary air conditioners  100  described herein. 
     Because of the attenuation of power line communications over relatively short distances, unitary air conditioners  100  of the same multi-unit building that are being serviced by the same, local distribution transformer  218  can form self-contain local area networks due to the propagation problem noted above. This means that the strength of the signals for power line communications are such that usually only air conditioners  100  coupled to a distribution transformer can communicate with one another. Air conditioners  100  coupled to a first transformer will likely not be able to detect or communicate with other air conditioners which are coupled to a second transformer due to the losses of RF power in the communication signals when they are propagated over power lines  106  for significant distances and through two or more transformers  218 . 
     Specifically, there is typically high frequency loss through the transformer. And usually, a signal from a first multiunit dwelling to a second multiunit dwelling would typically pass through two distribution transformers. Also, in a network distribution system where feeder transformer secondary windings are interconnected, the high frequency loss due to propagation distance and the increased noise due to the large number of loads on the network will tend to limit the propagation distance of the PLC. 
     The power line communication (PLC) systems can include Home Plug 1.0 which is a specification for home networking technology that couples devices to each other through power lines  106  in a building. Home Plug certified products may couple personal computers and other devices such as air conditioners  100  that may also use other communication standards such as Ethernet, USB (Universal Serial Bus) and wireless local area network communications such as IEEE 802.11. Many devices may have the Home Plug standard built in such as the air conditioners  100  illustrated in  FIG. 1 . With the Home Plug standard built-in into an air conditioner  100 , to connect the air conditioner  100  to a network, all that is required is to plug the air conditioner  100  into an outlet of a wall in a home such that it may communicate with other devices that support the Home Plug standard. 
     Since the power line communication signals may travel a short distance outside of a home to a distribution transformer  218 , like many other network standards, the Home Plug power line communication standard includes the ability to set an encryption password. As with many other networking products, most Home Plug devices are secured by default in which the standard may require that all devices supporting the standard are set to a default out-of-box password, which may be a common one. Users of the devices are encouraged to change this password for obvious reasons. 
     Devices which support the Home Plug power line communication standard may function as transparent network bridges which may allow computers running on any operating system to use them for network access. The Home Plug communication standard supports the ability to use Ethernet in a bus topology in which it has carrier sense, multiple access and collision detection. 
     This is achieved by the use of advanced orthogonal frequency division multiplexing (OFDM) that allows co-existence of several distinct data carriers along the same power-supplying wire. Use of OFDM allows turning off (masking) one or more of the subcarriers which overlap previously-allocated radio spectrum in a given geographical region. In North America, some Home Plug standards may only use 917 of an available 1,155 subcarriers. 
     In addition to receiving control signals, the communications transceiver  107  can communicate status signals or relay control signals (such as the token  502 ) described below. In this way, a central controller (not illustrated) separate from the air conditioners  100  can monitor the status and control many different air conditioners  100 . 
     Referring back again to  FIG. 1 , the switches or relays  165  of the unitary air conditioner  100  can comprise an electromagnetic relay (not illustrated). The relays  165  may comprise a coil of wire surrounding a soft iron core or an iron yoke, which provides a low reluctance path for magnetic flux, a moveable iron armature, and a set, or sets, of contacts. The armature may be hinged to the yoke and mechanically linked to a moving contact or contacts. It may be held in place by a spring so that when the relay is de-energized there is an air gap in the magnetic circuit. The relays  165  may have more or fewer sets of contacts depending on their function. The relays  165  may also have a wire connecting the armature to the yoke. This may ensure continuity of the circuit between the moving contacts on the armature, and the circuit track on a Printed Circuit Board (PCB) via the yoke, which may be coupled to a PCB, such as by a soldering. 
     When an electric current is passed through the coil of a relay  165 , the resulting magnetic field attracts the armature and the consequent movement of the movable contact or contacts either makes or breaks a connection with a fixed contact. If the set of contacts was closed when the relay  165  was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity may also be used. 
     Most relays  165  are manufactured to operate quickly. In a low voltage application, this speed may help to reduce noise. In a high voltage or high current application, this is to reduce arcing. The switches or relays  165  of the inventive system  100  may include, but is not limited to, those of a latching type, a reed type, a mercury-wetted type, a polarized type, a contactor type, a solid-state type, a solid-state contactor type, a buchholz type, and a forced-guided contacts type. 
     The relays  165  may be interposed between the compressor  115  and the NC control logic  125 , and between the exterior vent fan/condenser fan  120  and NC control logic  125 . The A/C control logic  125  can comprise any one of a combination of programmable circuitry. For example, the NC control logic  125  can comprise firmware in combination with a microcontroller, a microprocessor, a digital signal processor, or a state machine implemented in an application specific integrated circuit (ASIC), programmable logic, or other numerous forms of hardware and/or software without departing from the scope of the invention. The NC control logic  125  can be coupled to a memory device  105  and a thermostat  150 . 
     The memory device  105  can comprise volatile or non-volatile memory. If the memory device  105  comprises volatile memory it can comprise RAM. If the memory device  105  comprises non-volatile memory, it can comprise ROMs or EEPROMS. Other hardware configurations for the memory device  105  are not beyond this scope of the invention. 
     The NC control logic  125  an also be coupled to an interior blower motor  135  which is coupled to an interior blower  140 . The A/C control logic  125  can also be coupled an exterior vent fan  120  which may blow outside or external air over the condenser coils  110 . Meanwhile, the interior blower or fan  140  is designed to recirculate air taken from the living space over the evaporator coils  145 . 
     The evaporator coils  145  are coupled to an expansion valve  155  and condenser coils  110  through conduits  160 A,  160 B. The condenser coils  110  are coupled to the compressor  115  through another conduit. The compressor  115  is also coupled to the expansion valve  155  via conduit  160 B. 
     As understood to one of ordinary skill in the art, during operation of the air conditioner  100 , the compressor  115  compresses a refrigerant while it is in a liquid state. The refrigerant can comprise any one of hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) such as R-11, R-12, R-22, R-134A, and R-410A. The pressure on the refrigerant is allowed to drop when it passes through the expansion valve  155 . 
     The refrigerant in a liquid state and at low pressure absorbs any heat from the living space and is transformed to vapor as it passes through the evaporator coils  145 . The compressor  115  forces the vapor through the condenser coils  110  at which the vapor condenses to a liquid while also releasing the energy or heat that was absorbed at the evaporator stage of the cycle. The refrigerant then continues again through the compressor  115 . 
     Within the housing  102 , the exterior vent fan/condenser fan  120 , the condenser coils  110 , and compressor  115  can be separated from the interior blower motor  135 , interior blower  140 , and evaporator coils by an barrier or wall  130 . The communications receiver  107 , A/C control logic  125 , thermostat  150 , and memory  105  can be placed on either side of the barrier or wall  130 . It is noted that the condenser fan  120  and the interior blower  140  can share a common motor such as motor  135 . In this case, the motor  135  will drive both units when it is on. Since the vast majority of the energy in a room air conditioner  100  is used by the compressor  115 , the control of this common motor  135  is not a major concern in reducing power consumption. 
     With the inventive air conditioner  100 , a communications signal may be received by the communications transceiver  107  to activate the relays  165 A,  165 B which control power to the exterior vent fan/condenser fan  120  and the compressor  115 . Meanwhile, the A/C control logic  125  can still allow power to be supplied to the interior blower motor  135  and the interior blower  140 . In this way, a substantial reduction in energy being consumed by the unitary air conditioner  100  while allowing the interior air to circulate, thus improving comfort compared to turning off the entire unitary air conditioner  100 . 
     According to an alternate exemplary embodiment, the compressor  115  and exterior vent fan/condenser fan  120  may not be controlled directly by the communications transceiver  107 . Instead, the communications transceiver  107  may be coupled directly to the NC control logic  125  as indicated with a dashed line. The NC control logic  125  could then control the relays  165  to turn power on and off for the fan  120  and compressor  115 . 
     Referring now to  FIG. 2A , this figure is a functional block diagram illustrating an exemplary token ring network  200  formed by unitary air conditioners  100  of the various living spaces  402  (See  FIG. 4 ) of a multiunit dwelling  400  (See  FIG. 4 ) according to one exemplary embodiment of the invention. The token ring network  200  can be employed such that each unitary air conditioner  100  is brought online at different times relative to another unitary air conditioner  100 . The logical token ring network  200  illustrates how a token from a first unitary air conditioner  100 A can be passed along the logical token ring  200  to the next air conditioner  100 B which could be the second air conditioner  100 B so that the second air conditioner  100 B comes online and establishes electrical connection along power line  106  when the second air conditioner  100 B has the token. The exemplary logical token ring  200  indicates how a token can be passed along the logic suggested by this figure. However, as will be described below, the token can be passed between respective air conditioners  100  based on priority which may cause the token to skip over one or more air conditioners  100  that form the logical ring  200 . 
     That is, for example, after the first unitary air conditioner  100 A has finished its cooling cycle to a desired temperature, the token maybe passed to the next prioritized unitary air conditioner  100 B which is a member of the logical token ring  200 . So this means, if a third unitary air conditioner  100 C has a higher priority relative to a second unitary air conditioner  100 B, then the third unitary air conditioner  100 C would receive the next available token before the second unitary air conditioner  100 B would receive a token. 
     Referring now to  FIG. 2B , this figure illustrates an exemplary token ring network in which a first token  502 A has been assigned to a first unitary air conditioner  100 A according to one exemplary embodiment of the invention. The token  502 A illustrated in  FIG. 2B  indicates a first unitary air conditioner  100 A can establish an electrical connection with the distribution transformer  218  along a power line  106 A. The remaining air conditioners  100 B- 100 E have been illustrated without power lines  106 B-E to signify that these air conditioners  100  have not established an electrical connection between themselves and the distribution transformer  218 . The token  502 A can simply be flag in a list stored in memory  105  or in a central location apart from the air conditioners  100  which may enumerate a token order or rank in a list of air conditioners  100  that maybe part of a particular token ring system or network to the  400 . Further details of the token  502 A will be described below with respect to the flow charts of  FIG. 3 . 
     Referring now to  FIG. 2C , this figure illustrates a second token  502 B assigned to another unitary air conditioner  100 E of a token ring network according to one exemplary embodiment of the invention.  FIG. 2C  also illustrates that the first token  502 A illustrated in  FIG. 5  is no longer present. Alternatively, this conceptual diagram of  FIG. 2C  illustrates that the first token  502 A may have been passed to the fifth unitary air conditioner  100 E based on priority. Since the fifth unitary air conditioner  100 E has the token  502 B, the fifth unitary air conditioner  100 E can establish an electrical connection between the distribution transformer  218  and itself along the power line  106 E. The fifth unitary air conditioner  100 E may draw power from the distribution transformer  218 . One of ordinary skill in the art will recognize that the invention is not limited to a single token distribution and any number of tokens  502  can be distributed along the logical token ring  400  as long as the amount of tokens  502  which allow unitary air conditioners  100  to couple themselves to the distribution transformer  218  do not cause excessive loads for the distribution transformer  218 . 
     As noted above, in an alternative exemplary embodiment, the token passing system could be used to implement a token  502  that acts in the opposite sense, that is, if a unit  100  receives a token  502 , the air conditioner unit  100  is turned off and then follows a preset procedure to determine when to pass on the token  502  to the next unit  100 . After passing the token, the unitary air conditioner  100  would then be enabled to turn on. This alternate arrangement would be more efficient in a situation where the majority of air conditioners  100  would be allowed to run. Hence, fewer tokens  502  would be required. 
     Referring now to  FIG. 3 , this figures illustrates a logic flow diagram  300  of a method for managing air conditioners  100  coupled to a distribution transformer  218 . Logic flow diagram  300  highlights some key functional features of the unitary air conditioners  100  as illustrated in  FIG. 1 . As noted above, one of ordinary skill in the art will appreciate that the process functions of the unitary air conditioner  100  may comprise firmware code executing on a microcontroller, microprocessor, a DSP, or state machines implemented in application specific integrated circuits, or programmable logic, or other numerous forms without departing from the spirit and scope of the invention. 
     In other words, these steps illustrated in  FIG. 3  and other logic flow diagrams of this disclosure may be provided as a computer program which may include a machine-readable medium having stored there on instructions which maybe used to program a computer (or other electronic devises) to perform a process according to the invention. The machine-readable medium may include, but is not limited, optical disk, CD-ROM, magneto-optical disks, ROMs, RAMs, EEPROMs, EEPROMs, magneto-optical cards, flash memory, or other type of medias/machine-readable mediums suitable for storing electronic instructions. 
     Certain steps in the processes or process flow described in all of the logic flow diagrams refer to in this specification must naturally precede others for the invention to function as described. However, the invention is not limited to the order of the steps described if such order or sequence does not alter the functionality of the present invention. That is, it is recognized that some steps may perform before, after, or parallel other steps without departing from the scope and spirit of the invention. Further, one of ordinary skill and programming would be able to write such a computer program or identify appropriate hardware at circuits to implement the disclosed invention without difficulty based on the flow charts and associated description in the application text, for example. 
     Therefore, disclosure of a particular set of program code instructions or detailed hardware devices is not considered necessary for an adequate understanding of how to make and use the invention. The inventive functionality of the claimed computer implemented processes would be explained in more detail in the following description and in conjunction with the remaining figures illustrating other process flows. 
     Step  305  is the first step of the process  300  in which one or more unitary air conditioners may be coupled to a power line communications network that can comprise power lines  106  as illustrated in  FIG. 2A . Next, in Step  310 , each control logic  125  of an unitary air conditioner  100  can store a list of the air conditioners  100  in its memory  105 . This list identifies the air conditioners  100  which are part of the logical token ring  200  as illustrated in  FIG. 2A . Alternatively, this list can be stored in a central location, by a central controller (not illustrated) apart from all the air conditioners  100 . 
     In Step  320 , the assignment of the first token or group of tokens can be made according to predetermined criteria. For example, such predetermined criteria can include an assessment of the permanent serial numbers that maybe assigned to each unitary air conditioner  100 . An unitary air conditioner  100  with the highest or lowest serial number may be provided with the first token  502 . Other criteria beyond serial identification of the air conditioners  100  for assigning the first token or first set of tokens is within the scope of the invention. For example, token priority could be weighted by external environmental factors, like sunlight. 
     This calculation of token priority based on external environmental factors, like sunlight, can occur when the unitary air conditioners  100  are built or the identification can occur when each unit  100  downloads information from its respective computer network when installed in a room or both. This means that each unit  100  can have the capability of being modified through a download from a computer network even if a unit  100  was provided with a weighted token priority at build-time in a manufacturing center. Alternatively, or in addition to these ways, the token priority of a unit  100  based on its environmental factors can be computed locally in each air conditioner  100  with a pre-stored algorithm. 
     In Step  325 , each of the air conditioners  100  can record the status of the first token assigned in the logical token ring  200 . Next, in Step  330 , the first air conditioner  100  such as the air conditioner  100 A as illustrated in  FIG. 2B  which has the first token  502 A can determine the priority or order in which the token or set of tokens should be passed from one unitary air conditioner  100  to the next. Once this order of priority list is established with the first unitary air conditioner  100 A, the token  502  can be passed to the appropriate unitary air conditioner  100  with highest priority as illustrated by step  335  in  FIG. 3 . 
     In Step  340 , power of the unitary air conditioner  100  with the highest priority can be initiated. In this step, a communications signal can be sent to a communications transceiver  107  of the unitary air conditioner so that the communications transceiver  107  or programmable logic  125  can control the relay  165 A to the compressor  115 . Alternatively, if the token ring list is stored in memory  105  of the unitary air conditioner  100 , then the programmable logic  125  can activate the compressor  120  by activating the relays  165 . In routine  345 , the unitary air conditioner  100 A with the token  502  can monitor the status of other token ring members as well as other variables such as internal and external temperature changes. 
     Next, in decision Step  350 , it is determined whether the unitary air conditioner  100  with the token  502  has completed its cooling cycle to a desired temperature. If the inquiry to decision Step  350  is negative, then the “no” branch is followed back up to routine  345 . If the inquiry to decision Step  350  is positive, then the “yes” branch is followed to Step  355 . 
     In Step  355 , the token  502  can be passed to the unitary air conditioner  100  with the next highest priority in the token ring list. In decision Step  360 , it is determined if all unitary air conditioners  100  who are members of a particular logical token ring network  200  have reached their desired temperatures. 
     If the inquiry to decision Step  360  is negative, then the “no” branch is followed back to Step  340  in which powering of the air conditioner  100  with the next highest priority is initiated. If the inquiry to decision Step  360  is positive, then the “yes” branch is followed and the process can then can end. As noted above, one of ordinary skill in the art recognizes that multiple tokens  502  can be distributed in any given logical token ring network  200 . 
     Referring now to  FIG. 4  is a diagram illustrating exemplary different cooling loads of a multiunit building  400  which may be caused by external environmental elements such as sunlight  404  according to one exemplary embodiment of the invention. A first living space  402 A may have a current temperature of eighty-eight degrees Fahrenheit and a desired temperature setting of seventy-five degrees Fahrenheit. The desired temperature setting may be the temperature set by the occupant on the thermostat  150 . The current temperature may be displayed by the thermometer which can be part of the thermostat  150 . The first living space can have a first window  407 A and a first unitary air conditioner  100 A. 
     Similarly, a second living space  402 B may have a current temperature of eighty-six degrees Fahrenheit and a desired temperature setting of seventy-two degrees Fahrenheit. The second living space can have a second window  407 B and a secondary unitary air conditioner  1008 . 
     The third living space  402 C may have a current temperature of eighty-two degrees Fahrenheit and a desired temperature setting of seventy-six degrees Fahrenheit. The third living space  402 C can have a third window  407 C and a third unitary air conditioner  1008 . 
     The fourth living space  402 D may have a current temperature of eighty degrees Fahrenheit and a desired temperature setting of seventy degrees Fahrenheit. The fourth living space  402 D can have a fourth window  407 D and a four unitary air conditioner  100 D. 
     The first and second living spaces  402 A,  402 B may comprise units which face the south direction in the northern hemisphere. This means that that these two units may receive a significant amount of sunlight  404  during the day which can increase the cooling load for these two spaces  402 A,  402 B. Meanwhile, the third and fourth living spaces  402 C and  402 D may face a north direction in the northern hemisphere. This means that these two units, compared to the first two units, may receive a reduced amount of sunlight  404  due to shading from the building or multiunit structure  400 . 
     One of ordinary skill in the art recognizes that other current temperatures and desired temperatures, higher or lower than those discussed and illustrated, are not beyond the scope of this inventive system. Further, other temperature units besides Fahrenheit, such as the Celsius scale, can be used without departing from the invention. Also, any number of units  402  could be part of the multiunit structure  400  such as on the order of one hundred units  402  or two hundred units  402  like in apartments or hotels without departing from the invention. 
       FIG. 5  is a logic flow diagram illustrating an exemplary method  500  for controlling unitary air conditioners  100  in a multiunit building  400  by assigning each unitary air conditioner  100  to predetermined groups based on environmental factors which may impact cooling loads according to one exemplary embodiment of the invention. Step  505  is the first step in the process or method  500  in which units  402  that are significantly impacted by environmental factors (like sunlight  404 ) are identified. In the exemplary embodiment illustrated in  FIG. 4 , this means that the first and second units  402 A and  402 B would be identified as units which are significantly impacted by sunlight  404 . 
     Next, in step  510 , these two units  402 A,  402 B would be assigned to a first group of units  402 . In step  515 , those units  402  which are not impacted by environmental factors, like sunlight, would be identified. For the exemplary embodiment illustrated in Figure, the third and fourth units  402 C,  402 D would be identified. Then, in step  520 , these third and fourth units  402 C,  402 D which are not impacted by environmental factors would be assigned to a second group. 
     Next, in routine  520 , the air conditioners  100  of the first group would be activated according to a predetermined sequence, such as according to the token algorithm  300  of  FIG. 3 . Subsequently or in parallel with routine  520 , in routine  530 , air conditioners  100  of the second low environmental impact group would be activated according to a predetermined sequence, such as according to the token algorithm  300  of  FIG. 3 . Then in optional routine  535 , if the external environmental factors have diminished, then both groups can be combined and the air conditioners  100  of both groups may be activated according to a predetermined sequence, such as by the token algorithm  300  of  FIG. 3 . 
     Alternative embodiments of algorithms for controlling the unitary air conditioners  100  will become apparent to one of ordinary skill in the art to which the invention pertains without departing from its spirit and scope. Thus, although this invention has been described in exemplary form with a certain degree of particularity, it should be understood that the present disclosure is made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts or steps may be resorted to without departing from the scope or spirit of the invention. Accordingly, the scope of the present invention may be defined by the appended claims rather than the foregoing description.