Patent Publication Number: US-11654462-B1

Title: Air conditioning system heat exchanger cleaner apparatus

Description:
BACKGROUND 
     Field 
     The present disclosure relates generally to air-conditioning systems, and more particularly to providing cleaner chemical compositions to clean outer surfaces of heat exchangers of air handlers of air-conditioning systems without manual intervention. 
     Description of Related Art 
     Air-conditioning systems may include an air handler, also referred to as an air handling unit (AHU) that may circulate and cool air within a space and/or structure. An air handler may move air, via operation of an air mover such as a blower or fan, to flow in thermal communication with a heat exchanger such as an air coil. The air handler may circulate a refrigerant through the heat exchanger to absorb (e.g., remove) heat from the flow of air to cool the air, and the air-conditioning system may circulate the refrigerant through a heat exchanger to discharge the absorbed heat into a heat sink (e.g., the ambient environment). 
     In some cases, cooling air due to the heat exchanger absorbing heat from the air may result in condensation of moisture (e.g., condensate) out of the cooled air at the heat exchanger. The condensate may be collected and discharged from the air handler via a condensate drain line. 
     SUMMARY 
     According to some example embodiments, a heat exchanger cleaner apparatus for spraying a cleaning composition into an air handler of an air conditioning system to contact with an outer surface of a heat exchanger of the air handler may include a spray outlet assembly, a pump device, a connector interface, and a controller. The spray outlet assembly may be configured to be inserted into an interior of the air handler to be directly exposed to the outer surface of the heat exchanger. The pump device may be configured to be operated to pump an amount of the cleaning composition through the spray outlet assembly such that the spray outlet assembly sprays the amount of the cleaning composition as a fluid stream at least partially contacting the outer surface of the heat exchanger. The connector interface may be configured to detachably couple with a complementary connector interface of a cartridge having a cartridge reservoir configured to hold the cleaning composition, to establish flow communication between the cartridge reservoir and the pump device, such that the pump device is in fluid communication between the connector interface and the spray outlet assembly, and the pump device is configured to be operated to pump the amount of the cleaning composition from the cartridge reservoir and through the spray outlet assembly. The controller may be configured to operate the pump device to cause the amount of the cleaning composition to be supplied through the spray outlet assembly without manual intervention. 
     The spray outlet assembly may include a conduit and a spray nozzle. The conduit may have a proximate end and a distal end, the proximate end coupled in fluid communication with an outlet of the pump device, the conduit configured to extend at least from the proximate end and through an opening in an outer housing of the air handler into the interior of the air handler such that the distal end of the conduit is within the interior of the air handler. The spray nozzle may be coupled to the distal end of the conduit and configured to spray the amount of the cleaning composition to spray the amount of the cleaning composition as the fluid stream at least partially contacting the outer surface of the heat exchanger. 
     The conduit may include a plurality of structures coupled in series between the spray nozzle and the pump device. 
     The connector interface of the heat exchanger cleaner apparatus or the complementary connector interface of the cartridge may include a check valve that is configured to open in response to the connector interface of the heat exchanger cleaner apparatus coupling with the complementary connector interface of the cartridge to establish the fluid communication between the cartridge reservoir and the pump device. 
     The heat exchanger cleaner apparatus may include an internal reservoir that is in fluid communication between the check valve and the pump device, such that the connector interface is configured to detachably couple with the complementary connector interface of the cartridge to establish flow communication from the cartridge reservoir to the internal reservoir, and the pump device has an inlet that is exposed to the internal reservoir and is configured to be operated to pump the amount of the cleaning composition from the internal reservoir and through the spray outlet assembly. The controller may be configured to operate the pump device such that the pump device causes at least a portion of the cleaning composition held in the internal reservoir to flow from the internal reservoir to the spray outlet assembly through the pump device. 
     The controller may be configured to operate the pump device to pump the amount of the cleaning composition from the cartridge reservoir and through the spray outlet assembly in response to an elapse of a particular period of time. 
     The controller may be configured to repeatedly operate the pump device at a fixed time interval that is the particular period of time, based on monitoring a timer that increments a timer value at a fixed frequency, operating the pump device to pump the amount of the cleaning composition in response to the timer value reaching a particular time value corresponding to the elapse of the particular period of time, and resetting the timer value to an initial timer value in response to operating the pump device. 
     The controller may be configured to monitor a counter that increments a counter value in response to each operation of the pump device by the controller to pump the cleaning composition and generate a depletion signal in response to the counter value reaching a particular counter value that corresponds to at least partial depletion of a fixed reservoir of the cleaning composition. 
     The controller may be configured to cause the counter value to be reset to an initial counter value in response receiving a reset signal. 
     The heat exchanger cleaner apparatus may further include a network communication interface that is configured to establish a network communication link with a remote computing device. The controller may be configured to perform at least one of causing the depletion signal to be transmitted to the remote computing device via the network communication link, or causing the counter value to be reset to the initial counter value in response to receiving the reset signal from the remote computing device via the network communication link. 
     The heat exchanger cleaner apparatus may further include a network communication interface that is configured to establish a network communication link with a remote computing device. The controller may be configured to operate the pump device to pump the amount of the cleaning composition in response to a pumping command signal received from the remote computing device via the network communication link. 
     The heat exchanger cleaner apparatus may further include a structure connector that is configured to detachably couple with an outer housing of the heat exchanger cleaner apparatus, the structure connector configured to connect the heat exchanger cleaner apparatus to an external structure to at least partially hold the heat exchanger cleaner apparatus in place in relation to an opening of the air handler. 
     The controller may be configured to cause at least a portion of the air conditioning system to shut down. 
     According to some example embodiments, a method for operating the heat exchanger cleaner apparatus may include controlling the pump device of the heat exchanger cleaner apparatus to cause the pump device to pump the amount of the cleaning composition from an apparatus through the spray outlet assembly without manual intervention. 
     The method may further include operating the pump device in response to an elapse of a particular period of time. 
     The method may further include repeatedly operating the pump device at a fixed time interval that is the particular period of time, based on monitoring a timer that increments a timer value at a fixed frequency, operating the pump device in response to the timer value reaching a particular time value corresponding to the elapse of the particular period of time, and resetting the timer value to an initial timer value in response to operating the pump device. 
     The method may further include monitoring a counter that increments a counter value in response to each operation of the pump device and generating a depletion signal in response to the counter value reaching a particular counter value that corresponds to at least partial depletion of a fixed reservoir of the cleaning composition. 
     The method may further include causing the counter value to be reset to an initial counter value in response to receiving a reset signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various features and advantages of the non-limiting embodiments herein may become more apparent upon review of the detailed description in conjunction with the accompanying drawings. The accompanying drawings are merely provided for illustrative purposes and should not be interpreted to limit the scope of the claims. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. For purposes of clarity, various dimensions of the drawings may have been exaggerated. 
         FIG.  1    is a schematic view of an air-conditioning system and a heat exchanger cleaner apparatus system according to some example embodiments. 
         FIGS.  2 A and  2 B  are schematic views of a heat exchanger cleaner apparatus system including a heat exchanger cleaner apparatus and a cartridge according to some example embodiments. 
         FIG.  3 A  is a perspective top-front-right view of a heat exchanger cleaner apparatus system according to some example embodiments. 
         FIG.  3 B  is a perspective bottom-rear-left view of the heat exchanger cleaner apparatus system of  FIG.  3 A  according to some example embodiments. 
         FIG.  3 C  is a perspective cross-sectional view of the heat exchanger cleaner apparatus system along cross-sectional view line IIIC-IIIC′ of  FIG.  3 A  according to some example embodiments. 
         FIG.  3 D  is a plan cross-sectional view of the heat exchanger cleaner apparatus system along cross-sectional view line IIID-IIID′ of  FIG.  3 A  according to some example embodiments. 
         FIG.  3 E  is a perspective cross-sectional view of the heat exchanger cleaner apparatus system along cross-sectional view line IIIE-IIIE′ of  FIG.  3 A  according to some example embodiments. 
         FIG.  3 F  is a plan cross-sectional view of the heat exchanger cleaner apparatus system along cross-sectional view line IIIF-IIIF′ of  FIG.  3 A  according to some example embodiments. 
         FIG.  4 A  is a perspective top-front-right view of the heat exchanger cleaner apparatus shown in  FIG.  3 A  according to some example embodiments. 
         FIG.  4 B  is a plan cross-sectional view of the heat exchanger cleaner apparatus along cross-sectional view line IVB-IVB′ of  FIG.  4 A  according to some example embodiments. 
         FIG.  4 C  is a plan cross-sectional view of the heat exchanger cleaner apparatus along cross-sectional view line IVC-IVC′ of  FIG.  4 A . 
         FIG.  4 D  is a plan top view of the of the heat exchanger cleaner apparatus of  FIG.  4 A  according to some example embodiments. 
         FIG.  5 A  is a perspective top-front-right view of the cartridge shown in  FIG.  11 A  according to some example embodiments. 
         FIG.  5 B  is a perspective bottom-rear-left view of the cartridge shown in  FIG.  5 A  according to some example embodiments. 
         FIG.  5 C  is a plan cross-sectional view of the cartridge along cross-sectional view line VC-VC′ of  FIG.  5 A  according to some example embodiments. 
         FIG.  5 D  is a plan cross-sectional view of the cartridge along cross-sectional view line VD-VD′ of  FIG.  5 A  according to some example embodiments. 
         FIG.  6 A  is a perspective bottom-rear-left view of the structure connector shown in  FIG.  3 A  according to some example embodiments. 
         FIG.  6 B  is a perspective top-front-right view of the structure connector shown in  FIG.  6 A  according to some example embodiments. 
         FIG.  6 C  is a perspective view of the heat exchanger cleaner apparatus according to some example embodiments. 
         FIG.  6 D  is a plan bottom view of the heat exchanger cleaner apparatus according to some example embodiments. 
         FIG.  7    is a schematic view of a computing device according to some example embodiments. 
         FIG.  8    is a flowchart illustrating a method of operation of the heat exchanger cleaner apparatus according to some example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Some detailed example embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. Example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the example embodiments set forth herein. 
     Accordingly, while example embodiments are capable of various modifications and alternative forms, example embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but to the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of example embodiments of the inventive concepts. 
     Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of example embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     It will be understood that elements and/or properties thereof (e.g., structures, surfaces, directions, or the like), which may be referred to as being “perpendicular,” “parallel,” “flush,” or the like with regard to other elements and/or properties thereof (e.g., structures, surfaces, directions, or the like) may be “perpendicular,” “parallel,” “flush,” or the like or may be “substantially perpendicular,” “substantially parallel,” “substantially flush,” respectively, with regard to the other elements and/or properties thereof. 
     Elements and/or properties thereof (e.g., structures, surfaces, directions, or the like) that are “substantially perpendicular” with regard to other elements and/or properties thereof will be understood to be “perpendicular” with regard to the other elements and/or properties thereof within manufacturing tolerances and/or material tolerances and/or have a deviation in magnitude and/or angle from “perpendicular,” or the like with regard to the other elements and/or properties thereof that is equal to or less than 10% (e.g., a. tolerance of ±10%). 
     Elements and/or properties thereof (e.g., structures, surfaces, directions, or the like) that are “substantially parallel” with regard to other elements and/or properties thereof will be understood to be “parallel” with regard to the other elements and/or properties thereof within manufacturing tolerances and/or material tolerances and/or have a deviation in magnitude and/or angle from “parallel,” or the like with regard to the other elements and/or properties thereof that is equal to or less than 10% (e.g., a. tolerance of ±10%). 
     Elements and/or properties thereof (e.g., structures, surfaces, directions, or the like) that are “substantially flush” with regard to other elements and/or properties thereof will be understood to be “flush” with regard to the other elements and/or properties thereof within manufacturing tolerances and/or material tolerances and/or have a deviation in magnitude and/or angle from “flush,” or the like with regard to the other elements and/or properties thereof that is equal to or less than 10% (e.g., a. tolerance of ±10%). 
     It will be understood that elements and/or properties thereof may be recited herein as being “the same” or “equal” as other elements, and it will be further understood that elements and/or properties thereof recited herein as being “identical” to, “the same” as, or “equal” to other elements may be “identical” to, “the same” as, or “equal” to or “substantially identical” to, “substantially the same” as or “substantially equal” to the other elements and/or properties thereof. Elements and/or properties thereof that are “substantially identical” to, “substantially the same” as or “substantially equal” to other elements and/or properties thereof will be understood to include elements and/or properties thereof that are identical to, the same as, or equal to the other elements and/or properties thereof within manufacturing tolerances and/or material tolerances. Elements and/or properties thereof that are identical or substantially identical to and/or the same or substantially the same as other elements and/or properties thereof may be structurally the same or substantially the same, functionally the same or substantially the same, and/or compositionally the same or substantially the same. 
     It will be understood that elements and/or properties thereof described herein as being the “substantially” the same and/or identical encompasses elements and/or properties thereof that have a relative difference in magnitude that is equal to or less than 10%. Further, regardless of whether elements and/or properties thereof are modified as “substantially,” it will be understood that these elements and/or properties thereof should be construed as including a manufacturing or operational tolerance (e.g., ±10%) around the stated elements and/or properties thereof. 
     When the terms “about” or “substantially” are used in this specification in connection with a numerical value, it is intended that the associated numerical value include a tolerance of ±10% around the stated numerical value. When ranges are specified, the range includes all values therebetween such as increments of 0.1%. 
       FIG.  1    is a schematic view of an air conditioning system  100  according to some example embodiments. The air conditioning system  100 , which may be interchangeably referred to as an air conditioning system, air conditioner, or the like, may be configured to provide cooling of air within an interior of a structure  1  and may be at least partially located within the structure  1 , but example embodiments are not limited thereto. The air conditioning system  100  may be included as a part of a Heating, ventilation, and air conditioning (HVAC) system, but example embodiments are not limited thereto, and in some example embodiments the air conditioning system  100  may be separate from any heating system. 
     Referring to  FIG.  1   , the air conditioning system  100  may include an air handler  102  and a condenser assembly  104  that are configured to draw return air  106  from an interior of the structure  1 , cool (e.g., absorb heat from) the drawn return air  106  into conditioned air  114 , and discharge (e.g., supply) the conditioned air  114  back into the interior of the structure  1 . The air handler  102  may include, within a housing  101  that may at least partially comprise metal (e.g., steel) and at least define an interior  192  space, an air intake  103 , an air filter  105 , an air mover  108  (e.g., fan, blower, etc.), a heat exchanger  110  (e.g., evaporator coil), an expansion valve  111 , a drip pan  122 , a condensate drain line  124  (also referred to herein as a condensate drain conduit, condensate drain pipe, etc.), a controller  140 , a float switch  160 , and an air outlet  112 . The condenser assembly  104  may include a compressor  150 , a second heat exchanger  152  (e.g., condenser coil), and an air mover  154  (e.g., fan, blower, etc.). 
     It will be understood that example embodiments of an air conditioning system, air handler, condenser assembly, or the like may have different arrangements of devices therein and may omit or add to the aforementioned elements of the air conditioning system  100  as shown in  FIG.  1   . It will be understood, for example, that elements shown as being included in the air handler  102  may in some example embodiments be located in the condenser assembly  104  (e.g., the controller  140  may be located in the condenser assembly  104  instead of the air handler  102 ). As shown, the condenser assembly  104  may be located external to the structure  1  while the air handler  102  is located internal to the structure  1 , but example embodiments are not limited thereto. 
     In some example embodiments, the air conditioning system  100  may draw return air  106  into the air handler  102  via the air intake  103  and through the air filter  105 , where the air filter  105  may be any known air filter that is configured to remove some matter (e.g., particulate matter, including dust) from the return air  106 . The air mover  108  (e.g., blower) may induce the flow of air into, through, and out of, the air handler  102 . The air mover  108  may cause return air  106  to be drawn through the air filter  105  to remove some matter and may move (e.g., blow) the return air  106  through the air mover  108  and to the heat exchanger  110 . The return air  106  may flow in thermal communication with (e.g., in contact with outer surfaces of) one or more coils of the heat exchanger  110  so that heat is removed from the return air  106  to cool the return air  106  into conditioned air  114 . The air handler  102  may move the conditioned air  114  out of the air handler  102  and back into an interior space of the structure  1  via the air outlet  112 . 
     The air conditioning system  100  may circulate a working fluid (e.g., a refrigerant, including known R22 refrigerant, R410A refrigerant, or any known refrigerant) between the heat exchangers  110  and  152  to remove heat from the return air  106  when the return air  106  flows in thermal communication (e.g., through and/or in contact with one or more coils of) the heat exchanger  110 . The heat exchanger  110  may include any known heat exchanger used for an air conditioning system, for example an evaporator coil exchanger that includes one or more coils of one or more tubes through which the working fluid flows (e.g., as a cooled liquid). The heat exchanger  110  may cause heat to be transferred from the return air  106  and into the working fluid when the return air  106  is caused to flow across (e.g., in contact with, in thermal communication with, etc.) the one or more coils (e.g., one or more outer surfaces  110   s  thereof), thereby resulting in the working fluid becoming heated (e.g., heated into a low-pressure gas). The heated working fluid may be drawn, via fluid line  116  (e.g., fluid conduit, pipe, etc.) into the condenser assembly  104 . 
     The air conditioning system  100  may include, in the condenser assembly  104 , a compressor  150  (which may be any known compressor) that induces flow of the working fluid through the air conditioning system  100 . The compressor  150  may draw the heated working fluid from the fluid line  118  and may compress the heated working fluid into a high-pressure gas. The heated working fluid may pass (e.g., flow), for example as the high-pressure gas, from the compressor  150  to the heat exchanger  152  (which may be any known heat exchanger and may be referred to as a condenser coil). The air mover  154  may cause ambient air  198  from the ambient environment  190  to be drawn across (e.g., in thermal communication with) one or more tubes of the heat exchanger  152  to remove heat from the heated working fluid passing through the one or more tubes of the heat exchanger  152 , thereby discharging the heat originally removed from the return air  106  into the ambient environment  190  which serves as a heat sink for the air conditioning system  100 . As a result, the working fluid passing through the heat exchanger  152  may be cooled back into a liquid. The working fluid may then pass (e.g., flow, circulate, etc.) back to the air handler  102  via a fluid line  118 , where the working fluid may pass through an expansion valve  111  (which may be any known expansion valve) to cool the working fluid which then passes into the heat exchanger  110  to remove additional heat from return air  106 . 
     As noted above, the circulation of working fluid through the heat exchanger  110 , heat exchanger  152 , fluid lines  116  and  118 , and expansion valve  111  may be induced by operation of the compressor  150 . 
     As further shown, the air conditioning system  100  may include a controller  140  that is configured to control elements of the air conditioning system  100 , including for example controlling operation of the air handler  102 , condenser assembly  104 , or any part thereof. As described further below, the controller  140  may be implemented by a computing device, including a memory storing a program of instructions and a processor configured to execute the program of instructions. While the controller  140  is shown as being included within the housing  101  of the air handler  102 , it will be understood that the controller  140  may be located external to the housing  101  and, in some example embodiments, may be located within the condenser assembly  104  or may be attached to an exterior of the air handler  102  for ease of manual access. 
     Still referring to  FIG.  1   , when heat is removed from the return air  106  based on the return air  106  passing in thermal communication with the heat exchanger  110 , water may condense out of the cooled return air as condensate  120  at the heat exchanger  110 , for example on one or more outer surfaces  110   s  thereof. The air handler  102  may include a drip pan  122  located beneath the heat exchanger  110 , and the condensate  120  may fall under gravity from the one or more outer surfaces  110   s  of the heat exchanger  110  to collect in the drip pan  122 . The air handler  102  may further include a condensate drain line  124  having an inlet opening  128  coupled to the drip pan  122  (e.g., a bottom surface where the drip pan  122  has an inclined surface that is angled downwards towards the inlet opening  128  of the condensate drain line  124 ) and an outlet opening  130  that is external to the structure  1  and open to the ambient environment  190 , as shown. Condensate  120  collected in the drip pan  122  may pass under gravity to the inlet opening  128  of the condensate drain line  124 , and the condensate drain line  124  may direct the condensate  120  to flow out of the air handler  102  and out of the structure  1  to the ambient environment  190  via the outlet opening  130  of the condensate drain line  124 . 
     As shown in  FIG.  1   , the air conditioning system  100  may include a float switch  160  that is located in the drip pan  122  and/or in the condensate drain line  124  (e.g., at an opening  125  into the condensate drain line  124  as shown). The float switch  160  may be a switch that is configured to be actuated based on backflow and/or overflow of condensate  120  in the condensate drain line  124 . For example, the float switch  160  may be any known float switch and may be configured to be closed or opened (e.g., actuated) based on accumulation of condensate  120  in the drip pan  122  to at least a threshold volume held therein. The float switch  160  may be communicatively (e.g., electrically) coupled to the controller  140 , and the controller  140  may be configured to shut down some or all of the air conditioning system  100  (e.g., shut down the air handler  102 , the air mover  108 , the compressor  150 , and/or the air mover  154 ) in response to the float switch  160  being actuated, thereby reducing or preventing damage being caused in the structure and/or air conditioning system  100  due to the condensate  120  accumulation. 
     In some example embodiments, various substances may accumulate on one or more outer surfaces  110   s  of one or more elements of the heat exchanger  110  (e.g., an evaporator coil through which the liquid working fluid may circulate to remove heat from the return air  106 ) due to condensation of condensate  120  on the one or more outer surfaces  110   s . Such substances may include, for example, mold, algae, mildew, bacteria, fungi, dander, pollen, zooglea (also referred to as  zoogloea ), any combination thereof, or the like. Such accumulation of substances on the outer surface(s) of the heat exchanger  110  elements may cause reduced heat exchange (e.g., heat transfer) performance of the heat exchanger  110  in removing heat from the return air  106 . Additionally or alternatively, such accumulation of substances on the outer surface(s) of the heat exchanger  110  elements may cause reduced performance of the air conditioning system due to clogging air flow conduits through portions of the heat exchanger  110  (e.g., reducing cross-sectional flow area between adjacent heat exchanger tubes, coils, structures, or the like) which may cause the air conditioning system to become overworked to sustain a flow rate of air therethrough and more prone to breakdown and/or damage (e.g., of damage to the air mover  108  and/or of the heat exchanger  110 ). Additionally, such substances may accumulate in one or more portions of the air conditioning system  100  (e.g., the drip pan  122 , the condensate drain line  124 , etc.), which may clog one or more portions of the condensate removal elements (e.g., drip pan  122 , condensate drain line  124 , etc.) of the air handler  102 , which may cause damage to the air handler  102  and/or to a structure in which the air handler  102  is included, including water damage. 
     Still referring to  FIG.  1   , in some example embodiments a heat exchanger cleaner apparatus system  1100  may be coupled to the air handler  102  at an opening  109  into the interior  192  of the air handler  102  which is at least partially defined by the housing  101  of the air handler  102 . The heat exchanger cleaner apparatus system  1100  may be configured to dispense a cleaning composition into contact with an outer surface  110   s  of a heat exchanger  110  of the air handler  102 . As described herein, an outer surface  110   s  of a heat exchanger may include any of an upper surface, a lower surface, an inward-facing surface, an outward-facing surface, a side surface, any combination thereof, or the like of any portion of the heat exchanger  110 , where any portion of the heat exchanger  110  may include any coils, tubes, or the like included in the heat exchanger  110 . As described herein, the heat exchanger cleaner apparatus system  1100  may be configured to dispense (e.g., pump, spray, etc.) a cleaning composition into the interior  192  of the air handler  102  to contact an outer surface  110   s  of the heat exchanger  110  (e.g., an outer surface of an evaporator coil) to reduce, remove, and/or prevent accumulation of various substances (e.g., mold, algae, mildew, bacteria, fungi, dander, pollen, zooglea (also referred to as  zoogloea ), any combination thereof, or the like) on the outer surface  110   s  of the heat exchanger  110 , thereby improving heat transfer performance of the heat exchanger  110  (e.g., between the working fluid in the heat exchanger  110  coils and the return air  106  passing in thermal communication with the heat exchanger  110 ) and thus improve operational efficiency and/or performance of the air conditioning system  100  at least with regards to cooling the return air  106 . The cleaning composition  230  sprayed onto one or more outer surfaces  110   s  of the heat exchanger  110  may then, together with any byproducts of removal of substances from the one or more outer surfaces  110   s  by the cleaning composition, fall as material  234  into the drip pan  122  to be removed from the air handler  102  via the condensate drain line  124 . The cleaning composition included in material  234  may further remove, break down, etc. accumulated substances (e.g., mold, algae, mildew, bacteria, fungi, dander, pollen, zooglea (also referred to as  zoogloea ), any combination thereof, or the like) in the drip pan  122  and/or the condensate drain line  124  as the cleaning composition falls from the one or more outer surfaces  110   s  into the drip pan  122  and is further drawn into the condensate drain line  124 , thereby mitigating clogging of the drip pan  122  and/or the condensate drain line by said substances. 
     In some example embodiments, the heat exchanger cleaner apparatus  200  may be configured to dispense (e.g., pump, spray, etc.) the cleaning composition into contact with the outer surface  110   s  of the heat exchanger  110  without human intervention (e.g., automatically), for example to dispense discrete amounts (e.g., a particular amount, which may be a particular volume and/or particular mass) of the cleaning composition at a particular (or, alternatively, predetermined) fixed time interval, thereby reducing or preventing accumulation of the various substances on the one or more outer surface  110   s  of the heat exchanger  110  (e.g., evaporator coil) while reducing or minimizing human intervention and/or effort expended to implement the dispensing. Because the heat exchanger cleaner apparatus  200  is configured to dispense the cleaning composition (e.g., repeatedly at a fixed time interval) without human intervention, the accumulation of potential substances (e.g., mold, algae, mildew, bacteria, fungi, dander, pollen, zooglea (also referred to as  zoogloea ), any combination thereof, or the like) on the one or more outer surface  110   s  of the heat exchanger  110  (e.g., evaporator coil) may be reduced, removed, or prevented. Such reduction, removal, or prevention of substance accumulation on the one or more outer surfaces  110   s  of the heat exchanger may thereby improve overall heat transfer efficiency and/or performance of the air handler  102  and thus improve performance of the air conditioning system  100 , at least with regard to cooling the return air  106 , and may further reduce or prevent the likelihood of condensate  120  backup and/or overflow which might otherwise result in shutdown of at least the air handler  102  and/or air conditioning system  100 , flooding damage to the air handler  102  and/or structure in which the air handler  102  is located, or the like. Because human intervention is not required to implement the dispensing (e.g., pumping, spraying, etc.) of the cleaning composition, particularly dispensing of the cleaning composition repeatedly at a fixed time interval, the likelihood of such accumulation resulting in significant reduction in air conditioning system performance and/or efficiency, and/or resulting in damage to at least one of the air conditioning system  100  or the structure  1 , due to a missed or forgotten manual dispensing of cleaning composition by a human operator is reduced or prevented, thereby improving operational performance and/or efficiency of the air conditioning system  100  and reducing workload by a human operator. 
     As shown in  FIG.  1   , the heat exchanger cleaner apparatus system  1100  may include a heat exchanger cleaner apparatus  200  and a cartridge  300  that is coupled (e.g., detachably coupled) to the heat exchanger cleaner apparatus  200  to supply cleaning composition to the heat exchanger cleaner apparatus  200  to be further supplied into the interior  192  of the air handler  102  to be sprayed onto an outer surface  110   s  of the heat exchanger. The heat exchanger cleaner apparatus  200  may include a housing  201 , in which a pump device  208  may be located, a connector interface  204  coupled in fluid communication with an inlet of the pump device  208  (e.g., via one or more internal conduits, reservoirs, or the like within the housing  201 ), and a spray outlet assembly  240  coupled in fluid communication with an outlet of the pump device  208  (e.g., via one or more internal conduits, reservoirs, or the like within the housing  201 ). The pump device  208  may be any well-known pump device (e.g., a gear pump, screw pump, or the like) configured to be operated (e.g., actuated) to selectively supply (e.g., pump) an amount of cleaning composition to the spray outlet assembly  240 . 
     As shown, the connector interface  204  may be configured to couple with a complementary connector interface  314  of a cartridge  300  which has a cartridge reservoir  304  configured to hold the cleaning composition, to establish flow communication from the cartridge reservoir  304  to the pump device  208 , such that the pump device  208  is in fluid communication between the connector interface  204  and the spray outlet assembly  240 , and the pump device  208  is configured to be operated to pump the amount of the cleaning composition from the cartridge reservoir  304  and through the spray outlet assembly  240 . 
     As shown, the heat exchanger cleaner apparatus  200  may include an internal reservoir  206  which may be located in fluid communication between connector interface  204  and the inlet of the pump device  208 , although it will be understood that in some example embodiments the internal reservoir  206  may be omitted. The connector interface  204  may be configured to supply cleaning composition from the cartridge reservoir  304  to the internal reservoir  206 , where the volume of the internal reservoir  206  may be equal to or greater than the volume of the particular amount of cleaning composition that the heat exchanger cleaner apparatus  200  is configured to supply (“dispense”) to the heat exchanger  110  outer surface  110   s . The connector interface  204  may include, for example, a check valve, where the check valve is configured to open in response to the connector interface  204  coupling (e.g., detachably coupling, reversibly coupling, etc.) with the complementary connector interface  314 . The connector interfaces  204  and  314  may be complementary connectors, including bayonet connector interfaces, threaded connector interfaces, or the like. The cartridge  300  may correspond to any example embodiments of the cartridge  300  as described herein. 
     The spray outlet assembly  240  may be configured to extend from the heat exchanger cleaner apparatus  200  (e.g., from the housing  201  thereof) into the interior  192  of the air handler  102  via an opening  109  in the housing  101  of the air handler from the exterior (at which the heat exchanger cleaner apparatus  200  is located) so that the spray outlet assembly  240  is at least partially located within the interior  192  of the air handler  102  and that a distal end of the spray outlet assembly  240  that is distal from the housing  201  of the heat exchanger cleaner apparatus  200  (and which may include a spray nozzle, also referred to herein as a spray head) is directly exposed to (e.g., without any interposing structures) an outer surface  110   s  of the heat exchanger  110  of the air handler  102 . The spray outlet assembly  240  may be configured to receive cleaning composition discharged by the pump device  208  outlet and spray a fluid stream  232  of the cleaning composition  230  into the air handler  102  interior  192  to contact one or more outer surfaces  110   s  of the heat exchanger  110 . The spray outlet assembly  240  may include any known spray outlet head, spray head, spray nozzle, or the like configured to cause the fluid stream  232  to have any particular stream shape (e.g., spray pattern) to control the trajectory of the cleaning composition in the fluid stream  232 . Additionally, the spray outlet assembly  240  may be configured to be positioned at least partially in the air handler interior  192  so that the fluid stream  232  deposits cleaning composition on at least a portion (or, in some example embodiments, an entirety) of one or more outer surfaces  110   s  of the heat exchanger  110  (e.g., outer surfaces of one or more evaporator coils of an air handler heat exchanger  110  (e.g., an evaporator) which are directly exposed to the spray outlet assembly  240  in the interior  192  of the air handler  102 . For example, in some example embodiments the spray outlet assembly  240  (e.g., the spray nozzle at the distal end thereof) may be configured to direct cleaning composition  230  pumped into the spray outlet assembly  240  from a pump device  208  into the air handler interior  192  as a conical fluid stream (e.g., conical spray pattern) configured to deposit one or more droplets of cleaning composition to contact one or more outer surfaces directly exposed to the spray outlet assembly  240  in the air handler interior  192 . 
     The controller  210  may correspond to (e.g., include any of the elements of) any of the example embodiments of the controller  210  as described herein and may be configured to operate (e.g., control) the pump device  208  to cause the amount of the cleaning composition to be supplied (e.g., sprayed, pumped, discharged, etc.) through the spray outlet assembly  240  by the pump device  208  without manual intervention. The heat exchanger cleaner apparatus  200  may include a power source (e.g., batteries) and the controller  210  may be configured to selectively supply power to the pump device  208  to operate the pump device  208  to discharge (e.g., pump) a particular amount of cleaning composition (e.g., a volume corresponding to the volume of internal reservoir  206 ) into the spray outlet assembly  240  via the outlet of the pump device  208 . 
     The heat exchanger cleaner apparatus  200  may be configured to be coupled (e.g., detachably coupled) to the air handler  102  via a structure connector  220 . The structure connector  220  may correspond to the structure connector  220  according to any of the example embodiments as described herein and may be configured to be coupled (e.g., detachably coupled) to the housing  201  and/or to the air handler  102  (e.g., housing  101 ) similarly to any of the example embodiments of the structure connector  220  as described herein. 
     In some example embodiments, the heat exchanger cleaner apparatus  200  may include a network communication interface (e.g., as part of the controller  210  or as a separate element according to any of the example embodiments of the heat exchanger cleaner apparatus  200 ) and the controller  210  may be configured to operate the pump device  208  based on receiving and processing command signals received at the heat exchanger cleaner apparatus  200  via the network communication interface. 
       FIGS.  2 A and  2 B  are schematic views of a heat exchanger cleaner apparatus  200  according to some example embodiments. Referring to  FIGS.  2 A and  2 B  in reference to  FIG.  1   , the heat exchanger cleaner apparatus  200  is configured to pump (also referred to herein as supply, dispense, drive, or the like) a cleaning composition  230  through a spray outlet assembly  240  into an interior  192  of the air handler  102  shown in  FIG.  1    to spray a fluid stream  232  (also referred to as a fluid spray stream, a spray stream, a spray pattern, or the like) of the cleaning composition  230  that at least partially contacts an outer surface  110   s  of a heat exchanger  110  (e.g., evaporator coil) of the air handler  102 . Cleaning composition  230  sprayed in the fluid stream  232  to contact an outer surface  110   s  of the heat exchanger  110  may subsequently fall from the outer surface  110   s  as part of material  234  falling under gravity into the drip pan  122  to be removed from the air handler  102  via the condensate drain line  124 , along with any substances caused to be removed (e.g., cleaned) from the outer surface  110   s  by the cleaning composition. 
     Referring to  FIGS.  2 A and  2 B , the heat exchanger cleaner apparatus  200  may include a housing  201  at least partially defining an interior of the heat exchanger cleaner apparatus  200 , and apparatus reservoir  202  (which may be at least partially defined by the housing  201 ) and which is configured to at least partially accommodate and hold a cartridge  300  configured to hold the cleaning composition  230  therein, a spray outlet assembly  240 , an internal reservoir  206 , and a pump device  208  that is configured to be actuated (e.g., operated) to selectively pump (also referred to interchangeably as “pump”) an amount (e.g., a particular amount, which may be a particular volume and/or a particular mass) of the cleaning composition  230  from an inlet  208   i  of the pump device  208  (which may be open, such as directly exposed to, the internal reservoir  206 ) to the spray outlet assembly  240  extending through the opening  201   x  in the housing  201  via the outlet  208   o  of the pump device  208 . 
     As shown in  FIGS.  2 A and  2 B , the apparatus reservoir  202  (which may be at least partially defined by one or more surfaces of the housing  201 ) may include an inner surface  202 S at least partially defining an interior volume space in which a cartridge  300  may be at least partially accommodated and held. The apparatus reservoir  202  may further include an apparatus reservoir outlet  202 A that is configured to be in fluid communication with the pump device  208  to enable cleaning composition  230  to flow from the apparatus reservoir  202  to the pump device  208 . For example, the apparatus reservoir outlet  202 A may be open to the internal reservoir  206 , such that the apparatus reservoir outlet  202 A is configured to establish fluid communication from the apparatus reservoir  202  to the pump device  208  inlet  208   i  via the internal reservoir  206 . In some example embodiments, where the internal reservoir  206  is omitted from the heat exchanger cleaner apparatus  200 , the apparatus reservoir outlet  202 A may be open to the inlet  208   i  of the pump device  208  (e.g., directly, wherein the inlet  208   i  is the same as the apparatus reservoir outlet  202 A, or via a conduit), such that the apparatus reservoir outlet  202 A is configured to establish fluid communication from the apparatus reservoir  202  to the pump device  208  inlet  208   i  via the internal reservoir  206 . 
     Still referring to  FIGS.  2 A and  2 B , the heat exchanger cleaner apparatus system  1100  may include both the heat exchanger cleaner apparatus  200  and a cartridge  300 , also referred to interchangeably as a “cleaner cartridge,” “cleaning composition cartridge,” or the like according to some example embodiments. In some example embodiments, the heat exchanger cleaner apparatus  200  may be configured to receive and couple with a cartridge  300  that contains (e.g., holds) the cleaning composition  230  within a cartridge reservoir  304  such that a flow path is established between the cartridge reservoir  304  and the pump device  208 . The cartridge  300  may be provided instead of the cleaning composition  230  being poured into, and directly held within, the apparatus reservoir  202  in contact with the inner surface  202 S thereof. Replenishment of the cleaning composition  230  held in the heat exchanger cleaner apparatus  200  may be simplified based on the cleaning composition  230  being held in the cartridge  300  which is coupled (e.g., detachably coupled) with the heat exchanger cleaner apparatus  200  to position the cartridge reservoir  304  in fluid communication with at least the inlet  208   i  of the pump device  208 , as replenishment of the total cleaning composition  230  held in the heat exchanger cleaner apparatus system  1100  (e.g., in the heat exchanger cleaner apparatus  200 ) may involve replacing a cartridge  300  that is coupled (e.g., detachably coupled) to the heat exchanger cleaner apparatus  200  based on being inserted into the apparatus reservoir  202  instead of directly pouring the cleaning composition  230  directly into the apparatus reservoir  202 . Such simplification may include reducing or preventing inadvertent spilling of cleaning composition  230  during the replenishment process. 
     As shown in  FIGS.  2 A and  2 B , the cartridge  300  may include a cartridge housing  302  that has at least an inner surface  302 I defining an interior volume space which may at least partially be a cartridge reservoir  304  which may hold the cleaning composition  230  therein, such that the inner surface  302 I may be understood to at least partially define the cartridge reservoir  304 . In some example embodiments, the cartridge reservoir  304  may have a particular volume, for example 36 oz and thus may be configured to hold the particular volume (e.g., 36 oz) of cleaning composition  230 . 
     As further shown, the apparatus reservoir  202  and the cartridge  300  may be sized and shaped so that the cartridge  300  may be received (e.g., accommodated) at least partially into the apparatus reservoir  202  to establish a sliding contact fit between the outer surface  302 S of the cartridge housing  302  and the inner surface  202 S of the apparatus reservoir  202 , for example so that the cartridge  300  occupies all or substantially all of the internal volume space of the apparatus reservoir  202  when the cartridge  300  is coupled to the heat exchanger cleaner apparatus  200 . 
     As shown in  FIGS.  2 A and  2 B , the cartridge  300  may have a greater volume than the apparatus reservoir  202  and may protrude out of the opening  2020  of the apparatus reservoir  202  when the cartridge  300  is received into the apparatus reservoir  202  and coupled (e.g., detachably coupled) with the heat exchanger cleaner apparatus  200 . Such protrusion of the cartridge  300  may enable easier human access to grasp the cartridge  300  to simplify replacement of cartridges  300 , but example embodiments are not limited thereto: in some example embodiments the cartridge  300  may be located entirely within the apparatus reservoir  202  when the cartridge  300  is coupled to the heat exchanger cleaner apparatus  200 . 
     As shown in  FIGS.  2 A and  2 B , the heat exchanger cleaner apparatus  200  may include the apparatus reservoir  202  which is configured to receive the cartridge  300  to enable the cartridge  300  to be coupled with the heat exchanger cleaner apparatus  200 , but example embodiments are not limited thereto. For example, in some example embodiments, the apparatus reservoir  202  may be entirely absent from the heat exchanger cleaner apparatus  200 , and the cartridge  300  (e.g., a connector interface  314  thereof) may couple with a port (e.g., having a complementary connector interface  204 ) that is exposed at the outer surface of the housing  201  of the heat exchanger cleaner apparatus  200  to put the cartridge reservoir  304  in fluid communication with the pump device  208  (e.g., the inlet  208   i  thereof). 
     As shown, the cartridge  300  may have a cartridge housing  302  that defines a cartridge outlet  302 A through which the cleaning composition  230  may exit the cartridge reservoir  304  when a flow path is established between the cartridge reservoir  304  and the pump device  208  (e.g., via apparatus reservoir outlet  202 A, internal reservoir  206 , etc.). 
     The cartridge outlet  302 A may include a connector interface  314  configured to establish a connection with the heat exchanger cleaner apparatus  200 , and the heat exchanger cleaner apparatus  200  (e.g., the apparatus reservoir  202 , the internal reservoir  206 , the housing  201 , any combination thereof, or the like) may further include a complementary connector interface  204  to enable a complementary connection with the cartridge  300  to thereby detachably couple the cartridge  300  to the heat exchanger cleaner apparatus  200 . Such complementary connector interfaces  204  and  314  may include any known connector interface, for example a friction fit connector, a threaded connector, a bayonet connector, any combination thereof, or the like. 
     As further shown, at least one of the cartridge  300  or the heat exchanger cleaner apparatus  200  may include a check valve  306  that is configured to be opened based on the heat exchanger cleaner apparatus  200  being coupled with the cartridge  300  (e.g., in response to establishing a threaded connection, bayonet connection, friction fit connection, or the like between the complementary connector interfaces  204  and  314  of the heat exchanger cleaner apparatus  200  and the cartridge  300 ). For example, as shown in  FIGS.  2 A and  2 B , the check valve  306  may be a check valve  306   a  included in the heat exchanger cleaner apparatus  200  (e.g., coupled to the apparatus reservoir outlet  202 A, the internal reservoir  206 , the connector interface  204 , the apparatus reservoir  202 , the housing  101 , the pump device  208 , any combination thereof, or the like) and configured to selectively open to establish fluid communication through the apparatus reservoir outlet  202 A to the inlet  208   i  of the pump device  208  based on cartridge  300  coupling with the heat exchanger cleaner apparatus  200  (e.g., via connector interfaces  204  and  314  detachably coupling). In another example, as shown in  FIGS.  2 A and  2 B , the check valve  306  may be a check valve  206   b  included in the cartridge  300  (e.g., coupled to the cartridge outlet  302 A, the cartridge reservoir  304 , the connector interface  314 , the housing  201 , any combination thereof, or the like) and configured to selectively open to establish fluid communication through the cartridge outlet  302 A from the cartridge reservoir  304  to the inlet  208   i  of the pump device  208  based on cartridge  300  coupling with the heat exchanger cleaner apparatus  200  (e.g., via connector interfaces  204  and  314  detachably coupling). In another example, check valves  306  and  306   b  may be separate portions of a check valve  306  and which engage to form the check valve  306  and to open same in response to the cartridge  300  coupling with the heat exchanger cleaner apparatus  200  (e.g., via connector interfaces  204  and  314  coupling). The check valve  306  may be configured to actuate to open a flow path between the cartridge reservoir  304  and the apparatus reservoir  202  and/or between the cartridge reservoir  304  and the pump device  208  and/or between the cartridge reservoir  304  and the internal reservoir  206  in response to the heat exchanger cleaner apparatus  200  being coupled with the cartridge  300 , so that the cartridge reservoir  304  is in fluid communication with the pump device  208  (e.g., the inlet  208   i ) via the cartridge outlet  302 A, the check valve  306 , the apparatus reservoir outlet  202 A, and the like. 
     In an example, the check valve  306  may at least partially be a part of the cartridge  300  (e.g., as check valve  306   b ) such that the check valve  306  is fixed to the cartridge housing  302  (e.g., via adhesive and/or the cartridge housing  302  being a plastic material (e.g., high density polyethylene or HDPE) that is formed to at least partially enclose the check valve  306   b ). In another example, the check valve  306  may at least partially be a part of the heat exchanger cleaner apparatus  200  (e.g., as check valve  306   a ) such that the check valve  306  is fixed to the housing  201  (e.g., via adhesive and/or the housing  201  being a plastic material (e.g., high density polyethylene or HDPE) that is formed to at least partially enclose the check valve  306   a ). For example, in some example embodiments, the check valve  306  may be fixed to the apparatus reservoir  202  and/or the pump device  208  as check valve  306   a . The check valve  306  may be included in a connector (e.g., connector interface  204 ) that is configured to couple with the cartridge  300  to establish the detachable coupling between the heat exchanger cleaner apparatus  200  and the cartridge  300 . For example, the check valve  306  may be included in a threaded connector, bayonet connector, friction fit connector, or the like. In another example, the check valve  306  may be removably (e.g., detachably) coupled to the apparatus reservoir  202 , housing  201 , internal reservoir  206 , connector interface  204 , and/or the pump device  208  via a set of complementary connectors (e.g., threaded, bayonet, etc.), and the check valve  306  may be detached from the heat exchanger cleaner apparatus  200  and coupled to the cartridge  300  prior to coupling of the heat exchanger cleaner apparatus  200  with the cartridge  300 , and the check valve  306  may be detached from the cartridge  300  subsequent to removal of an empty cartridge  300  from the heat exchanger cleaner apparatus  200  and then attached to a new, full cartridge  300  prior to coupling of the full cartridge  300  to the heat exchanger cleaner apparatus  200 , such that a check valve  306  may be re-used between separate cartridges  300 . 
     Accordingly, in some example embodiments, the heat exchanger cleaner apparatus  200  (e.g., the apparatus reservoir  202 ) may be configured to receive (e.g., at least partially accommodate) a cartridge  300  that includes a cartridge reservoir  304  configured to hold the cleaning composition  230 , and a cartridge outlet  302 A, and the heat exchanger cleaner apparatus  200  may be configured to couple with the cartridge  300  (e.g., based on detachable coupling of the complementary and respective connector interfaces  204  and  314  of the heat exchanger cleaner apparatus  200  and the cartridge  300 ) so that the cartridge reservoir  304  is in fluid communication (e.g., via an open flow channel) with at least the pump device  208  (e.g., the inlet  208   i  thereof) via the cartridge outlet  302 A. Additionally, in some example embodiments, the heat exchanger cleaner apparatus  200  or the cartridge  300  may include a check valve  306  that is configured to open in response to the heat exchanger cleaner apparatus  200  coupling with the cartridge  300  to establish the fluid communication between the cartridge reservoir  304  and at least the pump device  208  via the cartridge outlet  302 A. 
     Still referring to  FIGS.  2 A and  2 B , the pump device  208  may be configured to pump (e.g., selectively pump) an amount of cleaning composition  230  that is a particular amount (e.g., a particular volume, particular mass, etc.) so that the heat exchanger cleaner apparatus  200  may pump a particular amount of cleaning composition  230 , drawn through the inlet  208   i , through the outlet  208   o  (e.g., repeatedly at a fixed time interval). For example, in some example embodiments, the amount of cleaning composition  230  as described herein that is pumped from the inlet  208   i  (e.g., from the internal reservoir  206 , apparatus reservoir  202 , and/or cartridge reservoir  304  via the inlet  208   i ) when the pump device  208  is operated once may be 3 oz of cleaning composition  230 , and the pump device  208  may be configured to be operated (e.g., may be configured to operate for a particular period of time associated at the controller  210  with pumping a corresponding particular amount of cleaning composition  230 ) to cause the particular amount of cleaning composition  230  to be pumped from the cartridge reservoir  304  of the cartridge  300  (e.g., via internal reservoir  206 ) to the spray outlet assembly  240  to be sprayed into the interior  192  of the air handler  102  as fluid stream  232  to contact one or more outer surfaces  110   s  of the air handler heat exchanger  110 . 
     The spray outlet assembly  240  may include a conduit  252  having a proximate end  252   a  and a distal end  252   b , where the proximate end  252   a  is coupled in fluid communication with the outlet  208   o  of the pump device  208 , the conduit  252  is configured to extend at least from the proximate end  252   a , through an opening  201   x  in the housing  201  of the heat exchanger cleaner apparatus  200 , and through an opening  109  in the housing  101  of the air handler  102  into the interior  192  of the air handler  102  such that a distal end  252   b  of the conduit  252  is within the interior  192  of the air handler  102 . The spray outlet assembly  240  may further include a spray nozzle  250  coupled to the distal end  252   b  of the conduit  252 . The conduit  252  partially or entirely comprise a rigid piece of material, such as a metal (e.g., stainless steel) tube, a plastic (e.g., rigid polyvinylchloride) tube, or the like. The conduit  252  may partially or entirely comprise a flexible piece of material, such as rubber, flexible polyvinylchloride, silicone, or the like. In some example embodiments, the opening  109  may have a diameter of about ½ inches to about ⅝ inches. In some example embodiments, some or all of the spray outlet assembly  240 , including any conduit structures, connectors, or the like comprising the conduit  252 , the spray nozzle, or the like a diameter (in the direction perpendicular to the longitudinal or central axis thereof) of about ½ inches to about ⅝ inches. 
     The spray nozzle  250  may be any known spray nozzle (e.g., spray head) configured to cause a received fluid (e.g., cleaning composition  230 ) to be sprayed in a fluid stream  232  having a particular spray pattern/shape (e.g., a conical spray pattern, a planar or flat spray pattern, etc.). In some example embodiments, the cleaning composition  230  pumped into the conduit  252  via the proximate end  252   a  from the outlet  208   o  of the pump device  208  may be directed by the conduit  252  to the spray nozzle  250  via the distal end  252   b  of the conduit  252 . The spray nozzle  250  may be configured to cause the cleaning composition  230  directed to the spray nozzle  250  through the conduit  252  to be sprayed as a fluid stream  232  into the interior  192  of the air handler  102  to at least partially contact the outer surface  110   s  of the heat exchanger  110 . The spray nozzle  250  may be any known type of spray nozzle, spray head, or the like and may be configured to spray the cleaning composition as the fluid stream  232  in any type of spray pattern (e.g., a conical spray pattern, a flat planar spray pattern, etc.). The spray nozzle  250  may be configured to have an outer diameter that is equal to or less than an outer diameter of the conduit  252  to enable ease of insertion of the spray nozzle  250  into the interior  192  of the air handler  102  via the opening  109 . 
     The spray nozzle  250  and the distal end  252   b  of the conduit  252  may have complementary connectors (e.g., threaded connectors, bayonet connectors, etc.) configured to enable ease of replacement of the spray nozzle  250  coupled to the conduit  252  with different spray nozzles  250  configured to spray fluid streams having different spray patterns, thereby improving ease of configuration of the spray outlet assembly  240  to spray cleaning composition to contact one or more outer surfaces  110   s  of the heat exchanger  110 . However, it will be understood that in some example embodiments the spray nozzle  250  may be fixed to the distal end of the conduit  252  (e.g., via the spray nozzle  250  being bonded via adhesive, welding, or the like to the distal end  252   b ). 
     The outlet  208   o  of the pump device  208  and the proximate end  252   a  of the conduit  252  may have complementary connectors (e.g., threaded connectors, bayonet connectors, etc.) configured to enable ease of replacement of the spray outlet assembly  240 . However, it will be understood that in some example embodiments the proximate end  252   a  of the conduit  252  may be fixed to the outlet  208   o  of the pump device  208  (e.g., via the proximate end  252   a  being bonded via adhesive, welding, or the like to the outlet  208   o  of the pump device  208 ). 
     In some example embodiments, the conduit  252  may be a single structure (e.g., a single tube that is a single, unitary piece of material extending continuously from the proximate end  252   a  to the distal end  252   b . In some example embodiments, for example as shown in  FIGS.  2 A to  2 B , the conduit  252  may include a plurality of separate structures, such as a plurality of separate conduit structures  242 ,  244 ,  248 , which are coupled in series between the spray nozzle  250  and the pump device  208  (e.g., directly or via one or more connectors  202   x  and/or  246 ). For example, as shown, the conduit  252  may include a first conduit structure  242  coupled (e.g., detachably via complementary connectors or fixed via adhesive, welding, or the like) at a first end to the outlet  208   o  of the pump device  208  and coupled (e.g., detachably via complementary connectors or fixed via adhesive, welding, or the like) at an opposite second end to a connector  202   x  that is at (e.g., at least partially extends through) the opening  201   x  in the housing  201  of the heat exchanger cleaner apparatus  200  such that the first conduit structure  242  extends through an interior of the heat exchanger cleaner apparatus  200 . The connector  202   x  at the opening  201   x  may include a connector interface (e.g., a threaded connector, bayonet connector, fitting, or the like) that is configured to detachably or fixedly couple with a separate conduit structure comprising the conduit  252  that is external to the housing  201  of the heat exchanger cleaner apparatus  200 , to thereby couple the separate conduit structure in fluid communication with the first conduit structure  242  via the opening  201   x  and any fitting or connector thereof. 
     As shown, the conduit  252  may include a second conduit structure  244  coupled (e.g., detachably via complementary connectors or fixed via adhesive, welding, or the like) at a first end to the first conduit structure  242  or connector  202   x  at the opening  201   x  and coupled (e.g., detachably via complementary connectors or fixed via adhesive, welding, or the like) at an opposite second end to a connector  246  located within the opening  109  of the housing  101  of the air handler  102 . In some example embodiments, the connector  202   x  may be a flange, bracket, gasket, fitting, or the like which may be configured to at least seal a connection between the first and second conduit structures  242  and  244 . The connector  246  may be a flange, bracket, gasket, fitting, or the like which may be configured to at least seal a connection between the conduit  252  and the housing  101  of the air handler  102 . The connector  246  may include a first complementary connector interface (e.g., a threaded or bayonet connector) configured to detachably couple with the second conduit structure  244  outside the air handler  102  and a second, opposite complementary connector interface (e.g., a threaded or bayonet connector) configured to detachably couple with the third conduit structure  248  within the interior  192  of the air handler  102 . The conduit  252  may include a third conduit structure  248  coupled (e.g., detachably via complementary connectors or fixed via adhesive, welding, or the like) at a first end to the connector  246  and coupled (e.g., detachably via complementary connectors or fixed via adhesive, welding, or the like) at an opposite second end to the spray nozzle  250 . 
     Adjacent structures of the first to third conduit structures  242 ,  244 , and/or  248 , the connector  202   x , and/or the connector  246  may be coupled to each other via complementary connectors, including for example complementary threaded connectors, bayonet connectors, or the like. The third conduit structure  248  and the spray nozzle  250  may be coupled to each other via complementary connectors, including for example complementary threaded connectors, bayonet connectors, or the like. The first conduit structure  242  and the outlet  208   o  of the pump device  208  may be coupled to each other via complementary connectors, including for example complementary threaded connectors, bayonet connectors, or the like. 
     One or more of the first to third conduit structures  242 ,  244 , and/or  248 , connector  202   x , connector  246 , and/or spray nozzle  250  may be integrated into a single, unitary piece of material. For example, in some example embodiments the conduit structures  244  and  248  may be integrated together in a single, unitary piece of material that is a rigid (e.g., metal) or flexible (e.g., plastic) tube coupled at a first end to a connector  202   x  at the opening  201   x  to be coupled (e.g., detachably or affixed via welding, molding, adhesive, or the like) to the separate first conduit structure  242  via the connector  202   x  and coupled (e.g., detachably or affixed via welding, molding, adhesive, or the like) at a second, opposite end to the spray nozzle  250 , where the first conduit structure  242  may be a same or different material composition as the integrated conduit structures  244 ,  248 , and where the connector  246  may be omitted or may be a gasket surrounding an outer surface of the conduit  252  (e.g., the single unitary piece of material defining the tube that is integrated conduit structures  244 ,  248 ) and filling an annular space between the outer surface of the conduit  252  and an inner edge of the opening  109 . The connector  246  may further include a seal, O-ring, or the like along the inner surface of the opening  109  to further establish a connection with the outer surface of the conduit  252 . In some example embodiments, the connector  246  may include an adaptor (e.g., a variable inner diameter connector) that is configured to couple different serially-coupled conduit structures of the conduit  252  (e.g., conduit structures  244  and  248 ) that have different outer diameters and/or inner diameters. In another example, in some example embodiments the conduit structures  242  and  244  may be integrated together in a single, unitary piece of material that is a rigid (e.g., metal) or flexible (e.g., plastic) tube coupled (e.g., detachably or affixed via welding, molding, adhesive, or the like) at a first end to the outlet  208   o  of the pump device  208  and coupled (e.g., detachably or affixed via welding, molding, adhesive, or the like) at a second, opposite end to the third conduit structure  248  (e.g., directly or via connector  246 ), where the third conduit structure  248  may be a same or different material composition as the integrated conduit structures  242 ,  244 , and where the connector  202   x  may be omitted or may be a gasket surrounding an outer surface of the conduit  252  (e.g., the single unitary piece of material defining the tube that is integrated conduit structures  242 ,  244 ) and filling an annular space between the outer surface of the conduit  252  and an inner edge of the opening  201   x . The connector  202   x  may further include a seal, O-ring, or the like along the inner surface of the opening  201   x  to further establish a connection with the outer surface of the conduit  252 . In some example embodiments, the connector  202   x  may include an adaptor (e.g., a variable inner diameter connector) that is configured to couple different serially-coupled conduit structures of the conduit  252  (e.g., conduit structures  242  and  244 ) that have different outer diameters and/or inner diameters. 
     In another example, in some example embodiments the conduit structures  242 ,  244 , and  246  may be integrated together in a single, unitary piece of material that is a rigid (e.g., metal) or flexible (e.g., plastic) tube coupled (e.g., detachably or affixed via welding, molding, adhesive, or the like) at a first end to the outlet  208   o  of the pump device  208  and coupled (e.g., detachably or affixed via welding, molding, adhesive, or the like) at a second, opposite end to the spray nozzle  250 , where the spray nozzle  250  may be a same or different material composition as the integrated conduit structures  242 ,  244 ,  248 , and where one or both of the connectors  246  and/or  202   x  may be omitted or may be a gasket surrounding an outer surface of the conduit  252  (e.g., the single unitary piece of material defining the tube that is integrated conduit structures  242 ,  244 ,  248 ) and filling an annular space between the outer surface of the conduit  252  and an inner edge of the openings  201   x  or  109 . 
     In some example embodiments, at least a portion of the conduit  252  may be integral to (e.g., fixed to via welding, adhesive, or the like, part of a same piece of material as at least a portion of, etc.) at least a portion of the pump device  208  and thus may be considered to be part of a same device as the pump device  208 . For example, in some example embodiments the first conduit structure  242  may be considered to be a part (e.g., discharge conduit) of the pump device  208 , such that a distal end of the first conduit structure  242  that is proximate to the opening  201   x  may be considered to be the outlet  208   o  of the pump device  208 , and said distal end may be coupled to the second conduit structure  244  directly or via a connector  202   x  at the opening  201   x . The second conduit structure  244  may be a same piece of material as or a separate, coupled piece of material with regard to the third conduit structure  248  and coupled thereto directly or via connector  246 . It will be understood that in some example embodiments the connector  202   x  may be absent such that separate conduit structures  242  and  244  may be directly coupled to each other via respective complementary connector interfaces (e.g., complementary threaded interfaces, bayonet interfaces, etc.), and where the first conduit structure  242  may extend through opening  201   x  to be coupled to the second conduit structure  244  externally to the housing  201 . It will be understood that in some example embodiments the connector  246  may be absent such that separate conduit structures  244  and  248  may be directly coupled to each other via respective complementary connector interfaces (e.g., complementary threaded interfaces, bayonet interfaces, etc.). 
     In some example embodiments, the conduit  252  may be at least partially adjustable in length, to enable variable positioning of the spray nozzle  250  in the interior  192  of the air handler  102 . For example, the conduit  252  may include the conduit structures  244  and  248  integrated together into a single telescopically extendable tube device configured to be telescopically extendable along its respective longitudinal axis to enable adjustment of the distance of the spray nozzle  250  along the longitudinal axis from the housing  201  of the heat exchanger cleaner apparatus  200 , thereby enabling adjustable positioning of the spray nozzle  250  in the interior  192  of the air handler  102  to adjustably control a spacing distance of the spray nozzle  250  from the heat exchanger  110  to adjustably control the impingement of the fluid stream  232  sprayed by the spray nozzle on one or more outer surface  110   s  of the heat exchanger  110  (e.g., adjustably control an area of the outer surface(s) impinged by the fluid stream  232 ) based on adjustable positioning of a spacing distance of the spray nozzle  250  from the heat exchanger  110 . 
     The spray outlet assembly  240  is configured to establish fluid communication between the outlet  208   o  of the pump device  208  of the heat exchanger cleaner apparatus  200  and the interior  192  of the air handler  102  and to direct a fluid stream  232  (e.g., an amount) of cleaning composition  230  pumped into the conduit  252  by the pump device  208  as a fluid stream  232  into the interior to contact an outer surface  110   s  of the heat exchanger  110  to reduce and/or remove substances (e.g., mold, algae, mildew, bacteria, fungi, dander, pollen, zooglea (also referred to as  zoogloea ), any combination thereof, or the like) from the outer surface  110   s  of the heat exchanger  110 , thereby improving heat transfer efficiency and/or performance of the heat exchanger  110  and thus of the air conditioning system  100  to remove heat from the air  106 . 
     In some example embodiments, the heat exchanger cleaner apparatus  200  includes a structure connector  220  that is configured to connect the heat exchanger cleaner apparatus  200  to an external structure (e.g., a housing  101  of the air handler  102  as shown) to at least partially hold the heat exchanger cleaner apparatus  200  in place in relation to the opening  109  through the housing  101  of the air handler  102  (e.g., at least partially structurally support the heat exchanger cleaner apparatus  200  in relation to the opening  109 ). As described further herein, the structure connector  220  may have various structures. For example, the structure connector  220  may include an adhesive connector, a magnet, or the like to couple with the housing  101  of the air handler  102 . 
     In some example embodiments, the pump device  208  may include any known positive displacement pump, a gear pump, or the like that is configured to operate for a particular period of time to move the amount of the cleaning composition  230  from the inlet  208   i  which is in fluid communication with the apparatus reservoir  202 , cartridge reservoir  304 , internal reservoir  206 , or the like to the outlet  208   o  which is in fluid communication with the spray outlet assembly  240 , based on a control signal generated by the controller  210 . 
     As described herein, a cleaning composition  230  may be any known chemical composition (e.g., solution, liquid, fluid, etc.) that may be configured to clean (e.g., remove) potential buildup substances (e.g., mold, algae, mildew, bacteria, fungi, dander, pollen, zooglea (also referred to as  zoogloea ), any combination thereof, or the like) from an outer surface  110   s  of the heat exchanger  110  of the air handler  102 . In some example embodiments, the cleaning composition  230  may be a chemical substance that is or includes a chelating agent (e.g., chelant) including, for example, sodium hexametaphosphate, that is configured to remove potential buildup substances from the outer surface  110   s  of the heat exchanger  110  of the air handler  102  based on chelation upon contact with the potential buildup substances. For example, the cleaning composition  230  may be a liquid solution that includes 3%-7% sodium hexametaphosphate, by weight of the total weight of the cleaning composition  230 . Based on the heat exchanger cleaner apparatus  200  being configured to pump cleaning composition  230  through the spray outlet assembly  240 , where the cleaning composition  230  is dispensed into the interior  192  of the air handler  102  to contact an outer surface  110   s  of the heat exchanger  110  of the air handler, the heat exchanger cleaner apparatus  200  may be configured to enable removal of potential buildup substances (e.g., mold, algae, mildew, bacteria, fungi, dander, pollen, zooglea (also referred to as  zoogloea ), any combination thereof, or the like) from an outer surface  110   s  of the heat exchanger  110  of the air handler  102  by the cleaning composition  230 , which may thereby reduce or prevent the reduction in heat transfer performance of the heat exchanger  110  due to the potential buildup substances. 
     As shown in  FIGS.  2 A and  2 B , the heat exchanger cleaner apparatus  200  may include a power supply  212  that is configured to supply electrical power to devices included therein, including the controller  210 , the pump device  208 , a network communication interface  224 , a sensor, or the like. As shown, the power supply  212  may include a battery  214 , which may include any known rechargeable battery (e.g., a lithium ion battery). As further shown, in some example embodiments the power supply  212  may include a wired power connection  216  which may be configured to couple to a power outlet provided at the structure  1  and/or the air handler  102 . The power supply  212  may further include a charging circuit  218  that may be configured to recharge the battery  214  from the wired power connection  216  and may be configured to enable the battery  214  to supply power to operate the heat exchanger cleaner apparatus  200  in the absence of electrical power being received via the wired power connection  216 . 
     As shown in  FIGS.  2 A and  2 B , the controller  210  may be configured to operate the pump device  208  to cause a particular amount of the cleaning composition  230  to be pumped from the inlet  208   i  (e.g., from the apparatus reservoir  202 , internal reservoir  206 , and/or cartridge reservoir  304  via the inlet  208   i ) and through the spray outlet assembly  240  (e.g., via the outlet  208   o ) without manual intervention. For example, the controller  210  may be configured to cause an electrical signal to be generated and transmitted to the pump device  208  to cause the pump device  208  to operate for a period of time (e.g., a particular, or alternatively predetermined prior of time), to thus cause a particular amount of the cleaning composition  230  to be pumped from the inlet  208   i  to the outlet  208   o.    
     The controller  210  may include a memory (e.g., a solid state drive, or SSD) storing a program of instructions, and the controller  210  may include a processor (e.g., a Central Processing Unit, or CPU) configured to execute the program of instructions to implement any functionality of the controller  210  according to any example embodiments. However, example embodiments are not limited thereto. For example, in some example embodiments, the controller  210  may include circuitry that is configured to implement a timer circuit (e.g., a clock, timer, or any combination thereof) and is configured to generate a signal to operate the pump device  208  based on the timer circuit counting a particular time interval. 
     In some example embodiments, the controller  210  is configured to operate the pump device  208  to cause the pump device  208  to pump an amount of cleaning composition  230  through the spray outlet assembly  240  to be sprayed through the spray nozzle  250  thereof into the interior  192  of the air handler  102  into contact with an outer surface  110   s  of a heat exchanger  110  of the air handler  102 . In some example embodiments, the controller  210  may be configured to generate a signal to cause at least a portion of the pump device  208  to operate to pump cleaning composition  230  therethrough for a particular period of time that is associated, at the controller  210 , with causing a particular amount of cleaning composition  230  to be pumped by the pump device  208 . The controller  210  may cause a particular amount of cleaning composition  230  to be pumped based on accessing a look-up-table that is stored in a memory of the controller  210 , where the look-up-table is empirically generated and associates a period of time of pump device operation of at least a portion of the pump device  208  (e.g., a period of time of generation of a control signal) with pumping (e.g., selective pumping) of a corresponding amount of cleaning composition  230  by the pump device  208 . The controller  210  may determine a particular amount of cleaning composition  230  to be pumped, access the look-up-table to determine a corresponding duration or period of applied control signal to the pump device  208 , and then generate a control signal that is transmitted to the pump device  208  to cause at least a portion of the pump device  208  to be operated for the corresponding duration or period. 
     In some example embodiments, the controller  210  is configured to operate the pump device  208  to cause an amount of cleaning composition  230  (e.g., 3 oz) to be pumped in response to an elapse of a particular period of time (e.g., 7 days, or 168 hours). The controller  210  may be configured to operate the pump device  208  repeatedly upon repeated elapse of the particular period of time, which may be referred to as a “fixed time interval” (e.g., a fixed time interval of 7 days). In some example embodiments, the apparatus reservoir  202 , cartridge reservoir  304 , and/or internal reservoir  206  may be configured to hold a total volume of 36 oz, so that the heat exchanger cleaner apparatus  200  may be configured to pump 3 oz of cleaning composition  230  to be sprayed as a fluid stream  232  in the interior  192  of the air handler  102  to at least partially contact an outer surface  110   s  of the heat exchanger  110  every 7 days for a period of 12 weeks (84 days). 
     The controller  210  may be configured to repeatedly operate the pump device  208  at a fixed time interval (e.g., 7 days), based on monitoring a timer that increments a timer value at a fixed frequency, operating the pump device  208  in response to the timer value reaching a particular time value corresponding to the elapse of the particular period of time, and resetting the timer value to an initial timer value (e.g., 0 days) in response to operating the pump device  208 . For example, the controller  210  may include and/or implement a clock and/or timer that counts a period of elapsed time from an initial timer value (e.g., increments from 0 days) at a fixed frequency (e.g., counts days, hours, minutes and/or seconds at a fixed frequency of days, hours, minutes and/or seconds). In response to determining that a threshold timer value is reached (e.g., a timer value corresponding to the particular period of time and/or fixed time interval of 7 days), the controller  210  may generate a signal to cause the pump device  208  to operate for at least a particular (e.g., predetermined) period of time to cause an amount (e.g., particular amount) of the cleaning composition  230  to be pumped through the spray outlet assembly  240  via the outlet  208   o  and further re-set the timer value so that the controller  210  may subsequently cause the pump device  208  to pump another amount of the cleaning composition  230  upon a re-elapse of the particular period of time. The controller  210  may be configured to perform this process repeatedly so long as electrical power is supplied to the controller  210  (e.g., from power supply  212 ), so that the process may be performed (e.g., repeatedly at a fixed time interval) without human intervention. 
     In some example embodiments, the controller  210  is configured to implement a counter that increments a counter value, starting from an initial value (e.g., 0), in response to each operation of the pump device  208 . As a result, where the controller  210  repeatedly operates the pump device  208  at a fixed time interval, the controller  210  may track the number (e.g., quantity) of pumpings of an amount of cleaning composition  230  (e.g., the number of operations of the pump device  208 ) over time. Therefore, where the heat exchanger cleaner apparatus  200  and/or heat exchanger cleaner apparatus system  1100  is configured to hold a particular total amount of cleaning composition  230  (e.g., 36 oz) (e.g., in the cartridge reservoir  304 ), the controller  210  may track the counter value to determine when the total amount of cleaning composition  230  available to be pumped to be sprayed in the fluid stream  232  into the interior  192  of the air handler  102  is about to be depleted or is depleted and may generate a signal (e.g., a depletion signal) in response to the counter value reaching a value that corresponds to partial or complete (e.g., total, final, etc.) depletion of the cleaning composition  230  held by the heat exchanger cleaner apparatus system  1100 . 
     For example, where the cartridge  300  is configured to hold a particular total amount of cleaning composition  230  that is 36 oz, and where the controller  210  is configured to cause the pump device  208  to pump an amount of 3 oz of cleaning composition  230  at a fixed time interval of 7 days, the total amount of cleaning composition  230  may be depleted upon completion of 12 dispensings (e.g., pumpings). The controller  210  may store a threshold counter value of 10, 11, or 12 that corresponds to partial depletion, near-depletion, or total depletion of the total amount of cleaning composition  230  held in the heat exchanger cleaner apparatus system  1100  (e.g., held in the cartridge reservoir  304  of the cartridge  300 . The controller  210  may implement and/or monitor a counter that increments a counter value in response to each operation of the pump device  208 , and generate a depletion signal in response to the counter value reaching a particular counter value that corresponds to at least partial depletion of a fixed reservoir (e.g., the cartridge reservoir  304 ) of the cleaning composition (e.g., 10, 11, or 12). As described herein, the controller  210  may transmit the depletion signal to a display interface (e.g., an LED, an audio speaker), which may be included in the heat exchanger cleaner apparatus  200  or may be included in a remote computing device, to provide a depletion warning. The controller  210  may further or alternatively be configured to cause the depletion signal to a remote computing device (e.g., via a network communication interface  224  as described herein) in order to inform a remote human user supported by the remote computing device of the partial or complete depletion (e.g., final depletion) of the total amount of cleaning composition  230  held in the heat exchanger cleaner apparatus system  1100 . The human user may then be informed of the partial or complete depletion so that the human user may take action to replenish the cleaning composition held in the heat exchanger cleaner apparatus system  1100  (e.g., based on detaching and replacing the depleted cartridge  300  with a new, full cartridge  300  coupled to the heat exchanger cleaner apparatus  200 . 
     Additionally, the heat exchanger cleaner apparatus  200  may include a counter reset interface  222  (e.g., a button) that is configured to cause the counter value to be reset to an initial counter value (e.g., 0) in response to human interaction with the counter reset interface  222  (e.g., in response to a human user pushing the button after replenishing the total amount of cleaning composition  230  held in the heat exchanger cleaner apparatus system  1100 , for example in the cartridge reservoir  304  of the cartridge  300  that is coupled to the heat exchanger cleaner apparatus  200  based on the cartridge  300  being detachably coupled to the heat exchanger cleaner apparatus  200 ). 
     Still referring to  FIGS.  2 A and  2 B , the heat exchanger cleaner apparatus  200  may include a network communication interface  224  that is communicatively coupled to the controller  210 . It will be understood that the network communication interface  224  may be separate from the controller  210  as shown or may be included in and/or implemented by the controller  210 . The network communication interface  224  may be any known network communication transceiver, including a wireless network communication transceiver such as a WI-FI transceiver, 5G cellular network communication transceiver, an ad hoc network communication transceiver such as a Bluetooth® transceiver, any combination thereof, or the like. 
     The controller  210  may be configured to establish a network communication link (which may be a wired network communication link, a wireless network communication link, an ad hoc wireless network communication link, or the like) with a remote computing device as described herein and may engage in one-way or two-way communication with the remote computing device via the network communication link. 
     In some example embodiments, the controller  210  may communicate signals over the network communication link that indicate operations of the controller  210  (e.g., indicating operation of the pump device  208  at particular points in time, a present timer value, a present counter value, etc.). In some example embodiments, the controller  210  may communicate the depletion signal (generated in response to the counter value reaching a threshold value) to the remote computing device  700  via the network communication link  702 . 
     In some example embodiments, the controller  210  may be configured to perform operations in response to receiving signals from the remote computing device via the network communication link. For example, the controller  210  may be configured to cause the counter value of the counter value to be reset to an initial counter value (e.g., 0) in response to receiving a reset signal from the remote computing device via the network communication link (which may be transmitted by the remote computing device in response to a human user replenishing the total amount of cleaning composition  230  held in the heat exchanger cleaner apparatus system  1100  for example based on detaching a cartridge  300  with a substantially empty cartridge reservoir  304  from the heat exchanger cleaner apparatus  200  and further coupling a new cartridge  300  with a cartridge reservoir  304  substantially full of cleaning composition  230  to the heat exchanger cleaner apparatus  200 ). 
     Still referring to  FIGS.  2 A and  2 B , in some example embodiments, the heat exchanger cleaner apparatus system  1100  (e.g., the heat exchanger cleaner apparatus  200 ) may be communicatively coupled to a remote computing device  700  communicatively via a network communication link  702 . 
     In some example embodiments, the network communication interface  224  (e.g., a wireless network communication transceiver) is configured to establish a network communication link with a remote computing device  700 . The remote computing device  700  may be configured to support a human user. 
     As shown, the remote computing device  700  may include a processor  720  (e.g., a CPU), a memory  730  (e.g., a SSD), a power supply  740  (e.g., a rechargeable battery), a network communication interface  750  (e.g., a wireless network communication transceiver), and an interface  760  that may include a display device (e.g., an LED display panel, an OLED display panel, or the like) a button, a touchscreen display device, any combination thereof, or the like that are communicatively and/or electrically coupled via a bus connection  710 . 
     At least some of the remote computing device  700 , including for example the processor  720 , the memory  730 , the network communication interface  750 , or any combination thereof, may be included in, and/or may be implemented by one or more instances (e.g., articles, pieces, units, etc.) of processing circuitry such as hardware including logic circuits; a hardware/software combination such as a processor executing software; or a combination thereof. For example, the processing circuitry more specifically may include, but is not limited to, a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, application-specific integrated circuit (ASIC), or any other device or devices capable of responding to and executing instructions in a defined manner. It will be understood that any type of non-transitory computer readable storage device may be used as the memory  730  in addition or alternative to an SSD. In some example embodiments, the processing circuitry may include a non-transitory computer readable storage device, or memory (e.g., memory  730 ), for example a solid state drive (SSD), storing a program of instructions, and a processor (e.g., processor  720 ) that is communicatively coupled to the non-transitory computer readable storage device (e.g., via a bus connection  710 ) and configured to execute the program of instructions to implement the functionality of some or all of any of the devices and/or mechanisms of any of the example embodiments and/or to implement some or all of any of the methods of any of the example embodiments. It will be understood that, as described herein, an element (e.g., processing circuitry, digital circuits, any part of the remote computing device  700 ) will be understood to implement the functionality of said implemented element (e.g., the functionality of the remote computing device  700 ). 
     As shown, the network communication interface  224  of the heat exchanger cleaner apparatus  200  may be configured to establish a network communication link  702  with the remote computing device  700  (e.g., with network communication interface  750 ) and may be configured to implement one-way or two-way communication between the heat exchanger cleaner apparatus  200  and the remote computing device  700 . 
     In some example embodiments, the controller  210  is configured to generate and transmit signals to the remote computing device  700  via the wireless network communication link  702 . 
     In some example embodiments, the controller  210  may communicate signals over the network communication link  702  that indicate operations of the controller  210  (e.g., indicating actuation of the pump device  208  at particular points in time, a present timer value, a present counter value, etc.). In some example embodiments, the controller  210  may communicate the depletion signal (generated in response to the counter value reaching a threshold value) to the remote computing device  700  via the network communication link  702 . 
     In some example embodiments, the controller  210  may be configured to perform operations in response to receiving signals from the remote computing device  700  via the network communication link  702 . Such signals may be generated at the remote computing device  700  based on operation of at least a portion of the remote computing device  700  (e.g., based on operation of the processor  720 ), which may be based on human user interaction with at least a portion of an interface of the remote computing device  700  (e.g., the interface  760 , which may be a touchscreen display). For example, the remote computing device  700  may generate a reset signal based on human interaction with an interface  760  to indicate that the amount of cleaning composition  230  held in the heat exchanger cleaner apparatus system  1100  (e.g., held in the cartridge  300  coupled to the heat exchanger cleaner apparatus  200 ) has been replenished (e.g., via replacement of a cartridge  300  coupled to the heat exchanger cleaner apparatus  200 ). The remote computing device  700  may transmit the reset signal to the heat exchanger cleaner apparatus  200  via the network communication link  702 , and the controller  210  may be configured to cause the counter value of the counter value to be reset to an initial counter value (e.g., 0) in response to receiving the reset signal from the remote computing device  700  via the network communication link  702 . As a result, a human user may be able to remotely reset the counter value used by the heat exchanger cleaner apparatus  200  in response to cleaning composition  230  replenishment without direct interaction with the heat exchanger cleaner apparatus (e.g., via a button on the heat exchanger cleaner apparatus  200 ). 
     In some example embodiments, the controller  210  may be communicatively coupled to the air conditioning system  100  via communication link  704 , which may be a wired connection and/or wireless communication link with one or more portions of the air conditioning system  100  (e.g., with controller  140 ). The controller  210  may be configured to communicate (e.g., transmit and/or receive signals) with the air conditioning system  100  (e.g., controller  140 ) via the communication link  704  to cause some or all of the air conditioning system  100  to shut down in response to receiving a shutdown command signal from the remote computing device  700  via the network communication link  702 . For example, the remote computing device  700  may display a warning notification to a supported user (e.g., via interface  760 ) in response to receiving the warning signal to the remote computing device  700 . The remote computing device  700  may enable the human user to interact with the interface  760  (e.g., a touchscreen display) to command the remote computing device  700  to transmit a shutdown signal to the heat exchanger cleaner apparatus  200  in response to the warning signal via the network communication link  702 . The remote computing device  700  may transmit the shutdown signal to the heat exchanger cleaner apparatus  200  via the network communication link  702 . The controller  210  may be communicatively coupled to the controller  140  of the air handler  102  via the communication link  704  which may include a wired electrical connection, a wireless network communication link, or the like. The controller may generate a signal, and transmit the signal via communication link  704 , to cause some or all of the air conditioning system  100  to shut down (e.g., transmit a signal to the controller  140  via a wired electrical connection, a network communication link with a network communication interface of the air conditioning system  100  that may be included in and/or implemented by controller  140 , etc.), for example based on causing the controller  140  to shut down some or all of the air conditioning system  100  in response to receiving the shutdown signal. 
     In some example embodiments, the controller  210  may be configured to shut down operation of the heat exchanger cleaner apparatus system  1100  (e.g., disable or inhibit operation of the pump device  208 , regardless of timer and/or counter values) in response to receiving a signal from the air conditioning system  100  and/or a remote computing device  700 , where the signal may indicate (e.g., based on being processed by the controller  210 ) that the air conditioning system  100  is at least partially shut down. Such a received signal may be received at the controller from a part of the air conditioning system  100  (e.g., controller  140 ) via a communication link  704  which may include a wired electrical connection between the heat exchanger cleaner apparatus  200  and the part of the air conditioning system  100  (e.g., air handler  102 , controller  140 , etc.). Such a received signal may be received at the controller from a part of the air conditioning system  100  (e.g., controller  140 ) via a communication link  704  which may include a wireless network communication link between the heat exchanger cleaner apparatus  200  and the part of the air conditioning system  100  (e.g., air handler  102 , controller  140 , etc.). Such a received signal may be received at the controller from the remote computing device  700  via a wireless network communication link  702  between the heat exchanger cleaner apparatus  200  and the remote computing device  700 . The controller  210  may be further configured to enable operation of the pump device  208  (e.g., enable causing the pump device  208  to operate based on pumping command signals, timer values, and/or counter values as described herein) in response to receiving an enable command from a part of the air conditioning system  100  (e.g., controller  140 ) via a communication link  704  (e.g., a wired electrical connection and/or wireless communication link) and/or a remote computing device  700  via wireless network communication link  702 . 
     In some example embodiments, the remote computing device  700  may enable the human user to interact with the interface  760  (e.g., via a touchscreen display) to command the remote computing device  700  to transmit a pumping signal to the heat exchanger cleaner apparatus  200  to cause the controller  210  to implement an immediate operation of the pump device  208  to immediately pump an amount of the cleaning composition  230  to the spray outlet assembly  240 , thereby allowing more frequent or user-commanded pumpings of cleaning composition. The remote computing device may transmit the pumping signal to the heat exchanger cleaner apparatus  200  via the network communication link  702 , and the controller  210  may operation the pump device  208  in response to receiving the pumping signal. 
       FIG.  3 A  is a perspective top-front-right view of a heat exchanger cleaner apparatus system according to some example embodiments.  FIG.  3 B  is a perspective bottom-rear-left view of the heat exchanger cleaner apparatus system of  FIG.  3 A  according to some example embodiments.  FIG.  3 C  is a perspective cross-sectional view of the heat exchanger cleaner apparatus system along cross-sectional view line IIIC-IIIC′ of  FIG.  3 A  according to some example embodiments.  FIG.  3 D  is a plan cross-sectional view of the heat exchanger cleaner apparatus system along cross-sectional view line IIID-IIID′ of  FIG.  3 A  according to some example embodiments.  FIG.  3 E  is a perspective cross-sectional view of the heat exchanger cleaner apparatus system along cross-sectional view line IIIE-IIIE′ of  FIG.  3 A  according to some example embodiments.  FIG.  3 F  is a plan cross-sectional view of the heat exchanger cleaner apparatus system along cross-sectional view line IIIF-IIIF′ of  FIG.  3 A  according to some example embodiments. 
       FIG.  4 A  is a perspective top-front-right view of the heat exchanger cleaner apparatus shown in  FIG.  3 A  according to some example embodiments.  FIG.  4 B  is a plan cross-sectional view of the heat exchanger cleaner apparatus along cross-sectional view line IVB-IVB′ of  FIG.  4 A  according to some example embodiments.  FIG.  4 C  is a plan cross-sectional view of the heat exchanger cleaner apparatus along cross-sectional view line IVC-IVC′ of  FIG.  4 A .  FIG.  4 D  is a plan top view of the of the heat exchanger cleaner apparatus of  FIG.  4 A  according to some example embodiments. 
       FIG.  5 A  is a perspective top-front-right view of the cartridge shown in  FIG.  11 A  according to some example embodiments.  FIG.  5 B  is a perspective bottom-rear-left view of the cartridge shown in  FIG.  5 A  according to some example embodiments.  FIG.  5 C  is a plan cross-sectional view of the cartridge along cross-sectional view line VC-VC′ of  FIG.  5 A  according to some example embodiments.  FIG.  5 D  is a plan cross-sectional view of the cartridge along cross-sectional view line VD-VD′ of  FIG.  5 A  according to some example embodiments. 
     It will be understood that the heat exchanger cleaner apparatus  200  shown in  FIGS.  3 A- 4 D  may include any of the elements of any of the example embodiments of the heat exchanger cleaner apparatus shown in any of the drawings and/or described herein. It will be understood that the cartridge  300  shown in  FIGS.  3 A- 3 F and  5 A- 5 D  may include any of the elements of any of the example embodiments of the cartridge shown in any of the drawings and/or described herein. The heat exchanger cleaner apparatus  200  may be referred to interchangeably herein as a heat exchanger cleaner base, a heat exchanger cleaner apparatus base, a heat exchanger cleaner system base, a heat exchanger cleaner base device, a coil cleaner, or the like. 
     Referring generally to  FIGS.  3 A- 5 D , in some example embodiments, the heat exchanger cleaner apparatus  200  includes a housing  201  include a side housing  1104  and a base housing  1106  which are coupled together to at least partially define an interior of the heat exchanger cleaner apparatus  200 . As shown, the side housing  1104  may at least partially define one or more portions of the heat exchanger cleaner apparatus  200  including, for example, the apparatus reservoir  202 , a connector interface  1110 C of the heat exchanger cleaner apparatus  200 , or the like. 
     Referring to  FIGS.  3 A- 4 D  and further referring to  FIGS.  5 A- 5 D , the heat exchanger cleaner apparatus  200  may be coupled (e.g., detachably coupled, reversibly coupled, etc.) with a cartridge  300  having a cartridge housing  302  enclosing a cartridge reservoir  304  holding the cleaning composition in order to establish flow communication between the cartridge reservoir  304  and the pump device  208  (e.g., an inlet, also referred to as an inlet port, of the pump device  208 ) of the heat exchanger cleaner apparatus  200 . As shown, the apparatus reservoir  1102  (corresponding to the apparatus reservoir  202  shown in  FIGS.  2 A and  2 B ), also referred to herein interchangeably as a connection port structure, cartridge sleeve structure, internal reservoir, or the like, is configured to receive and accommodate at least a portion of the cartridge  300  holding the cleaning composition when the cartridge  300  is detachably coupled with the heat exchanger cleaner apparatus  200 , such that the apparatus reservoir  1102  may include one or more inner surfaces  1102   s  that may define at least a portion of an open cylindrical enclosure  1102   c  which may at least partially enclose at least the cartridge outlet  302 A of the cartridge  300  coupled to the heat exchanger cleaner apparatus  200 . 
     As shown, the heat exchanger cleaner apparatus  200  may include a connector interface  1110  configured to couple with one or more complementary connector interfaces of the cartridge  300  to couple the cartridge  300  at the cartridge outlet  302 A with the heat exchanger cleaner apparatus  200 . The connector interface  1110  may include a connector structure  1111  configured to engage the cartridge outlet  302 A and to establish a friction fit seal with the cartridge housing  302  to enable flow communication to be established between the cartridge reservoir  304  and the pump device  208 . The connector structure  1111  may include an upper disc structure  1110 A having a top surface  1110 U configured to be directly exposed to the cartridge reservoir  304  when the cartridge  300  is coupled with the connector interface  1110  and a cylindrical sidewall structure  1110 B having an outer sidewall surface  1110 S and one or more O-rings  1112  extending circumferentially around the outer sidewall surface  1110 S. As further shown, the connector structure  1111  may include one or more elements at least partially defining a check valve  306 , such as the cylindrical structure  1120 , but example embodiments are not limited thereto. Each of the interfaces and/or structures  1110 A,  1110 B,  1110 C, and/or  1111  may be referred to, individually or collectively, as a connector interface of the heat exchanger cleaner apparatus  200 . 
     The one or more complementary connector interfaces of the cartridge  300  may include, for example, connector interface  1208 A and connector interface  1208 B. Connector interface  1208 A is a bayonet connector and complementary to bayonet connector interface  1110 C. Connector interface  1208 B is an inner surface of the cartridge housing  302  at the cartridge outlet  302 A and configured to engage and establish a friction fit with an outer sidewall surface  1110 S of the connector interface  1110  and/or an O-ring  1112  extending around the outer sidewall surface  1110 S. The bayonet connector interface  1110 C may be configured to couple with the connector interface  1208 A of the cartridge  300  to establish a bayonet interface connection between the heat exchanger cleaner apparatus  200  and the cartridge  300 . As shown, the connector interface  1110 C and the connector interface  1208 A of the cartridge  300  may be complementary interfaces, including complementary bayonet connector interfaces, but example embodiments are not limited thereto and may include any type of complementary connector interfaces including, for example, complementary threaded connector interfaces. 
     As shown, the connector interface  1110 C may be a structure (e.g., bayonet connector interface structure) at least partially defined by a surface and/or structure of the apparatus reservoir  1102 . For example, the apparatus reservoir  1102  structure may have an inner surface  1102   s  at least partially defining an open cylindrical enclosure  1102   c  configured to receive at least a portion of the cartridge housing  302  including the cartridge outlet  302 A and in some example embodiments further include one or more complementary connector interfaces  1208 B and/or  1208 A, where the inner surface  1102   s  at least partially defines lateral sidewalls of the open cylindrical enclosure  1102   c  from which the connector interface  1110 C structure (e.g., a bayonet interface structure configured to establish a bayonet connection with a complementary connector interface  1208 A of the cartridge  300 ) extends into the open cylindrical enclosure  1102   c . In some example embodiments, either or both of the complementary connector interfaces  1110 C/ 1208 A and/or  1110 B/ 1208 B may couple (e.g., detachably couple) the cartridge  300  with the heat exchanger cleaner apparatus  200 . In some example embodiments, the complementary connector interfaces  1110 B/ 1208 A may be configured to couple the cartridge outlet  302 A with the heat exchanger cleaner apparatus  200  to establish flow communication between the cartridge reservoir  304  and the pump device  208  via at least the inlet port  1136 , and the complementary connector interfaces  1110 C/ 1208 A may secure (e.g., reversibly lock) the cartridge  300  to the heat exchanger cleaner apparatus  200 . 
     As shown in at least  FIG.  4 B , the heat exchanger cleaner apparatus  200  may include an electrical switch device  1280  that may include a structure extending into the open cylindrical enclosure  1102   c  and configured to be engaged and moved from a switch-open position to a switch-closed position by at least a portion of the cartridge  300  when a connector interface of the cartridge  300  (e.g., connector interface  1208 A) couples with a connector interface of the heat exchanger cleaner apparatus  200  (e.g., connector interface  1110 C). The electrical switch device  1280  may be configured to close an electrical circuit that includes the controller  210  when moved to the switch-closed position, thereby enabling an electrical signal to be received at the controller  210 . The controller  210  may be configured to apply electrical power to the circuit and may be configured to determine that the cartridge  300  is coupled with the heat exchanger cleaner apparatus  200  in response to determining that the circuit including the electrical switch device  1280  is closed such that an electrical signal (e.g., an induced current) is present in the circuit). The controller  210  may be configured to selectively enable or disable operating of the pump device  208  based upon whether a cartridge  300  is determined to be coupled to the heat exchanger cleaner apparatus  200  (e.g., based upon receiving an electrical signal via the circuit including the switch device  1280  to determine that the circuit is closed and thus a cartridge  300  is coupled with the heat exchanger cleaner apparatus  200  to move the switch device  1280  to the switch-closed position). 
     Still referring to  FIGS.  3 A- 4 D , the heat exchanger cleaner apparatus  200  may include a reservoir  1130  (corresponding to the internal reservoir  206  shown in  FIGS.  2 A and  2 B ), also referred to herein as a pump reservoir, apparatus reservoir, first reservoir of the heat exchanger cleaner apparatus  200 , internal reservoir, or the like. While the reservoir  1130  is shown in  FIGS.  3 A- 4 D  to be separate from the pump device  208 , it will be understood that the reservoir  1130  may be referred to as being a pump reservoir included within the pump device  208 , separately from pump of the pump device  208 . 
     As shown, the heat exchanger cleaner apparatus  200  may be configured to establish flow communication from the cartridge reservoir  304  of a coupled (e.g., detachably coupled) cartridge  300  to the reservoir  1130  of the heat exchanger cleaner apparatus  200 , where the reservoir  1130  is in flow communication between at least one connector interface of the heat exchanger cleaner apparatus  200  (e.g., the connector interface  1110 ) and an inlet  208   i  of the pump device  208 , which may be the same as any of the pump devices  208  described herein according to any of the example embodiments. The pump device  208  may further be understood to be configured to be in fluid communication between the connector interface  1110  (e.g., via at least the reservoir  1130  and the inlet port  1136  and inlet  208   i ) and the spray outlet assembly  240  (e.g., the first conduit structure  242  coupled to the outlet  208   o  of the pump device  208 ). The pump device  208  may thus be configured to be operated (e.g., by controller  210 ) to pump (e.g., selectively pump) an amount (e.g., a particular amount) of the cleaning composition  230  from the cartridge reservoir  304  and through the spray outlet assembly  240  (e.g., via the reservoir  1130 ). The pump device  208  may be configured to be controlled by the controller  210  to be operated similarly to any of the valves of any of the example embodiments of the pump device  208 . The controller  210  may be configured to operate the pump device  208  to cause the amount of the cleaning composition to be pumped through the spray outlet assembly  240  to be sprayed as a fluid stream  232  in the interior  192  of the air handler  102  without manual intervention. 
     In some example embodiments, the pump device  208  may include a pump (e.g., any known positive displacement pump) that is configured to operate for a particular period of time to move an amount of the cleaning composition  230  from the cartridge reservoir  304  and through the spray outlet assembly  240  (e.g., via the reservoir  1130 ), based on a control signal generated by the controller  210 . 
     Still referring to  FIGS.  3 A- 4 D , the connector interface  1110  may include an upper disc structure  1110 A and a cylindrical sidewall structure  1110 B which may be separate parts of a single piece of material (e.g., plastic) or separate pieces of material of the connector structure  1111 , and where the cylindrical sidewall structure  1110 B may include one or more circumferential grooves configured to accommodate separate, respective O-rings  1112  or any other known seal structure. The outer sidewall surface  1110 S of the cylindrical sidewall structure  1110 B and/or the O-ring(s)  1112  may be configured to engage a complementary inner surface of the cartridge housing  302  at the cartridge outlet  302 A which defines the connector interface  1208 B of the cartridge  300 . As a result, the outer sidewall surface  1110 S of the cylindrical sidewall structure  1110 B, alone or in combination with one or more of the O-rings  1112 , establishes a fluid seal (e.g., air-tight seal) between the cylindrical sidewall structure  1110 B (and thus the connector interface  1110 ) and the cartridge housing  302 , thereby minimizing or preventing leaking of cleaning composition from the cartridge reservoir  304  to an exterior of the cartridge  300  independently of being supplied through the spray outlet assembly  240  by the pump device  208 , for example minimizing or preventing leaking of cleaning composition from the cartridge reservoir  304  into the open cylindrical enclosure  1102   c.    
     As shown, when the connector structure  1111  and thus the connector interface  1110  couples with the connector interface  1208 B of the cartridge  300  (e.g., at the cylindrical sidewall structure  1110 B where the coupling is sealed by one or more surfaces of the cylindrical sidewall structure  1110 B, the connector interface  1208 B, and/or one or more of the O-rings  1112 ), the upper disc structure  1110 A of the connector interface  1110  may be exposed directly to an interior of the cartridge reservoir  304  and at least some or any cleaning composition held in the cartridge reservoir  304 . 
     Still referring to  FIGS.  3 A- 4 D , the connector interface  1110  may include a check valve  306  which may be configured to open in response to the connector interface  1110  coupling with one or more connector interfaces  1208 A and/or  1208 B of the cartridge  300  to establish fluid communication between the cartridge reservoir  304  and the pump device  208  (e.g., via the reservoir  1130 ). As shown, the check valve  306  may be at least partially defined by a cylindrical structure  1120  (which may be a part of a single piece of material with at least the upper disc structure  1110 A of the connector structure  1111 ) having an inner surface  1120  is defining cylindrical side surfaces of an internal cylindrical conduit  1118 , a top plate  1116  defining a top surface of the internal cylindrical conduit  1118  and having one or more ports  1114 , also referred to interchangeably as openings, extending therethrough to the cylindrical conduit  1118  and configured to be directly exposed to at least the open cylindrical enclosure  1102   c  and thus to the cartridge reservoir  304  when the cartridge  300  is coupled with the connector interface  1110 , a bottom structure  1122  defining a bottom surface of the internal cylindrical conduit  1118 , a seal  1121  such as an O-ring extending around a lower portion of the bottom structure  1122 , and a spring  1117  in contact between the top plate  1116  and the bottom structure  1122 . 
     As shown, the bottom structure  1122  may include a pin protrusion extending axially through the cylindrical conduit  1118  and which may extend through a central opening in the top plate  1116 . The bottom structure  1122 , alone or together with the seal  1121 , may be configured to engage against a ledge structure  1120 L of the cylindrical structure  1120  to selectively seal an interface between the bottom structure  1122  and the cylindrical structure  1120 . As further shown, the reservoir  1130  may be at least partially defined by a cylindrical side structure  1124  and a bottom disc structure  1126 , where the bottom disc structure  1126  may at least partially define the inlet port  1136  to the pump device  208 . As shown, the cylindrical side and bottom disc structures  1124  and  1126  may define an open cylindrical enclosure that is enclosed at a top end by the combined cylindrical structure  1120  and ledge structure  1120 L thereof and a bottom surface of the bottom structure  1122  extending through an opening space between opposing surfaces of the ledge structure  1120 L, such that inner surfaces of the structures  1124 ,  1126 ,  1120 , and  1122  at least partially define the reservoir  1130 . As further shown, the heat exchanger cleaner apparatus  200  may include a fixed structure  1128  which may be coupled to the bottom disc structure  1126  and may be a part of a same single piece of material as the bottom disc structure  1126 . The fixed structure  1128  may project upwards into the reservoir  1130  under the bottom structure  1122  of the check valve  306 . 
     Still referring to  FIGS.  3 A- 4 D , the connector interface  1110  is configured to move axially downwards  1202  (e.g., toward the pump device  208 ) in response to the cartridge  300  coupling with the heat exchanger cleaner apparatus  200  (e.g., the connector interface  1110  coupling with one or more of the connector interfaces  1208 A and/or  1208 B of the cartridge  300 ), for example based on the weight of the cartridge  300  and the cleaning composition held within pushing the connector interface  1110  downwards  1202 . As shown, the outer surface  1120   os  of the cylindrical structure  1120  coupled to the upper disc structure  1110 A is configured to engage and establish a seal (in some example embodiments with one or more O-rings) with the inner surface  1124   s  of the cylindrical side structure  1124  at least partially defining the reservoir  1130 , thereby minimizing or preventing leakage of cleaning composition from the reservoir  1130  via the interface between surfaces  1120   os  and  1124   s.    
     As the connector interface  1110  moves downward  1202  due to the weight of the cartridge  300  and cleaning composition therein (which may directly contact the top surface of the upper disc structure  1110 A and the top plate  1116 ) may push the top plate  1116  and the cylindrical structure  1120  downwards  1202  axially, where the spring  1117  may further push the bottom structure  1122  axially downwards based on the top plate  1116  pushing the top end of the spring  1117  downwards. As shown, the top plate  1116  may engage an underside of a ledge or lip structure of the upper disc structure  1110 A so that the downwards  1202  axial movement of the upper disc structure  1110 A causes the top plate  1116  to move downwards  1202  axially together with the upper disc structure  1110 A. As a result, the top plate  1116  together with the spring  1117  may cause the bottom structure  1122  and the cylindrical structure  1120  to move downwards  1202  together until a bottom surface of the bottom structure  1122  contacts (e.g., directly contacts) a top surface of the fixed structure  1128  in the reservoir  1130  interior. As the fixed structure  1128  is fixed to a surface at least partially defining the reservoir  1130  (e.g., fixed to the bottom disc structure  1126 ), the contact between opposing surfaces of the bottom structure  1122  and the fixed structure  1128  may arrest downwards axial movement of the bottom structure  1122  and compress the spring  1117  while the cylindrical structure  1120 , top plate  1116 , and connector interface  1110  continue to move axially downwards  1202 , thereby causing the relative movement of the bottom structure  1122  in relation to the cylindrical structure  1120  to be upwards  1204 , opening an annular passage  1250  between the downwards-moving ledge structure  1120 L and the arrested bottom structure  1122  (and any washer or seal such as an O-ring seal  1121  configured to seal an interface between the bottom structure  1122  and the ledge structure  1120 L) fixed in place between the spring  1117  and the fixed structure  1128 . The opened annular passage  1250  may enable a flow along flow path  1192  (e.g., based on enabling fluid communication) through the cylindrical conduit  1118  to the reservoir  1130  via ports  1114  and the opened annular passage  1250 . 
     As long as the weight of the cartridge  300  and the cleaning composition held therein on the connector interface  1110  is greater than the spring force of the spring  1117 , the top plate  1116  and the bottom structure  1122  contacting the fixed structure  1128  may compress the spring  1117  and open the annular passage  1250  to the reservoir  1130  to enable a flow of cleaning composition along the flow path  1192  from the cartridge reservoir  304  to the reservoir  1130  via the check valve  306 . When the weight of the cartridge  300  and the cleaning composition held therein on the connector interface  1110  is smaller than the spring force of the spring  1117 , the spring force of the spring  1117  may enable the spring  1117  to push the top plate  1116 , and thus the connector interface  1110  upwards  1204  axially away from the bottom structure  1122  and/or seal  1121  to close the annular passage  1250  and close the fluid communication between the cartridge reservoir  304  and the reservoir  1130 . 
     Still referring to  FIGS.  3 A- 4 D , the connector structure  1111  may establish (e.g., define) an air volume  1132  in fluid communication with the ambient environment via the open cylindrical enclosure  1102   c , and the connector interface  1110  (e.g., the connector structure  1111 ) may include an air tube  1134  extending through the connector interface to the upper disc structure  1110 A to establish fluid connection between the air volume  1132  and a top region of the cartridge reservoir  304  when the cartridge  300  is coupled to the heat exchanger cleaner apparatus  200 . The air tube  1134  may be configured to supply air into the upper portion of the cartridge reservoir  304  as cleaning composition leaves the cartridge reservoir  304  via the cartridge outlet  302 A (e.g., via the check valve  306 ) to equalize pressure in the cartridge reservoir  304 , thereby preventing vacuum in the cartridge reservoir  304  and preventing loss of flow rate of the flow along flow path  1192  into the reservoir  1130 . The air tube  1134  may include a backflow prevention valve  1134   v , such as a duckbill valve which may also be interchangeably referred to as a duck mouth valve, at a distal end, where the backflow prevention valve  1134   v  may be configured to reduce, minimize, or prevent flow of cleaning composition from the cartridge reservoir  304  into the air volume  1132  via the air tube  1134  while still enabling air to flow into the cartridge reservoir  304  from the air volume  1132  via the air tube  1134 . 
     Still referring to  FIGS.  3 A- 4 D , the pump device  208  may be configured to be controlled (e.g., selectively operated, operated, etc.) by the controller  210  to selectively induce a flow of cleaning composition drawn along the flow path  1194  from the reservoir  1130  to the spray outlet assembly  240  (e.g., via at least the first and second conduit structures  242  and  244  as shown), thereby dispensing the cleaning composition from the heat exchanger cleaner apparatus  200 . The pump device  208  may operate, and/or may be configured to be controlled to operate, in the same way as any of the pump devices  208  described herein according to any of the example embodiments. 
     Accordingly, as shown in at least  FIGS.  3 A- 4 D , the pump device  208  may be configured to be operated (e.g., selectively operated) based on a control signal (e.g., an electrical current) generated (e.g., transmitted) by the controller  210  to establish a flow path  1194  through the pump device  208  (e.g., through inlet  208   i  and outlet  208   o ) to the spray outlet assembly  240 , and the heat exchanger cleaner apparatus  200  may include a reservoir  1130  (e.g., internal reservoir) that is in flow communication between the check valve  306  and the pump device  208 , such that the connector interface  1110  is configured to detachably couple with the connector interface  1208 A of the cartridge  300  to establish flow communication (e.g., flow path  1192 ) from the cartridge reservoir  304  to the reservoir  1130 , and the pump device  208  may be configured to be operated (e.g., by controller  210 ) to pump (e.g., selectively pump) an amount of the cleaning composition from the reservoir  1130  and through the spray outlet assembly  240 . 
     While  FIGS.  3 A- 4 D  show a heat exchanger cleaner apparatus  200  and cartridge  300  configured to couple via a connector interface  1110  which includes a check valve  306 , it will be understood that example embodiments are not limited thereto, and in some example embodiments different configurations of connector interfaces  1110  and/or connector structures  1111  may be present in the heat exchanger cleaner apparatus  200 . In some example embodiments, the check valve  306  may be omitted. For example, in some example embodiments the cartridge  300  may include a flexible membrane (e.g., a silicone membrane) extending transversely across the cartridge outlet  302 A, and the connector interface  1110  may include at least a puncturing structure (e.g., one or more needles) configured to puncture the membrane when the cartridge  300  is coupled with the connector interface  1110  in order to establish fluid communication between the cartridge reservoir  304  and the pump device  208  (e.g., via reservoir  1130 ). The connector interface  1110  may include another puncturing structure (e.g., similar in function to air tube  1134 ) configured to allow air to flow into an upper portion of the cartridge reservoir  304  to enable pressure equalization as cleaning composition flows out of the cartridge reservoir  304 . The connector interface  1110  may include a protecting plate defining a recess having openings aligned with the puncturing structures and that is spring-loaded by a spring and is configured to move vertically between an upper rest position where the puncturing structures are underneath the protecting plate and external to the recess and a lower compressed position where the spring is compressed and where the puncturing structures extend through the openings in the protecting plate to be located within the recess. The protecting plate may be configured to receive the cartridge outlet  302 A into the recess such that the cartridge  300  pushes the protecting plate downwards against the spring to expose the puncturing structures to puncture the membrane of the cartridge  300  and to establish fluid communication between the cartridge reservoir  304  and the pump device  208  (e.g., via the reservoir  1130 ). Upon removal of the cartridge  300  from the heat exchanger cleaner apparatus  200 , the protecting plate may rise, under load from the spring, back to the rest position to obscure the puncturing structures. A distal portion of the cartridge  300  including the cartridge outlet  302 A may be indented (e.g., include a notch structure or cavity) in relation to a remainder to the cartridge housing  302 , and the heat exchanger cleaner apparatus  200  may include a spring-loaded locking mechanism configured to engage and couple with the indented portion of the cartridge  300  when the cartridge  300  is inserted into the apparatus reservoir  1102  to hold the cartridge  300  coupled with the heat exchanger cleaner apparatus  200 . The locking mechanism may further be configured to lock the protecting plate in the upper rest position when the locking mechanism is in a spring-loaded rest position. The locking mechanism may be configured to move (e.g., move horizontally) against the spring to a compressed position to unlock the vertical movement of the protecting plate, based on the locking mechanism engaging a surface of a cartridge  300  being inserted into the heat exchanger cleaner apparatus  200 , thereby enabling the cartridge outlet  302 A to enter the recess of the protecting plate and push the protecting plate downwards to expose the puncturing structures. The cartridge  300  may be configured to include the indented portion that is positioned to engage the locking mechanism when the cartridge outlet  302 A is inserted into the bottom of the recess of the protecting plate and the protecting plate is moved downwards to the lower, compressed position. When the locking mechanism engages the indented portion, the locking mechanism may return from the compressed position to an at least partial rest position, where the locking mechanism engaged with the indented portion may be in locking engagement with the cartridge  300  and may lock the cartridge  300  in place in relation to the heat exchanger cleaner apparatus  200 . The heat exchanger cleaner apparatus  200  may include a release mechanism configured to release the locking mechanism from locking engagement with the cartridge  300  to enable decoupling of the cartridge  300  from the heat exchanger cleaner apparatus  200 . 
     As further shown in  FIGS.  3 A- 4 D , the heat exchanger cleaner apparatus  200  may include a power supply compartment  1140  which may be at least partially defined by the housing  201  (e.g., the side housing  1104 ) and in which a power supply (e.g., batteries  1142  may be located and may be electrically coupled (e.g., via internal circuitry of the heat exchanger cleaner apparatus  200 ) with the pump device  208 , the controller  210 , a network communication interface  224 , etc., or the like of the heat exchanger cleaner apparatus  200 . The heat exchanger cleaner apparatus  200  may include a power supply cover plate  1108  which may be configured to couple with the housing  201  to cover the power supply compartment  1140  and to at least partially define an outer surface of the heat exchanger cleaner apparatus  200 . 
     Still referring to  FIGS.  3 A- 4 D , the heat exchanger cleaner apparatus  200  may include a user interface  1182  (e.g., a button) with which a user may interact (e.g., press the button) to control operation of the heat exchanger cleaner apparatus  200 , for example to turn the heat exchanger cleaner apparatus  200  on or off (e.g., activate or deactivate the heat exchanger cleaner apparatus  200 ), to cause the controller  210  to enable/activate controlling of the pump device  208  to be operated to pump cleaning composition at fixed intervals and/or to cause the controller  210  to disable/deactivate the pump device  208  from being actuated at fixed intervals. It will be understood that the controller  210  of the heat exchanger cleaner apparatus  200  may include any of the elements of any of the example embodiments of the controller  210  as described herein and/or illustrated in any of the drawings. It will be understood that the heat exchanger cleaner apparatus  200  shown in  FIGS.  3 A- 4 D  may include any of the elements of any of the example embodiments of the heat exchanger cleaner apparatus  200  as described herein and/or illustrated in any of the drawings, including for example a network communication interface  224 . 
     The heat exchanger cleaner apparatus  200  and/or any portion thereof (e.g., controller  210 , network communication interface  224 , etc.) may be configured to perform any of the functions described herein and/or illustrated in any of the drawings with regard to any of the example embodiments. For example, in some example embodiments the controller  210  may be configured to operate the pump device  208  in response to a determination, by the controller  210 , of an elapse of a particular (e.g., predetermined, fixed) period of time. The controller  210  may be configured to repeatedly operate the pump device  208  at a fixed time interval that is the particular period of time, based on monitoring a timer (which may be implemented by the controller  210 ) that increments a timer value at a fixed frequency, operating the pump device  208  in response to the timer value reaching a particular time value corresponding to the elapse of the particular period of time, and resetting the timer value to an initial timer value in response to operating the pump device  208 . The controller  210  may be configured to monitor a counter (which may be implemented by the controller  210 ) that increments a counter value in response to each operation of the pump device  208 , and generate a depletion signal (which may be communicated to an external device via the network communication interface  224  and/or may be used to generate a visual signal by one or more light indicators  1184  such as activating a yellow LED thereof) in response to the counter value reaching a particular counter value that corresponds to at least partial depletion of a fixed reservoir (e.g., the reservoir  1130  and/or the cartridge reservoir  304 ) of the cleaning composition. 
     In some example embodiments, the controller  210  may be configured to adjust (e.g., calibrate) the particular counter value to correspond to a number of operations of the pump device  208  corresponding to a particular volume of the cartridge reservoir  304 . For example, in some example embodiments, the cartridge reservoir  304  is configured to hold a volume of about 36 oz of cleaning composition, but example embodiments are not limited thereto; for example, the heat exchanger cleaner apparatus  200  may be configured to couple with various sizes of cartridges  300  having similar connector interfaces  1208 A and  1208 B configured to couple with the connector interface  1110  of the heat exchanger cleaner apparatus  200  but having different volumes of cartridge reservoir  304 , including a volume of 36 oz, 72 oz, or the like. The controller  210  may be configured to determine a volume of the cartridge reservoir  304  in response to receiving a command signal indicating the volume of the cartridge reservoir, and adjust the particular counter value based on the determination of the volume of the cartridge reservoir. For example, in some example embodiments the heat exchanger cleaner apparatus  200  may be configured to receive a command signal indicating the cartridge reservoir  304  volume of a coupled cartridge  300  via a command from a remote computing device  700  received via the network communication interface  224  based on human user interaction with at least a portion of an interface of the remote computing device  700  (e.g., the interface  760 , which may be a touchscreen display) to cause the remote computing device  700  to inform the heat exchanger cleaner apparatus  200  of the volume of the coupled cartridge  300  and/or to command the heat exchanger cleaner apparatus  200  to adjust the particular counter value to correspond to the volume of the coupled cartridge  300 . In another example, in some example embodiments the heat exchanger cleaner apparatus  200  may be configured to receive a command signal indicating the cartridge reservoir  304  volume of a coupled cartridge  300  via a command received from a user interface  1182  of the heat exchanger cleaner apparatus  200  via user interaction therewith. 
     In another example, in some example embodiments the heat exchanger cleaner apparatus  200  may be configured to receive a command signal indicating the cartridge reservoir  304  volume of a coupled cartridge  300  based on sensor data generated by a sensor device of the heat exchanger cleaner apparatus  200 . The heat exchanger cleaner apparatus  200  may include a pressure sensor (e.g., any known pressure sensor) that is exposed to the reservoir  1130 , the cylindrical conduit  1118 , the upper surface of the upper disc structure  1110 A configured to be directly exposed to the cartridge reservoir  304  of a coupled cartridge  300 , or any portion of the heat exchanger cleaner apparatus  200  configured to be in fluid communication with the cartridge reservoir  304  of a coupled cartridge  300 . The pressure sensor may generate sensor data indicating a static pressure of cleaning composition at the location of the pressure sensor in the heat exchanger cleaner apparatus  200  and may communicate such sensor data to the controller  210 . The controller may be configured to process the sensor data to determine a pressure value indicated by the sensor data and may determine a corresponding volume of cleaning composition held in a cartridge reservoir  304  of a coupled cartridge  300  based on applying the sensor data and/or pressure value indicated thereby to an empirically-determined look-up table that associates sensor data and/or indicated pressure values with corresponding magnitudes of volume of cleaning composition held in the cartridge reservoir  304  of a coupled cartridge  300 . The controller  210  may be configured to monitor variations in the pressure data and/or corresponding volume indicated by the sensor data and look-up table over time. In response to a rate of change of the pressure and/or volume indicated by the sensor data that exceeds a threshold rate of change that is stored at the controller, where exceeding the threshold rate is associated with an at least partially depleted cartridge  300  being replaced with a new, more full cartridge  300  being newly coupled to the heat exchanger cleaner apparatus  200 , the controller  210  may responsively monitor a new volume indicated by the sensor data and look-up table subsequent to the rate of change of indicated volume/pressure value subsequently dropping below the threshold rate to indicate that the newly-coupled cartridge  300  is stabilized, where the new volume determined based on processing the sensor data in view of the look up corresponds to the volume of the cartridge reservoir  304 . The controller  210  may responsively adjust the particular counter value to a value corresponding to a quantity of pumpings (each pumping corresponding to causing the pump device  208  to pump (e.g., dispense, supply, etc.) a particular amount (e.g., volume) of cleaning composition (such as 3 oz) that is at least a particular proportion of the determined volume of the new cartridge reservoir  304  (e.g., 90% of the determined volume). 
     In some example embodiments, the heat exchanger cleaner apparatus  200  may include a network communication interface  224  that is configured to establish a network communication link with a remote device (e.g., a remote computing device). The controller  210  may be configured to cause a depletion signal to be transmitted to the remote computing device  700  via the network communication link. The controller  210  may be configured to cause the counter value to be reset to an initial counter value in response to receiving a reset signal from the remote computing device via the network communication link. It will be understood that the controller  210  and/or the network communication interface  224  may be configured to perform any of the communications and/or interactions with one or more remote computing devices  700  as described herein with regard to any of the example embodiments of the heat exchanger cleaner apparatus  200 , the remote computing device  700 , or the like, including the operations and/or interactions between the heat exchanger cleaner apparatus  200  and a remote computing device  700  via network communication link  702  as described herein with regard to at least  FIGS.  2 A,  2 B .  7 ,  8 , or the like. 
     Still referring to  FIGS.  3 A- 4 D , the heat exchanger cleaner apparatus  200  may include light indicators  1184  (e.g., light emitting diodes, or LEDs) which may extend through respective openings in the housing  201  (e.g., respective openings in the side housing  1104  as shown) and may be configured to provide visible indications of a status of the heat exchanger cleaner apparatus  200 . For example, referring to  FIG.  11 A , the light indicators  1184  may include a left-most green LED configured to selectively emit green light, a center-left yellow LED configured to selectively emit yellow light, a center-right red LED configured to selectively emit red light, and a right-most blue LED configured to selectively emit blue light. The controller  210  may selectively activate the green LED to emit green light to indicate that the heat exchanger cleaner apparatus  200  is activated (e.g., based on human user interaction with the user interface  1182  and/or with a remote computing device  700  to cause the remote computing device  700  to command the heat exchanger cleaner apparatus  200  to activate via a network communication link  702 ) and/or to indicate that the controller  210  is presently implementing a timer to enable operating the pump device  208  at a fixed frequency (e.g., fixed intervals). The controller  210  may be configured to selectively activate the yellow LED to emit yellow light to indicate a depletion signal in response to a determination that a counter value implemented by the controller  210 , as described herein, reaches a particular counter value that corresponds to at least partial depletion of a fixed reservoir (e.g., the cartridge reservoir  304 ) of the cleaning composition as described herein according to any of the example embodiments. It will be understood that the controller  210  may be configured to selectively deactivate operation of at least the pump device  208  (e.g., disable the periodic operation of the pump device  208 ), activate a visual indicator such as the yellow LED, and/or transmit a warning signal to a remote computing device  700  via a network communication link  702  to cause the remote computing device to generate (e.g., transmit) a warning (e.g., a graphic indication shown on the interface  760 ) to warn a supported human user that the cartridge reservoir  304  is at least partially depleted in response to determination that the counter value has reached or exceeded the particular counter value. The controller  210  may be configured to selectively activate the red LED to emit red light in response to a determination that the electrical circuit including the electrical switch device  1280  is open, such that the controller  210  determines that the heat exchanger cleaner apparatus  200  is not coupled with a cartridge  300  while the heat exchanger cleaner apparatus  200  is activated. It will be understood that the controller  210  may be configured to selectively deactivate operation of at least the pump device  208  (e.g., disable the periodic operation of the pump device  208 ), activate a visual indicator such as the red LED, and/or transmit a warning signal to a remote computing device  700  via a network communication link  702  to cause the remote computing device to generate (e.g., transmit) a warning (e.g., a graphic indication shown on the interface  760 ) to warn a supported human user that the heat exchanger cleaner apparatus  200  has disabled operation of the pump device  208  due to non-coupling of the heat exchanger cleaner apparatus  200  with a cartridge  300 . The controller  210  may be configured to selectively activate the blue LED to emit blue light to indicate that the network communication interface  224  has established an active network communication link  702  with at least one remote computing device  700 . 
       FIG.  6 A  is a perspective bottom-rear-left view of the structure connector shown in  FIG.  3 A  according to some example embodiments.  FIG.  6 B  is a perspective top-front-right view of the structure connector shown in  FIG.  6 A  according to some example embodiments.  FIG.  6 C  is a perspective view of the heat exchanger cleaner apparatus according to some example embodiments.  FIG.  6 D  is a plan bottom view of the heat exchanger cleaner apparatus according to some example embodiments. It will be understood that the structure connector  220  and the heat exchanger cleaner apparatus  200  shown in  FIGS.  6 A- 6 D  may include any of the elements of any of the example embodiments of the structure connector and/or the heat exchanger cleaner apparatus shown in any of the drawings and/or described herein. 
     As shown in  FIGS.  6 A- 6 D , the structure connector  220  may include a housing structure  228  (e.g., a plastic structure), a coupling structure  221  that is coupled (e.g., adhered via an adhesive) to the housing structure  228 , and an interface structure  226  configured to engage a complementary coupling structure  1172  of the heat exchanger cleaner apparatus  200  to couple the structure connector  220  to the heat exchanger cleaner apparatus  200  and thus enable the structure connector  220  to couple the heat exchanger cleaner apparatus  200  to the fixed structure to which the coupling structure  221  is coupled. 
     In some example embodiments, the coupling structure  221  is or includes a magnet configured to magnetically attach the structure connector  220  to a fixed external structure, such as a metal surface of the external structure, for example a metal housing  101  of an air handler  102  as shown in  FIG.  1   . Thus, the magnet coupling structure  221  may configure the structure connector  220  to be magnetically coupled to a metal external structure such as a metal housing  101  of an air handler  102 . In some example embodiments, the coupling structure  221  may include an adhesive material configured to adhere to a surface of an external structure. 
     As shown in  FIGS.  6 A- 6 D , in some example embodiments, the interface structure  226  may include a flange or bracket structure configured to slidably engage with a complementary, downwards-opening complementary coupling structure  1172  (e.g., complementary flange or bracket structure) at least partially defining a slot or cavity  1402  in the heat exchanger cleaner apparatus  200  housing  201  that is configured to accommodate at least a portion of the structure connector  220  due to relative downwards motion of the heat exchanger cleaner apparatus  200  in relation to the structure connector  220  (e.g., downwards sliding engagement of the complementary coupling structure  1172  with the interface structure  226  of the structure connector  220  so that at least a closed top portion of the complementary coupling structure  1172  engages a top portion of the interface structure  226  to transfer a load or weight of the heat exchanger cleaner apparatus  200  and any cartridge  300  coupled thereto to the structure connector  220 . As a result of the structure connector  220  being coupled (e.g., magnetically coupled) to a fixed external structure via the coupling structure  221  (e.g., magnet) being coupled to the fixed external structure, the heat exchanger cleaner apparatus  200  and any cartridge  300  coupled thereto (e.g., the heat exchanger cleaner apparatus system  1100 , which may be referred to interchangeably herein as a heat exchanger cleaner system, coil cleaner system, coil cleaner, or the like) may at least partially rest upon the structure connector  220  to be held in place in relation to the external structure (e.g., to at least partially transfer a load or weight of the heat exchanger cleaner apparatus system  1100  to the fixed external structure via the structure connector  220 . It will be understood that the heat exchanger cleaner apparatus  200  and the cartridge  300  coupled (e.g., connected, detachably connected, etc.) thereto may collectively partially or entirely comprise the heat exchanger cleaner apparatus system  1100 , which may be referred to interchangeably herein as a heat exchanger cleaner system. 
     It will be understood that the structures of the interface structure  226  and the complementary coupling structure  1172  may be different from the example embodiments shown in  FIGS.  3 A- 3 F and  6 A- 6 D . As shown, the interface structure  226  of the structure connector  220  may be a protruding tab (e.g., male, or flange) connector structure and the complementary coupling structure  1172  may be a complementary slot (e.g., female) connector structure configured to slidably engage the interface structure  226  to receive the structure connector  220  into the cavity  1402 , but example embodiments are not limited thereto. For example, in some example embodiments, the interface structure  226  of the structure connector  220  may be a slot (e.g., female) connector structure and the complementary coupling structure  1172  may be a complementary protruding tab (e.g., male, or flange) connector structure configured to slidably engage the interface structure  226  to receive the structure connector  220  into the cavity  1402 . In some example embodiments, the heat exchanger cleaner apparatus  200  may include an interlock structure configured to lock the structure connector  220  together with the heat exchanger cleaner apparatus  200 . In some example embodiments, the structure connector  220  may be configured to be detachably coupled to the heat exchanger cleaner apparatus  200  or may be a fixed part of the heat exchanger cleaner apparatus  200 , omitting the interface structure  226  while the heat exchanger cleaner apparatus  200  omits the complementary coupling structure  1172 , that is configured to not be detached from the heat exchanger cleaner apparatus  200 . 
       FIG.  7    is a schematic view of a controller of a computing device  1000  according to some example embodiments. The computing device  1000  may implement any of the computing devices, controllers, processors, or the like according to any of the example embodiments, including controller  140 , controller  210 , and any portion of remote computing device  700 . 
     As shown in  FIG.  7   , the computing device  1000  may include some or all of a processor  1020  (e.g., a CPU), a memory  1030  (e.g., a solid state drive, or SSD), a communication interface  1040  (e.g., a wireless network communication interface, which may for example implement network communication interface  224 , network communication interface  750 , a network communication interface of the air conditioning system  100 , or the like), and a power supply  1050  that are communicatively coupled together via a bus connection  1010 . It will be understood that any type of non-transitory computer readable storage device may be used as the memory  1030  in addition or alternative to an SSD. The computing device  1000  may include additional devices, including a user interface device  1060  (e.g., “interface”) that may include a display device (e.g., an LED display screen, OLED display screen, etc.), a touchscreen display, a button interface, any combination thereof, or the like. The user interface device  1060  may be communicatively coupled to the bus connection  1010 . 
     In some example embodiments, some or all of any of the computing device  1000  may include, may be included in, and/or may be implemented by one or more instances (e.g., articles, pieces, units, etc.) of processing circuitry such as hardware including logic circuits; a hardware/software combination such as a processor executing software; or a combination thereof. For example, the processing circuitry more specifically may include, but is not limited to, a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, application-specific integrated circuit (ASIC), or any other device or devices capable of responding to and executing instructions in a defined manner. In some example embodiments, the processing circuitry may include a non-transitory computer readable storage device, or memory (e.g., memory  1030 ), for example a solid state drive (SSD), storing a program of instructions, and a processor (e.g., processor  1020 ) that is communicatively coupled to the non-transitory computer readable storage device (e.g., via a bus connection  1010 ) and configured to execute the program of instructions to implement the functionality of some or all of any of the devices and/or mechanisms of any of the example embodiments and/or to implement some or all of any of the methods of any of the example embodiments. It will be understood that, as described herein, an element (e.g., processing circuitry, digital circuits, etc.) that is described as “implementing” an element (e.g., controller  210 , heat exchanger cleaner apparatus  200 , controller  140 , air conditioning system  100 , remote computing device  700 , etc.) will be understood to implement the functionality of said implemented element and/or any other elements (e.g., the functionality of the controller  210 , the functionality of the heat exchanger cleaner apparatus  200 , the functionality of the controller  140 , the functionality of the air conditioning system, the functionality of the remote computing device  700 , etc.). 
       FIG.  8    is a flowchart illustrating a method of operation of the heat exchanger cleaner apparatus according to some example embodiments. The method shown in  FIG.  8    may be implemented by any example embodiment of the heat exchanger cleaner apparatus  200  according to any example embodiments. 
     It will be understood that operations of the method shown in  FIG.  8    may be changed in order relative to what is shown in  FIG.  8   . It will further be understood that one or more operations of the method shown in  FIG.  8    may be omitted from the method shown in  FIG.  8   . It will further be understood that one or more operations may be added to the method shown in  FIG.  8   . 
     The method shown in  FIG.  8    includes a method for operating a heat exchanger cleaner apparatus  200  according to any of the example embodiments to pump (e.g., dispense, supply, etc.) a cleaning composition  230  into an interior  192  of an air handler  102  to contact an outer surface  110   s  of a heat exchanger  110  (e.g., evaporator coil) of the air handler  102 . As shown, the method of  FIG.  8    includes controlling a pump device  208  of the heat exchanger cleaner apparatus  200  to cause the pump device  208  to pump an amount (e.g., 3 oz) of the cleaning composition  230  from a reservoir in fluid communication with an inlet of the pump device  208  (e.g., an internal reservoir  206  of the heat exchanger cleaner apparatus  200 , a cartridge reservoir  304  of a cartridge  300  detachably coupled to the heat exchanger cleaner apparatus  200 ) and through the spray outlet assembly  240  without manual intervention (e.g., without human intervention). It will be understood that some or any of the operations shown in  FIG.  8    may be performed (e.g., performed by controller  210 ) without human intervention (e.g., some or any operations may be performed by controller  210  based on programming of the controller  210  and may be performed independently of any commands or signals received at the controller  210  based on human interaction with an interface (e.g., button, touchscreen display, etc.)). 
     At S 802  and S 804 , a timer of the controller  210  may count (e.g., increment a timer value at a fixed frequency) from an initial timer value (e.g., 0). At S 806 , the controller  210  compares the timer value with a threshold (e.g., particular) timer value (e.g., 7 days) that may be stored at the controller  210  and determines whether the present timer value has reached (e.g., is equal to or greater than) the threshold timer value. If not, the controller  210  permits the timer to continue to increment at S 804 . If so, at S 808 , the controller  210  operates the pump device  208  (e.g., causes electrical power to be supplied to the pump device  208  to cause the pump device  208  to operate) in response to cause the pump device  208  to operate to pump (e.g., dispense, supply, etc.) a particular amount of cleaning composition  230  (e.g., 3 oz), thereby operating the pump device  208  in response to an elapse of a particular period of time. 
     At S 810 , in response to the pumping at S 808 , the controller  210  causes the timer to reset to the initial timer value (0) and resume counting to enable a repeated performance of S 802 -S 808  (at least partially depending upon an outcome of the determination at S 826 , described further below), thereby repeatedly operating the pump device  208  to pump a particular amount of cleaning composition at a fixed time interval that is the particular period of time, based on monitoring a timer that increments a timer value at a fixed frequency at S 802 -S 806 , operating the pump device  208  at S 808  in response to the timer value reaching a particular time value corresponding to the elapse of the particular period of time, and resetting the timer value to an initial timer value at S 810  in response to pumping the pump device  208  at S 808 . 
     At S 812 , in response to the operating at S 808 , the controller  210  causes a counter to count (e.g., increment) a counter value from an initial counter value (e.g., 0), thereby tracking a quantity of pumping operations (S 808 ) and thus a cumulative amount of cleaning composition  230  that is pumped. 
     At S 826 , a determination is made regarding whether a pumping command signal is received, for example based on human interaction with an interface (e.g., button) of the heat exchanger cleaner apparatus  200  and/or based on a pump signal being received from a remote computing device  700  via a network communication link  702  based on a pumping (e.g., selective pumping) of cleaning composition  230  being commanded at the remote computing device  700 . If not, the method continues at S 814 . If so, the method moves to S 808  and the controller  210  operates the pump device  208 . 
     At S 814 , the controller  210  compares the counter value with a threshold (e.g., particular) counter value (e.g., 10, 11, 12, etc.) that may be stored at the controller  210  and determines whether the present counter value has reached (e.g., is equal to or greater than) the threshold counter value. If not, the controller  210  returns to S 802  and continues the method. If so, at S 816 , the controller  210  generates a warning signal. The controller  210  may monitor multiple possible threshold values, including a partial depletion threshold counter value (e.g., 10 and/or 11) and a final depletion threshold counter value (e.g., 12) and the controller  210  may generate a particular warning signal (e.g., indicating partial depletion or final depletion (e.g., complete depletion) of cleaning composition  230  held in the heat exchanger cleaner apparatus  200 ) based on which threshold is determined to be reached at S 814 . 
     At S 818 , a determination is made regarding whether to reset the counter to the initial counter value. The determination may include a determination of whether a reset signal that indicates a command to reset the counter value is received. Such a determination may be based upon receiving a reset signal, which may be received from a counter reset interface  222  of the heat exchanger cleaner apparatus  200  (e.g., a button) and/or from a remote computing device  700  via a network communication link  702  (e.g., via network communication interface  224 ). If a reset is determined to be commanded at S 818  (e.g., a reset signal is determined to be received at S 818 ), at S 820  the controller  210  resets the counter value to the initial counter value. If not, at S 822  a further determination is made regarding whether the threshold determined to be reached at S 814  is a final depletion threshold (e.g., 12) that indicates complete depletion (e.g., final depletion) of cleaning composition  230  in the heat exchanger cleaner apparatus  200 . 
     If a final depletion threshold is not reached at S 822  (S 822 =NO, e.g., a partial depletion threshold of 11 was determined to be reached at S 814 ), then at S 828  the controller  210  may cause a command signal may be generated and/or transmitted from the heat exchanger cleaner apparatus  200  to a remote computing device  700  via network communication link  702  (e.g., based on the controller  210  controlling the network communication interface  224 ) which causes the remote computing device  700  to execute a purchase order of one or more new cartridges  300  to be purchased and delivered to a specific mailing address. Thus, the controller  210  may be understood to command the purchase order (e.g., purchase and/or delivery) of one or more new cartridges  300  to replace the at least partially-depleted cartridge  300  that is coupled to the heat exchanger cleaner apparatus  200  (the at least partial depletion being indicated based on S 814 =YES). The remote computing device  700  may store a delivery address information (e.g., information indicating a delivery mailing address) and purchase information which may be used to implement the purchase order (e.g., credit card information, bank account information, etc.). The remote computing device  700  may be configured to implement the purchase order, for example based on network communication with a remote purchase ordering service (which may be supported and/or implemented by one or more computing devices which may have a similar structure and configuration to the remote computing device  700  as illustrated and described herein), in response to receiving the signal generated and/or transmitted from the heat exchanger cleaner apparatus  200  (e.g., based on operation of the controller  210  to control the network communication interface  224 ) at S 828 . The remote computing device  700  may implement the purchase order (e.g., generate and/or transmit a command to purchase and deliver one or more new cartridges  300  to a specified mailing address which may be stored at the remote computing device and/or at the remote purchase ordering service) using the mailing address information, purchase information, or the like. Subsequent to the commanding of the purchase order at S 828 , the method may return to S 802 . 
     In some example embodiments, operation S 828  may not be performed (e.g., may be skipped) in response to each determination of S 822 =NO. For example, operation S 828  may be performed once in response to a first determination of S 814 =YES and S 822 =NO but may be skipped in response to subsequent determinations of S 814 =YES and S 822 =NO until a subsequent determination of S 818 =YES and/or performance of the resetting at S 820 , after which operation S 828  may be performed in response to the next subsequent determination of S 814 =YES and S 822 =NO. For example, if, subsequent to performing the commanding of a purchase order at S 828 , the controller  210  subsequently determines that a final depletion threshold is not reached at S 822  prior to a determination that a final depletion threshold is reached (e.g., determining S 822 =NO subsequent to performing S 828  and proceeding back to S 802 , and prior to determining S 822 =YES), the operation at S 828  may be skipped in response to subsequent determinations of S 822 =NO, and such subsequent determinations of S 822 =NO may proceed directly to S 802  until S 820  is performed in response to a determination of S 818 =YES. In some example embodiments the threshold counter value at S 814  is one value less than the final depletion threshold value at S 822  (e.g., S 814 =YES if the counter value is equal to or greater than 11 and S 822 =YES if the counter value is equal to or greater than 12), such that the operation S 828  is not skipped if S 814 =YES and S 822 =NO as the next subsequent determination at S 822 , subsequent to an incrementing of the counter value at S 812 , causes the counter value to reach the final depletion threshold value (S 822 =YES). 
     If a final depletion threshold is reached at S 822  (e.g., S 822 =YES), at S 824  the controller  210  may inhibit further operation of the pump device  208  (e.g., disable the pump device  208 ) until a determination is made at S 818  to perform a reset at S 820  (e.g., until a reset signal is determined to be received at S 818 ). Such operations at S 822  and S 824  may reduce or prevent the likelihood of the heat exchanger cleaner apparatus  200  continuing to operating the pump device  208  in the absence of cleaning composition  230  in the heat exchanger cleaner apparatus  200 . At S 824 , the controller  210  may further generate another warning signal indicating that the pump device  208  is inhibited (e.g., disabled). Additionally or alternatively, such an indication may be included in the warning signal generated at S 816  in response to a determination at S 814  that a final threshold counter value is reached. 
     In some example embodiments, in response to receiving and processing a signal, from a part of the air conditioning system  100  (e.g., controller  140 ) and/or a remote computing device via a wired or wireless connection, to determine that the air conditioning system  100  is at least partially shut down and/or to determine that pump device  208  inhibition is commanded, the controller  210  may inhibit (e.g., disable) further operation of the pump device  208 . In some example embodiments, in response to receiving and processing a signal, from a part of the air conditioning system  100  (e.g., controller  140 ) and/or a remote computing device via a wired or wireless connection, to determine that the air conditioning system  100  is at least partially started (e.g., initialized) and/or to determine that pump device  208  activation is commanded, the controller  210  may activate (e.g., enable) further operation of the pump device  208  as shown in  FIG.  8   . 
     Example embodiments have been disclosed herein; it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.