Abstract:
Systems and methods are disclosed that involve detecting a flammable refrigerant associated with a heating, ventilating, and air conditioning (HVAC) system. In one instance a damper covers an access port allowing a single sensor to monitor at least two separate spaces. In another instance, a multi-probe sensor allows a single sensor to monitor at least two separate spaces. Other systems and methods are presented.

Description:
FIELD 
     This application is directed, in general, to heating, ventilating and air conditioning or cooling (HVAC) systems, and more specifically, to methods and systems with economical refrigerant leak detection. 
     BACKGROUND 
     Heating, ventilating, and air conditioning (HVAC) systems can be used to regulate the environment within an enclosed space. Typically, an air blower is used to pull air (i.e., return air) from the enclosed space into the HVAC system through ducts and push the air into the enclosed space through additional ducts after conditioning the air (e.g., heating, cooling or dehumidifying the air). Unless otherwise indicated, as used throughout this document, “or” does not require mutual exclusivity. Various types of HVAC systems may be used to provide conditioned air for enclosed spaces. 
     The cooling aspect of the HVAC system utilizes a working fluid, or refrigerant, that cycles through various phases to realize cooling at a desired location. In the past, refrigerants were selected that were in large measure non-toxic and non-flammable. These refrigerants were not, however, as desirable with respect to global warming potential. In more recent times, a push has been made to use refrigerants that have a low or lower global warming potential. Because such refrigerants are often at least mildly flammable, the refrigerant could pose a potential risk to the user in some situations. 
    
    
     
       BRIEF DESCRIPTION 
       Illustrative embodiments of the present invention are described in detail below with reference to the attached drawing figures, which are incorporated by reference herein and wherein: 
         FIG. 1  is a schematic elevation view diagram of an HVAC system according to an illustrative embodiment; 
         FIG. 2  is a schematic plan view diagram of portion of an HVAC having a leak detector according to an illustrative embodiment; 
         FIG. 3  is an illustrative flow chart of an aspect of a method of detecting a refrigerant leak according to an illustrative embodiment; 
         FIG. 4  is a schematic plan view diagram of portion of an HVAC having a leak detector according to an illustrative embodiment; 
         FIG. 5  is a schematic diagram of portion of an HVAC having a leak detector according to an illustrative embodiment; and 
         FIG. 6  is an illustrative flow chart of an aspect of a method of detecting a refrigerant leak according to an illustrative embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the invention, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the claims. 
     Referring now to the drawings and primarily to  FIG. 1 , a heating, ventilating, and air conditioning (HVAC) system  100  is presented. The HVAC system  100  is for providing conditioned air to a first closed space  102 , such as the interior of a building. At least a portion of the HVAC system  100  is disposed within a second closed space  104 , or equipment space. The spaces may be defined by a plurality of walls  105 . In this embodiment, a portion  106  of the system  100  is located within the building, i.e., within the second closed space  104 , and a portion  108  outside the building. 
     The HVAC system  100  includes an HVAC unit  110  that is disposed within the second closed space  104 , or equipment space. The HVAC unit  110  includes a return air duct  112  that receives air  115  from the first closed space  102 . The return air duct  112  may include or be coupled to a transition duct  114  that may include one or more filters  116 . A blower  118  pulls the return air into the return air duct  112 . The blower  118  is fluidly coupled to the return air duct  112 . The blower  118  moves air into a conditioning compartment  120 . 
     The conditioning compartment  120  is fluidly coupled to the blower  118  for receiving air therefrom to be treated. The conditioning compartment  120  is formed with a plurality of compartment walls and formed with a sampling port  122  on one compartment wall. The conditioning compartment  120  may include a portion of a delivery duct  132  in some embodiments. The sampling port  122  is selectively covered by a damper  124  ( FIG. 2 ). The damper  124  is includes activation devices, e.g., motor or solenoid or other motive device, whereby a damper-control signal may be sent to the damper  124  to open or close the damper  124 . 
     The conditioning compartment  120  includes a heating device  126  and a cooling unit  128 . The order of the heating device  126  and cooling unit  128  could be varied. The heating device  126  may be a furnace, hot water manifold, an electric heating element, or any source of heat. If the heating device  126  is a furnace it may include flue pipe  127 . The heating device  126  is fluidly coupled to the conditioning compartment  120  for selectively heating air therein. The cooling unit  128  is fluidly coupled to the conditioning compartment  120  for selectively cooling air therein. The cooling unit  128  includes a flammable refrigerant, or working fluid. The cooling unit  128  may be an evaporator coil or device for receiving heat from the air flowing over the cooling unit. The cooling unit  128  includes at least one heat exchange surface. 
     While the system  100  will work with many refrigerants, the system  100  is primarily concerned with flammable refrigerants. Flammable refrigerants include even mildly flammable refrigerants that if exposed to an ignition source under certain conditions could pose a risk of fire. Accordingly, leak detection is an issue of considerable interest and will be described further below. The flammable refrigerant may be, without limitation, any of the following: any A2L, A2, A3, B2, or B3 refrigerant; R1234YF by Honeywell and DuPont; methylene chloride (R30); methyl chloride (R40); ethane (R170); propane (R290); N-Butane (R600); isobutene (R-600A); methyl formate (R611); ammonia (R717); sulfur dioxide (R764); ethylene (R1150); hydrocarbon refrigerants; halo-hydrocarbon blends; difluoromethane (R-32); etc. 
     Whether heated by heating device  128  or cooled by cooling unit  128 , the conditioning compartment  120  produces a treated air  130  that is delivered into the first closed space  102  by the delivery duct  132 . The delivery duct  132  is fluidly coupled to the conditioning compartment  120  for discharging the treated air  130  from the conditioning compartment  120  into the first closed space  102 . 
     Referring additionally to  FIG. 2 , the processing unit  134  is associated with the HVAC unit  110 . The processing unit  134  includes one or more processors  136  and one or more memories  138 . The processing unit  134  may include an input  140  (e.g., touchpad, keyboard, etc.) and an output  142  (e.g., display). The processing unit  134  may be communicatively coupled (in communication through wires, wireless, or other means) with the blower  118 , damper  124 , or other devices to be monitored or controlled within the system  100 . 
     The one or more processors  136  are configured to execute one or more sequences of instructions, programming or code stored on or in the one or more memories  138 , which includes all types of memory devices and includes readable medium used for storage. The processor  136  can be, for example, a general purpose microprocessor, a microcontroller, a digital signal processor, an application specific integrated circuit, a field programmable gate array, a programmable logic device, a controller, a state machine, a gated logic, discrete hardware components, an artificial neural network or any like suitable entity that can perform calculations or other manipulations of data. The memory  138  may include one or more the following: random access memory (RAM), flash memory, read only memory (ROM), programmable read only memory (PROM), erasable PROM, registers, hard disks, removable disks, CD-ROMS, DVDs, or any other suitable storage devices. 
     The cooling unit  128  is associated with a cooling subsystem  144 . The cooling subsystem  144  is any system that is operational to develop a chilled working fluid for receiving heat within the cooling unit  128 . In one embodiment, the cooling subsystem  144  includes a closed-conduit pathway  145 , or circuit. The flammable refrigerant is disposed within the closed conduit pathway  145 . The closed-conduit pathway  145  includes a first refrigerant line  146  and a second refrigerant line  148 . It will be appreciated that the first and second refrigerant lines  146 ,  148  in this embodiment are disposed partially within the second closed space  104  and if they were to leak, could deliver the flammable refrigerant into the second closed space  104  and thereby pose a potential safety risk—particularly if a source of ignition is present. Similarly if the refrigerant leaks within the cooling unit  128  and therefore within the conditioning compartment  120 , a risk may be posed by potential ignition sources, e.g., an open flame from a furnace. Additional spaces may need detectors, particularly if a refrigerant line in the space has a joint. 
     The cooling subsystem  144  also includes a compressor  150  fluidly coupled to the closed-conduit pathway  145  for compressing the flammable refrigerant therein. A condenser  152  is fluidly coupled to the closed-conduit pathway  145  downstream of the compressor  150  for cooling the refrigerant. The condenser  152  may include on or more fans  154 . An expansion device  156  is coupled to the closed-conduit pathway  145  downstream of the condenser  152  for decreasing a pressure of the refrigerant at the cooling unit  128 . The cooling unit  128  includes a heat-exchange surface (not explicitly shown) and is fluidly coupled to the closed-conduit pathway  145  for receiving the flammable refrigerant. 
     A control unit  158  may be disposed within the first closed space  102 . The control unit  158  may include a thermostat for providing control signals to the blower  118 , heating device  126 , or cooling unit  128  (or cooling subsystem) in response to a temperature in the first closed space  102 . The control unit  158  may include an input device and a display, such as a touch-screen display  160  and a speaker  162  for audible alerts or instructions. The control unit  158  is communicatively coupled, e.g., by wireless signal  164  or wired signal, to the processing unit  134 . In some embodiments, the control unit  158  and the processing unit  134  may be the same unit. 
     A flammable-component detector  166  is disposed within the second closed space  104  and positioned proximate the HVAC unit  110  such that any flammable refrigerant within the conditioned compartment  120  would flow through the sampling port  122  when the damper  124  ( FIG. 2 ) is open and onto the flammable-component detector  166 . The flammable-component detector  166  is operable to produce a detection signal indicative of the level of the flammable component detected or a signal that a lower threshold has been reached. 
     Referring now primarily to  FIG. 2 , a portion of an HVAC system  100  is presented that is analogous most respects to that of  FIG. 1 . The HVAC unit  110  is shown disposed within the second closed space  104 . In this figure, the damper  124  covering sampling port  122  is shown. The damper  124  is communicatively coupled to a processing unit  134 , such as a by a wireless connection or by wires  168 . The processing unit  134  is communicatively coupled to the damper  124  for selectively providing a damper-control signal thereto to open and close the damper  124 . The damper  124  includes an activation device to open or close the damper over the sampling port  122 . Located proximate to the sampling port  122  and damper  124  and preferably at a lower elevation is a flammable-component detector  166 . The flammable-component detector  166  is communicatively coupled to the processing unit  134  by a wireless connection or by a wired connection  165  or other means. 
     The processing unit  134  may be further communicatively coupled to the blower  118  to receive an operational-status signal from the blower  118 . In some embodiments, the processing unit  134  is able to monitor operation of the blower  118  and provide control signals thereto to effect the operation of the blower  118 . 
     The flammable-component detector  166  is positioned so that if there is a leak of the flammable refrigerant within the conditioning compartment  120 , when the sampling port  120  is in an open position, the refrigerant will pour from the sampling port  120  onto the flammable-component detector  166 . In this way, the flammable-component detector  166  is able to monitor and detect a leak of refrigerant within the conditioning compartment  120  when the damper  124  is open and also monitor the second closed space  104  where the flammable-component detector  166  is positioned. It should be noted that when the blower (see  118  in  FIG. 1 ) is operative, any refrigerant leak is diluted and therefore should pose no risk. When the blower is off, the damper  124  may be opened and potential leaks monitored. 
     If the detection signal from the flammable-component detector  166  that is delivered to the processing unit  134  exceeds an alert threshold, responsive action is taken. The response may include sending an alert signal to the control unit  158 . The alert signal may be presented as a visual alert on the screen  160 , an audible alert through speaker  162  ( FIG. 1 ), or other alert. This allows an active warning to the user in the first closed space  102  of the potential danger posed elsewhere, namely in the conditioning compartment  120  or second closed space  104 . 
     The responsive action may include closing the damper  124  and activating the blower  118  ( FIG. 1 ) or may include activating a ventilator  170 . The ventilator  170  may be a fan that pulls air out of the second closed space  104  or moves air into the second closed space  104  for the purpose of diluting any leaked refrigerant. The ventilator  170  is communicatively coupled to the processing unit  134 , e.g., by wireless or wired  172  connection or other means. 
     In one illustrative embodiment, the at least one processor  136  and at least one memory  138  are configured to perform the following steps: receive the operational-status signal from the blower  118 ; open the damper  124  when the operational-status signal from the blower indicates that the blower  118  is not operating; and close the damper  124  when the operational-status signal from the blower  118  indicates that the blower  118  is operating. The at least one processor  136  and at least one memory  138  may be further configured to monitor the detection signal from the flammable-component detector  166  and to send an alert when the detection signal is indicative a flammable component at least equal to an alert threshold. The alert may be an alert signal sent to the control unit  158  ( FIG. 1 ) present a visual or audible alert for the user in the first closed space  102 . The user may have to select something to clear the alert. The processing unit  134  may prepare a blower-control signal to active the blower in response a detection signal indicative of a flammable component at or near an alert threshold. In another embodiment, the processing unit  134  also prepares a ventilation-activation signal that is sent to the ventilation blower  170  to assist with diluting any leaked refrigerant in the second closed space  104 , or equipment space. 
     It will be appreciated that the processing unit  134  may be configured to carryout numerous steps or functions within the system  100 . As one example, reference is now made primarily to  FIG. 3 . In an illustrative process  200  in  FIG. 3 , the process  200  first considers whether the blower is on at interrogatory  202 . If it is on, any refrigerant leak within the conditioning compartment  120  would be diluted and so the damper  124  is closed at step  204  to prevent air from entering the conditioning compartment  120 . If the blower is not on, a leak could be an issue, and so the damper  124  is opened at step  206 . In this way, the flammable-component detector  166  is effectively monitoring both the second closed space  104  and the conditioning compartment  120 . If the flammable-component detector  166  detects a level of one or more flammable components that exceeds an alert threshold, responsive action is taken. This question is considered at interrogatory  208 . If the alert threshold is exceeded, responsive action is taken at step  210 . The response may include sounding an audible alarm, presenting a visual alert, sending an email to the user or service provide or emergency personnel, activating the blower  118 , activating a ventilator  170 , etc. If the flammable-component detector  166  does not detect one or more flammable components exceeding an alert threshold, normal operation continues as shown as step  212  and the process returns to  202 . 
     The alert threshold may be set at a conservative percentage of a lower flammability limit. For example, the alert threshold may be set at 25% of the lower flammability limit for the flammable refrigerant being used. Other safety margins—greater or lesser than 25% —may be used. For example, without limitation, the alert threshold may be 10, 20, 30, 40, or 50% of the lower flammability limit. 
     Referring now primarily to  FIG. 4 , a portion of an HVAC system  100  is shown. The HVAC system  100  of  FIG. 4  is analogous in most respects to the HVAC system of  FIG. 1 , and accordingly, some parts are labeled but not further described here. In addition, components referenced but not explicitly shown are analogous to those previously presented. In this embodiment, however, there is no sample port, but rather a flammable-component detector  166  has a first probe  174  and a second probe  176  fluidly coupled to the detector  166 . The first probe  174  is fluidly coupled to the flammable-component detector  166  and to the conditioning compartment  120 . The second probe  176  is fluidly coupled to the flammable-component detector  166  and to the second closed space  104 . This illustrative embodiment also includes a selector  178  for selectively providing fluid flow through the first probe  174  and for selectively providing fluid flow through the second probe  176  to the flammable-component detector  166 . The selector  178  may be a plurality of valves, a plurality of sample blowers, or other devices. 
     Referring now additionally to  FIG. 5 , the first probe  174  and second probe  176  are shown in more detail with associated components in one illustrative embodiment. For illustration purposes, a plurality of valves  180  is shown. In addition a sample blower  182  is shown that pulls fluid  184  through either open probe  174 ,  176  across the flammable-component detector  166 . The plurality of valves  180  is controlled by the processing unit  134  and is shown communicatively coupled by wires  185  but of course it could be coupled by wireless or by other communication techniques. Similarly, the sample blower  182  may be controlled by the processing unit  134  and is shown coupled by wire  186  but of course it could be coupled by wireless or by other communication techniques. 
     In some embodiments, only valves are needed because of the flammable-component detector  166  is positioned at a location where any leaking refrigerant will run through the probe to the flammable-component detector  166 . In some embodiments, a sample blower  182  may be added to pull sample fluid past the flammable-component detector  166  and be used with valves  178 ,  180  or may be blowers individually associated with the probes  174 ,  176  and individually activated. The flammable-component detector  166  may, for example, be used for ten seconds with the first probe  174  and then for ten second with the second probe  176  and so forth. Other time intervals may be used. This approach allows one flammable-component detector  166  to monitor two spaces. It will be appreciated that this approach may be extended to a third space with a third probe and so on. 
     With respect to the monitoring of the flammable-component detector  166  by the processing unit, it will be appreciated that the fluid delivered by each probe  174 ,  176  may be diluted by the fluid in the other, and accordingly the alert threshold may be set to account for the dilution. This is shown in an the illustrative process flow of  FIG. 6 . 
     It will be appreciated that the processing unit  134  of  FIGS. 4-5  may be configured to carryout numerous steps or functions within the system  100 . As one example, reference is now made primarily to  FIG. 6 . The process  300  begins at  302  and at  304  the number of probes (P) is entered. For example, if the system of  FIG. 5  were involved, two would be entered. If the number of probes were one, the process proceeds from interrogatory  306  to step  308 , which sets the alert threshold at a normal limit (N), e.g., 25% lower flammability limit. If the answer to interrogatory  306  is negative, interrogatory  310 , which asks if there are two probes, is considered. If there are two probes, at step  312 , the alert threshold is set to ½ of normal limit (N), or base limit, e.g., 12.5% of the lower flammability limit (if the normal limit is 25% of the lower flammability limit). 
     If the answer to interrogatory  310  is negative, interrogatory  314 , which asks if there are three probes, is reached. If affirmative, at step  316  the alert threshold is set to ⅓ of normal limit (N), e.g., 8.3% lower flammability limit (if the normal limit is 25% of the lower flammability limit). This approach could continue as suggested by  318  to accommodate other numbers of probes. 
     In one embodiment, the processing unit  134  considers samples from both probes  174 ,  176  and compares the results against each other. In this way, errors from calibration or drift may be cancelled out. If the difference between the two is greater than a difference threshold, an alert is triggered. 
     According to an illustrative embodiment, an HVAC system for providing conditioned air to a first closed space is provided, wherein at least a portion of the system is disposed within a second closed space, includes a cooling unit including a flammable refrigerant and at least one compartment wall separating the cooling unit from an equipment space. The at least one compartment wall is formed with an access port therethrough. The system further includes a controllable damper associated with the access port for selectively covering the access port and a flammable-component detector disposed within the equipment space proximate the access port, which is through the at least one compartment wall. The system also includes a processing unit communicatively coupled to the damper for opening and closing the damper. 
     Unless otherwise specified, any use of any form of the terms “connect,” “engage,” “couple,” “attach,” or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. Coupling includes in some instances communicatively coupled, which may be a wireless connection or a wired connection. Coupled in some instances may refer to fluid coupling. In the discussion herein and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ” 
     It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. It will further be understood that reference to “an” item refers to one or more of those items. 
     The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. 
     Although the present invention and its advantages have been disclosed in the context of certain illustrative, non-limiting embodiments, it should be understood that various changes, substitutions, permutations, and alterations can be made without departing from the scope of the invention as defined by the claims. It will be appreciated that any feature that is described in a connection to any one embodiment may also be applicable to any other embodiment.