NZ612231A

NZ612231A - Control system for a refrigerated merchandiser

Info

Publication number: NZ612231A
Application number: NZ612231A
Authority: NZ
Inventors: Norman E Street; Doron Shapiro; Jony M Zangari; Tobey D Fowler; Ramakrishna Krishnaswamy; Derek Lea
Original assignee: Hussmann Corp
Priority date: 2013-02-12
Filing date: 2013-06-20
Publication date: 2014-05-30
Also published as: CA2818345A1; MX2013008873A; US20140223931A1; AU2013204120A1

Abstract

612231 A method of controlling a refrigerated merchandiser (45) to prevent ignition of any leaking refrigerant is disclosed. The method includes refrigerating a product display area (65) of the merchandiser using a refrigerant, detecting (160) a presence of an air-refrigerant mixture in the refrigerated merchandiser, activating a fan (145) in response to detecting the presence of an air-refrigerant mixture, and at least partially evacuating an interior of the merchandiser in response to fan activation. A refrigerated merchandiser is also disclosed.

Description

CONTROL SYSTEM FOR A REFRIGERATED MERCHANDISER BACKGROUND The present invention relates to refrigerated merchandisers, and more particularly to a control system for erated merchandisers that utilize hydrocarbon refrigerants.

Refrigerated merchandisers are used by grocers to store and display food items in a t disPIay area that must be kept within a ermined temperature range. These merchandisers generally include a case that is conditioned by a refrigeration system that has a compressor, a condenser, and at least one evaporator connected in series with each other.

Typically, existing ndisers use reﬁigerants such as R404a, R134a, or carbon dioxide.

Some reﬁigeration systems utilize hydrocarbon-based refrigerant (e.g., propane) that has a higher tendency to be ﬂammable relative to conventional refrigerants. There are ways to reduce the risk of the ignition of a hydrocarbon-based refrigerant such as using intrinsically safe electrical components, and y control to minimize any potential for leaks. However, a ﬂammable mixture ofreﬁigerant and air may exist inside the merchandiser and an ignition source such as a static electrical rge may occur, g the air and reﬁigerant mixture to ignite. When there is no path for the energy ed by the ignition to escape, which is especially common in sealed cases, the excessive internal pressure may cause the case to explode.

SUMMARY [0003a] Aspects ofthe present invention are described herein and in New Zealand speciﬁcation 619157, which is divided from the t cation. Reference may be made in the description to subject matter which is not in the sc0pe of the appended claims but relates to subject matter claimed in the parent speciﬁcation. That t matter should be readily identiﬁable by a person skilled in the art and may assist putting into practice the invention as deﬁned in the appended claims.

There is provided a refrigerated merchandiser including a case g a product display area and including a reﬁigeration circuit that circulates a hydrocarbon refrigerant operable to condition the product display area via heat exchange with air passing through an evaporator ofthe refrigeration circuit. A refrigerant leakage sensor is coupled to the case and is operable to determine the presence ofgaseous erant in the air, and a control unit is in communication with the sensor and responsive to a signal from the sensor indicative of gaseous refrigerant above a predetermined threshold to manage the risk of erant ignition. A fan or blower is coupled to the merchandiser, for example, on the exterior of the case, to clear a ﬂammable mixture ofrefrigerant gas and air from the case. [0004a] The term ‘comprising’ as used in this speciﬁcation and claims means ‘consisting at least in part of’ . When interpreting statements in this speciﬁcation and claims which include the term ‘comprising’, other features besides the features prefaced by this term in each statement can also be present. Related terms such as ‘comprise’ and ‘comprised’ are to be interpreted in r manner.

The present invention provides a method of controlling a erated merchandiser.

The method comprises reﬁigerating a product display area ofthe merchandiser using a refrigerant, detecting a presence ofan air—refrigerant mixture in the refrigerated merchandiser, activating a fan in response to detecting the presence ofan air-reﬁ'igerant e, and at least partially evacuating an interior of the merchandiser in response to fan activation by either blowing air into the product display area from outside the merchandiser, or drawing air from outside the ndiser into the product display area.

There is provided a method of controlling a rated merchandiser. The method includes reﬁigerating a product y area ofthe merchandiser using a refrigerant, ing a presence of an air-refrigerant mixture in the reﬁigerated merchandiser, and initiating an action in response to the detected air-refrigerant mixture ng a predetermined threshold relative to a lower ﬂammability limit ofthe reﬁ'igerant.

The present ion also provides a refrigerated merchandiser comprising a case deﬁning a product display area and a eration system including an evaporator d to the case and through which a hydrocarbon refrigerant is ated to condition the product display area. The merchandiser also comprises a sensor that is coupled to the case and red to detect an air—refrigerant mixture within the merchandiser and to generate a signal indicative of 63 32696_l .docx the detected air-reﬁ'igerant mixture. The merchandiser also comprises a fan operable to at least partially evacuate an or of the merchandiser by either g air into the product display area from outside the merchandiser, or drawing air ﬁom outside the merchandiser into the product display area. A controller is mmed to initiate an action in response to the signal indicative ofthe air-refrigerant mixture reaching a predetermined threshold relative to a lower ility limit ofthe erant.

Other aspects ofthe invention will become apparent by consideration of the detailed description and anying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic View of an exemplary multi-circuit refrigeration system including a plurality of reﬁigerated merchandisers.

Fig. 2 is perspective View ofone refrigerated merchandiser ofFig. l embodying the invention.

Fig. 3 is a schematic View ofthe reﬁigerated merchandiser ofFig. 2 including a refrigeration system.

Fig. 4 is another schematic view of the erated merchandiser ofFig. 2 the refrigeration system and a blower.

Fig. 5 is a perspective view of a portion of the refrigerated merchandiser including the blower coupled to an exterior of the merchandiser.

Fig. 6 is a schematic View of the refrigerated merchandiser illustrating a control system ofthe merchandiser.

Fig. 7 is a ﬂow chart illustrating an exemplary control s of the l .

Fig. 8 is ﬂow chart illustrating another exemplary control process of the control system.

Before any embodiments ofthe invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement ofcomponents set forth in the following description or illustrated in the ing 6332696_l.docx drawings. The invention is capable of other ments and ofbeing ced or ofbeing carried out in various ways.

DETAILED DESCRIPTION Fig. 1 illustrates an exemplary multi—circuit ration system 10 that can be used in a commercial g (e.g., a retail store, arket, or an rial setting) or other settings that have temperature-controlled environments. The multi-circuit reﬁigeration system 10 includes a primary circuit 15 that circulates a ﬁrst reﬁigerant, a plurality of secondary circuits 20 that circulates a second refrigerant (e.g., a hydrocarbon reﬁigerant such as propane), and a pump circuit 25 that circulates a third refrigerant in heat exchange relationship with the reﬁigerants in the primary circuit 15 and the secondary circuits 20. Part or all ofthe primary circuit 15 can be located remote ﬁom the secondary refrigeration ts 20.

The primary circuit 15 includes a primary compressor assembly 30 (e.g., one or more compressors), a primary ser 35, and a chiller 40 h which the ﬁrst refrigerant (e.g., R134a) is circulated to withdraw heat ﬁ'om the third refrigerant. The primary circuit 15 also can include other components (e.g., a receiver or accumulator, an expansion valve, etc.).

With reference to Figs. 1-3, each secondary t 20 includes one or more merchandisers 45 that have an evaporator assembly 50 in ﬂuid communication with a compressor 55 (e.g., one compressor or several compressors in an assembly) and a condenser 60 that provides heat exchange between the secondary circuit 20 and the pump circuit 25. The evaporator 50 is in heat exchange onship with a product display area 65 of the merchandiser 45, and is ﬂuidly coupled to the compressor 55 via a suction line 70 to deliver evaporated second refrigerant from the evaporator 50 to the compressor 55. The evaporator 50 is also ﬂuidly coupled with the condenser 60 via an inlet line 75 to receive cooled (e.g., condensed) second refrigerant from the condenser 60. A discharge line 80 ﬂuidly connects the compressor 55 to the condenser 60 to direct the ssed second refrigerant to the condenser 60, where heat from the second refrigerant can be transferred to the third refrigerant in the pump circuit 25. As will be appreciated, the secondary circuit 20 can include other components (e.g., receiver or accumulator, an expansion valve, etc.).

As shown in Fig. 1, the pump circuit 25 includes a pump 85 that circulates the third refrigerant (e.g., water) between the water chiller 40 of the primary circuit 15 and the condensers 60 ofthe secondary circuit 20. As illustrated, the reﬁigeration system 10 also es an outdoor heat exchanger 90 that is in communication with the pump circuit 25. In some constructions, the heat exchanger 90 can be d on a rooftop ofthe commercial setting to discharge energy from the third refrigerant in the pump circuit 25 to the surrounding environment. The heat ger 90 is in ﬂuid communication with the pump circuit 25 via an inlet line 93 and an outlet line 95. A valve (not shown) can be coupled to the inlet line 93 and/or the outlet line 95 to control ﬂow igerant between the pump circuit 25 and the heat exchanger 90 based at least in part on the temperature of the surrounding environment. When the heat exchanger 90 is used to cool the third reﬁigerant, the primary circuit 15 can be shutdown, or the primary circuit 15 and the heat exchanger 90 can operate aneously to cool the third refn'gerant.

The merchandiser 45 can be a low or medium temperature merchandiser. Fig. 2 shows that the merchandiser 45 is a horizontal merchandiser including a case 100, although the merchandiser 45 can take other forms (e.g., a vertical merchandiser with an open or door- enclosed customer access). The case 100 has a base 105 and sidewalls 110, a front wall 115, and a rear wall 120 atively deﬁning the product display area 65 that supports food product.

The case 100 also deﬁnes an interior area 125 trated in Fig. 3 below the product display area 65) that supports at least a portion ofthe secondary circuit 20. As illustrated, lids or doors 130 are disposed over the product display area 65 to substantially enclose the product display area 65 and to ively provide access (e.g., by sliding) to product supported in the product display area 65.

Referring to Fig. 3, the second reﬁigerant in the evaporator 50 absorbs heat from an airﬂow 135 passing over or h the evaporator 50, which decreases the temperature of the airﬂow 135. The refrigerated airﬂow 135 exiting the evaporator 50 is directed toward the product display area 65 to maintain product in the product display area 65 at desired conditions.

The ser 60 discharges heat from the second refrigerant to the third refrigerant in the pump circuit 25. Air passing through or over the condenser 60 can be ed from the condenser 60 to the environment surrounding the merchandiser 45 using exhaust fans 137 that direct the air through an exhaust 140 coupled to the case 100. The compressor 55 and the condenser 60 can be disposed in the reﬁigerated merchandiser 45 within an interior area 125 ofthe case 100, or located remote from the case 100.

Hydrocarbon rant are lly more ﬂammable than conventional refrigerants. The ﬂammability risk can be mitigated by reducing the refrigerant charge (i.e. the amount of second refrigerant) in the secondary circuits 20, using intrinsically save electrical components, and/or quality control to minimize any potential for refrigerant leakage. When hydrocarbon reﬁigerant leaks from the circuit 20, the leaked refrigerant mixes with air in the case 45 and can become le. As such, it is generally desirable to do at least one of the following: 1) Detect when a mixture of air and refrigerant is present in the merchandiser 45; 2) determine r the ﬁigerant mixture has reached or exceeded a predetermined threshold (e.g., a percentage of a lower ﬂammability limit at which the mixture s highly ﬂammable); 3) determine the presence of an ignition source (e.g., static electricity, electrical power ed to components in the merchandiser 45, etc.) in or surrounding or adjacent the merchandiser 45; and 4) clear the frigerant mixture ﬁ'om the merchandiser 45.

To this end, and with reference to Figs. 4 and 5, the merchandiser 45 includes a blower 145 that is coupled to the case 100 (e.g., on one ofthe side walls 110, the front wall 115, and the rear wall 120) to selectively direct air h the case 100. As illustrated, the blower 145 is coupled to an exterior of the case 100 to avoid frosting the blower 145 in view of the substantially colder temperature in the case 100, although in some circumstances the blower 145 can be coupled to an interior the case 100 or suitable other locations. The illustrated blower 145 operates at a vely high speed (e.g., 20,000 to 30,000 RPMs) to introduce a large volume of ambient air into the case 100 over a relatively short period oftime. Depending on how the blower 145 is connected to the merchandiser 45, the blower 145 can be energized to draw ambient air into the case 100, or the blower can push ambient air into the case 100.

With reference to Fig. 5, the blower 145 mounted to the case by a mounting bracket 147 and is in ﬂuid communication with the interior ofthe ndiser 45 Via an inlet pipe 150.

As will be appreciated by one of ordinary skill in the art, the blower 145 is connected to a power source (e. g., one or more batteries, a powered connection via the merchandiser 45, or another source ofpower). As shown in Fig. 5, a check valve 155 is coupled to the inlet pipe 150 downstream ofthe blower 145 (in the direction of airﬂow through the blower 145) to provide unidirectional ambient airﬂow into the case 100 when the blower 145 is activated. That is, the check valve 155 inhibits ﬂow ofreﬁigerated air into the blower 145.

With reference to Figs. 3 and 4, the merchandiser 45 es one or more sensors 160 (e.g., gas detector) that are mounted in the interior area 125 of the case 100 to detect the presence, if any, of leaked reﬁigerant within the merchandiser 45. That is, the sensor 160 detects the presence ofany second reﬁigerant that is mixed with air inside the ndiser 45. The sensor 160 can be coupled to the case 100 in any suitable location (e.g., on a wall of the case 100, within the interior area 125, adjacent one or more of the refrigeration components in the ndiser 45, adjacent or in the t display area 65, etc.).

The sensor 160 is operable to generate a signal indicative of the presence of second refrigerant in the merchandiser 45 and to icate the signal to a control unit 165 that is in communication (e.g., wired, wireless, etc.) with the sensor 160. With reference to Figs. 3 and 4, the control unit 165 is disposed inside the merchandiser 45 (e.g., within the or area 125), although the l unit 165 can be located remote from the merchandiser 45 . In se to the signal from the sensor 160, the control unit 165 is programmed to control the secondary circuit and electrically-powered or electronic components 170 ofthe merchandiser 45 to mitigate the risk of igniting the air-refrigerant mixture. For example, the electronic components 170 can include the compressor assembly 55, pumps (not shown), light assemblies (not shown) within the merchandiser 45 or other components ofthe merchandiser 45 that could provide a ial ignition source for the leaked refrigerant. As described in detail below, the control unit 165 controls the exhaust fanS'l37 and/or the blower 145 separately from the electronic components 170 so that the exhaust fans 137 or the blower 145, or both, can Operate when the electronic ents 170 are shutdown or disabled to clear the ﬂammable air-refrigerant mixture from the merchandiser 45.

With reference to Fig. 6, the control unit 165 is in communication with one or more spark-free alarm indicators 175 (e.g., lights, sound devices, etc.) to indicate one or more of the presence ofreﬁigerant in the merchandiser 45, a malfunctioning sensor 160, and other parameters ofthe merchandiser 45. For example, the alarm tors 175 can be coupled to the case 100 within the product display area 65 to convey an alarm condition to people located adjacent the merchandiser 45. Some or all ofthe alarm indicators 175 can also or atively be located remote from the merchandiser 45 (e.g., in a control room).

Fig. 7 illustrates an exemplary control process that is programmed into the control unit 165 to control the merchandiser 45 and to indicate, as necessary, abnormal ions associated with the merchandiser via the alarm indicators 175. The control unit 165 determines whether the merchandiser 45 is powered on at step 200. For example, the control unit 165 determines whether the secondary circuit 20 is circulating erant and whether other components ofthe merchandiser 45 are operational and d. If "No," the control process again determines r the merchandiser is powered on after a predetermined time has elapsed. If the control unit 165 ines the merchandiser 45 is on at step 200 (i.e. "Yes"), the control unit 165 determines at step 205 whether the sensor 160 is conﬁgured or present in the merchandiser 45. If "No" at step 205, the control unit 165 controls the merchandiser 45 based on normal operating conditions. In some constructions, the control process then returns to step 200 and repeats.

If the sensor 160 is detected and installed for operation (i.e. "Yes" at step 205), the l process proceeds to step 215 to detect whether the sensor 160 has been conﬁgured for operation and that the sensor 160 is communicating with the control unit 165. If "No" at step 215, the control process determines whether a ﬁrst predetermined time (e.g., 30 seconds) has elapsed at step 220. If the ﬁrst predetermined time has not d (i.e. "No at step 220), the process returns to step 215 to again determine whether the sensor 160 has been conﬁgured.

If the control unit 165 determines that the ﬁrst predetermined time has elapsed and the sensor 160 is not conﬁgured properly, the control process proceeds to step 225 to de—energize the electrical/electronic components 170 ofthe merchandiser 45. In some constructions, the control unit 165 also can concurrently or consecutively energize the fans 137 and/or the blower 145 at step 245 and activate the alarm indicators 175 at step 250 before returning to step 200 and repeating the control process. Generally, the l unit 165 tes an alarm when an abnormal ion associated with the merchandiser 45 (e.g., detection of refrigerant in the air within the merchandiser 45, a malfunctioning component such as the blower 145 or the sensor 160, etc.) is detected, and the control unit 165 then operates the merchandiser 45 in a failsafe mode.

In other constructions, the control process can proceed directly from step 225 to step 200 without energizing the fans 137 or the blower 145 and without ting the alarm indicators 175. The electrical components 170 are de-energized or powered down to minimize the risk of ng a ﬂammable air-refrigerant mixture that may exist in the merchandiser 45.

The merchandiser 45 can be manually or automatically restarted at step 200 after the electrical components 170 have been de-energized, and in some cases after air in the case 100 has been cleared by the fans 137 or the blower 145.

Returning to step 215, if the sensor 160 has been properly red, the control process proceeds to step 230 to wait (e.g., 30 seconds, 60 seconds, 90 seconds, 5 minutes, etc.) until the sensor 160 is ready for use. When the sensor 160 is ready for use, the control process proceeds to step 235 to monitor data detected by the sensor 160. In some constructions, the control process can be provided without steps 215 and/or 230. That is, the control s can detect the presence ofthe sensor 160 at step 205 and, if the sensor 160 is detected, proceed directly to step 235.

At step 235, the control process determines r data detected by the sensor 160 is valid. Generally, sensor data is valid when the data is consistent or m relative to baseline data associated with the sensor 160 and/or the conditions in the merchandiser 45. Stated another way, the sensor data is deemed invalid, for example, when a fault condition associated with the sensor 160 is detected by the control unit 165 (e.g., on the basis of data ed or not received from the sensor 160, the state ofthe sensor 160, a nected or severed Wire connected to or in the sensor 160, etc.) after a period oftime (e.g., 30 seconds, 60 seconds, etc.) has elapsed.

Because the sensor 160, in some constructions, can have x circuitry and may include several components, determining whether sensed data is valid (i.e. indicative of the conditions in the merchandiser 45) can be useful when controlling the merchandiser 45 based on the sensed data.

If the control unit 165 determines that the sensor data is invalid (i.e. "Yes" at step 235), the control unit 165 de-energizes the merchandiser 45 at step 225, energizes the fans 137 and/or the blower 145 at step 245, and activates the alarm indicators 175, as necessary, as described above. If the control unit 165 determines that the sensor data is valid (i.e. "No" at step 235, the control process proceeds to step 240 to determine whether the sensor 160 has detected a reﬁigerant—gas mixture that reaches or exceeds a predetermined value or threshold over a third predetermined time. That is, the control process determines at step 240 whether any refrigerant has leaked from the secondary circuit 20, and whether the amount ofleaked refrigerant creates a potential .

In particular, the control unit 165 determines whether the amount of refrigerant mixed with the air reaches a lower ﬂammability limit ("LFL") based on the type ofrefrigerant being used in the secondary circuit 20. The LFL deﬁnes the lowest percentage threshold at which a gaseous refrigerant mixed with air becomes ﬂammable. As bed herein, the LFL is sed as the threshold percentage ofrefrigerant that, when mixed with air, s ﬂammable. For example, when propane is used as the second refrigerant, the LFL of a propane air-refrigerant mixture is approximately 2% by volume of erant in the air. In other words, when the air-reﬁigerant e is comprised ofapproximately 2% propane by volume, the mixture is deﬁned as a ﬂammable mixture.

The rated sensor 160 monitors the air within the merchandiser 45 (i.e. the sensor 160 is initiated to determine r refrigerant is present in the air) every 3 seconds, gh the sensor 160 can monitor the air continuously or at intervals shorter or longer than 3 seconds.

With continued reference to Fig. 7, the illustrated control process determines whether the sensor 160 has detected a air—refrigerant mixture comprised of a quantity or volume of refrigerant that reaches a ﬁrst predetermined percentage ofthe LFL (e.g., 25% ofthe LFL) for a predetermined time (e.g., 30 seconds, which equates to ten utive sensing cycles of the illustrated sensor 160), or a second predetermined percentage of the LFL (e.g., 50% of the LFL) for a predetermined time (6 s, which equates to two consecutive cycles of the sensor 160).

Generally, the control process more quickly de-energizes the merchandiser 45 when the volume ofrefrigerant reaches a higher predetermined percentage ofthe LFL to avoid a scenario in which the volume ofreﬁigerant reaches or s 100% ofthe LFL and, as a result, the air—refrigerant mixture becomes ﬂammable.

In other constructions, the l unit 165 can control the merchandiser 45 based on a detected volume of reﬁ'igerant that reaches other predetermined percentages of the LFL (e.g., % ofthe LFL, 25% ofthe LFL, 33% ofthe LFL, 50% ofthe LFL, 60% ofthe LFL, 75%, 90%, etc.) for an associated period oftime that is based on the likelihood the air-refrigerant mixture may become ﬂammable. lly, the amount oftime that the merchandiser 45 is operational after detecting a volume of reﬁigerant in the air within the merchandiser 45 s on the volume of refrigerant detected.

When the control unit 165 determines at step 240 that 1) no refrigerant is detected by the sensor 160, 2) the volume of reﬁ'igerant detected by the sensor 160 has not exceeded the ﬁrst predetermined percentage of the LFL, or 3) the volume ofrefrigerant detected by the sensor 160 has not exceeded the ﬁrst or second predetermined percentages ofthe LFL for the associated predetermined time, the control unit 165 ds to step 210 to control the merchandiser 45 based on normal operating conditions. Stated r way, the control unit 165 determines at step 240 that the merchandiser 45 can be operated normally because there is a minimal or no risk ofﬂammability.

If the control unit 165 determines at step 240 that a volume of refrigerant has been detected within the air in the merchandiser 45 (i.e. the air—refrigerant e has been ed) and that the refrigerant volume is at or has exceeded either the ﬁrst predetermined percentage of the LFL or the second predetermined percent ofthe LFL for the associated predetermined time, the control unit proceeds to step 225 to de-energize the merchandiser 45. The fans 137 and/or the blower 145 are energized to clear the air in the merchandiser 45. In particular, the exhaust fans 137 dryer out ofthe case 100, whereas the illustrated blower 145 pushes air into the case 100 to quickly clear the frigerant mixture from the merchandiser 45. The control unit 165 also initiates an alarm via the alarm indicators 175 at step 252 alert people adjacent the merchandiser 45, and in some cases, people remote from the merchandiser 45, that an alarm ion exists in the merchandiser 45 . The control process then proceeds to step 200 and repeats.

Fig. 8 illustrates r exemplary l process for the system that, except as described below, is the same as the control process described with regard to Fig. 7. With reference to Fig. 8, if the control unit 165 determines at step 240 that the refrigerant volume is at or has exceeded either the ﬁrst predetermined percentage ofthe LFL or the second predetermined percent of the LFL for the associated predetermined time, as described above, the control process proceeds to step 255 to determine whether an ignition source is present in or adjacent the merchandiser 45 . If no on source is detected (i.e. "No" at step 255), the control process proceeds to step 260 to energize the fans 137 or the blower 145 to assist with reducing or ng the air-reﬁigerant mixture that is present in the case 100. The control process then proceeds to step 210 to operate the merchandiser 45 normally before returning to step 200. If the control unit 165 detects an on source (Le. "Yes" at step 255), the control process proceeds to step 225 to de-energize the system as described above.

In some constructions, the control unit 165 can activate one or both of the fans 137 and the blower 145 periodically, even when a ﬂammable mixture is not detected in the merchandiser 45, to remove debris that may accumulate in the blower 145 or to limit icing of the blower 145 due to cold air that may enter the blower 145 during inactivity. Also, other controls can be incorporated into the control unit 165 to operate the merchandiser 45 and to maintain the product display area 65 within normal operating conditions.

Several secondary ts 20 can be coupled together and cooled through the pump t 25 Where the third refrigerant is cooled through the primary t 20 or al heat exchanger 90. The closed secondary circuit 20 within each merchandiser 45 reduces the charge ofhydrocarbon reﬁigerant in the merchandiser 45 without sacriﬁcing cooling capacity for the product display area 65. The risk of ignition in the merchandiser 45 is mitigated by minimizing the charge of the hydrocarbon refrigerant that is present in the secondary circuit 20. Also, in the unlikely event that a air-refrigerant mixture ignites in one merchandiser 45, the closed secondary circuit 20 s with limiting any damage that may occur by isolating the on to that merchandiser 45. As bed with regard to Figs. 7 and 8, the control unit 165 is programmed to control the merchandiser 45 based in part on the volume of reﬁigerant, if any, that is ed within the case 100 by shutting down at least some electrical components of the merchandiser 45. The control unit 165 is ﬁlrther programmed to initiate one or more fans 137 or the blower 145 to expel the air—refrigerant mixture out of the merchandiser 45 and to initiate an alarm Via the alarm indicators 175 so that people adjacent the merchandiser 45, and possibly , are aware that an ignition risk may exist.

Various features and advantages ofthe invention are set forth in the following claims.

Claims

WHAT WE CLAIM IS:

1. A method ofcontrolling a refrigerated ndiser, the method comprising: refrigerating a product display area of the merchandiser using a reﬁigerant; ing a presence of an air-refrigerant mixture in the refrigerated merchandiser; activating a fan in se to detecting the presence ofan air-reﬁigerant mixture; and at least partially ting an interior of the merchandiser in response to fan activation by either blowing air into the product y area from outside the merchandiser, or drawing air from outside the ndiser into the product display area.

2. The method ofclaim 1, further comprising de-energizing electrical components of the merchandiser in response to detecting the presence of an air-refrigerant mixture.

3. The method ofclaim 2, ﬁirther comprising activating the fan and de—energizing the electrical components in response to the detected air-refrigerant mixture reaching approximately 25% ofa lower ﬂammability limit ofthe refrigerant.

4. The method ofclaim 1, ﬁirther comprising activating an alarm in response to ing the air-refrigerant mixture.

5. The method ofclaim 2, wherein the refrigerant is a hydrocarbon refrigerant, and wherein detecting a presence of an air-refrigerant mixture es detecting the air~ref1igerant mixture reaching approximately 25% ofa lower ility limit ofthe hydrocarbon reﬁigerant.

6. The method of claim 1, further comprising determining a presence of an ignition source prior to activating the fan.

7. The method ofclaim 1, r comprising initiating an action in response to the detected air—reﬁigerant mixture reaching a predetermined threshold relative to a lower ﬂammability limit of the refrigerant.

8. The method ofclaim 7, wherein initiating an action includes at least one of activating a fan, de-energizing one or more electrical components of the merchandiser, and activating an alarm.

9. The method ofclaim 8, further comprising de-energizing the one or more components; and activating the fan after the one or more components are rgized.

10. The method ofclaim 7, further comprising determining a presence of an ignition source prior to initiating the action.

11. The method ofclaim 10, further comprising activating a fan to clear an interior of the merchandiser ofthe detected air-reﬁigerant mixture regardless ofwhether an ignition source is detected.

12. The method m 7, further comprising ining whether a predetermined time has elapsed after detecting the presence of the air-reﬁigerant mixture reaching the predetermined threshold before initiating the action.

13. The method ofclaim 1, substantially as herein described with reference to any embodiment disclosed.

14. A refrigerated ndiser comprising: a case ng a product display area; a refrigeration system including an ator d to the case and through which a hydrocarbon reﬁigerant is circulated to condition the product display area; a sensor coupled to the case and conﬁgured to detect an air-refrigerant mixture within the merchandiser and to generate a signal indicative of the detected air-refrigerant e; a fan operable to at least partially evacuate an interior of the merchandiser by either blowing air into the product display area from outside the ndiser, or drawing air ﬁom outside the merchandiser into the product display area; and a controller programmed to te an action in response to the signal indicative of the air-refrigerant mixture reaching a predetermined threshold relative to a lower ﬂammability limit ofthe refrigerant.

15. The refrigerated merchandiser ofclaim 14, wherein the controller is in communication with at least one of 1) the fan to clear the interior of the ndiser of the detected air- refrigerant mixture, 2) one or more electrical components ofthe merchandiser to selectively de— energize the components, and 3) an alarm indicator to signal the presence of an air—reﬁigerant mixture in the merchandiser.

16. The refrigerated merchandiser ofclaim 15, n the controller is programmed to activate the fan after the one or more electrical components are de-energized.

17. The rated merchandiser of claim 14, wherein the controller is programmed to initiate the action after a predetermined time has elapsed.

18. The refrigerated merchandiser ofclaim 14, wherein the predetermined threshold is approximately 25% ofthe lower ﬂammability limit.

19. The reﬁigerated merchandiser of claim 14, wherein the controller is ﬁlrther programmed to determine the presence ofan on source prior to tion ofthe action.

20. The refrigerated merchandiser ofclaim 19, n the controller is programmed to activate the fan to clear the interior of the merchandiser ofthe detected air-refrigerant mixture regardless ofwhether the presence ofan ignition source is detected.

21. The refrigerated merchandiser of claim 14, ntially as herein described with reference to any embodiment disclosed. 6408657_l.docx ALARM INDICATORS EVAPORATOR PRODUCT DISPLAY COLD AIR AREA CIRCULATION UNIT l—NLETLINE 80 COMPRESSOR SUCTION DISCHARGE LINE GAS DETECTOR EXTERNAL HEAT EXCHANGE \20 45\ 175 130 55 ALARM INDICATORS EVAPORATOR 135 50 115 PRODUCT DISPLAY COLD AIR AREA CIRCULATION 120 l—NLETLINE 80 COMPRESSOR 125 SUCTION RGE LINE PRESSURE BLOWER GAS DETECTOR EXTERNAL HEAT EXCHANGE 160 CONTROL UNIT NDISER ELECTRONIC DEVICES TO SHUT DOWN GAS DETECTOR MERCHANDISER ON? N0 DETECT NORMAL SENSOR? CONTROL 215 NOT PROPERLY PROPER CON