JPS62141482A - Method and device for monitoring frosting of refrigeration and cold storage open showcase - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for monitoring frost formation on a cooler of a freezer/refrigerated open showcase.

[Prior art]

In freezer/refrigerated open showcases, if the frost buildup on the cooler exceeds a certain amount, the cooling efficiency decreases, so defrosting the cooler is performed at predetermined intervals to keep the cooling efficiency of the cooler constant. It is customary to ensure that it does not drop more than that.

This defrosting of the cooler is normally carried out using a timer at regular intervals of, for example, 3 to 4 hours, as shown in FIG. 8 (timed defrosting method).

When defrosting a cooler, the cooler is usually heated to above the freezing point by a heater, etc. Due to this heating, the heat accumulated in the cooler is transferred to the cold air immediately after defrosting, and is further transferred to the storage room. This heat is known to deteriorate the quality of stored products. Therefore, it is preferable to reduce the frequency of defrosting as much as possible in order to prevent deterioration in the quality of stored items.

However, the defrosting cycle usually takes into account that the amount of frost grows to a predetermined amount early due to moisture mixed in with the cold air, and when the amount of frost is the most, the amount of frost becomes less than the predetermined amount. This means that defrosting will be performed before the amount of frost on the cooler reaches the predetermined amount.
The frequency of defrosting is high, which is disadvantageous in terms of preventing deterioration of the quality of stored products.

From the viewpoint of preventing deterioration in the quality of stored items, it is most preferable to detect the actual amount of frost on the cooler and perform defrosting when the amount of frost reaches a predetermined amount.

However, there is still no control method or device for a freezing/refrigerating open showcase that detects the amount of frost on the cooler and starts defrosting when the amount of frost actually grows to a predetermined amount.

Therefore, like an automatic defrost device in a refrigerator, it detects the temperature of the cold air, and when the temperature of the cold air exceeds a predetermined defrost reference temperature, it assumes that the amount of frost has grown to a predetermined amount and starts defrosting. It is possible that

[Problem that the invention seeks to solve]

This method is effective in cases where the influence of outside air is almost negligible, such as in refrigerators, but in cases where the influence of outside air temperature and humidity is large, such as in frozen/refrigerated open showcases, the temperature of the cold air is Even when the amount of frost exceeds a predetermined value, the amount of frost does not grow to the predetermined amount, and even if the temperature of the cold air is below the predetermined value, the amount of frost often grows to the predetermined amount or more. Even in places with relatively well-equipped air conditioning facilities, such as Supermarkets 1~, the temperature of the outside air surrounding the frozen and refrigerated open showcases fluctuates in the range of 18 to 27 degrees Celsius depending on the day and night or season. The cold air temperature corresponding to the amount of frost changes depending on the temperature change of the outside air. For example, as shown in FIG. 8, the outside air temperature Tc
When the temperature Tb increases, the cold air temperature Tb also increases, and defrosting is performed even if the amount of frost on the cooler has not reached a predetermined amount, causing a problem that the quality of stored items is likely to deteriorate. Furthermore, when the outside air temperature Tc becomes low, the cold air temperature Tb becomes lower than the predetermined value even though the amount of frost has grown to a predetermined amount or more, and defrosting is not performed and the cooling efficiency decreases to the predetermined value. It may be worse than it is worth.

[Measures to resolve the problem]

The present invention has been made in consideration of the above circumstances, and includes:
without reducing the cooling efficiency of the cooler below a predetermined value.
The object of the present invention is to provide a method and device for monitoring frost formation on the coolers of frozen and refrigerated open showcases, which makes the defrosting cycle as long as possible so that deterioration in the quality of stored products is less likely to occur. be.

In order to achieve such an objective, the freezing and
In the method of monitoring frost formation on the cooler of a refrigerated open showcase, the cooler temperature and the blowing cold air temperature are detected, the temperature difference between the cooler temperature and the blowing cold air temperature is calculated, and the temperature difference is determined by a predetermined value (f). It is determined whether the amount of frost on the cooler exceeds a predetermined amount based on whether the amount of frost on the cooler is large or not, and if it is determined that the amount of frost on the cooler exceeds the predetermined amount, defrosting of the cooler is started. Defrost command is output.

The temperature difference between the cooler temperature and the blown-out cold air temperature increases in proportion to the heat transfer efficiency from the cooler to the cold air, that is, the amount of decrease in cooling efficiency, regardless of the outside air temperature. Therefore, the temperature difference increases in proportion to the amount of frost formation, and by determining whether or not the temperature difference exceeds a predetermined value, it is possible to accurately determine whether or not the amount of frost formation exceeds a predetermined value.

Furthermore, the apparatus for monitoring frost formation on the cooler of a frozen/refrigerated open showcase according to the present invention executes the above method for monitoring frost formation on the cooler of a frozen/refrigerated open showcase according to the present invention. To achieve this purpose, we have a cooler temperature sensor that detects the cooler temperature and outputs an electrical signal corresponding to the cooler temperature, and a cooler temperature sensor that detects the temperature of the cold air blown out and outputs an electrical signal corresponding to the cold air temperature. a temperature difference calculation unit that calculates the temperature difference between the cooler temperature and the cold air temperature, and a temperature difference calculation unit that calculates the amount of frost on the cooler depending on whether the calculated temperature difference is larger than a predetermined value. The invention is characterized by being provided with a frost formation determination means that determines whether the amount of frost formation exceeds a fixed amount and outputs a defrosting command to start defrosting when it is determined that the amount of frost formation has exceeded a predetermined value once. It is something.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 2 is a block diagram of the main parts of the control circuit of the refrigerated open showcase, and this control circuit 1 includes a frost monitoring circuit 2 that determines whether the amount of frost on the cooler (not shown) exceeds a predetermined amount. Based on the determination results, the machines in the refrigeration cycle (the compressor, the motor that drives it, the refrigerant piping) are It has a temperature adjustment control section 3 that controls the operation of valves, etc.) and a defrost control section 4 that controls the defrosting operation of the cooler.

As shown in FIG. 1, the build-up/frost monitoring circuit 2 includes a cooler temperature sensor 5 that detects a cooler temperature Ta and outputs a cooler temperature signal Sa consisting of an electrical signal corresponding to the cooler temperature Ta. and the temperature of the cold air blown from the cold air path into the storage room,
That is, there is a blowout cold air temperature sensor 6 that detects the blowout cold air temperature Tb and outputs a blowout cold air temperature sb consisting of an electrical signal corresponding to the blowout cold air temperature Tb, and A temperature difference calculating section 7 calculates the temperature difference]゛ and outputs a temperature difference signal S corresponding to this temperature difference T, and a temperature difference calculating section 7 that calculates the temperature difference T, and outputs a temperature difference signal S corresponding to the temperature difference T, and a temperature difference signal S corresponding to the temperature difference T, Determine whether the amount of frost exceeds a predetermined amount,
If the amount of frost is less than a predetermined amount, a normal operation command SN that instructs the temperature adjustment control section 3 to operate is output, and if it is determined that the amount of frost exceeds a predetermined value, the defrost control section 4
It has a frost formation determination unit 8 that outputs a defrost command 5IIF that causes the defrost control to be executed.

As shown in FIG. 1, this frost formation determination section 8 includes a reference voltage generation circuit 9 that outputs a reference voltage signal SDR corresponding to a predetermined maximum temperature difference TIIH, and a reference voltage signal S, A that is connected to a positive phase input terminal. The comparison circuit 10 inputs the output S of the temperature difference calculation unit 7 to the negative phase input terminal, and the normal operation command output port 11 and the inverter 12 connected to the output terminal of this comparison circuit 10. It has a defrosting command output port 13 connected to the output end of the circuit IO.

1, the temperature difference T0 between the cooler temperature Ta detected by the cooler temperature sensor 5 and the outlet cold air temperature Tb detected by the outlet cold air temperature sensor 6 is calculated by the temperature difference calculation unit 7, It is input to the negative phase input terminal of No. 10. This calculated temperature difference TD is the reference voltage generation circuit 9
If the maximum temperature difference TDI+ is less than or equal to the maximum temperature difference TDI+ set by . As a result, the temperature adjustment control section 3 controls the operation of the refrigeration cycle machine so that the temperature of the storage room falls within a predetermined refrigeration temperature range. If the calculated temperature difference TD exceeds the maximum temperature difference Tn++ set by the reference voltage generation circuit 9, the output of the comparison circuit 10 becomes a low value I, and the defrost command Snr, which is a high value signal, is transmitted to the inverter 12 and the defrost command It is output to the defrosting control section 4 via the output boat 13. As a result, the control by the temperature adjustment control section 3 is interrupted, and the defrosting control section 4 defrosts the cooler. During defrosting, controls are executed such as, for example, operating a heater (not shown) for a predetermined period of time, or moving a cooler to the outside of the cold air path in order to perform natural defrosting using outside air for a predetermined period of time. Ru.

The control circuit according to another embodiment of the present invention shown in FIGS. 3 to 5 includes an operating state monitoring section 14 including the frost formation monitoring circuit 2, and a temperature adjustment control section 3, as shown in FIG. , a defrosting control section 4, and a safety operation control section 15 which is activated when various types of failures described below are detected.

As shown in FIG. 3, the operating state monitoring section 14 includes a cooler temperature sensor 5, a blowout cold air temperature sensor 6, a temperature difference calculation section 7, a normal operation command output boat 11, and a removal In addition to the frost command output boat 13, there is a fan failure detection unit 16 that outputs a fan stop signal SF consisting of a low value signal when the cold air circulation fan is stopped.
, a temperature difference area determination section 17 , a large temperature difference cause analysis section 18 , and a small temperature difference cause analysis section 19 .

As shown in FIG. 5, the temperature difference region determination unit 17 generates a reference voltage signal S91. corresponding to a predetermined maximum temperature difference TDM. and a reference voltage generation circuit 20 that outputs a reference voltage signal SDL corresponding to the predetermined minimum temperature difference TDL;
A temperature difference signal S is obtained by inputting a reference voltage signal 5D11 corresponding to No. 11 to the positive phase input terminal, and a voltage signal corresponding to the calculated temperature difference T. Comparison circuit 10 which inputs into the negative phase input terminal
and a comparison circuit 21 and both comparison circuits 10 and 21 which input the temperature difference signal SD to the positive phase input terminal and input the reference voltage signal 5ILL corresponding to the minimum temperature difference 'rnt to the negative phase input terminal.
It has an AND gate circuit 22 which inputs the output of.

The output of this AND gate circuit 22 is connected to the temperature adjustment control section 3 via the normal operation command output port 11.

The large temperature difference cause analysis section 18 includes an inverter 12 that inverts the output of one comparison circuit 10 of the temperature difference region determination section 17.
and the AND gate circuit 23 which inputs the output of the other comparison circuit 21 of the temperature difference region determination section 17 and the output of the fan failure detection section 16, and the output of the inverter 12 and the output of the AND gate circuit 23. an AND gate circuit 24, an inverter 25 that inverts the output of the fan failure detection section 16, an AND gate circuit 26 that inputs the outputs of both inverters 12 and 25, and this AND gate circuit 2.
It has an inverter 27 that inverts the output of 6. Further, this large temperature difference cause analysis section 18 has a defrosting command output port 13 connected to the output end of the AND gate circuit 24, and a fan failure detection signal output port 2B connected to the output end of the inverter 27. ing.

The small temperature difference cause analysis section 19 includes an inverter 29 that inverts the output of the other comparison circuit 1i'821 of the temperature difference region discrimination section 17, and a predetermined minimum cool air temperature Tb. A reference value setting circuit 30 outputs a reference signal sb□7 corresponding to , this reference signal Sb, , is inputted to the negative phase input terminal, and the output sb of the cooler temperature sensor 5 is inputted to the positive phase input terminal. A comparison circuit 31, an inverter 32 that inverts the output of the comparison circuit 29, and each inverter 29.
．． It has an AND gate circuit 33 which inputs the output of 32. The output terminal of Antogame 1 to circuit 33 is connected to inverter 3.
4 to the gas leak detection signal output boat 35.

In addition, this small temperature difference cause analysis section 19
It has an AND gate circuit 36 which inputs the output of 9 and the output of the comparison circuit 31.
The output end of is connected to a mechanical failure detection signal output port 38 via an inverter 37.

A fan failure detection signal output from the fan failure detection signal output port 28, a gas leak detection signal output from the gas leak detection signal output port 35, and a mechanical failure detection signal output from the mechanical failure detection signal output port 38 are input. The operation of the safety operation control circuit 15 can be set in various ways as necessary. In this case, for example, in response to each signal, a display device that indicates fan failure, gas leak, or mechanical failure may be activated, and a buzzer, sound,
An alarm device that notifies the user of a malfunction using music or other music is activated, and in particular, if a malfunction is detected that does not affect the safety of shoppers, such as a gas leak or mechanical malfunction, the system will stop or close the machine during the refrigeration cycle. A safety operation control circuit 15 is configured to safely operate the valves and the like.

Next, the operation of the control device configured as above will be explained.

If the amount of frost on the cooler exceeds a predetermined value (frost formation mode), or if the fan malfunctions and rotates abnormally slow or stops (fan failure mode), the cooler temperature Ta and The temperature difference Tn of the blown cold air temperature Tb exceeds a predetermined maximum temperature difference Tゎ,1.

In the case of such a large temperature difference, the temperature difference area determination unit 17
The output of one comparison circuit 10 becomes a low value, and the output of the other comparison circuit 21 becomes a high value. Therefore, the output of the AND gate 22 becomes low-cost, and the operation of the temperature adjustment control section 3 is stopped. In the large temperature difference cause analysis section 18, when the cause of the large temperature difference is frost formation, the output of the fan failure detection section 16 is high, so the output of the AND gate circuit 23 is high, and the antgame 1. Both inputs of the circuit 24 become high values, and a defrost command S□ consisting of a high value signal is outputted from the AND gate circuit 23 to the defrost control section 4 via the defrost command output port 13. The output of the AND gate circuit 26 which inputs the output of the inverter 25 which inverts the output of the fan failure detection section 16 is low in price, and the output of the fan failure detection signal output port 28 has a high value. When the cause of the large temperature difference is a fan failure, the fan failure detection unit 16 outputs a low-value fan stop signal SF.
3 has a low price, and the output of the AND gate circuit 26 has a high value. As a result, a low-value fan failure detection signal is output from the fan failure detection signal output port 28.

In the case of this large temperature difference, since the output of the other comparison circuit 21 of the temperature difference area discrimination section 17 is a high value, each AND gate circuit of the small temperature difference cause analysis section 19 inputs an inverted signal of this high value signal. The outputs of 33 and 36 are both low values, and the gas leak detection signal output port 1-35 and mechanical failure detection signal output port 38 are high values.

If the frost on the cooler is below the specified amount, the fan and refrigeration cycle machinery are operating normally, and there is no leakage of refrigerant into the cold air path, the operating state is normal (normal operating mode). .

In this case, the temperature difference T between the cooler temperature Ta and the blowing cold air temperature Tb is less than or equal to the predetermined maximum temperature difference Tn++ and greater than or equal to the predetermined minimum temperature difference Tl1L, and the temperature difference area determination unit 17 compares the two. The outputs of the circuits 10 and 21 both become high values, and the normal operation command SN is output from the anime game 1 circuit 22 to the temperature adjustment control section 3.

Each AND gate circuit 24 of the large temperature difference cause analysis section 18
．． Since the output of the inverter 12 inputted to the inverter 1-26 is a low value, and the outputs of both the anti-games 1-21 and 26 are both low values, the defrosting command capo-1-13 becomes a low value, which may cause a fan failure. The detection signal output port 28 becomes high. In addition, since the output of the other comparison circuit 21 of the temperature difference region discriminating section 17 is high, the outputs of each AND gate circuit f$33.36 of the small temperature difference cause analysis section 19 are both low in price. The leakage detection signal output port 35 and the mechanical failure detection signal ratio capo-1-38 become high values.

If there is a mechanical failure during the refrigeration cycle (mechanical failure mode) or if refrigerant is leaking from the cooler to the cold air path (gas leakage mode), the temperature between the cooler temperature Ta and the cold air temperature Tb The difference T, is below a predetermined minimum temperature difference TnL. In such a case, the outputs of both comparison circuits 10.degree. 21 of the temperature difference region determination section 17 both become low values. As a result, the output of the AND gate circuit 22 becomes a low value, and the operation of the temperature adjustment control section 3 is stopped. In the large temperature difference cause analysis section 18, the outputs of the AND gates 23 and 24 and the defrosting command output port 13 have low values, and the output of the AND gate 26 has a high value or a low value depending on whether or not there is a fan failure. That is, when a fan stop failure occurs, the inputs of the AND gate 26 are both high, and the output thereof is high. As a result, a low-value fan failure detection signal is output from the fan failure detection signal output port 28. When there is no fan failure, the output of the inverter 25 is low, so the output of the analog game 1 circuit 26 is low, and the fan failure detection signal output port 28 is high. When the cause of the small temperature difference is a mechanical failure during the refrigeration cycle (machine failure mode), the temperature Tb of the cold air blown out is close to the outside air temperature, and when the cause is a leakage of refrigerant from the cooler to the cold air path (gas leakage) mode), the blown-out cold air temperature Tb is set to the predetermined blown-out cold air minimum temperature Tbff1. , it becomes even colder than. Therefore, when the cause of the small temperature difference is a mechanical failure during the refrigeration cycle (a-mechanical failure mode), the comparator circuit 3
1 becomes a high value, and as a result, the output of the AND gate circuit 33 becomes a low value, and as a result, the output of the gas leak detection signal output port 35 becomes a high value. In addition, since the output of the AND gate 36 becomes a high value, the mechanical failure detection signal output port 3B outputs a low value (
A mechanical failure detection signal will be output. When the cause of a small temperature difference is a leak of refrigerant from the cooler to the cold air path (gas leak mode), the output of the comparison circuit 31 becomes a low value, and the output of the AND gate circuit 33 becomes a high value, resulting in gas leakage. A low-value mechanical failure detection signal is output from the detection signal output port 35.

Further, since the output of the AND gate 36 becomes a low value, the mechanical failure detection signal output port 38 becomes a high value.

The safety operation control circuit 15, which manually receives the fan failure detection signal, gas leak detection signal, and mechanical failure detection signal, operates a display device that displays fan failure, gas leak, and mechanical failure, respectively, in response to each signal, and also operates a buzzer. A notification device that notifies the occurrence of a failure using audio, music, etc. is activated, and if necessary, the machine that is in the refrigeration cycle takes safety actions such as stopping or closing valves.

In this way, in this control circuit, the operating state monitoring circuit 14
In this system, only three detection means, namely, the cooler temperature sensor 5, the blowout cold air temperature sensor 6, and the fan failure detection unit 16, are used to determine the operating status from normal operation mode, frost formation mode, fan failure mode, mechanical failure mode, and gas leakage mode. It is classified into five modes and detected, and operation control corresponding to each mode is executed. In defrosting, as shown in FIG.
D) It will be executed when the temperature exceeds l.

FIG. 7 is a block diagram showing a modification of the driving state discriminating circuit 14. As shown in FIG.

This operating state determination circuit 14 includes a cooler temperature sensor 5,
This embodiment is the same as the above-mentioned embodiments in that it includes a blowout cold air temperature sensor 6, a temperature difference calculating section 7, a normal operation command output boat 11, and a defrosting command output boat 13.

It also includes a reference voltage generation circuit 9 that outputs a reference voltage signal corresponding to a predetermined maximum temperature difference Tnu, and a voltage signal corresponding to the temperature difference T that is calculated by inputting this reference voltage to the positive phase input terminal. This embodiment is the same as the embodiment shown in FIGS. 1 and 2 in that it includes a comparator circuit 10 that inputs the temperature difference signal SD to its negative phase input terminal and an inverter 12 that inverts its output.

Furthermore, the reference value setting circuit 30 outputs a reference signal corresponding to the predetermined minimum cool air temperature Tb, , fi, and the output of the cool air temperature sensor 6 is input to the positive phase input terminal, and the reference voltage generating circuit 30 Comparison circuit 3 that inputs the output to the negative phase input terminal
1, a fan failure detection signal output port 28, a gas leak detection signal output port 35, and a mechanical failure detection signal output port 38.

This operating state determination circuit 14 further includes a reference voltage generation circuit 39 that outputs a reference voltage signal Samay corresponding to a predetermined maximum cooler temperature Ta□8, and a negative phase input terminal for the output of the cooler temperature sensor 5. input, reference voltage generation circuit 39
a comparator circuit 40 which inputs the output of the above to the positive phase input terminal, an AND gate circuit 41 which inputs the output of each comparator circuit 10, 31°40 and whose output terminal is connected to the normal operation command output port 11; An AND gate circuit 42 is provided to manually input the output of the inverter 12 and the output of the fan failure detection section 16.

In the above configuration, in the case of frost formation mode or fan failure mode, the output of the comparison circuit IO becomes a low value, and the output of the AND gate circuit 41 and the normal operation command output port 1
1 is a low value. Since the output of the inverter 12 becomes a high value, if there is no fan failure, the output of the AND gate circuit 42 becomes a high value, and the defrost command S is sent from the defrost command output port 13.
. , while the fan failure detection signal output port 2
8 is a high price. When there is a fan failure, the output of the AND gate 42 and the defrosting command output port 13 become low values, while the fan failure detection signal output port 28 outputs a low value fan failure detection signal. In addition, in the case of gas leak mode, the comparator circuit 31 has a low value, so the output of the AND gate 41 and the normal operation command output port 11 have low values, and a low value gas leak detection signal is output from the gas leak detection signal output port 35. is output. Furthermore, in the case of mechanical failure mode, the comparator circuit 40 becomes a low value, the output of the AND gate circuit 41 and the normal operation command output port 11 become low values, and the low value mechanical failure detection signal is output from the mechanical failure detection signal output port 38. A signal is output.

Of course, the freezing/refrigerating open-case cooler frost monitoring device according to the present invention is not limited to the above-mentioned embodiment. For example, in the embodiment shown in FIG. It is possible to make the set voltages of the circuits 30 and 39 the same, and in this case, it is possible to make one of the side reference voltage generation circuits 30 and 39 serve as the other, and to omit the other one.

〔Effect of the invention〕

As described above, the method for monitoring frost formation on the cooler of a frozen/refrigerated open showcase according to the present invention determines the temperature difference between the temperature of the cooler and the temperature of cold air, and determines whether the temperature difference exceeds a predetermined value. Since it is determined whether the amount of frost on the cooler exceeds the predetermined amount based on the amount of frost formed on the cooler, it can be accurately determined whether the amount of frost on the cooler exceeds the predetermined amount without being influenced by outside air. As a result, it is possible to detect when the frost on the cooler reaches a predetermined amount and start defrosting at that point. This can be done for as long as possible to prevent deterioration in the quality of stored products.

In addition to the above-described effects, the frost formation monitoring device for the cooler of a frozen/refrigerated open showcase according to the present invention has advantages such as a simple circuit configuration of 11"L and can be implemented at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a main part of a frost monitoring device for a cooler of a freezing/refrigerating open showcase according to the present invention, and FIG. 2 is a main part of a control circuit for a freezing/refrigerating open showcase according to the present invention. FIG. 3 is a block diagram of the main parts of an operating state monitoring circuit according to another embodiment of the present invention, and FIG. 4 is a control circuit for a frozen/refrigerated open showcase according to another embodiment of the present invention. Fig. 5 is a logic circuit diagram of the main part, Fig. 6 is a temperature change diagram showing changes in outside air, cooler temperature, and cold air temperature in the embodiment described in -.
FIG. 8 is a block diagram of an operating state monitoring circuit for a frozen/refrigerated open showcase according to another embodiment of the present invention.
The figure is a temperature change diagram in a conventional defrosting method. 5... Cooler temperature sensor, 6... Cold air temperature sensor, 7... Temperature difference calculation section, 8... Frost formation determination means (frost formation determination section), 18... Frost formation determination means (Large temperature difference cause analysis department). Patent applicant: Japan Maintenance Co., Ltd.)
■ ('l”) (Y)

Claims (2)

[Claims] (1) Detect the cooler temperature and the cold air temperature, calculate the temperature difference between the cooler temperature and the cold air temperature, and determine the amount of frost on the cooler depending on whether the temperature difference is larger than a predetermined value. The refrigeration system is characterized by determining whether or not the amount of frost on the cooler exceeds a predetermined amount, and outputting a defrosting command to start defrosting the cooler when it is determined that the amount of frost on the cooler exceeds a predetermined amount. How to monitor frost formation in refrigerated open showcases. (2) A cooler temperature sensor that detects the cooler temperature and outputs an electrical signal corresponding to the cooler temperature; and a cooler air temperature sensor that detects the temperature of the cold air blown out and outputs an electrical signal corresponding to the cold air temperature. A sensor, a temperature difference calculation unit that calculates the temperature difference between the cooler temperature and the cold air temperature blown out, and a temperature difference calculation unit that calculates whether the amount of frost on the cooler exceeds a predetermined amount depending on whether the calculated temperature difference is larger than a predetermined value. The refrigeration system is characterized in that it is provided with a frost formation determination means that outputs a defrosting command to start defrosting when it is determined that the amount of frost formation exceeds a predetermined value.
Frost monitoring device for refrigerated open showcases.