Refrigerant charge slide calculator

A refrigerant slide calculator for determining proper refrigerant charge displays on a single side representations for performance characteristics, measured temperatures and pressures for more than one refrigerant, preferably both R22 and R410a. The slide calculator has an operator a sleeve, with the operator being a card which slidably fits within the sleeve. The operator has superheat data areas and subcooling data areas. The sleeve has different portions defined as a superheat region and a subcooling region, with windows matching the various measured wet bulb and dry bulb temperatures. In the superheat region, vapor pressure windows are provided which correspond to the different refrigerants, and a singular required vapor line temperature is displayed corresponding required superheat. In the subcooling region, a required liquid line temperature window and required subcooling data field are provided along with a liquid pressure window representing two different refrigerants.

TECHNICAL FIELD OF THE INVENTION

The present invention relates in general to air conditioning systems, and in particular to a slide calculator for determining proper refrigerant charge for operating an air conditioning system.

BACKGROUND OF THE INVENTION

Prior art slide calculators have been provided for calculating proper refrigerant charge for refrigeration systems, such as for use in servicing building air conditioning systems for heating and cooling. Typically, the pressure and temperature of the refrigerant at one point in the refrigeration system is measured, and then compared to desired refrigeration performance characteristics to determine whether there is a proper amount of refrigerant within the system. The prior art slide calculators have been used to translate the measured temperature and pressure for comparison in relation to the performance characteristics. However, prior art slide calculators provide data in tabular format that is data tables, rather than graphical representations in which positions in linear and logarithmic scales represent various changes in temperatures and pressures according to corresponding performance characteristics and measured pressures and temperatures. Recently, due to environmental concerns, refrigerants such as R22 have been replaced with new refrigerants such as R410a which are perceived as less harmful to the environment. The older refrigerants utilize hydro fluorocarbons and newer refrigerants utilize difluoromethane. This has resulted in prior art refrigerant charge slide calculators being required for each type of refrigerant being used. This is cumbersome with service technicians often required to carry numerous refrigerant charge slide calculators, at least one per type of refrigerant used. Since prior art slide calculators use tabular forms rather than graphical representations, it is not practical to provide prior art slide calculators with tabular representations in which more than one type of refrigerant is displayed for a refrigerant charge slide calculator.

SUMMARY OF THE INVENTION

A refrigerant slide calculator is disclosed in which the proper refrigerant charge for more than one refrigerant may be determined using a single calculator, with representations for performance characteristics and measured temperatures and pressures displayed on a singular side of the slide calculator for more than one refrigerant. A superheat region and a subcooling region are provided on different portions of a sleeve for the refrigerant charged slide calculator. The superheat region will have a wet bulb temperature window for the interior space being cooled, and a required superheat window based on the ambient dry bulb temperature exterior of the space being cooled. A vapor pressure window is provided for a first type of refrigerant, preferably R22, and a second vapor pressure window is provided for a second type refrigerant, preferably R410a. Then, a singular required vapor line temperature for a corresponding user indexed pressure is displayed in a singular graphical representation line. In the subcooling region, a required liquid line temperature window and a unit required subcooling data field are provided along with a liquid pressure window that is indexed to represent the pressure of the corresponding refrigerant. The sleeve further has a superheat instruction field and a subcooling instruction field for providing instructions for use. The operator is a card which slidably fits within the sleeve. The sleeved superheat data areas and subcooling data areas with various data fields providing desired performance characteristics and measured pressures and temperatures within respective ones of the various windows.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 3are side elevation views of a refrigerant charge slide calculator having a sleeve26andFIGS. 2 and 4are side elevations view of an operator58for the refrigerant charge slide calculator.FIG. 3is a depiction of a refrigerant slide calculator, by which the various fields for the sleeve may be viewed. The sleeve26has a superheat region28and a subcooling region30. The superheat region28includes a wet bulb temperature window32, a required superheat window34, a required vapor line temperature window36, and a first window38for depicting the vapor pressure for one type of refrigerant, preferably R22, and a second vapor pressure window40for depicting a second type of refrigerant, preferably R410a. The subcooling region30has a required liquid line pressure window42, a liquid pressure window44for a first type of refrigerant, preferably R22, and a liquid pressure window46for a second type of refrigerant, preferably R410a. The superheat region28further includes a superheat instruction field50, in which instructions for operation of the refrigerant slide charge calculator24are provided. Similarly, a subcooling instruction field52provides instructions within the subcooling region30for an operator to use the refrigerant charge slide calculator24.

The operator58is preferably a sliding card which slidably engages within the sleeve26for aligning various data fields64through78with corresponding windows noted above for the sleeve26. Various performance parameters and characteristics are displayed within or by the windows aligning with various ones of the fields64through78according to the procedures noted herein below. The operator58has the superheat data area60and a subcooling data area62for aligning with respective ones of the superheat region28and the subcooling region30of the sleeve26. The data field64corresponds to window32for entry of the wet bulb temperature. The data field66corresponds to window36which provides a listing of the desired vapor line temperature for proper operation of the refrigeration system. The data field68corresponds to a tabular listing or tabular format for the required superheat for the unit to operate properly. The data field70corresponds to the window40, the entered vapor pressure for the second refrigerant R410a. The date field72corresponds to the window38for entry of the measured vapor pressure of the first refrigerant, preferably R22. In the subcooling data area62, the data field74corresponds to the window42for display of the desired liquid line temperature for proper operation of the refrigeration system. The data field76corresponds to the window44for indexing of the liquid line pressure measured of the first refrigerant R22. The data field78corresponds to the data field displayed through the window76for displaying the measured liquid line pressure of the second refrigerant, preferably R410a.

The superheat region28of the refrigerant charge slide calculator24is used for refrigeration systems which have pistons with a fixed orifice. First, the required superheating is needed to determine the performance characteristics for the refrigeration system. This is preferably done by taking a wet bulb temperature of the airflow entering the evaporator coil of the system, and measuring the vapor pressure and temperature of the refrigerant at the suction line to the compressor. The indoor wet bulb temperature is indexed in window32by sliding the card until it is displayed within the window32. Then the window34is viewed with graduated markings48alongside the window34to align the dry bulb temperature of the air flow across the condenser with a numerical reading displayed within the window34. The alignment of the numbers displayed in the window34with the window34is set by aligning the measured wet bulb temperature within the window32. The reading in the window34then goes through required superheat that is superheat for the refrigerant at the suction line suction of the compressor. Then, the measured vapor pressure at the suction line is set by indexing the correct numeral display with the respective ones of the windows38and40, depending upon which of the refrigerants is contained in the system. For this alignment, the operator58is moved within the sleeve26until the proper measured pressure aligns respective with markings50and52within respective ones of the windows38and40. Once the operator is properly aligned within the sleeve26such that the proper measured vapor pressure at the suction is aligned with respective ones of the alignment marks50and52, then the window36is viewed to determine the required vapor line temperature at the suction for the compressor. Graduation markings54are printed along the sleeve26immediately beneath the window36to find a corresponding required superheat previously determined in window34. If this temperature is higher than the actual temperature measured, then refrigerant should be added to the system. If the required vapor line temperature actually measures lower than that displayed in the window36, then refrigerant should be removed from the system and then retested until the measured vapor line temperature closely approximates that of the required temperature at the section.

For subcooling, the subcooling region30is used when there is a TXV valve present, that is an expansion valve which regulates the refrigerant flow according to measured parameters. This is well know in the art. Here, the amount of subcooling is either determined by reviewing manufacturer specifications for a particular unit, or using an approximate value such as 8-10 degrees. Then, the liquid line pressure and temperature are measured at one point, on the discharge of the condenser, or prior to the expansion valve, and then the measured pressure of the refrigerant is indexed in the corresponding refrigerant window, for respective ones of the refrigerant windows44or46, depending on the type of refrigerant, to align alignment markings55and57with the pressures displayed on the operator58which are visible through the respective ones of the windows44and46until the operator is properly aligned with the sleeve26. Then, the graduated markings displayed on the sleeve26beneath the window42are viewed for referencing the subcooling and determining the required temperature of the liquid line for proper operation of the refrigeration unit. For subcooling, if the measured temperature is higher than the desired liquid line temperature, then refrigerant should be added. If the measured liquid line temperature is lower than the desired liquid line temperature, then refrigerant should be removed, and the unit retested until it is operating within acceptable ranges.

The present invention provides a refrigerant charge slide calculator24for determining when proper charge or whether to add or remove refrigerant from an air conditioning system for both subcooling and superheating on a single side of the charge slide calculator24for two different refrigerants. Various temperature data is displayed in graphical presentation on the operator58within which is slidably extensible from within the sleeve26.