US 3831663 A
A room air conditioner having an electrical heater that is energized continuously while the evaporator coil is alternately energized and deenergized, in provision of a dehumidification and reheat cycle of operation under conditions characterized by relatively low temperatures and high relative humidity.
Description (OCR text may contain errors)
111 3,831,663 Aug. 27, 1974 United States Patent [191 Pithie Butterfield............................ Newton............,...
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 Appl. No.: 348,203
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BACKGROUND OF THE INVENTION This invention relates to air conditioners, and more particularly to improvements in room air conditioners.
SUMMARY OF THE INVENTION In achievement of the foregoing as well as other objectives, the invention proposes apparatus affording improved humidity control for a room air conditioner operating over a wide range of dry bulb temperatures, which apparatus is characterized by inclusion of a cyclically operated refrigerant cooling coil means, and means for energizing a heating element continuously while air is caused to flow sequentially over the cooling coil means and the heating element, in provision of a dehumidification phase of operation. Should the dry bulb temperature rise above a predetermined value, the control apparatus will operate to deenergize the heating element as the cooling coil means continues to perate.
Advantageously, the improved control means is, in effect. relative-humidity responsive without need for a humidistat, due to the fact that as the relative humidity in the conditioned space decreases, the cooling capacity ofthe air conditioner, previously dissipated as latent heat of condensation in the removal of moisture, becomes more effective in removal of sensible heat, thereby to lower the ambient temperature in an amount sufficient to deenergize the compressor. Lowering of the moisture content of the air leaves outer, heatexchange surfaces of the evaporator coil means comparatively dry, so that minimal re-evaporation of moisture from the coil means will occur.
The manner in which the foregoing as well as other objectives and advantages of the invention may best be achieved will be more fully understood from the follow ing description, taken in light of the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective showing of a room air conditioner embodying the invention;
FIG. 2 is a plan view of the air conditioner shown in FIG. 1, with the top wall removed and other portions fragmented for convenience of illustration; and,
FIG. 3 is a diagrammatic showing of electrical con trol and energization circuitry for apparatus seen in the preceding figures, and embodying features of the invention.
. DESCRIPTION OF THE PREFERRED EMBODIMEN With more detailed reference to the drawing, there is seen in FIGS. 1 and 2 a room air conditioner 10, of the window-mounted type, including an outer shell 11 and a front wall provided with inlet and outlet air grilles 12 and 13, respectively. The front wall further includes a control panel 14 provided with a thermostat control knob 15 and a function selector knob 16, both to be described in more detail in what follows. A third control knob 17 operates means (not shown) for venting the room to the outside. I
With further reference to FIG. 2, in which the top wall of outer shell 11 has been removed, a base pan 21 serves as the bottom wall for the air conditioner and serves as a frame for supporting a central, vertically extending partition 22 that cooperates with outer shell 11 to form a condensing unit compartment to one side and an evaporator compartment to the other side. Side walls of shell 11 are provided with air inlet grilles 18 for the condensing unit compartment (see also FIG. 1).
In the condensing unit compartment, base pan 21 supports a condensing coil 23, a motor-compressor 24, a condenser fan 25, a fan motor 26, and a fan shroud 32. In the evaporator compartment, base pan 21 supports an evaporator coil 27, a blower housing 28, a blower wheel 29, and electrical heater coils 30 and 31. Compressor 24, condenser coil 23, and evaporator coil 27 are connected in the usual series refrigerant flow circuit, with a capillary tube restrictor (not shown) serving as the means interconnecting condenser 23 and evaporator 27.
With particular reference to FIG. 3, energy to operate air conditioner 10 is derived from a source of voltage L, connected on the one hand to a selector switch 35, and on the other hand to a thermostatic switch 36. Selector switch 35 includes four switch arms a, b, c and d each connectible to a corresponding one of four contacts 1, 2, 3 and 4. Switch arm 35b further is connectible with a contact 5. Thermostatic switch 36 includes a pair of single-pole, double-throw switches a and b, the arms of which are connected to the source of voltage L and the contacts 6, 7 and 8 of which are connected as shown to one side of the motorcompressor, to one side of electrical heaters, 30, 31, the purpose of which will be described in more detail, and to one side of the coil 37a of fan motor relay 37 which controls a single-pole, double-throw relay switch 37b interconnecting one side of voltage source L and the high and low speed terminals (see HI and LO, FIG. 3) of fan motor 26. Of selector switch 35: contact 1 is connected to the other terminal of fan motor 26; contact 2 is connected to heater element 31; selector switch contact 3 is connected to heater element 30; selector switch contact 4 is connected to motor compressor 24; and selector switch contact 5 is connected to the fan motor relay coil 37a.
In keeping with objectives of the invention, operation of the apparatus thus far described will be explained in detail in connection with its Dehumidify mode, as may be selected by setting knob 16, and with reference to the switch positions seen in FIG. 3. In this illustrated mode of operation, and with reference also to the switch chart seen in FIG. 3, contacts 1, 2 and 4 of switch 35 are closed (X), and contacts 3 and 5 of the same switch are open (0). Also, and further by way of example, thermostat '36 is set through selective adjustments of knob to its coldest position, so that its switches will be positioned as shown in F IG. 3 for a corresponding room temperature of about 67.5F.
Closure of contact -1 by arm 35a causes fan motor 26 to be energized at its low speed; closure of contact 35-2 by arm 35b, together with normally-closed highlimit thermostat 33, establishes an energization circuit for heater 31, but since contact 367 is still open, it will not be energized; and closure of contact 35-4 by arm 35d establishes an energization circuit for compressor 24 along with closure of contact 366. Closure of the switches in the aforementioned combination energizes motor-compressor 24 and fan motor 26 at its low speed. Operation of the fan and motor compressor progressively lowers the room temperature until thermostat 36 senses an air temperature of about 64 F, at which time thermostat switch arm 36a moves to its upper contact 367, thereby energizing heater coil 31, while compressor 24 continues to run. In effecting this mode of simultaneous cooling and reheating, it has been determined, from testing, that by adding electric heat equal to about 45 percent of the rated cooling capacity (BTU/Hr.) of the air conditioner, efficient dehumidification may be achieved in the 65 to 75 F room air temperature range without affecting, to a substantial degree, the dry bulb temperature of the room being cooled.
Upon progressive removal of a preponderance of the moisture from air in the room or enclosure undergoing dehumidification, the sensible heat loading of the compressor will increase progressively, lowering the temperature of the air flowing over the control an amount sufficient (i.e., to about 6l F) to cause the thermostatic switch arm 36b to move to its contact 369, thereby deenergizing motor compressor 24 while fan motor 26 and heater 3] remain energized. As a result of heater energization alone, temperature of the room will rise progressively, and upon the thermostats sensing of a temperature of about 645 F, motorcompressor 24 will again be energized by movement of thermostatic switch arm 36!) to close contact 366.
Since the compressor is caused to cycle between the temperature limits applied to contacts 366 and 369 as shown in the right-hand portion of FIG. 3, the heater energizing contact 367 will remain closed by thermostat switch arm 3611. Should the temperature of air flowing over the thermostat rise, for some reason, to values in excess of 67.5 F, the switch arm 36a will move to open contact 367, leaving heater 31 deenergized, as the compressor continues to operate in its dehumidification cycle.
Although but one mode of operation of the disclosed air conditioner has been described, i.e., the Dehumidify mode, it will be understood that other modes are available upon operation of selector switch knob 16 to position the several arms of switch 35 in accordance with the chart appearing in FIG. 3.
Advantageously, the above disclosed apparatus affords a mode of operation that achieves, over a wide range of dry-bulb temperatures. constant moisture removal and reduction in relative humidity in excess of the capability afforded by conventional room air conditioners of similar size.
1. ln air conditioning apparatus, cooling means, means for energizing said cooling means, heating coil means, means for energizing said heating coil means, a fan means for moving air sequentially over said cooling means and said heating coil means, single selectively adjustable thermostatic control means for regulating energization of said cooling means and said heating coil means in response to dry bulb temperatures of air being caused to move over the cooling and heating coil means, said control means being operable to maintain continuous energization of said heating coil means during cyclic energization and deenergization of said cooling means.
2. Air conditioning apparatus according to claim 1, and characterized in that said control means is operable to effect cyclic energization and deenergization of said cooling means between a first pair of higher and lower temperatures, and of said heating coil means between a second pair of higher and lower temperatures, the lower temperature of said second pair being less than the higher temperature of said first pair but more than the lower temperature of said first pair of temperatures.
3. Air conditioning apparatus according to claim 1 and characterized in that said heating coil means comprises an electric heater.
4. Air conditioning apparatus according to claim 2 and characterized in that said heating coil means comprises an electrical resistance heater.
5. Apparatus according to claim 4 and characterized further in that said cooling means comprises a refrigerant evaporator energizable at above-freezing temperatures, and said means for energizing said cooling means comprises a refrigerant motor-compressor.
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