Abstract:
A control circuit for a cool/heat pump in which two separate motors are utilized, each with a main winding and an auxiliary winding. A single dual rated capacitor is provided in series with the auxiliary windings and an alternating current line and a selectively operative switch, which may be in the form of a thermostat, is provided in series between one of the alternating current lines and a main winding of one of the motors to selectively terminate power to that main winding while maintaining power to both auxiliary windings and the main winding of the other motor. Such a control circuit allows a de-icing operation with the cool/heat pump working in a heating mode, without blowing cold air into the room which is to be heated.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a control circuit and more specifically to a control circuit for a cool/heat pump room air conditioner. 
     Room air conditioners are well known and are of the type that generally fit in a window or in a sleeved opening formed through the wall of a room. Most such room air conditioners utilize a fluid refrigerant which is caused to alternately expand and condense to provide the desired cooling effect inside the room and to expel heat outside of the room. The refrigerant flows through a system which includes an evaporator where liquid refrigerant is permitted to evaporate thereby cooling a coil surface of the evaporator in order to extract heat from air within the room. A fan is used to cause room air to flow over the coil of the evaporator. The refrigerant then flows to the compressor where it is returned to a high pressure gas state. The refrigerant then flows to a condenser, generally positioned outside of the room wherein the refrigerant vapor condenses and gives off heat. Generally a fan is also provided on the condenser side to provide a flow of outside air over the condenser coil to remove heat therefrom. Refrigerant then flows to an expansion device where it is turned to a low pressure liquid state before flowing again to the evaporator. 
     It is known that by reversing the flow through the system, the air conditioner can act as a heat pump to draw heat from exterior of the room and to provide that heat to the interior of the room. In such an arrangement the refrigerant flow is reversed and what was the evaporator now acts as the condenser to release heat and what was the condenser now acts as the evaporator to absorb heat from the surrounding air. 
     Control systems for room air conditioners are well known and in such control circuits generally include a switch for powering a compressor motor and a fan motor as well as sometimes controlling other components. 
     Generally the type of motors utilized in such air conditioners have both a main winding and an auxiliary winding with capacitors in series with the auxiliary winding. Control circuits which have been provided for such air conditioning units and motors are disclosed in the following U.S. Pat. No(s). 2,242,370; 2,782,351; 3,045,159; 3,146,387; 3,385,077; and 3,852,648. Such circuits are limited to air conditioner units, however, and do not appear to provide the necessary controls for heat pump operation. 
     The above listed patents describe various types of control circuits and including circuits in which a single, dual rated capacitor is used in series with each of the two motor auxiliary windings. 
     Applicant has determined that in the application where such a room air conditioner is also being utilized as a heat pump, additional considerations arise over those necessary for controlling a room air conditioner, including the need to provide a de-icing circuit for the evaporator when the unit is being operated as a heat pump and, during such operation, the refrigerant flow must be reversed so as to provide a warming to the evaporator coil. Since the heat pump is generally being used to heat the interior space, it would be detrimental for the interior fan to run during the de-icing operation because during the de-icing operation the interior coil is acting as an evaporator and would thus result in cold air being blown from the evaporator coils. Therefore, it would be an improvement in the art for there to be provided a control circuit for a cool/heat pump room air conditioner which will control the various components with minimum number of parts, yet provide the desired heating and cooling and prevent undesired cooling effect within the room during a de-icing operation. 
     SUMMARY OF THE INVENTION 
     The present invention provides a control circuit for a cool/heat pump room air conditioner which utilizes a minimum number of circuit parts, including only a single dual rated capacitor to control both the compressor motor and the fan motor, the control circuit providing means for terminating power to the main winding of one of the motors while maintaining power to both the auxiliary windings and the other main winding of the second motor. The means for terminating power to one of the main windings is a thermostat switch which also controls a solenoid to provide a reversing of the refrigerant flow through the cool/heat pump room air conditioner system. Thus, when the thermostat detects a condition which requires de-icing of the evaporator, the switch opens, terminating power to the fan motor and the solenoid, thus reversing the flow of refrigerant causing the evaporator to now function as a condenser and the interior condenser to operate as an evaporator. Thus, the exterior evaporator, now operating as a condenser, gives off heat to warm the coils and to effect a de-icing of that heat exchanger and, as the refrigerant flows through the interior heat exchanger, no fan is operated and therefore the cooling effect of the interior heat exchanger is kept at a minimum. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a cool/heat pump room air conditioner embodying the principles of the present invention. 
     FIG. 2 is a top elevational view of the cool/heat pump of FIG. 1 with the cover removed. 
     FIG. 3 is a sectional view through a central portion of the cool heat pump showing the &#34;exterior&#34; side of the unit. 
     FIG. 4 is a side sectional view of the cool/heat pump of FIG. 1. 
     FIG. 5 is an electrical schematic of the control circuit for the cool/heat pump. 
     FIG. 6 is a schematic diagram of the refrigerant system with a reversing valve in a heating position. 
     FIG. 7 is a schematic illustration of the refrigerant system with a reversing valve shown in a cooling position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a cool/heat pump room air conditioner generally at 20 which embodies the principles of the present invention. Although the present invention may be utilized in other circuits where two motors are to be controlled, it has particular utility in a cool/heat pump room air conditioner and will be described in that environment. 
     The cool/heat pump room air conditioner has a front panel 22 which faces the interior of a room to be cooled or heated when the cool/heat pump unit is placed in an open window or in a through the wall sleeve. A central portion 24 of the panel constitutes an air inlet grill through which air flows into a portion of the cool/heat pump unit. The air is returned to the room through a pair of laterally spaced outlet grills 26. 
     A plurality of controls 28 are provided on a control panel area above the inlet grill. Positioned above the inlet grill 24 and below the controls is a slot 30 within which is received an air filter element 32. 
     The internal components of the cool/heat pump unit are shown in greater detail in FIGS. 2-4. Directly behind the front inlet grill is located a first heat exchange unit 60 which is mounted within a sheet metal shroud or housing 46. The housing 46 has central rear opening 48 which is positioned directly in front of an air moving device, preferably a blower wheel. The blower wheel 50 is mounted on a forwardly extending drive shaft 52 of an electric motor 54. The motor 54 also has a rearwardly extending drive shaft 56 to which a fan blade 58 is mounted. The drive shafts 52, 56 extend along the center line of the cool/heat pump unit. Directly behind the fan blade is a second heat exchanger 44. A compressor 62 is provided as is known in the art. 
     The forwardly extending drive shaft 52 extends through an opening 64 in a barrier wall 66 provided between the blower wheel 50 and the motor 52. The barrier wall 66 separates the two heat exchange units 44, 60 to prevent a short circuiting of the thermal effects generated by the unit. A barrier of expanded polystyrene 68 is provided along the barrier wall 66 which provides an insulation against heat transfer. 
     A base pan assembly 70 is provided as a mounting platform for a large number of the components of the cool/heat pump unit. 
     A control circuit for the cool/heat pump is illustrated in FIG. 5. A control switch 100, which may be one of the controls 28 on the front panel of the unit shown in FIG. 1 is provided for the user to select an operating mode for the cool/heat pump. The illustrated operating modes include three speeds each of heating and cooling, a fan only operating mode and an off mode. Other components of the circuit include the fan motor 54, a motor 102 for the compressor 62, an adjustable thermostat 104 having an upper temperature contact 106 and a lower temperature contact 108, a de-icer thermostat 110, a solenoid 112 and a single dual rated capacitor 114. Single phase alternating current is provided to the circuit on a pair of lines 114, 116. Fan motor 54 has a main winding 120 and an auxiliary winding 122 and the compressor motor 102 also has a main winding 124 and an auxiliary winding 126. 
     Alternating current line 114 is connected to the main and auxiliary windings 120, 122, 124, 126 through the control switch 100 and appropriate contacts therein. For the connection to the fan motor auxiliary winding 122, the alternating current line 114 is connected to a selected one of lines 130, 132, 134 depending upon whether the fan is to be run at a high, medium or low speed. Lines 130, 132 and 134 are connected to different taps in the auxiliary winding 122 of the fan motor. The main winding 120 is then connected through the de-icer thermostat 110 in series with lines 136 and 138 to the second line 116 of the alternating current supply. The auxiliary winding 122 is connected through line 140 to a terminal 142 of the capacitor 114. A central terminal of the capacitor 114 in turn is connected to the second alternating current line 116. 
     The compressor motor 102 main winding 124 is connected to the first alternating current line 114 through appropriate contacts in the control switch 100. During a heating mode of operation the connection from line 114 to the main winding is through line 142 and upper temperature contact 106 in line 144. During cooling operation line 114 is connected to the main winding 124 through line 146, lower temperature contact 108 and line 144. An overload fuse 148 is provided in line 144 to protect the compressor motor 102. The main winding 124 is then connected through line 150 to alternating current line 116. The compressor auxiliary winding 126 is connected to line 114 in precisely the same manner as the main winding. The auxiliary winding 126 is then connected through line 154 to a second terminal 156 of capacitor 114 which, again, is then connected directly to alternating current line 116 at its center terminal. 
     Solenoid 112 operates a pilot valve 160 as best seen in FIGS. 6 and 7. The pilot valve in turn is connected to a main valve 162 which provides for reversing flow of refrigerant through the system. Specifically, the compressor 62 is utilized to compress a refrigerant and to pump it, under high pressure, through line 170. Line 170 connects to an inlet port 172 on valve 162. In the position of valve 162 in FIG. 6 where a valve slide member 174 has been moved to a right hand position by the pilot valve 160, the refrigerant follows a flow path 176 to an outlet port 178 from where it flows through line 180 to heat exchange unit 60. In this arrangement heat exchange unit 60 acts as a condenser to reject heat to the surrounding air. The refrigerant condenses from a gas to a liquid in heat exchange unit 60. 
     From heat exchange unit 60 the refrigerant flows through line 182 to the second heat exchange unit 44 which, in this operating mode, acts as an evaporator where the now liquid refrigerant evaporates to a gas and absorbs heat from the surrounding air. From the second heat exchange unit 44 the now gaseous refrigerant flows through line 184 to a second inlet port 186 of valve unit 162 and along a flow path 188 to a second outlet port 190 of the valve member 162. From outlet port 190 the low pressure gaseous refrigerant flows through line 192 to a suction inlet on the compressor 62. 
     In a second position of solenoid 112, the pilot valve 160 is moved to a second position thus permitting its suction connection line 158 to be connected with line 159, and its pressure connection line 161 to be connected with line 163 to draw the slide member 174 to a left most position. Again, the compressor 62 operates in the same fashion and causes a flow of high pressure gaseous refrigerant through line 170 to inlet port 172. The refrigerant now flows on flow path 194 to what is now an outlet port 186 and through line 184 to the heat exchange unit 44. Now heat exchange unit 44 acts as a condenser rejecting heat to the surrounding atmosphere. The now liquid refrigerant flows through line 182 to the second heat exchange unit 60 which, in this mode of operation, functions as an evaporator to return the refrigerant to a gaseous state. The now low pressure liquid flows through line 180 through what is now an inlet port 178, along flow path 196 to outlet port 190, and through line 192 to again return to the suction side of the compressor 62. 
     In the heating mode selected by selector switch 100, the solenoid 112 is energized and thus causes the slide member 174 of valve 162 to move to the right most position as shown in FIG. 6. In this condition the heat exchange unit 60, which is positioned towards the interior of the room, acts as the condenser and gives off heat to the room. Heat is absorbed into the refrigerant in heat exchange unit 44 which is positioned on the exterior of the room. 
     During certain operating conditions it is possible for the coils of the exterior heat exchange unit 44 to become coated with ice due to condensation of moisture in the outside air on to the coils which have a temperature below freezing. This condition is not desirable in that it severely impairs the efficiency of the outside heat exchange unit 44. Therefore, the de-icer thermostat 110 is provided to detect such icing condition, as is known in the art. 
     When such an icing condition is detected, the thermostat 110 causes a switch connection to open thereby de-energizing the solenoid 112 causing the slide member 174 to move to the position shown in FIG. 7. In this position the outside heat exchange unit 44 now acts as the condenser whereby the heat given off by the refrigerant condensing causes the ice on the heat exchanger coils to melt. Since this de-icing operation occurs while the interior of the room is to be heated, it is not desirable to have the fan motor 54 operating (which would blow cool air into the room), although it is required to have the compressor motor 102 operating. Therefore, the de-icer thermostat 110 is also positioned in series with the main winding 120 of the fan motor 54. Thus, when the de-icer thermostat detects an icing condition, the main winding of the fan motor is de-energized. The main and auxiliary windings 124, 126 of the compressor motor 102 continue to be energized as does the auxiliary winding 122 of the fan motor. The energization of the fan motor auxiliary winding is not sufficient to cause the fan motor to operate, but it does provide the benefit of generating heat in the fan motor (which is positioned on the exterior (cold) side of barrier wall 66) thus assisting in the start up of the fan motor when the unit is returned to the heating mode. Since the start up of a cold motor is significantly harder and more energy consumptive than start up of a warm motor, the continued energization of the auxiliary winding to the fan motor provides a real benefit. 
     The use of a single dual rated capacitor 114 in the circuit significantly reduces the complexity of the circuit and reduces its cost in the reduction of components and in assembly time. During the cooling mode selected by selector switch 100 the solenoid 112 is not energized and thus operation and position of valve 162 is that shown in FIG. 7. During such operation, however, power is supplied to the fan motor main winding 120. 
     As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.