Abstract: An apparatus and method for operating an air conditioning unit incorporating both an economizer and a two speed fan are described. When the economizer is in operation the fan is typically operated at high speed regardless of refrigeration circuit operation to circulate sufficient outdoor air to the enclosure. When the economizer is closed, indicating the outdoor air is too warm to provide cooling to the enclosure, the fan is typically operated at low speed saving fan energy. An override control is provided for operating the fan at high speed regardless of the outdoor temperature should sufficient cooling demand be detected.

Abstract: Apparatus and a method for providing a combination of non-reverse and reverse defrost for a refrigeration circuit are disclosed. A three-way valve is provided for initially circulating hot gaseous refrigerant directly from the compressor to the heat exchanger requiring defrost. An intermediate header is provided as part of the internal circuiting of the outdoor heat exchanger, said intermediate header serving to direct hot gaseous refrigerant from the three-way valve into all of the circuits of the outdoor heat exchanger simultaneously to effect defrost thereof. If, after a predetermined time period, the first mode of defrost directing hot gaseous refrigerant directly to the outdoor heat exchanger fails to accomplish defrost then the three-way valve is returned to its original position and the system is operated in a second defrost mode with the reversing valve being changed such that the system operates in the cooling mode and the outdoor heat exchanger serves as a condenser until defrost is completed.

Abstract: Apparatus and method of assembly of a heat exchange unit wherein an annular orifice having a U-shaped cross section is assembled to a heat exchange assembly. The grille of the unit is supported on a support ledge of the fan orifice. An annular top cover having an L-shaped cross section may be engaged to the fan orifice to define a control area space therebetween. The top cover engages a top cover support ledge of the fan orifice and the grille engages a grille support ledge of the fan orifice to form a subassembly.

Abstract: Apparatus for modulating the capacity of a reciprocating compressor having a cylinder chamber and a valve assembly extending over the cylinder chamber, defining fluid inlet and outlet paths, and including a suction valve for regulating vapor flow through the inlet path. The capacity modulating apparatus comprises a lever, a fulcrum, and control means. The lever extends through the fluid inlet path and above the suction valve, and has a first end located outside the valve assembly and a second end engaging the suction valve. Both the fulcrum and the control means engage the lever, and the control means is provided for applying a variable force to the lever wherein the lever transmits the force to the suction valve to urge the suction valve to an open position.

Abstract: Apparatus for securing wires passing through a partition of an air conditioning unit is disclosed. A wire slot having rounded edges is formed in a partition. A wire seal is slidably secured to the partition having a flare portion extending through the wire slot. Upon assembly, the wire seal is slid downwardly with the flare portion extending through the wire slot such that the wires are secured at the bottom of the slot and the remainder of the slot has a body portion of the wire seal preventing air flow therethrough. The wire seal is secured in position via fastening means and the flare portion acts to not only compress the wires at the bottom of the wire slot but to angle them downwardly preventing moisture from flowing along the wires into the indoor section of the unit.

Abstract: A fluid temperature measuring device, which includes a resistance temperature detector (RTD), is disclosed for measuring the temperature of a fluid flowing through one of several heat exchange conduits which empty into a channel of a heat exchanger of a refrigeration system. The device is simple, inexpensive, reliable, easy to replace, and may be used with a microprocessor control system for the refrigeration system.

Abstract: A feedback control system for a pulsed direct current (DC) arc welding system is disclosed wherein the duty cycle of current pulses supplied by a power supply is controlled in response to resistance sensed at the arc gap of the system. The circuit comprises a voltage sensor, a high-low regulator, and a pulse width signal generator. The voltage sensor senses the voltage drop across the arc gap. This voltage is directly proportional to the resistance at the arc gap. The high-low regulator responds to the sensed voltage to generate an output signal when the voltage drop across the arc gap exceeds a high limit or is below a low limit. This output signal alters the control signal from the pulse width signal generator which controls the arc welding system power supply.

Abstract: An electric terminal comprising a body, a plurality of terminal pins and terminal nuts, a pin retainer, and retainer connecting apparatus releasably connecting the pin retainer to the terminal body. The terminal pins longitudinally extend through the body, and the terminal nuts encircle and engage upper portions of the terminal pins and are held thereby in pressure contact agains the body. The pin retainer longitudinally extends between terminal pins to insulate electrically the pins from adjacent pins, and transversely extends over the terminal nuts to maintain the terminal nuts and the terminal pins in place. The terminal pins longitudinally extend above the transversely extending portion of the pin retainer to provide access to the terminal pins.

Abstract: A control system for a pulsed DC arc welding system power supply is disclosed. The control system operates to automatically adjust the pulse width of the current pulses supplied at the arc gap by the power supply to control the power flow to the work pieces at the arc gap. An example of such a control system for a conventional pulsed DC arc welding system power supply comprises a variable resistance device connected in parallel with a normally closed time delay switch. This system is electrically connected in an impulsar control circuit of the power supply. The control system automatically changes the resistance within the conventional impulsar control circuit to provide an adjustment within the control circuit to alter the impulsar output signal which controls the pulse width of the current pulses supplied by the power supply.

Abstract: A method and control system for operating a vapor compression refrigeration system to prevent oil pump cavitation during startup of the refrigeration system is disclosed. The control system includes a temperature or pressure sensor located in the evaporator of the refrigeration system, a microprocessor, and an inlet guide vane control mechanism. During startup, the pressure of the gaseous refrigerant or the temperature of the liquid refrigerant in the evaporator of the refrigeration system, or compressor suction line pressure, is measured and an electrical signal corresponding to the measured pressure or temperature is processed by the microprocessor to determine the actual rate of pulldown of refrigerant pressure in the evaporator. The microprocessor compares the actual pulldown rate to a pulldown rate which has been predetermined to prevent compressor oil pump cavitation.

Abstract: Apparatus is disclosed for serving as both a reversing valve and an expansion device in a refrigeration circuit. A valve gate having passageways to direct refrigerant between the indoor and the outdoor heat exchangers to effect the function of a reversing valve is disclosed. In addition, the valve gate has multiple flow restriction devices which are selectively incorporated within a refrigeration circuit between the indoor heat exchanger and the outdoor heat exchanger to effect the appropriate amount of flow restriction dependent upon the mode of operation of the unit. These two functions may be incorporated into a single valve or they may be separated such that the separate functions are performed by separate valves. A cylindrical valve gate and multiple passageways for connecting the appropriate lines in a refrigeration circuit are described. The valve is rotated by a combination of an electromagnet spaced about the valve gate and a permanent magnet located within the valve gate.

Abstract: A system for protecting a three-phase motor is disclosed. The system includes a signal conditioning circuit which senses the magnitude of current flowing through each motor phase and generates a single-line, three-phase voltage output signal having each of its phases corresponding to a single motor current phase. This three-phase voltage output signal is efficiently utilized by a microcomputer system to detect motor current overload and motor current imbalance. The microcomputer system instructs a motor controller to shut down the motor in response to a motor current overload or motor current imbalance.

Abstract: Apparatus for use in a heat exchange unit having wound fin tubing includes a tube support having a vertical portion and multiple lateral portions, each lateral portion having an opening therein. A support tube is inserted through the openings in the lateral portions of the tube support such that runs of wound fin tubing are secured between the tube support and the support tube. A run support portion of the tube support may additionally define notches for securing the various runs of wound fin tubing. Pins or other means for securing the tubular support means are inserted into the ends of the tubular support such that the support tube is affixed to the tube support assembly. The pins are secured to either the base pan or the structural assembly of the unit providing a tube support assembly as an integral part of the heat exchange unit.

Abstract: A trip mechanism for a trip valve is made up of a reset lever and a bell crank operatively connected through a guide stem which is guidingly received in a flange portion of the valve housing. A valve stem and the guide stem are slidably connected to the reset lever which is provided with a spring bias which tends to move the reset lever in a valve closing position. When the bell crank and guide stem are in engagement the valve is held open and when the bell crank is subjected to an actuating force the bell crank and guide stem become disengaged causing the valve to close under the spring bias and to remain closed until manually reset.

Abstract: The fan motor of a variable speed drive for a fan is positioned in response to thermostatic demand and a feedback signal responsive to the position of the variable speed drive. Changing thermostatic demand causes movement of the fan motor until an equilibrium position is reached again.

Abstract: The efficiency of a centrifugal compressor is optomized over a wide range of flow rates by providing a diffuser which is a combination of fixed vanes and a movable wall member and which throttles the diffuser passage in accordance with compressor load.

Abstract: A multiple position leg assembly for a heat exchange unit is disclosed. A support surface has a pair of slots which coact with a leg such that the leg has a shipping position wherein it does not extend beyond the bottom of the unit and has a support position wherein it is securely fastened in the slots of the support surface to maintain the unit a preselected distance from a mounting structure. The leg is designed such that internal forces act to secure narrowed portions of the leg in the slots to provide a secure support for the unit.

Abstract: In a centrifugal gas compressor the capacity and the prewhirl of the entering gas are both controlled by reciprocating a plug which is located in the flow path. The plug coacts with tapering walls of the flow path to vary the minimum cross-sectional area of the flow path. Additionally vanes are provided either in the wall of the flow path or on the plug. The vanes transition from an axial direction to a helical direction and of reducing height in a downstream direction so as to produce increasing prewhirl with decreasing capacity. Alternatively, prewhirl may be provided without capacity control.

Abstract: A torque control for a fluid operated motor includes a first gear to be driven through operation of the motor and a second gear in driving engagement with said motor and maintained in a generally stationary position during normal operation thereof. The torque control further includes a drive mechanism connected to the first gear and to a load to be rotationally driven through operation of the motor. A valve is provided in the fluid supply to the motor to open and close the supply of fluid thereto. Disconnect means is operatively connected to the second gear and the valve to maintain said valve in an open position to permit supply of fluid to said motor when the second gear is stationary. The second gear rotates when the torque required from the motor to rotate the load exceeds a predetermined magnitude to move the disconnect means relative to the valve to close the valve to terminate the supply of fluid to the motor.

Abstract: A refrigeration purging system for the removal of non-condensible gases such as air and condensible contaminants such as water is disclosed. A portion of the refrigerant in the refrigeration system is placed in a first purge chamber which condenses the refrigerant and condensible contaminants such as water leaving non-condensibles such as air and a small portion of the refrigerant at the top of the chamber. The non-condensibles and remaining refrigerant is extracted from the first chamber pumped to a higher pressure and passed to a second purged chamber wherein the remaining refrigerant is condensed and returned to the first purged chamber. The non-condensible gases remaining are released to the atmosphere. The condensible contaminants are extracted from the first purged chamber and the condensed refrigerant is returned to the refrigeration system.