Abstract: A dished head header assembly for a heat exchanger having a containment body that includes a rounded, or dished, wall portion forming an interior cavity. A flange attaches to the containment body and fastens the header assembly to the heat exchanger. A plurality of refrigerant passageways are extended through an opening in the containment body into the interior cavity. At least one baffle is attached to the rounded wall portion. The baffle divides the interior cavity into a plurality of sub-cavities. At least one divider divides the sub-cavities into a plurality of chambers. The plurality of passageways includes an inlet connection and an outlet connection for a plurality of refrigerant circuits. Each passageway is disposed in a corresponding chamber of the plurality of chambers. Extensions into the headers with diffusers insure efficient operation and performance of the heat exchanger. The adjustable flow restrictor plate maintains optimum velocities to further enhance performance.

Abstract: A variable speed drive with a boost converter is provided for a chiller system driven by an induction motor. The boost converter can be a diode or thyristor rectifier followed by a boost DC/DC converter or a three-phase pulse width modulated boost converter. The boost converter provides a boosted voltage to the DC link, which results in a boosted voltage being applied to the induction motor by the inverter of the variable speed drive.

Abstract: A variable speed drive with a boost converter is provided for a chiller system driven by a switched reluctance motor. The boost converter can be a diode or thyristor rectifier followed by a boost DC/DC converter or a three-phase pulse width modulated boost converter. The boost converter provides a boosted voltage to the DC link, which results in a boosted voltage being applied to the switched reluctance motor by the inverter of the variable speed drive.

Abstract: A support system for an air handling unit (AHU) including a first rail supporting the AHU and a second rail supporting the first rail. A vibration isolator is disposed between the first rail and the second rail to vibrationally isolate the AHU from the second rail. The vibration isolator includes a spring secured between opposed spring retainers. An adjusting member threadedly receives the upper spring retainer. The first rail structurally carries the guide member along at least two positions. An angle is secured to the second rail, and the second end of the structural member slidably engages the guide member. Rotating the adjusting member with respect to the spring retainer in one direction compresses the spring between the spring retainers to support the weight of the first rail and the AHU. The angle constrains the AHU to movement along the guide member.

Abstract: A fin for a heat exchanger coil assembly and a method of manufacturing the fin is provided. The fin includes a heat transfer enhancement pattern which appears sinusoidal in shape. The base wavy pattern of the enhancement pattern includes two wavelengths within each tube row and includes seven discrete segments. Six of the seven segments are circular arc segments. The seventh segment comprises two linear segments which form a condensate channel. The segments are arranged in a particular order at specific distances offset (above and below) from a leading edge nominal air streamline (LENAS) by a fraction of a nominal fin pitch Pf. The LENAS is related to the “normal” base wavy pattern used in other fins.

Abstract: The present invention also includes a method for installing filters, particularly HEPA filters, into an air handling unit. The method includes providing a filter and a positioning frame, the positioning frame having a geometry that positions the filter adjacent to the frame. The positioning frame also has a latching mechanism for attaching the positioning frame and filter to the filter cabinet. The method further includes positioning the filter and the positioning frame into an opening in a filter cabinet. The frame is then secured to the cabinet by the latching mechanism where the latching mechanism provides a force to the positioning frame and filter, sealing the filter against the filter cabinet to help prevent the flow of air around the filter.

Abstract: An HVAC system having a main circuit and a subcooler circuit. The main circuit includes a main circuit evaporator, a main circuit expansion device, a main circuit condenser and a main circuit compressor connected in a closed refrigerant loop. The subcooler circuit includes a subcooler evaporator, a subcooler expansion device, a subcooler condenser and a subcooler compressor connected in a closed refrigerant loop. The subcooler evaporator is arranged and disposed to exchange heat between liquid refrigerant in the main circuit and the refrigerant in the subcooler circuit to cool the liquid refrigerant in the main circuit prior to entering the main circuit evaporator. The operation of the subcooler circuit provides an increased cooling capacity per unit of a mass flow of cooling fluid through the main circuit condenser and subcooler condenser for the HVAC system with a predetermined design efficiency.

Abstract: An HVAC system and method for configuring a controller to control a compressor including a detection system provided to determine a type of compressor. The detection system includes a processor; and a load sensing circuit connected between the processor and a controller. The controller has a plurality of output connections connectable to a compressor. The load sensing circuit senses whether a load is present on each output connection of the plurality of output connections and provides a load signal to the processor indicating whether a load is present on each output connection. The load signals are processed with the processor to determine the type of compressor is present. The controller is configured to control the compressor in response to the determined type of compressor.

Abstract: A variable speed drive with a converter that is controllable to precharge a DC link is provided. The variable speed drive also includes an inverter. The converter converts a fixed line frequency, fixed line voltage AC power from an AC power source into DC power. The DC link filters the DC power from the converter. Finally, the inverter is connected in parallel with the DC link and converts the DC power from the DC link into a variable frequency, variable voltage AC power. The converter includes a plurality of pairs of power switches, wherein each pair of power switches includes a reverse blocking power switch connected in anti-parallel to another reverse blocking power switch. Alternatively, each pair of power switches includes a reverse blocking power switch connected in anti-parallel with a silicon carbide controlled rectifier.

Abstract: A limited modulation furnace and a method for controlling the limited modulation furnace using a floating control algorithm are disclosed. The method includes providing a furnace comprising a modulating furnace stage and at least one fixed heat output furnace stage, each fixed heat output furnace stage having an operational status of either on or off, passing a heating fluid through the furnace, measuring a temperature of the heating fluid exiting the furnace, determining an error based on a difference between the measured temperature and a set-point temperature, the set-point temperature being associated with a thermostat setting, determining whether the error is within a deadband range for the set-point temperature, and modifying at least one of the heat output of the modulating furnace stage or the operational status of at least one of the fixed heat output furnace stages in response to the error being outside the deadband range.

Abstract: A method for configuring a controller for an HVAC system. The method comprises providing a closed loop refrigerant system and a control system to control the closed loop refrigerant system. The control system comprises a controller, an input device, and a processor including a signal sensing circuit. The input device is activated to provide one or more signals to the controller to control the components of the closed loop refrigerant system. One or more signals are sensed with the signal sensing circuit to determine whether signals are present between the input device and the controller. The signals are processed with the processor to determine what type of closed loop refrigerant system is present. The controller is then configured to control the type of system determined by the processor.

Abstract: A system and method are provided for variable speed operation of a screw compressor to obtain increased capacity and efficiency. The screw compressor is connected to an induction motor driven by a variable speed drive, wherein the screw compressor has a variable output capacity that is dependent on the output speed of the motor. To obtain increased capacity and efficiency, the screw compressor is operated at a speed greater than the screw compressor's rated speed and does not include a slide valve. The maximum operating speed of the screw compressor, which speed is greater than the rated speed, is related to the maximum operating speed of the motor when operated at a voltage and frequency provided by the variable speed drive that is greater than the motor's rated voltage and frequency in a constant flux or constant volts/Hz mode.

Abstract: A mixing chamber for an air handling unit having a first inlet, second inlet and an outlet. The first inlet receives a first air stream. The second inlet to receives a second air stream. The outlet discharges a mixed airflow. The first inlet includes a first damper having an opposed blade configuration for controlling the flow of the first air stream and the second inlet includes a second damper having an opposed blade configuration for controlling the flow of the second air stream. The mixing chamber also includes a control arrangement to control operation of the first and second damper. The control arrangement is configured to independently open and close each of the first and second dampers to regulate airflow into the mixing chamber.

Abstract: A method of clearing an HVAC control fault code memory is disclosed. The method includes assigning a predetermined reset code to an HVAC control system, the predetermined reset code comprising a plurality of control signals receivable by the HVAC control system, detecting control signals at the HVAC control system, determining whether the detected HVAC control input signals match the predetermined reset code and clearing a fault code memory of the HVAC control system in response to control signals matching the predetermined reset code.

Abstract: A discharge muffler (20) in an HVAC&R system (100) includes a plurality of tubes (34, 38, 42) of predetermined length that are disposed at a predetermined spacing in substantially mutual axial alignment by a plate (30). The tubes (34, 38, 42) are secured adjacent to a compressor discharge (24) to minimize pressure reduction, improve flow characteristics and improve efficiency of the HVAC&R system (100).

Abstract: A heating control method is provided for a multi-stage heating system including a heating circuit having a compressor, a condenser and an evaporator. An auxiliary heater is provided that is selectively controlled independently of the heating circuit. During a heating cycle in which the ambient outside temperature is greater than the balance point temperature associated with the operation of the heating circuit, the auxiliary heating circuit is normally prevented from operating. However, if the heating requirements are not satisfied after a predetermined time or the compressor is non-functional or operating improperly, the auxiliary heater is enabled.

Abstract: A screw compressor for acoustic resonance reduction and refrigeration systems including the screw compressor are disclosed. The screw compressor has an acoustic barrier integral with the compressor housing for use with a slide valve assembly that includes a piston connected to a slide valve. A shaft connecting the slide valve and the piston passes through an aperture in the barrier with the piston and the slide valve disposed on opposite sides of the barrier. The acoustic barrier protects the piston from discharge pulses of compressed fluid exiting the rotors of the screw compressor, thus attenuating acoustic resonance, reducing compressor noise and premature wear of the slide valve assembly and compressor housing.

Abstract: A method of providing ride-through capability in a chiller/refrigeration system employs a variable speed drive with an active converter stage, a DC link stage and an inverter stage for providing variable frequency and voltage to power at least one motor. An induction motor is coupled to the output of the inverter stage for driving a compressor in the chiller/refrigeration system. The ride-through method comprises operating the active converter to regulate the DC link voltage of the DC link stage to a predetermined voltage level until the current through the active converter equals a predetermined current limit, then transferring regulation of the DC link to the inverter upon reaching the current limit of the converter. The compressor is unloaded, and the power flow through the inverter is reversed to maintain the voltage level of the DC link stage.

Abstract: A system and method are provided to increase the horsepower of an induction motor. One technique for increasing the horsepower of a motor is to connect the motor to a variable speed drive that is providing an output voltage and frequency greater than the standard line voltage and frequency. The connection of the variable speed drive to the induction motor enables the motor to be operated in constant flux or constant volts/Hz mode and provide a greater output horsepower. Another technique for increasing the horsepower of a motor is to use a dual voltage motor configured for lower voltage operation and then provide the motor with the corresponding voltage and frequency for higher voltage operation. The higher voltage and higher frequency can be provided by a variable speed drive with or without voltage boost. A variable speed drive without voltage boost, but with frequency boost, can be used in situations where the standard main voltage is greater than the lower voltage rating.

Abstract: An HVAC system including a compressor, a condenser and an evaporator arrangement connected in a closed refrigerant loop. The evaporator arrangement includes a plurality of refrigerant circuits. The evaporator arrangement also includes at least one distributor configured to distribute and deliver refrigerant to each circuit of the plurality of circuits. The plurality of circuits are arranged into a first and second set of circuits. The evaporator arrangement also includes a valve configured and disposed to isolate the first set of circuits from refrigerant flow from the condenser and provide flow of refrigerant from the compressor in a dehumidification operation of the HVAC system.