Abstract: Method and system for controlling a compressor and a supply fan in a heating, ventilating and air conditioning (HVAC) system are disclosed. The system includes a compressor having a startup state and a running state, a supply fan, and a controller configured to control the compressor and the supply fan in the HVAC system. The compressor and the supply fan are controlled based on a dehumidification map and/or an efficiency map. The system also includes a cooling coil configured to receive a fluid in heat exchange relationship with refrigerant from an evaporator to cool air. The supply fan is configured to deliver the cooled air from the cooling coil to a conditioned space as supply air.

Abstract: This disclosure is directed to systems and methods for determining airflow in a heating, ventilation, air conditioning and refrigeration (HVACR) system to reduce overall power consumption. Methods include receiving efficiency data for one or more compressors of the HVACR system, receiving airflow power consumption data, determining, using a processor, a flow rate based on the efficiency data for the one or more compressors and the airflow power consumption data, and when the HVACR system is in a partial load condition and at least one of the one or more compressors are in operation, operating the HVACR system at the determined flow rate. Systems include one or more compressors, one or more blower fans, and a processor configured to determine an airflow rate for the one or more blower fans based on efficiency data for the one or more compressors and airflow power consumption data.

Abstract: This disclosure is directed to systems and methods for determining airflow in a heating, ventilation, air conditioning and refrigeration (HVACR) system to reduce overall power consumption. Methods include receiving efficiency data for one or more compressors of the HVACR system, receiving airflow power consumption data, determining, using a processor, a flow rate based on the efficiency data for the one or more compressors and the airflow power consumption data, and when the HVACR system is in a partial load condition and at least one of the one or more compressors are in operation, operating the HVACR system at the determined flow rate. Systems include one or more compressors, one or more blower fans, and a processor configured to determine an airflow rate for the one or more blower fans based on efficiency data for the one or more compressors and airflow power consumption data.

Abstract: A heating, ventilation, and air conditioning (“HVAC”) system and a method for controlling the HVAC system. The HVAC system includes a compressor and a variable speed discharge fan. The method includes determining, with a controller, a low fan capacity setting based on an operation of the compressor. The method also includes maintaining a discharge fan capacity at the low fan capacity setting, and varying a coil discharge air temperature between a low discharge air temperature limit and a high discharge air temperature limit. The method further includes when the coil discharge air temperature reaches the low discharge air temperature limit, varying the discharge fan capacity between the low fan capacity setting and a high fan capacity setting so as to maintain a space temperature at a space temperature setpoint, while maintaining the coil discharge air temperature at the low discharge air temperature limit.

Abstract: Methods to regulate a discharge fan and a coil of a HVAC system are described. The method may include regulating a discharge air temperature of the cooling/heating coil of the HVAC system while maintain the discharge fan at a low capacity setting. The method may also include maintaining the coil at a low discharge air temperature (or a high discharge air temperature) setting, while varying a fan capacity of the discharge fan. The method may include a discharge capacity boost that includes decreasing (or elevating) the discharge air temperature limit of the coil beyond the low discharge air temperature (or the high discharge air temperature) limit. The methods as described herein may be applicable to a HVAC system that has variable airflow capability.

Abstract: A heating, ventilation, and air conditioning (HVAC) system includes a fan with a variable fan capacity; a coil with a variable discharge air temperature; and a controller configured to control the variable fan capacity of the fan and the variable discharge air temperature of the coil. The controller is configured to vary the variable capacity of the fan to maintain a space temperature at a space temperature setpoint while maintaining the variable discharge air temperature of the coil at a low discharge air temperature limit. The controller is configured to vary the variable discharge air temperature between a high discharge air temperature limit and the low discharge air temperature limit to maintain the space temperature at the space temperature setpoint while maintaining the variable capacity of the fan at a low fan capacity setting.

Abstract: The embodiments disclosed herein are directed to systems and methods to control a HVAC system based on a state of an unloader of a compressor of the HVAC system.

Abstract: A system and method for controlling a system that includes a variable speed compressor are described. The method can provide improved accuracy in the control of a system, for example, a heating, ventilating, and air condition (HVAC) system that includes a variable speed compressor, and can reduce a compressor cycling frequency of the compressor when a required capacity is below a minimum capacity of the compressor.

Abstract: Methods and systems for detecting and recovering from control instability caused by impeller stall in a chiller system are provided. In one embodiment, an impeller stall detection and recovery component of a chiller control unit calculates a control error signal frequency spectrum for an evaporator leaving water temperature, determines whether a high frequency signal content of the control error signal frequency spectrum exceeds acceptable limits, and adjusts a surge boundary control curve downward by a predetermined incremental value in order to resolve instability caused by impeller stall.

Abstract: A system and method for controlling a system that includes a variable speed compressor are described. The method can provide improved accuracy in the control of a system, for example, a heating, ventilating, and air condition (HVAC) system that includes a variable speed compressor, and can reduce a compressor cycling frequency of the compressor when a required capacity is below a minimum capacity of the compressor.

Abstract: Methods to regulate a discharge fan and a coil of a HVAC system are described. The method may include regulating a discharge air temperature of the cooling/heating coil of the HVAC system while maintain the discharge fan at a low capacity setting. The method may also include maintaining the coil at a low discharge air temperature (or a high discharge air temperature) setting, while varying a fan capacity of the discharge fan. The method may include a discharge capacity boost that includes decreasing (or elevating) the discharge air temperature limit of the coil beyond the low discharge air temperature (or the high discharge air temperature) limit. The methods as described herein may be applicable to a HVAC system that has variable airflow capability.

Abstract: A method for regulating a discharge fan and a coil of a heating, ventilation, and air conditioning (“HVAC”) system includes maintaining a discharge fan capacity at a low fan capacity setting and varying a coil discharge air temperature between a low discharge air temperature limit and a high discharge air temperature limit. The method also includes, when the coil discharge air temperature reaches the low discharge air temperature limit, varying a fan speed of the variable speed discharge fan between a low fan speed setting and a high fan speed setting so as to maintain a space temperature at a space temperature setpoint set for a space, while maintaining the coil discharge air temperature at the low discharge air temperature limit.

Abstract: Methods and systems for detecting and recovering from control instability caused by impeller stall in a chiller system are provided. In one embodiment, an impeller stall detection and recovery component of a chiller control unit calculates a control error signal frequency spectrum for an evaporator leaving water temperature, determines whether a high frequency signal content of the control error signal frequency spectrum exceeds acceptable limits, and adjusts a surge boundary control curve downward by a predetermined incremental value in order to resolve instability caused by impeller stall.

Abstract: A system and method for controlling a system that includes a variable speed compressor are described. The method can provide improved accuracy in the control of a system, for example, a heating, ventilating, and air condition (HVAC) system that includes a variable speed compressor, and can reduce a compressor cycling frequency of the compressor when a required capacity is below a minimum capacity of the compressor.

Abstract: The embodiments disclosed herein are directed to systems and methods to control a HVAC system based on a state of an unloader of a compressor of the HVAC system.

Abstract: A return fan control system for an HVAC system comprises a supply fan control loop, a return fan control loop and a building pressure control system. The supply fan control loop comprises a duct pressure controller arranged to control a supply fan to a duct pressure setpoint. The return plenum pressure control loop comprises a return plenum pressure controller arranged to automatically control a return fan to a return plenum pressure setpoint determined by a setpoint reset function. The building pressure control system is operable to control a building pressure. The building pressure control system may comprise a building pressure control loop and an outside air control loop cooperatively arranged to control an exhaust damper in response to an outside air intake.

Abstract: Methods to regulate a discharge fan and a coil of a HVAC system are described. The method may include regulating a discharge air temperature of the cooling/heating coil of the HVAC system while maintain the discharge fan at a low capacity setting. The method may also include maintaining the coil at a low discharge air temperature (or a high discharge air temperature) setting, while varying a fan capacity of the discharge fan. The method may include a discharge capacity boost that includes decreasing (or elevating) the discharge air temperature limit of the coil beyond the low discharge air temperature (or the high discharge air temperature) limit. The methods as described herein may be applicable to a HVAC system that has variable airflow capability.

Abstract: A return fan control system for an HVAC system comprises a supply fan control loop, a return fan control loop and a building pressure control system. The supply fan control loop comprises a duct pressure controller arranged to control a supply fan to a duct pressure setpoint. The return plenum pressure control loop comprises a return plenum pressure controller arranged to automatically control a return fan to a return plenum pressure setpoint determined by a setpoint reset function. The building pressure control system is operable to control a building pressure. The building pressure control system may comprise a building pressure control loop and an outside air control loop cooperatively arranged to control an exhaust damper in response to an outside air intake.

Abstract: A return fan control system for an HVAC system comprises a supply fan control loop, a return fan control loop and a building pressure control system. The supply fan control loop comprises a duct pressure controller arranged to control a supply fan to a duct pressure setpoint. The return plenum pressure control loop comprises a return plenum pressure controller arranged to automatically control a return fan to a return plenum pressure setpoint determined by a setpoint reset function. The building pressure control system is operable to control a building pressure. The building pressure control system may comprise a building pressure control loop and an outside air control loop cooperatively arranged to control an exhaust damper in response to an outside air intake.

Abstract: A method of operating an HVAC system having an HVAC control and a humidity limiting control. The method comprises the steps of: determining a relative humidity limit for a space; monitoring relative humidity in the space; comparing the relative humidity to the relative humidity limit; operating the conventional HVAC control if the space humidity does not exceed the humidity limit; and integrating the HVAC control and dehumidification controls if the space conditions require humidity limiting action.