Compressor staging control architecture for hot gas reheat systems

Abstract

A method is provided for controlling a heating, ventilation, and air conditioning (HVAC) system. The method includes measuring a temperature and controlling a compressor of the HVAC system. The temperature is measured by a temperature sensor located between a metering device of the HVAC system and an evaporator coil of the HVAC system. The temperature is representative of a refrigerant temperature. The refrigerant temperature is a temperature of a refrigerant fluid flowing from the metering device to the evaporator coil. The compressor is controlled by control circuitry that is configured to perform the controlling in a dehumidify mode based, at least in part, on a value of a humidity parameter of air of an airflow through an evaporator coil and a reheat coil, where the value is determined using the temperature.

What is claimed is: 
     
         1 . A method for controlling a heating, ventilation, and air conditioning (HVAC) system, comprising:
 measuring a temperature, wherein
 the temperature is measured by a temperature sensor located between a metering device of the HVAC system and an evaporator coil of the HVAC system, 
 the temperature is representative of a refrigerant temperature, and 
 the refrigerant temperature is a temperature of a refrigerant fluid flowing from the metering device to the evaporator coil; and 
   controlling a compressor of the HVAC system, wherein
 the HVAC system further comprises a reheat coil and a condenser coil, 
 the compressor, the metering device, the evaporator coil, the reheat coil, and the condenser coil are in fluid communication with one another, with respect to the refrigerant fluid, 
 the compressor is controlled by control circuitry, 
 the control circuitry is configured to perform the controlling in a dehumidify mode based, at least in part, on a value of a humidity parameter of air of an airflow through the evaporator coil and the reheat coil, and 
 the value is determined using the temperature. 
   
     
     
         2 . The method of  claim 1 , wherein
 the humidity parameter is a dew point of the air.   
     
     
         3 . The method of  claim 1 , wherein
 the metering device is a thermostatic expansion valve.   
     
     
         4 . The method of  claim 1 , wherein
 the temperature sensor is a thermistor.   
     
     
         5 . The method of  claim 1 , wherein the controlling comprises:
 determining whether the temperature is sufficient to perform a staging operation by comparing the temperature to a first temperature threshold; and   in response to a determination that the temperature is not sufficient to perform the staging operation, causing the compressor to shut down.   
     
     
         6 . The method of  claim 5 , wherein the controlling further comprises:
 in response to a determination that the temperature is sufficient to perform a staging operation,
 comparing the temperature to a second temperature threshold, and 
 in response to a determination that the temperature exceeds the second temperature threshold, performing the staging operation. 
   
     
     
         7 . The method of  claim 6 , wherein
 the humidity parameter is a dew point of the air,   the staging operation comprises
 setting the dew point of the air by increasing a compressor load of the compressor using a proportional integral control process, and 
   an input to the proportional integral control process is the temperature.   
     
     
         8 . The method of  claim 7 , wherein
 another input to the proportional integral control is a temperature offset.   
     
     
         9 . The method of  claim 6 , wherein the controlling further comprises:
 in response to a determination that the temperature does not exceed the second temperature threshold, performing another staging operation, wherein
 the another staging operation causes the compressor to increase operation to full load. 
   
     
     
         10 . The method of  claim 9 , wherein
 the HVAC system further comprises a fan,   the fan causes to air to flow through the evaporator coil and the reheat coil, and   the another staging operation causes the fan to increase a velocity of the air through the evaporator coil and the reheat coil.   
     
     
         11 . A non-transitory computer-readable storage medium, comprising program instructions for controlling a heating, ventilation, and air conditioning (HVAC) system, which, when executed by one or more processors, perform a method comprising:
 measuring a temperature, wherein
 the temperature is measured by a temperature sensor located between a metering device of the HVAC system and an evaporator coil of the HVAC system, 
 the temperature is representative of a refrigerant temperature, and 
 the refrigerant temperature is a temperature of a refrigerant fluid flowing from the metering device to the evaporator coil; and 
   controlling a compressor of the HVAC system, wherein
 the HVAC system further comprises a reheat coil and a condenser coil, 
 the compressor, the metering device, the evaporator coil, the reheat coil, and the condenser coil are in fluid communication with one another, with respect to the refrigerant fluid, 
 the compressor is controlled by control circuitry comprising the one or more processors, 
 the control circuitry is configured to perform the controlling in a dehumidify mode based, at least in part, on a value of a humidity parameter of air of an airflow through the evaporator coil and the reheat coil, and 
 the value is determined using the temperature. 
   
     
     
         12 . The non-transitory computer-readable storage medium of  claim 11 , wherein
 the humidity parameter is a dew point of the air,   the metering device is a thermostatic expansion valve, and   the temperature sensor is a thermistor.   
     
     
         13 . The non-transitory computer-readable storage medium of  claim 11 , wherein the method further comprises:
 determining whether the temperature is sufficient to perform a staging operation by comparing the temperature to a first temperature threshold;   in response to a determination that the temperature is not sufficient to perform the staging operation, causing the compressor to shut down; and   in response to a determination that the temperature is sufficient to perform a staging operation,
 comparing the temperature to a second temperature threshold, and 
 in response to a determination that the temperature exceeds the second temperature threshold, performing the staging operation. 
   
     
     
         14 . The non-transitory computer-readable storage medium of  claim 13 , wherein
 the humidity parameter is a dew point of the air,   the staging operation comprises
 setting the dew point of the air by increasing a compressor load of the compressor using a proportional integral control process, 
   an input to the proportional integral control process is the temperature, and   another input to the proportional integral control is a temperature offset.   
     
     
         15 . The non-transitory computer-readable storage medium of  claim 13 , wherein the method further comprises:
 in response to a determination that the temperature does not exceed the second temperature threshold, performing another staging operation, wherein
 the another staging operation causes the compressor to increase operation to full load, 
 the HVAC system further comprises a fan, 
 the fan causes to air to flow through the evaporator coil and the reheat coil, 
 the another staging operation causes the fan to increase a velocity of the air through the evaporator coil and the reheat coil. 
   
     
     
         16 . A heating, ventilation, and air conditioning (HVAC) system, comprising:
 a hot-gas reheat dehumidification circuit, wherein
 the hot-gas reheat dehumidification circuit comprises an evaporator coil, a compressor, a reheat coil, and a metering device, 
 the evaporator coil, the compressor, the reheat coil, and the metering device are in fluid communication with one another, with respect to a refrigerant fluid, and 
 the metering device is in fluid communication with the evaporator coil via a refrigerant fluid line; 
   a sensor, wherein
 the sensor is positioned between the metering device and the evaporator coil such that the sensor is positioned to measure a parameter representative of a refrigerant fluid parameter of a portion of the refrigerant fluid flowing through the refrigerant fluid line; and 
   a system control unit, wherein
 the system control unit is configure to
 measure the parameter, wherein
 the parameter is measured by the sensor, and control the compressor in a dehumidify mode based, at least in 
 
 part, on a value of a humidity parameter of air of an airflow through the evaporator coil and the reheat coil, wherein the value is determined using the parameter. 
 
   
     
     
         17 . The HVAC system of  claim 16 , wherein
 the humidity parameter is a dew point of the air,   the metering device is a thermostatic expansion valve, and   the sensor is a thermistor.   
     
     
         18 . The HVAC system of  claim 16 , wherein
 the parameter is a temperature,   measurement of the temperature provides a temperature value,   the temperature value is representative of a refrigerant fluid temperature, and   the refrigerant fluid temperature is a temperature of the portion of the refrigerant fluid flowing through the refrigerant fluid line.   
     
     
         19 . The HVAC system of  claim 18 , wherein the system control unit is further configure to:
 determine whether the temperature is sufficient to perform a staging operation by comparing the temperature to a first temperature threshold;   in response to a determination that the temperature is not sufficient to perform the staging operation, cause the compressor to shut down; and   in response to a determination that the temperature is sufficient to perform a staging operation,
 compare the temperature to a second temperature threshold, and 
 in response to a determination that the temperature exceeds the second temperature threshold, perform the staging operation. 
   
     
     
         20 . The HVAC system of  claim 19 , wherein
 the humidity parameter is a dew point of the air,   the staging operation comprises
 setting the dew point of the air by increasing a compressor load of the
 compressor using a proportional integral control process, 
 
   an input to the proportional integral control process is the temperature, and another input to the proportional integral control is a temperature offset.   
     
     
         21 . The HVAC system of  claim 19 , wherein the system control unit is further configure to:
 in response to a determination that the temperature does not exceed the second temperature threshold, perform another staging operation, wherein
 the another staging operation causes the compressor to increase operation to full load, 
 the HVAC system further comprises a fan, 
 the fan causes to air to flow through the evaporator coil and the reheat coil, and 
 the another staging operation causes the fan to increase a velocity of the air through the evaporator coil and the reheat coil.