System and method for controlling an hvac unit

Abstract

Described herein is a system for controlling an HVAC unit. The system comprises a controller configured to monitor temperature of air upstream and downstream of an indoor coil of the HVAC unit, and control, based on the monitored temperature, speed of one or more fans configured with the indoor coil to maintain a temperature difference across the indoor coil.

1 . A system for controlling a heating, ventilation, and air conditioning (HVAC) unit, the system comprising:
 the HVAC unit comprising:
 an indoor coil; and 
 one or more fans configured with the indoor coil; and 
   a controller configured to:
 monitor temperature of air upstream and downstream of the indoor coil; and 
 control, based on the monitored temperature, speed of the one or more fans to maintain a temperature difference across the indoor coil. 
   
     
     
         2 . The system of  claim 1 , wherein during a cooling mode of operation of the HVAC unit, the temperature difference is selected based on an operating environment of an outdoor unit of the HVAC unit. 
     
     
         3 . The system of  claim 2 , wherein the operating environment is selected from one of a humid condition, a semi-arid condition, and a desert condition, wherein the humid condition pertains to a first range of humidity, a semi-arid condition pertains to a second range of humidity, and a desert condition pertains to a third range of humidity, and wherein the first range is greater than the second range and the second range is greater than the third range. 
     
     
         4 . The system of  claim 1 , wherein during a cooling mode of operation of the HVAC unit, the temperature difference is based on a humidity level. 
     
     
         5 . The system of  claim 2 , wherein the controller is further configured to monitor temperature and/or pressure of refrigerant vapor leaving the indoor coil during the cooling mode and correspondingly determine the operating environment of the HVAC unit. 
     
     
         6 . The system of  claim 2 , wherein the controller is further configured to monitor superheat control characteristics of an expansion valve of the HVAC unit during the cooling mode and correspondingly determine the operating environment of the HVAC unit. 
     
     
         7 . The system of  claim 2 , wherein the system further comprises a humidity sensor in communication with the controller, the humidity sensor configured to monitor specific humidity or relative humidity around an outdoor coil of the HVAC unit, and wherein the controller is further configured to determine the operating environment of the HVAC unit based on the monitored humidity. 
     
     
         8 . The system of  claim 1 , wherein during a heating mode of operation of the HVAC unit, the controller is configured to control the speed of the one or more fans to maintain a temperature downstream of the indoor coil. 
     
     
         9 . The system of  claim 1 , wherein the one or more fans are configured downstream and/or upstream of the indoor coil. 
     
     
         10 . The system of  claim 1 , wherein the system further comprises a first temperature sensor and a second temperature sensor positioned upstream and downstream, respectively, of the indoor coil of the HVAC unit, to monitor temperature of the air upstream and downstream, respectively, of the indoor coil. 
     
     
         11 . The system of  claim 1 , wherein the system further comprises a human-machine interface (HMI) device in communication with the controller, the HMI device configured to:
 display and/or allow selection of an operating environment during a cooling mode of operation of the HVAC unit;   display and/or allow selection of the temperature difference to be maintained across the indoor coil during the cooling mode and/or a heating mode of operation of the HVAC unit; and   display and/or allow selection of a temperature to be maintained downstream of the indoor coil during the heating mode.   
     
     
         12 . A method for controlling an HVAC unit, the HVAC unit comprising an indoor coil, and one or more fans configured with the indoor coil, the method comprising:
 monitoring, by a controller, temperature of air upstream and downstream of the indoor coil; and   controlling, by the controller, based on the monitored temperature, speed of the one or more fans to maintain a temperature difference across the indoor coil.   
     
     
         13 . The method of  claim 12 , wherein during a cooling mode of operation of the HVAC unit, the method comprises the step of selecting and maintaining, by the controller, the temperature difference based on an operating environment of an outdoor unit associated with the HVAC unit. 
     
     
         14 . The method of  claim 13 , wherein the operating environment is selected from one of a humid condition, a semi-arid condition, and a desert condition, wherein the humid condition pertains to a first range of humidity, a semi-arid condition pertains to a second range of humidity, and a desert condition pertains to a third range of humidity, and wherein the first range is greater than the second range and the second range is greater than the third range. 
     
     
         15 . The method of  claim 12 , wherein during a cooling mode of operation of the HVAC unit, the temperature difference is selected based on a humidity level. 
     
     
         16 . The method of  claim 13 , wherein the method further comprises the steps of monitoring temperature and/or pressure of refrigerant vapor leaving the indoor coil during the cooling mode and correspondingly determining the operating environment of the HVAC unit. 
     
     
         17 . The method of  claim 13 , wherein the method further comprises the steps of monitoring superheat control characteristics of an expansion valve of the HVAC unit during the cooling mode and correspondingly determining the operating environment of the HVAC unit. 
     
     
         18 . The method of  claim 13 , wherein the method further comprises the steps of:
 monitoring, using a humidity sensor of the HVAC unit, specific humidity or relative humidity around an outdoor coil of the HVAC unit; and   determining, by the controller, the operating environment of the HVAC unit based on the monitored humidity.   
     
     
         19 . The method of  claim 12 , wherein during a heating mode of operation of the HVAC unit, the method comprises the step of controlling, by the controller, the speed of the one or more fans to maintain a temperature downstream of the indoor coil.