Method and system to vary suction temperature to postpone frost formation

Abstract

A cooling system includes an evaporator coil and a compressor fluidly coupled to the evaporator coil. A circulation fan is arranged to direct air through the evaporator coil and through a discharge air duct into a conditioned space. At least one sensor is disposed in at least one of the discharge air duct, the conditioned space, and the evaporator coil. An HVAC controller is electrically coupled to the at least one sensor and electrically coupled to the compressor. The HVAC controller is configured to receive a measurement of an HVAC parameter from the at least one sensor, determine if the HVAC parameter indicates frost formation on the evaporator coil, and, responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, raise a saturated suction temperature of the evaporator coil.

What is claimed is: 
     
         1 . A cooling system, comprising:
 an evaporator coil;   a compressor fluidly coupled to the evaporator coil;   a circulation fan arranged to direct air through the evaporator coil and through a discharge air duct into a conditioned space;   at least one sensor, the at least one sensor being disposed in at least one of the discharge air duct, the conditioned space, and the evaporator coil;   an HVAC controller electrically coupled to the at least one sensor and the compressor;   wherein the HVAC controller is configured to:
 receive a measurement of an HVAC parameter from the at least one sensor; 
 determine if the HVAC parameter indicates frost formation on the evaporator coil; and 
 responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, raise a saturated suction temperature of the evaporator coil. 
   
     
     
         2 . The cooling system of  claim 1 , wherein the at least one sensor is at least one of:
 a temperature sensor disposed in the conditioned space; and   a flow meter disposed in the discharge air duct.   
     
     
         3 . The cooling system of  claim 2 , wherein the HVAC parameter is at least one of:
 a discharge air temperature measured by the temperature sensor; and   a discharge air velocity measured by the flow meter.   
     
     
         4 . The cooling system of  claim 2 , wherein the temperature sensor is electrically coupled to the HVAC controller via at least one of a wired connection and a wireless connection. 
     
     
         5 . The cooling system of  claim 2 , wherein the temperature sensor comprises at least one of a thermocouple, a thermometer, and a thermostat. 
     
     
         6 . The cooling system of  claim 1 , comprising an evaporator pressure regulator (“EPR”) fluidly coupled between the evaporator coil and the compressor. 
     
     
         7 . The cooling system of  claim 6 , wherein the EPR is electrically coupled to the HVAC controller via at least one of a wired connection and a wireless connection. 
     
     
         8 . The cooling system of  claim 7 , wherein, responsive to the determination that the HVAC parameter indicates frost formation on the evaporator coil, the HVAC controller is configured to signal the EPR to reduce flow of a refrigerant from the evaporator coil to the compressor thereby raising the saturated suction temperature of the evaporator coil. 
     
     
         9 . A method for operating a refrigerated display case, the method comprising:
 measuring, by at least one sensor, an HVAC parameter;   determining, by an HVAC controller electrically coupled to the at least one sensor, if the HVAC parameter indicates frost formation on an evaporator coil; and   responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, raise a saturated suction temperature of the evaporator coil.   
     
     
         10 . The method of  claim 9 , wherein the at least one sensor is at least one of:
 a temperature sensor disposed in the conditioned space; and   a flow meter disposed in the discharge air duct.   
     
     
         11 . The method of  claim 10 , wherein the HVAC parameter is at least one of:
 a discharge air temperature measured by the temperature sensor; and   a discharge air velocity measured by the flow meter.   
     
     
         12 . The method of  claim 10 , wherein the temperature sensor is electrically coupled to the HVAC controller via at least one of a wired connection and a wireless connection. 
     
     
         13 . The method of  claim 10 , wherein the temperature sensor comprises at least one of a thermocouple, a thermometer, and a thermostat. 
     
     
         14 . The method of  claim 9 , comprising an evaporator pressure regulator (“EPR”) fluidly coupled between the evaporator coil and a compressor. 
     
     
         15 . The method of  claim 14 , wherein the EPR is electrically coupled to the HVAC controller via at least one of a wired connection and a wireless connection. 
     
     
         16 . The method of  claim 14 , wherein, responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, signaling, by the HVAC controller, the EPR to reduce a flow of refrigerant from the evaporator coil to the compressor thereby raising the saturated suction temperature of the evaporator coil. 
     
     
         17 . A cooling system, comprising:
 an evaporator coil;   a compressor fluidly coupled to the evaporator coil;   a circulation fan arranged to direct air through the evaporator coil and through a discharge air duct into a conditioned space;   at least one sensor, the at least one sensor being disposed in at least one of the discharge air duct, the conditioned space, and the evaporator coil;   an evaporator pressure regulator (“EPR”) fluidly coupled between the evaporator coil and the compressor;   an HVAC controller electrically coupled to the at least one sensor, the EPR and the compressor;   wherein the HVAC controller is configured to:
 receive a measurement of an HVAC parameter from the at least one sensor; 
 determine if the HVAC parameter indicates frost formation on the evaporator coil; and 
 responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, the HVAC controller is configured to signal the EPR to reduce flow of a refrigerant from the evaporator coil to the compressor thereby raising the saturated suction temperature of the evaporator coil. 
   
     
     
         18 . The cooling system of  claim 17 , wherein the at least one sensor is at least one of:
 a temperature sensor disposed in the conditioned space; and   a flow meter disposed in the discharge air duct.   
     
     
         19 . The cooling system of  claim 18 , wherein the HVAC parameter is at least one of:
 a discharge air temperature measured by the temperature sensor; and   a discharge air velocity measured by the flow meter.   
     
     
         20 . The cooling system of  claim 18 , wherein the temperature sensor and the EPR are electrically coupled to the HVAC controller via at least one of a wired connection and a wireless connection.