Method of defrosting an energy recovery ventilator unit

Abstract

A method of defrosting an energy recovery ventilator unit. The method comprises activating a defrost process of an enthalpy-exchange zone of the energy recovery ventilator unit when an air-flow blockage in the enthalpy-exchange zone coincides with a frost threshold in the ambient environment surrounding the energy recovery ventilator unit. The method also comprises terminating the defrost process, including terminating the defrost process when an operating condition in the vicinity of the enthalpy-exchange zone substantially returns to a pre-frosting operating condition.

What is claimed is: 
     
         1 . A method of defrosting an energy recovery ventilator unit, comprising:
 activating a defrost process of an enthalpy-exchange zone of the energy recovery ventilator unit when an air-flow blockage in the enthalpy-exchange zone coincides with a frost threshold in the ambient environment surrounding the energy recovery ventilator unit; and   terminating the defrost process, including terminating the defrost process when an operating condition in the vicinity of the enthalpy-exchange zone substantially returns to a pre-frosting operating condition.   
     
     
         2 . The method of  claim 1 , wherein terminating the process to defrost further includes determining the operating condition, including measuring an air-pressure difference across the enthalpy-exchange zone while the energy recovery ventilator unit is operating. 
     
     
         3 . The method of  claim 2 , wherein terminating the defrost process includes terminating after the operating condition, corresponding to the measured air-pressure difference across the enthalpy-exchange zone, has decreased to substantially equal the pre-frosting operating condition, corresponding to an air-pressure difference across the enthalpy-exchange zone measured prior to activating the defrost process. 
     
     
         4 . The method of  claim 1 , wherein terminating the process to defrost further includes determining the operating condition, including measuring a heat transfer efficiency across the enthalpy-exchange zone while the energy recovery ventilator unit is operating. 
     
     
         5 . The method of  claim 4 , wherein terminating the process to defrost includes terminating after the operating condition, corresponding to the measured heat transfer efficiency, has decreased to be substantially equal to the pre-frosting operating condition, corresponding to an heat transfer efficiency across the enthalpy-exchange zone prior to activating the defrost process. 
     
     
         6 . The method of  claim 1 , wherein terminating the process to defrost includes terminating after a preselected time limit is reached. 
     
     
         7 . The method of  claim 1 , wherein the defrost process further includes activating a powered heat source configured to warm air in an intake air zone or an exhaust air zone located inside of the energy recovery ventilator unit. 
     
     
         8 . The method of  claim 7 , wherein the powered heat source includes a modular electric heater coupled to the outside of the energy recovery ventilator unit and located upstream of an air intake opening of the intake air zone. 
     
     
         9 . The method of  claim 7 , wherein activating the powered heat source further including adjusting the powered heat source to one of a plurality of different levels of heat generation as a function of an ambient air temperature surrounding the energy recovery ventilator unit. 
     
     
         10 . The method of  claim 1 , wherein the defrost process further includes reducing airflow from an air intake zone located inside of the energy recovery ventilator unit to the enthalpy exchange-zone. 
     
     
         11 . The method of  claim 10 , wherein the defrost process further includes activating an air controller assembly so as to allow air-flow through a secondary air-intake opening connected to a supply zone located inside of the energy recovery ventilator unit. 
     
     
         12 . The method of  claim 11 , wherein the reduction in the air flow from the air intake zone and an increase in the air-flow through the secondary air-intake opening are coordinated such that the air-pressure inside of the energy recovery ventilator unit substantially equals an ambient air pressure surrounding the energy recovery ventilator unit. 
     
     
         13 . The method of  claim 11 , wherein the defrost process further includes activating a heat source of an air-handling unit coupled to the energy recovery ventilator unit, such that the air exiting the air-handling unit is heated to a substantially same temperature than before the defrosting process was activated. 
     
     
         14 . The method of  claim 13 , wherein the heat source in the air-handling unit is activated at the same time, or before, the air controller assembly is activated. 
     
     
         15 . An energy recovery ventilator unit, comprising:
 a defrost control module configured to:
 activate a defrost process of an enthalpy-exchange zone of the energy recovery ventilator unit when an air-flow blockage in the enthalpy-exchange zone coincides with a frost threshold in the ambient environment surrounding the energy recovery ventilator unit; and 
 terminate the defrost process, including terminating the defrost process when an operating condition in the vicinity of the enthalpy-exchange zone substantially returns to a pre-frosting operating condition. 
   
     
     
         16 . The unit of  claim 15 , further including pressure transducers configured to measuring an air-pressure difference across the enthalpy-exchange zone while the energy recovery ventilator unit is operating and configured to transmit the measured air pressure difference to the defrost control module, and wherein the defrost control module is configured to determine the operating condition as including the air-pressure difference. 
     
     
         17 . The unit of  claim 15 , further including temperature sensors configured to measuring air temperatures of an intake air zone, a supply air zone, and a return air zone located inside of the energy recovery ventilator unit and configured to transmit the measured air temperatures to the defrost control module, and wherein the defrost control module is configured to determine the operating condition as including a heat transfer efficiency determined from the measured air temperatures. 
     
     
         18 . The unit of  claim 15 , wherein the defrost control module is further configured to terminate the defrost process after a preselected time limit is reached. 
     
     
         19 . The unit of  claim 15 , further including a powered heat source configured to warm air in an intake air zone or an exhaust air zone located inside of the energy recovery ventilator unit, wherein the defrost control module is configured to activate or deactivate the heat source. 
     
     
         20 . The unit of  claim 19 , wherein the powered heat source includes a modular electric heater configured to be coupled to the outside of the energy recovery ventilator unit and located upstream of an air intake opening of the intake air zone.