Method for measuring HVAC efficiency

Abstract

A method for measuring HVAC efficiency is disclosed which may be used to test various elements within the HVAC system to determine whether any element, such as a heating coil, is operating at an acceptable efficiency when compared to design specifications or previously established standards. The method may also be used to easily determine volumetric flow rate of air through the system at various points simply.

1 . A method for measuring HVAC efficiency for use with an HVAC system which includes at least one fan system for moving air through the system and at least one element which acts to affect heat transfer to or from the air within the system such as a heating or cooling coil, wherein the direction which the fan forces the air through a duct within the HVAC system is considered downstream and the opposite direction considered upstream, comprising:
 (1) turn off all elements and run the fan until the system reaches a steady state condition;   (2) measure the enthalpy of the air within the HVAC system downstream from all elements;   (3) turn on the element to be measured and run HVAC system until it reaches steady state;   (4) determine the change in the heat transfer rate introduced to the HVAC system by said element;   (5) measure the enthalpy of the air within the HVAC system at the same point at which enthalpy was measured previously; and   (6) use the change in heat transfer rate of said element and the change in enthalpy of the system air to calculate the air flow within the HVAC system.   
     
     
         2 . The method for measuring HVAC efficiency of  claim 1  in which the enthalpy of the air within the HVAC system is measured at a point downstream of said element closest to said element where the cross sectional temperature profile of the air within the duct varies less than 0.5 degrees F. 
     
     
         3 . The method for measuring HVAC efficiency of  claim 1  in which the enthalpy of the air within the HVAC system is measured at a point downstream of said element closest to said element where the air is thoroughly mixed. 
     
     
         4 . A method for measuring HVAC efficiency for use with an HVAC system which includes at least one fan for moving air through the system and at least one element which acts to affect heat transfer to or from the air within the system such as a heating or cooling coil, wherein the direction which the fan forces the air through a duct within the HVAC system is considered downstream and the opposite direction considered upstream, comprising;
 (1) turn off all elements and run the fan until the system reaches a steady state condition;   (2) measure the enthalpy of the air within the HVAC system downstream from all elements;   (3) turn on the element to be measured and run HVAC system until it reaches steady state;   (4) determine the change in the heat transfer rate introduced to the HVAC system by said element;   (5) compare the actual change in the heat transfer rate from said element to the rated heat transfer of said element; and   (6) if the difference between the actual heat transfer rate of said element and the rated heat transfer rate of said element is unacceptable, investigate the HVAC system to determine possible causes for the difference.   
     
     
         5 . The method for measuring HVAC efficiency of  claim 4  in which the enthalpy of the air within the HVAC system is measured at a point downstream of said element closest to said element where the cross sectional temperature profile of the air within the duct varies less than 0.5 degrees F. 
     
     
         6 . The method for measuring HVAC efficiency of  claim 4  in which the enthalpy of the air within the HVAC system is measured at a point downstream of said element closest to said element where the air is thoroughly mixed. 
     
     
         7 . A method for measuring HVAC efficiency for use with an HVAC system which includes at least one fan for moving air through the system and at least one element which acts to affect heat transfer to or from the air within the system such as a heating or cooling coil and wherein there is at least one passive element which does not act to significantly affect heat transfer to or from the air within the system, wherein the direction which the fan forces the air through a duct within the HVAC system is considered downstream and the opposite direction considered upstream, comprising;
 (1) turn off all elements and run the fan system until the system reaches a steady state condition;   (2) measure the enthalpy of the air within the HVAC system downstream from all elements;   (3) turn on any element which is not passive and run HVAC system until it reaches steady state;   (4) determine the change in the heat transfer rate introduced to the HVAC system by said element;   (5) measure the enthalpy of the air within the HVAC system at the same point at which enthalpy was measured previously;   (6) use the change in heat transfer rate of said element and the change in enthalpy of the system air to calculate the air flow within the HVAC system;   (7) add or modify passive element;   (8) run the HVAC system until it reaches steady state;   (9) measure the enthalpy of the air within the HVAC system at the same point at which enthalpy was measured previously;   (10) determine the change in the heat transfer rate introduced to the HVAC system by said passive element;   (11) use the change in the heat transfer rate and the change in enthalpy to calculate the air flow within the HVAC system; and   (12) compare the change in the heat transfer rate and the change in air flow between those values for the HVAC system without adding or changing said passive element to determine the efficacy of the addition or modification of said passive element.   
     
     
         8 . The method for measuring HVAC efficiency of  claim 7  in which the enthalpy of the air within the HVAC system is measured at a point downstream of said element closest to said element where the cross sectional temperature profile of the air within the duct varies less than 0.5 degrees F. 
     
     
         9 . The method for measuring HVAC efficiency of  claim 7  in which the enthalpy of the air within the HVAC system is measured at a point downstream of said element closest to said element where the air is thoroughly mixed. 
     
     
         10 . A method for measuring HVAC efficiency for use with an HVAC system which includes at least one fan for moving air through the system and at least one element which acts to affect heat transfer to or from the air within the system such as a heating or cooling coil, wherein the direction which the fan forces the air through a duct within the HVAC system is considered downstream and the opposite direction considered upstream, comprising;
 (1) turn off all elements and run the fan until the system reaches a steady state condition;   (2) measure the enthalpy of the air within the HVAC system downstream from all elements;   (3) turn on the element to be measured and run HVAC system until it reaches steady state; and   (4) determine the change in the heat transfer rate introduced to the HVAC system by said element.   
     
     
         11 . The method for measuring HVAC efficiency of  claim 10  in which the enthalpy of the air within the HVAC system is measured at a point downstream of said element closest to said element where the cross sectional temperature profile of the air within the duct varies less than 0.5 degrees F. 
     
     
         12 . The method for measuring HVAC efficiency of  claim 10  in which the enthalpy of the air within the HVAC system is measured at a point downstream of said element closest to said element where the air is thoroughly mixed. 
     
     
         13 . A method for measuring HVAC efficiency for use with an HVAC system which includes at least one fan for moving air through the system and at least one element which acts to affect heat transfer to or from the air within the system such as a heating or cooling coil and wherein there is at least one passive element which does not act to significantly affect heat transfer to or from the air within the system, wherein the direction which the fan forces the air through a duct within the HVAC system is considered downstream and the opposite direction considered upstream, comprising;
 (1) turn off all elements and run the fan until the system reaches a steady state condition;   (2) measure the enthalpy of the air within the HVAC system downstream from all elements;   (3) turn on any element which is not passive and run HVAC system until it reaches steady state;   (4) determine the change in the heat transfer rate introduced to the HVAC system by said element;   (5) measure the enthalpy of the air within the HVAC system at the same point at which enthalpy was measured previously;   (6) use the change in heat transfer rate of said element and the change in enthalpy of the system air to calculate the air flow within the HVAC system;   (7) add or modify passive element;   (8) run the HVAC system until it reaches steady state;   (9) measure the enthalpy of the air within the HVAC system at the same point at which enthalpy was measured previously;   (10) determine the change in the heat transfer rate introduced to the HVAC system by said passive element;   (11) use the change in the heat transfer rate and the change in enthalpy to calculate the air flow within the HVAC system; and   (12) compare the change in the heat transfer rate and the change in air flow between those values for the HVAC system without adding or changing said passive element to determine the efficacy of the addition or modification of said passive element.   
     
     
         14 . The method for measuring HVAC efficiency of  claim 13  in which the enthalpy of the air within the HVAC system is measured at a point downstream of said element closest to said element where the cross sectional temperature profile of the air within the duct varies less than 0.5 degrees F. 
     
     
         15 . The method for measuring HVAC efficiency of  claim 13  in which the enthalpy of the air within the HVAC system is measured at a point downstream of said element closest to said element where the air is thoroughly mixed.