Air handler unit fan installation and control method

Abstract

A method is provided including installing a variable frequency drive unit to drive a previously non-variable air handler fan of an HVAC system. The method includes setting a control strategy for the variable frequency drive. The control strategy includes a drive speed for each mode of the HVAC system. The method includes operating the HVAC system in each mode and monitoring the HVAC system. The method includes adjusting the HVAC system or the control strategy of the variable frequency drive to increase drive speed based on monitoring the HVAC system.

1  . A method comprising: 
 installing a variable frequency drive unit to drive a previously non-variable air handler fan of an HVAC system, said HVAC system having a cooling unit for operating in at least one cooling mode;    setting a control strategy for said variable frequency drive, said control strategy including a drive speed for each cooling mode of said at least one cooling mode;    operating said HVAC system in each cooling mode of said at least one cooling mode;    monitoring a superheat of an evaporator of said cooling unit and comparing said superheat with a predetermined superheat threshold, for operation of said HVAC system in each cooling mode of said at least one cooling mode;    adjusting at least one of an expansion valve of said evaporator and said control strategy of said variable frequency drive when said monitored superheat is less than said superheat threshold;    wherein said adjusting said expansion valve includes decreasing a flow of refrigerant in said evaporator and said adjusting said control strategy includes increasing said drive speed for at least one cooling mode.    
   
   
       2 . The method of  claim 1 , further comprising: 
 adjusting additional HVAC system components to increase air flow within said HVAC system when said monitored superheat is less than said superheat threshold.    
   
   
       3 . The method of  claim 1 , further comprising: 
 modifying program interlocks for said HVAC system when said monitored superheat is less than said superheat threshold;    wherein said modifying said program interlocks includes setting an HVAC system component to cycle based on a current mode of said HVAC system.    
   
   
       4 . The method of  claim 1  wherein said setting said control strategy includes setting a preset speed control strategy.  
   
   
       5 . The method of  claim 4  wherein said control strategy includes a maximum mode and a minimum mode, and wherein said setting said preset speed control strategy includes setting said maximum mode at about ninety percent capacity speed and said minimum mode at about sixty percent capacity.  
   
   
       6 . The method of  claim 5  wherein said control strategy includes an intermediate mode, and wherein said setting said present speed control strategy includes setting said intermediate mode at about seventy five percent capacity.  
   
   
       7 . The method of  claim 1  wherein said setting said control strategy includes setting a temperature based control strategy.  
   
   
       8 . The method of  claim 7  wherein said setting said temperature based control strategy includes setting a base capacity and a maximum capacity for said variable frequency drive and setting a start ramp-up temperature and an end ramp-up temperature.  
   
   
       9 . The method of  claim 8  wherein said base capacity is about sixty percent, said maximum capacity is about one hundred percent, said start ramp-up temperature is about fifty five degrees Fahrenheit and said end ramp-up temperature is about forty five degrees Fahrenheit.  
   
   
       10 . A method comprising: 
 installing a variable frequency drive unit to drive a previously non-variable air handler fan of an HVAC system, said HVAC system having a heating unit for operating in at least one heating mode;    setting a control strategy for said variable frequency drive, said control strategy including a drive speed for each heating mode of said at least one heating mode;    operating said HVAC system in each heating mode of said at least one heating mode;    monitoring a temperature of said heating unit and comparing said temperature with a predetermined temperature threshold, for operation of said HVAC system in each heating mode of said at least one heating mode;    adjusting at least one of a setpoint of said heating unit and said control strategy of said variable frequency drive when said monitored temperature is greater than said temperature threshold;    wherein said adjusting said setpoint includes decreasing a heating capacity of said heating unit and said adjusting said control strategy includes increasing said drive speed for at least one heating mode.    
   
   
       11 . The method of  claim 10 , further comprising: 
 adjusting additional HVAC system components to increase air flow within said HVAC system when said monitored temperature is greater than said temperature threshold.    
   
   
       12 . The method of  claim 10 , further comprising: 
 modifying program interlocks for said HVAC system when said monitored temperature is greater than said temperature threshold;    wherein said modifying said program interlocks includes setting an HVAC system component to cycle based on a current mode of said HVAC system.    
   
   
       13 . The method of  claim 10  wherein said setting said control strategy includes setting a preset speed control strategy.  
   
   
       14 . The method of  claim 13  wherein said control strategy includes a maximum mode and a minimum mode, and wherein said setting said preset speed control strategy includes setting said maximum mode at about sixty percent capacity speed and said minimum mode at about forty percent capacity.  
   
   
       15 . The method of  claim 14  wherein said control strategy includes an intermediate mode, and wherein said setting said present speed control strategy includes setting said intermediate mode at about fifty percent capacity.  
   
   
       16 . The method of  claim 10  wherein said setting said control strategy includes setting a temperature based control strategy.  
   
   
       17 . The method of  claim 16  wherein said setting said temperature based control strategy includes setting a base capacity and a maximum capacity for said variable frequency drive and setting a start ramp-up temperature and an end ramp-up temperature.  
   
   
       18 . The method of  claim 17  wherein said base capacity is about forty percent, said maximum capacity is about one ninety percent, said start ramp-up temperature is about eighty five degrees Fahrenheit and said end ramp-up temperature is about one hundred and five degrees Fahrenheit.  
   
   
       19 . A method comprising: 
 installing a variable frequency drive unit to drive a previously non-variable air handler fan of an HVAC system, said HVAC system having a cooling unit for operating in at least one cooling mode and a heating unit for operating in at least one heating mode;    setting a control strategy for said variable frequency drive, said control strategy including a drive speed for each cooling mode of said at least one cooling mode and each heating mode of said at least one heating mode;    operating said HVAC system in each cooling mode of said at least one cooling mode;    monitoring a superheat of an evaporator of said cooling unit and comparing said superheat with a predetermined superheat threshold, for operation of said HVAC system in each cooling mode of said at least one cooling mode;    adjusting at least one of an expansion valve of said evaporator and said control strategy of said variable frequency drive when said monitored superheat is less than said superheat threshold;    operating said HVAC system in each heating mode of said at least one heating mode;    monitoring a temperature of said heating unit and comparing said temperature with a predetermined temperature threshold, for operation of said HVAC system in each heating mode of said at least one heating mode;    adjusting at least one of a setpoint of said heating unit and said control strategy of said variable frequency drive when said monitored temperature is greater than said temperature threshold,    wherein said adjusting said expansion valve includes decreasing a flow of refrigerant in said evaporator, said adjusting said control strategy includes increasing said drive speed for at least one heating or cooling mode, and said adjusting said setpoint includes decreasing a heating capacity of said heating unit.    
   
   
       20 . The method of  claim 19  wherein setting said control strategy for said variable frequency drive includes setting at least one of a temperature based control strategy and a preset speed control strategy.