Method and apparatus for improving dehumidification

Abstract

Comfort temperature and humidity levels in a conditioned space are controlled by cycling the speed of an evaporator fan motor in such a manner that, during time periods when higher sensible capacity is desired, the time in which the fan motor operates at a higher speed is increased, and during time periods when a higher latent capacity is desired, the time in which the fan motor operates at a lower speed is increased. The fan motor may be a single speed motor that is switched between on and off positions, or it may be a multiple speed motor that is cycled between a higher speed and a lower speed.

1 . A method of controlling the humidity and temperature in a conditioned space comprising the steps of:
 providing an air conditioning system having an evaporator and an associated evaporator fan motor; and   selectively operating said fan motor by rapidly cycling between a first speed and a second speed, with said second speed being higher then said first speed, to change the latent or sensible capacity.   
     
     
         2 . A method as set forth in  claim 1  and further wherein, when a higher sensible capacity is desired, the time in which the fan motor operates at said second speed is increased, and when a higher latent capacity is desired, the time in which the fan motor operates at said first speed is increased. 
     
     
         3 . A method as set forth in  claim 1  wherein said evaporator fan motor is a single speed motor and further wherein said first speed comprises an “off” disengaged condition and said second speed comprises an “on” engaged condition. 
     
     
         4 . A method as set forth in  claim 3  wherein said evaporator fan motor is brought to a complete stop before starting the next consecutive cycle. 
     
     
         5 . A method as set forth in  claim 3  wherein said evaporator fan motor is not brought to a complete stop before starting the next consecutive cycle. 
     
     
         6 . A method as set forth in  claim 3  wherein said evaporator fan motor is electrically engaged and disengaged. 
     
     
         7 . A method as set forth in  claim 3  wherein an associated evaporator fan is mechanically engaged and disengaged from said evaporator fan motor. 
     
     
         8 . A method as set forth in  claim 7  wherein the engagement and disengagement mechanism is a clutch. 
     
     
         9 . A method as set forth in  claim 1  wherein said evaporator fan motor is a multiple speed motor and further wherein said first speed comprises a lower speed from an available set of speeds for the fan motor and said second speed comprises a higher speed from an available set of speeds for the fan motor. 
     
     
         10 . A method as set forth in  claim 9  wherein said multiple speed motor comprises a dual speed fan motor. 
     
     
         11 . A method as set forth in  claim 1  wherein said step of selectively operating said evaporator fan motor is accomplished by way of a relay, a contactor, an electro-magnetic switch or an optical switch. 
     
     
         12 . A method as set forth in  claim 1  wherein the fan motor cycling frequency is defined by at least one of reliability considerations for cycled components, temperature variations in a conditioned space, humidity variations in a conditioned space, airflow fluctuations, and evaporator freeze conditions. 
     
     
         13 . A method as set forth in  claim 1  wherein the time interval at which fan operates at said higher speed is defined by at least one of the latent capacity requirement and sensible capacity requirement. 
     
     
         14 . A method as set forth in  claim 1  wherein the time of a full cycle of operation for said fan motor comprised of the time of operation at said first speed plus the subsequent time of operation at said second speed is in the range of 5 seconds to 2 minutes. 
     
     
         15 . Apparatus for controlling the humidity and temperature in a conditioned space, comprising:
 an air conditioning system having an evaporator and an associated evaporator fan motor;   a switch capable for rapidly switching said fan motor between a first speed and a second speed; and   a controller for selectively operating said switch by rapidly cycling between said first speed and said second speed, with the second speed being higher then the first speed, to change the latent or sensible capacity.   
     
     
         16 . Apparatus as set forth in  claim 15  wherein said controller operates said switch in such a manner that, when a higher sensible capacity is desired, the time in which the fan motor operates at said second speed is increased, and when a higher latent capacity is desired, the time in which the fan motor operates at said first speed is increased. 
     
     
         17 . Apparatus as set forth in  claim 16  wherein said evaporator fan motor comprises a single speed motor and further wherein said first speed comprises an “off” disengaged condition and said second speed comprises an “on” engaged condition. 
     
     
         18 . Apparatus as set forth in  claim 17  wherein said evaporator fan motor is brought to a complete stop before starting the next consecutive cycle. 
     
     
         19 . Apparatus as set forth in  claim 17  wherein the evaporator fan motor is not brought to a complete stop before starting the next consecutive cycle. 
     
     
         20 . Apparatus as set froth in  claim 17  wherein said evaporator fan motor is electrically engaged and disengaged. 
     
     
         21 . Apparatus as set forth in  claim 17  wherein an associated evaporator fan is mechanically engaged and disengaged from said evaporator fan motor. 
     
     
         22 . Apparatus as set forth in  claim 21  wherein the engagement and disengagement mechanism is a clutch. 
     
     
         23 . Apparatus as set forth in  claim 15  wherein said evaporator fan motor comprises a multiple speed motor and further wherein said first speed comprises a lower speed from an available set of speeds for the fan motor and said second speed comprises a higher speed from an available set of speeds for the fan motor. 
     
     
         24 . Apparatus as set forth in  claim 23  wherein said multiple speed motor comprises a dual speed motor. 
     
     
         25 . Apparatus as set forth in  claim 15  wherein said switch comprises a relay, a contactor, an electro-magnetic switch or an optical switch. 
     
     
         26 . Apparatus as set forth in  claim 1  wherein the fan motor cycling frequency is defined by at least one of reliability considerations for cycled components, temperature variations in a conditioned space, humidity variations in a conditioned space, airflow fluctuations, and evaporator freeze conditions. 
     
     
         27 . Apparatus as set forth in  claim 1  wherein the time interval at which fan operates at said higher speed is defined by at least one of the latent capacity requirement and sensible capacity requirement. 
     
     
         28 . Apparatus as set forth in  claim 1  wherein the time of a full cycle of operation for said fan motor comprised of the time of operation at said first speed plus the subsequent time of operation at said second speed is in the range of 5 seconds to 2 minutes.