Clothes dryer booster fan system

Abstract

A dryer exhaust duct power ventilator which is free of any dedicated internal air flow contacting devices for sensing air pressure or measuring fan RPMs and free of any hall effect sensor, but instead utilizes the auxiliary winding of a PSC motor on a centrifugal duct fan to measure the rotation of the motor and fan and thereby determine the pressure in the duct. A clip-on current sensor is located in the dryer power connection compartment and is used to detect operation of the dryer.

1 . A system for controlling airflow in a duct comprising:
 a means for determining a difference in winding voltages; where the difference in winding voltages is representative of an internal duct air pressure characteristic;   a high static condition comparator; configured for comparing an output of said means for determining a difference in winding voltages and a high static set point; and   a low static condition comparator; configured for comparing an output of said means for determining a difference in winding voltages and a low static set point.   
     
     
         2 . The system of  claim 1  wherein:
 said means for determining a difference in winding voltages is a means for determining a difference in winding voltages; 
 said high static condition comparator is a high static condition comparator; 
 where said high static set point is a low speed high static set point; and 
 where said low static set point is a high speed low static set point. 
 
     
     
         3 . The system of  claim 1  further comprising:
 a medium static condition comparator configured to compare an output of said means for determining a difference in winding voltages with a low speed low static set point. 
 
     
     
         4 . The system of  claim 3  wherein:
 said high static condition comparator is a high static condition comparator; and 
 said low static condition comparator is a low RPM condition comparator. 
 
     
     
         5 . The system of  claim 1  wherein said internal duct air pressure characteristic is a dryer exhaust duct air pressure characteristic. 
     
     
         6 . The system of  claim 5  further comprising a means for detecting a remote current; which is configured to provide control signals. 
     
     
         7 . A system for controlling airflow in a duct comprising:
 a differential amplifier, coupled to a first winding and to a second winding; where a difference in voltages on the first winding and the second winding is representative of an internal duct air pressure characteristic;   a first static condition comparator; configured for comparing an output of said differential amplifier and a first static set point; and   a second static condition comparator; configured for comparing an output of said differential amplifier and a second static set point.   
     
     
         8 . The system of  claim 7  wherein:
 said first static condition comparator is a high static condition comparator; 
 where said first static set point is a low speed high static set point; and 
 where said second static set point is a high speed low static set point. 
 
     
     
         9 . The system of  claim 7  further comprising:
 a medium static condition comparator configured to compare an output of said differential amplifier with a low speed low static set point. 
 
     
     
         10 . The system of  claim 9  wherein:
 said first static condition comparator is a high static condition comparator; and 
 said second static condition comparator is a low RPM condition comparator. 
 
     
     
         11 . The system of  claim 7  wherein said internal duct air pressure characteristic is a dryer exhaust duct air pressure characteristic. 
     
     
         12 . The system of  claim 11  further comprising a remote current sensor;
 which is configured to provide control signals. 
 
     
     
         13 . The system of  claim 7  wherein said first winding is a main winding and said second winding is an auxiliary winding. 
     
     
         14 . A system for controlling airflow in a duct comprising:
 a differential amplifier, coupled to a first winding and to a second winding; where a difference in voltages on the first winding and the second winding is representative of an internal duct air pressure characteristic;   a first static condition comparator; configured for comparing an output of said differential amplifier and a first static set point;   a second static condition comparator; configured for comparing an output of said differential amplifier and a second static set point;   a medium static condition comparator configured to compare an output of said differential amplifier with a low speed low static set point;   said first static condition comparator is a high static condition comparator; and   said second static condition comparator is a low RPM condition comparator.