Humidity control algorithm

Abstract

A system and method is provided to control the operation of an HVAC system to remove humidity from an indoor air environment without cooling the indoor air environment. The system includes a thermostat that operates the HVAC system to remove humidity when the sensed humidity falls below a humidity set point. After operation of the HVAC system, the thermostat monitors whether the temperature within the indoor air environment falls due to the operation of the HVAC system. If the temperature within the indoor air environment falls consistently, the humidity control algorithm determines that the HVAC system cannot operate without cooling and prevents future operation of the HVAC system to provide only dehumidification. If, however, the humidity control algorithm determines that the HVAC system can operate to dehumidify without cooling, the humidity control algorithm operates the HVAC system accordingly.

1 . A method of operating an HVAC system capable of dehumidifying and cooling an indoor air environment comprising the steps of:
 sensing the humidity in a location having the indoor air environment controlled by the HVAC system;   comparing the sensed humidity to a humidity set point;   activating the HVAC system when the sensed humidity exceeds the humidity set point;   sensing a starting temperature in the location having the indoor air environment controlled by the HVAC system upon activation of the HVAC system;   monitoring a current temperature in the location having the indoor air temperature controlled by the HVAC system;   comparing the starting temperature to the current temperature; and   deactivating the HVAC system when the current temperature falls below the starting temperature by more than a temperature limit.   
   
   
       2 . The method of  claim 1  wherein the HVAC system is deactivated even when the sensed humidity exceeds the humidity set point when the change in temperature exceeds the temperature limit. 
   
   
       3 . The method of  claim 1  wherein the HVAC system is activated when the sensed humidity exceeds the humidity threshold and the current temperature is below a temperature set point. 
   
   
       4 . The method of  claim 3  wherein the temperature set point and the humidity set point are user selectable. 
   
   
       5 . The method of  claim 1  wherein the step of activating the HVAC system includes at least activating a dehumidifier and activating a blower to operate in concert with the dehumidifier. 
   
   
       6 . The method of  claim 1  wherein the HVAC system is deactivated when the current temperature falls below the start temperature by more than the temperature limit and the current temperature is below the temperature set point. 
   
   
       7 . A method of operating an HVAC system capable of dehumidifying and cooling an indoor air environment comprising the steps of:
 sensing the humidity in a location having the indoor air environment controlled by the HVAC system;   comparing the sensed humidity to a humidity set point;   activating the HVAC system when the sensed humidity exceeds the humidity set point;   sensing a starting temperature of the air flow from the HVAC system upon activation of the HVAC system;   monitoring a current temperature of the air flow from the HVAC system after activation of the HVAC system;   comparing the current temperature of the air flow to the starting temperature; and   deactivating the HVAC system when the current temperature of the air flow falls below the starting temperature by more than a temperature limit.   
   
   
       8 . The method of  claim 7  wherein the HVAC system is deactivated even when the sensed humidity exceeds the humidity set point when the current air flow temperature falls below the starting temperature by more than the temperature limit. 
   
   
       9 . The method of  claim 7  wherein the HVAC system is activated when the sensed humidity exceeds the humidity threshold and a current temperature of the indoor air environment controlled by the HVAC system is below a temperature set point. 
   
   
       10 . The method of  claim 9  wherein the temperature set point and the humidity set point are user selectable. 
   
   
       11 . The method of  claim 7  wherein the step of activating the HVAC system includes at least activating a dehumidifier and activating a blower to operate in concert with the dehumidifier. 
   
   
       12 . The method of  claim 7  wherein the HVAC system is deactivated when the air flow temperature falls below the starting temperature by more than the temperature limit and the current temperature is below the temperature set point. 
   
   
       13 . A method of operating a thermostat to control the activation of an HVAC system, the method comprising the steps of:
 sensing the humidity of an indoor air environment controlled by the HVAC system;   comparing the sensed humidity to a humidity set point entered into the thermostat;   activating the HVAC system when the sensed humidity exceeds the humidity set point;   sensing a starting temperature related to the indoor air environment upon activation of the HVAC system;   monitoring a current temperature related to the indoor air environment after activation of the HVAC system;   comparing the current temperature to the starting temperature; and   deactivating the HVAC system when the current temperature falls below the starting temperature by more than a temperature limit.   
   
   
       14 . The method of  claim 13  wherein the current temperature is the temperature of the indoor air environment controlled by the HVAC system. 
   
   
       15 . The method of  claim 14  wherein the current temperature is sensed by a temperature sensor within the thermostat. 
   
   
       16 . The method of  claim 14  wherein the HVAC system is deactivated even when the sensed humidity exceeds the humidity set point when the current temperature falls below the starting temperature by more than the temperature limit. 
   
   
       17 . The method of  claim 13  wherein the temperature set point and the humidity set point are user settable in the thermostat. 
   
   
       18 . The method of  claim 13  wherein the current temperature is the temperature of the air flow from the blower of the HVAC system. 
   
   
       19 . The method of  claim 18  further comprising the steps of:
 positioning an air flow temperature probe to detect the temperature of the air flow from the HVAC system; and   communicating the air flow temperature from the air flow temperature probe to the thermostat.   
   
   
       20 . A system for controlling the operation of an HVAC system capable of dehumidifying and cooling an indoor air environment, the system comprising:
 a thermostat positionable within the indoor air environment to be controlled by the HVAC system, the thermostat having operational output in communication with the HVAC system;   a temperature sensor coupled to the thermostat and operable to determine the air temperature of the indoor air environment;   a humidity sensor coupled to the thermostat and operable to determine the humidity of the indoor air environment; and   an air flow probe positionable downstream from the dehumidifier to sense the temperature of the air flow from the HVAC system.