Hvac air temperature safety system

Abstract

A system for operating an HVAC system in the event of a thermostat failure is provided. The system includes the steps of activating a safety control program upon determining the thermostat failure has occurred, resetting a first timer, determining if an amount of time in the first timer exceeds a first time period, activating an HVAC system blower when the time remaining first timer exceeds the first time period, measuring a temperature of conditioned air with a temperature sensor, determining whether the temperature of conditioned air is less than a preset minimum temperature, activating an HVAC system heating unit if the conditioned air is less than the preset minimum temperature, determining whether the temperature of conditioned air is greater than a preset maximum temperature, activating an HVAC system cooling unit if the conditioned air is greater than the preset maximum temperature, and repeating the process.

What is claimed is: 
     
         1 . A method for operating an HVAC system comprising:
 determining whether a failure of a thermostat in operable communication with an HVAC system has occurred;   activating a safety control program upon determining the thermostat failure has occurred, wherein the safety control program resides on electronically readable storage medium in operable communication with the HVAC system;   resetting a first timer;   determining if an amount of time in the first timer exceeds a first time period;   increasing the amount of time remaining in the first timer by a first time increment if the amount of time remaining in the first timer does not exceed the first time period;   activating an HVAC system blower when the time remaining first timer exceeds the first time period;   measuring a temperature of conditioned air on a temperature sensor, wherein the temperature sensor is in communication with the safety control program and is not associated with the failed thermostat;   determining whether the temperature of conditioned air is less than a preset minimum temperature;   activating an HVAC system heating unit if the conditioned air is less than the preset minimum temperature;   operating the heating unit until the conditioned air is greater than a heating temperature set point;   determining, if the conditioned air is not less than the preset minimum temperature, whether the temperature of conditioned air is greater than a preset maximum temperature;   activating an HVAC system cooling unit if the conditioned air is greater than the preset maximum temperature;   operating the cooling unit until the conditioned air is less than a cooling temperature set point; and   returning, if the temperature of conditioned air is not greater than the preset maximum temperature, to the step of resetting the first timer.   
     
     
         2 . The method of  claim 1 , wherein the first time period is preset. 
     
     
         3 . The method of  claim 1 , wherein the first time period equals thirty minutes. 
     
     
         4 . The method of  claim 1 , wherein the first time increment equals one second. 
     
     
         5 . The method of  claim 1 , wherein the step of determining whether the temperature of conditioned air is less than a preset minimum temperature further comprises determining whether the temperature of conditioned air is less than or equal to the preset minimum temperature. 
     
     
         6 . The method of  claim 1 , wherein the step of activating an HVAC system heating unit if the conditioned air is less than the preset minimum temperature further comprises activating an HVAC system heating unit if the conditioned air is less or equal to the preset minimum temperature. 
     
     
         7 . The method of  claim 1 , wherein the step of operating the heating unit until the conditioned air is greater than a heating temperature set point further comprises operating the heating unit until the conditioned air is greater than or equal to the heating temperature set point. 
     
     
         8 . The method of  claim 1 , wherein the step of determining, if the conditioned air is not less than the preset minimum temperature, whether the temperature of conditioned air is greater than to a preset maximum temperature further comprises determining, if the conditioned air is not less than the preset minimum temperature, whether the temperature of conditioned air is greater than or equal to a preset maximum temperature. 
     
     
         9 . The method of  claim 1 , wherein the step of activating an HVAC system cooling unit if the conditioned air is greater than the preset maximum temperature further comprises activating an HVAC system cooling unit if the conditioned air is greater than or equal to the preset maximum temperature. 
     
     
         10 . The method of  claim 1 , wherein the step of operating the cooling unit until the conditioned air is less than a cooling temperature set point further comprises operating the cooling unit until the conditioned air is less than or equal to a cooling temperature set point. 
     
     
         11 . The method of  claim 1 , wherein the second time period equals three minutes. 
     
     
         12 . The method of  claim 1 , wherein the preset minimum temperature equals forty degrees Fahrenheit. 
     
     
         13 . The method of  claim 1 , wherein the preset maximum temperature equals one hundred degrees Fahrenheit. 
     
     
         14 . The method of  claim 1 , wherein the heating temperature set point equals forty three degrees Fahrenheit. 
     
     
         15 . The method of  claim 1 , wherein the cooling temperature set point equals ninety seven degrees Fahrenheit. 
     
     
         16 . The method of  claim 1 , wherein the temperature sensor is provided in an air return duct. 
     
     
         17 . The method of  claim 1 , wherein after the step of activating an HVAC system blower when the time remaining first timer exceeds the first time period, further comprising:
 resetting a second timer;   determining if an amount of time in the second timer exceeds a second time period;   increasing the amount of time remaining in the second timer by a second time increment if the amount of time remaining in the timer does not exceed the second time period; and   measuring the temperature of conditioned air on a temperature sensor when the second timer exceeds the second time period;   
     
     
         18 . The method of  claim 17 , wherein the second time period is three minutes. 
     
     
         19 . The method of  claim 17 , wherein the second time increment is one second. 
     
     
         20 . A method for operating an HVAC system upon thermostat failure comprising:
 activating an HVAC safety control program;   resetting a first timer;   determining if an amount of time in the first timer exceeds a preset length of time between air sampling cycles;   increasing the amount of time remaining in the first timer by a first time increment if the amount of time remaining in the first timer does not exceed the preset length of time between air sampling cycles;   activating an HVAC system blower when the time remaining first timer exceeds the preset length of time between air sampling cycles;   measuring a temperature of conditioned air on a temperature sensor, wherein the temperature sensor is in communication with the HVAC safety control program;   determining whether the temperature of conditioned air is less than a low temperature limit set point;   activating an HVAC system heating unit if the conditioned air is less than the low temperature limit set point;   operating the heating unit until the conditioned air is greater than a target heating temperature set point;   determining, if the conditioned air is not less than the low temperature limit set point, whether the temperature of conditioned air is greater than a high temperature limit set point;   activating an HVAC system cooling unit if the conditioned air is greater than the high temperature limit set point;   operating the cooling unit until the conditioned air is less than a target cooling temperature set point; and   returning, if the temperature of conditioned air is not greater than the high temperature limit set point, to the step of resetting the first timer.