Patent ID: 8902071

Claim:
An HVAC controller configured to control one or more components of an HVAC system, the HVAC controller comprising: a user interface including a display; a memory; a controller connected to the memory and the user interface, the controller programmed to monitor a delta T that is representative of a difference in temperature between a return air side and a discharge air side of an HVAC system during operation of the HVAC system, and to determine a performance level of the HVAC system based, a least in part, on one or more delta T limits stored in the memory of the HVAC controller; and wherein the controller is configured to record a delta T fault in the memory of the HVAC controller if the monitored delta T falls outside of one or more of the delta T limits for at least a predetermined amount of time during a current HVAC cycle, the controller further configured to determine whether to display on the display of the HVAC controller a user alert based at least in part on a count of the delta T faults recorded within a predetermined period of time or during a predetermined number of HVAC cycles.