Auto test for delta T diagnostics in an HVAC system

An HVAC controller configured to control one or more components of an HVAC system, the HVAC controller comprising:

• a memory;
• an I/O block, for receiving one or more signals from the HVAC system including one or more signals related to a delta T parameter value of the HVAC system, wherein the delta T parameter represents a difference in air temperature between a return air side and a discharge air side of the HVAC system, and for providing one or more control signals to the HVAC system including one or more control signals to activate the HVAC system;
• a user interface;
• a controller operatively coupled to the memory, the I/O block and the user interface, the controller programmed to initiate a delta T test sequence in response to a request received via the user interface, and once initiated and without further user input, to execute a delta T test for each valid equipment stage combination of the HVAC system, each delta T test including:
• starting a timer to monitor an elapsed time;
• providing one or more control signals to activate a first/next valid equipment stage combination of the HVAC system;
• monitoring the one or more signals related to the delta T parameter value;
• determining the delta T parameter value;
• monitoring a rate of change of the delta T parameter value;
• determining when the rate of change of the delta T parameter value falls below a threshold value, indicating a stabilized delta T parameter value at a stabilized elapsed time;
• and
• recording the stabilized delta T parameter value and the stabilized elapsed time in the memory.

A method of monitoring a performance of an HVAC system having one or more components controlled at least in part by an HVAC controller, the HVAC controller having a memory and a controller, the method comprising:

• providing one or more control signals from the HVAC controller to activate the HVAC system;
• monitoring by the controller one or more signals from the HVAC system that are related to a delta T parameter value of the HVAC system, wherein the delta T parameter value represents a difference in air temperature between a return air side and a discharge air side of the HVAC system;
• determining, by the controller, the delta T parameter value;
• monitoring, by the controller, a rate of change of the delta T parameter value;
• determining by the controller when the delta T parameter value becomes stable, indicating a stabilized delta T parameter value;
• and
• recording by the controller the stabilized delta T parameter value in the memory of the HVAC controller.