Defrost learning algorithm based on time of defrost state operation

A heating, ventilation, and/or air conditioning (HVAC) system, comprising:

• an outdoor heat exchanger;
• a refrigeration coil temperature sensor configured to monitor a temperature of the outdoor heat exchanger;
• an ambient outdoor temperature sensor configured to monitor an ambient outdoor temperature;
• and
• a controller configured to:
• monitor the refrigeration coil temperature sensor and the ambient outdoor temperature sensor;
• calculate an Actual Coil Delta Temperature (ACDT);
• compare the calculated ACDT to an Initiate Delta Temperature (DTINIT) associated with a measured ambient outdoor temperature;
• initiate a defrost procedure in response to the calculated ACDT being greater than or equal to the DTINIT;
• determine if a duration of the defrost procedure is within a predetermined time threshold;
• adjust a parameter of a next defrost procedure in response to determining that a predetermined number of consecutive defrost procedures have occurred outside of the predetermined time threshold;
• estimate Clear Coil Delta Temperature (CCDT) values for a plurality of outdoor ambient temperatures using a first linear equation:
• Y1=MX+B, wherein the controller is further configured to estimate DTINIT values for the plurality of outdoor ambient temperatures using a second linear equation:
• Y2=MX+KB, and wherein Y1 and Y2 are Y-axis coordinates, M is a slope, X is an X-axis coordinate, B is a Y intercept, and K is a constant;
• and
• reduce the constant K in response to the controller determining that the predetermined number of consecutive defrost procedures occurred for a longer time than the predetermined time threshold.