Patent ID: 8417386

Claim:
A method of controlling a heating, ventilation, and air conditioning (HVAC) system, comprising: executing a field defrost algorithm; monitoring whether a condition meets a criteria, wherein the condition meeting the criteria comprises an ambient zone temperature being determined to be within a predetermined range; executing a certification defrost algorithm in parallel with the field defrost algorithm in response to the condition meeting the criteria; performing a certification defrost cycle if demanded by the certification defrost algorithm; performing a field defrost cycle if demanded by the field defrost algorithm; and exiting the certification defrost algorithm in response to the field defrost algorithm demanding a field defrost cycle while the ambient zone temperature is determined to be outside the predetermined range; wherein the predetermined range comprises (1) a low temperature in a range of about 30 degrees Fahrenheit to about 34 degrees Fahrenheit and (2) a high temperature in a range of about 34 degrees Fahrenheit to about 40 degrees Fahrenheit.