Adaptive defrost

The adaptive defrost concept operates on demand, initiating a defrost cycle only when needed, thereby saving energy and yet maintaining refrigeration system efficiency. This is accomplished by automatically adjusting the frost accumulation period to achieve an optimal predetermined defrost time. The optimal defrost time is previously determined for the particular refrigeration system and programmed into the control. The next frost accumulation time period is made a function of the optimal defrost time, the previous frost accumulation time, and the previous actual defrost time. The system thus operates according to the following relationships: Ta=(a -1)+K(Do-Da), where Ta=length of the next frost accumulation period; T(a-1)=length of the last frost accumulation period; Do=optimal defrost time; Da=length of the actual defrost time; and K=system constant that determines the multiple by which the frost accumulation period will change for each increment of error in the defrost time