I´m having some problems keeping the proper temperature in a new Hussmann ISF low temperature island. The unit is used for frozen packaged fish steaks. Most of the time, the steaks are rock-solid frozen, but recently I´ve noticed that the upper layer of the packages softens a little bit. I´m using four defrosts per day (one every 6 hours) with a 30 minutes failsafe adjustment. The defrost termination is by evaporator pressure, and it´s adjusted at 80 psig for R-22 . According to my data logger, the temperature at the product level gets up to 36 F during defrosts, and it takes almost two hours from defrost initiation to recover to 6-8 F. Does all of this sound normal or am I doing something wrong?
One thing I´ve noticed is that the defrost heater is not embedded in the evaporator coil, but it is located next to it, in the air flow duct, so that in order for the evaporator to defrost, the fan must be kept running as to force the heated air over the evaporator. Strangely, this heated air also circulates through the product section during defrosts. Couldn´t this defrost method lead to a little thawing of the merchanside?