Warm air coming in from outside of the refrigerator will lead to condensation when it comes in contact with a surface below the dew point. The equipment will be either a Type I (75degrees/55% humidity) or Type II (80 degrees/55% humidity). This ambient condition will be the max condition for the unit to be able to sustain. When outside that range, heat load onto the unit, or the lack of pre-chilled product can result in excess condensation that the equipment cannot keep up with.