Refrigerated units without proportional cooling have refrigeration systems which are either switched on or off. Systems with proportional cooling have a special electronic valve which automatically controls the cooling capacity. This allows for accurate control of the required cooling power and at the same time saves energy (up to 90 %) and waste heat. , Refrigerated units without proportional cooling have refrigeration systems which are either switched on or off. Systems with proportional cooling have a special electronic valve which automatically controls the cooling capacity. This allows for accurate control of the required cooling power and at the same time saves energy (up to 90 %) and waste heat.