 In practical situations, when an air coil freeze stat is not used, bypassed, or defeated, the air coil can freeze, and this causes a lack of air flow to the facility.By contrast, when a water coil freeze stat is not used, the water coil can get so cold that it can freeze the cooling liquid in the exchanger and burst the exchanger.A ruptured heat exchanger mixes contaminants such as freon and oil into the coolant.