The hot glycol runs through the Evaporator core in an independent circuit intended for defrosting only, promoting efficient melting at low cost. The glycol is heated in a heat exchanger that absorbs heat from the exhaust gas of one or more compressors. The heated glycol is kept in an insulated tank until a thaw cycle is required. Glycol pumps deliver hot glycol, maintained at 20°C, to the evaporator being defrosted. The hot glycol enters the secondary circuit tubes which are entwined with the refrigeration circuit so that heat can be conducted from the tubes to the coil fins, melting the ice. The drain pan is also heated by a coil where the hot glycol keeps the pan warm while the melted ice is drained.

Hot glycol defrost system for multiple evaporators


• Negligible heat dissipation inside the Chamber
• No thermal shock in the cooling circuit
• 80% less Annual Cost compared to electric defrost
• The group of control valves and defrost piping is simple and low cost


• Minimum chamber temperature with this defrost method is -18°C.• At this temperature of -18˚C or even below 0˚C the power of 

glycol pumping increases

due to the higher viscosity of the solution raising the pumping pressure needed to move the cold glycol solution out of the coil at the start of the defrost.
• The freezing point of the glycol solution must be kept below the evaporation temperature of the refrigerant in the coil to prevent freezing and bursting of the coil tubes during normal cooling operation.