Part Number 80-01111-9 7/10 135REFRIGERATION DIAGNOSTICSQM20The QM20 ice machines have a very small refrigerantcharge, 4.59 oz (130 g) and we do not recommenddiagnosing the ice machine using refrigerant pressures. Forthis reason we have not included refrigeration access fittings.Verify that your water flow is even across the entireevaporator before diagnosing the refrigeration system.Mineral build-up on the evaporator assembly can causewater tracking and an erratic ice fill pattern. Clean withManitowoc Ice Machine cleaner to remove any mineral build-up before entering the refrigeration system.The following can be used for diagnostics:Capillary Tube failures or low refrigerant charge will alwaysresult in a starving evaporator.Assume 86°F (30°C) air temperature 68°F (20°C) watertemperature.Suction line temperature at the compressor will range from86°F (30°C) three minutes into the cycle to 8°F (-13°C) at theend of the freeze cycle. An obstructed capillary tube or lowrefrigerant charge will have a suction line temperature higherthan normal.Discharge line temperature at the compressor will range from168°F (76°C) to 140°F (60°C) through the freeze cycle. Anobstructed capillary tube or low refrigerant charge will have alower discharge line temperature than normal.Suction line temperature at the compressor will range from64°F (18°C) to 111°F (44°C) through the harvest cycle. Anobstructed capillary tube will not affect suction linetemperature range during the harvest cycle. Low refrigerantcharge will have a lower temperature than normal.Discharge line temperature at the compressor will range from180°F (82°C) to 150°F (60°C) through the harvest cycle. Anobstructed capillary tube will not affect discharge linetemperature range during the harvest cycle. Low refrigerantcharge will have a lower temperature than normal.Ice fill pattern will vary depending on severity of theobstruction or refrigeration loss. Ice fill patterns will rangefrom no ice on the entire evaporator to thin only at theevaporator outlet (thin at the bottom, thick at the top of theevaporator).
