ICE MACHINES Q-Model Service Manual

Section 7Refrigeration SystemHARVEST VALVE TEMPERATURE CHECKNOTE: This procedure requires checking both harvestvalves on dual expansion valve Q1300 and Q1800 icemachines.GeneralA harvest valve requires a critical orifice size. Thismeters the amount of hot gas flowing into the evaporatorduring the harvest cycle. If the orifice is even slightly toolarge or too small, long harvest cycles will result.A too-large orifice causes refrigerant to condense toliquid in the evaporator during the harvest cycle. Thisliquid will cause compressor damage. A too-small orificedoes not allow enough hot gas into the evaporator. Thiscauses low suction pressure, and insufficient heat for aharvest cycle.Refer to the Parts Manual for proper valve application. Ifreplacement is necessary, Use only “original” Manitowocreplacement parts.Harvest Valve AnalysisSymptoms of a harvest valve remaining partially openduring the freeze cycle can be similar to symptoms ofeither an expansion valve or compressor problem. Thebest way to diagnose a harvest valve is by usingManitowoc’s Ice Machine Refrigeration SystemOperational Analysis Table.Use the following procedure and table to help determineif a harvest valve is remaining partially open during thefreeze cycle.1. Wait five minutes into the freeze cycle.3. Feel the compressor discharge line.! WarningThe inlet of the harvest valve and the compressordischarge line could be hot enough to burn yourhand. Just touch them momentarily.4. Compare the temperature of the inlet of the harvestvalves to the temperature of the compressordischarge line.FindingsThe inlet of theharvest valve is coolenough to touch andthe compressordischarge line is hot.The inlet of theharvest valve is hotand approaches thetemperature of a hotcompressordischarge line.Both the inlet of theharvest valve andthe compressordischarge line arecool enough totouch.CommentsThis is normal as the discharge lineshould always be too hot to touch andthe harvestharvest valve inlet,although too hot to touch duringharvest, should be cool enough totouch after 5 minutes into the freezecycle.This is an indication something iswrong, as the harvest valve inlet didnot cool down during the freeze cycle.If the compressor dome is also entirelyhot, the problem is not a harvest valveleaking, but rather something causingthe compressor (and the entire icemachine) to get hot.This is an indication something iswrong, causing the compressordischarge line to be cool to the touch.This is not caused by a harvest valveleaking.2. Feel the inlet of the harvest valve(s).ImportantFeeling the harvest valve outlet or across theharvest valve itself will not work for this comparison.The harvest valve outlet is on the suction side (coolrefrigerant). It may be cool enough to touch even ifthe valve is leaking.Part No. 80-1100-3 7-21