Section 7 Refrigeration System7-17HOT GAS VALVE TEMPERATURE CHECKGeneralA hot gas valve requires a critical orifice size. Thismeters the amount of hot gas flowing into theevaporator during the harvest cycle. If the orifice iseven slightly too large or too small, long harvestcycles 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-smallorifice does not allow enough hot gas into theevaporator. This causes low suction pressure, andinsufficient heat for a harvest cycle.Normally, a defective hot gas valve can be rebuilt.Refer to the Parts Manual for proper valveapplication and rebuild kits. If replacement isnecessary, Use only “original” Manitowocreplacement parts.Hot Gas Valve AnalysisSymptoms of a hot gas valve remaining partially openduring the freeze cycle can be similar to symptoms ofeither an expansion valve or compressor problem.The best way to diagnose a hot gas valve is by usingManitowoc’s Ice Machine Refrigeration SystemOperational Analysis Table.Use the following procedure and table to helpdetermine if a hot gas valve is remaining partiallyopen during the freeze cycle.1. Wait five minutes into the freeze cycle.2. Feel the inlet of the hot gas valves.ImportantFeeling the hot gas valve outlet or across the hotgas valve itself will not work for this comparison.The hot gas valve outlet is on the suction side (coolrefrigerant). It may be cool enough to touch even ifthe valve is leaking.3. Feel the compressor discharge line.WARNINGThe inlet of the hot gas 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 hotgas valves to the temperature of the compressordischarge line.Findings CommentsThe inlet of the hotgas valve is coolenough to touchand thecompressordischarge line ishot.This is normal as the dischargeline should always be too hotto touch and the hot gasvalve inlet, although too hot totouch during harvest, shouldbe cool enough to touch after5 minutes into the freeze cycle.The inlet of the hotgas valve is hotand approachesthe temperature ofa hot compressordischarge line.This is an indication somethingis wrong, as the hot gas valveinlet did not cool down duringthe freeze cycle. If thecompressor dome is alsoentirely hot, the problem is nota hot gas valve leaking, butrather something causing thecompressor (and the entire icemachine) to get hot.Both the inlet of thehot gas valve andthe compressordischarge line arecool enough totouch.This is an indication somethingis wrong, causing thecompressor discharge line tobe cool to the touch. This is notcaused by a hot gas valveleaking.
