S1800 Marine Model Ice Machines – Service Manual - Manitowoc Ice

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Refrigeration System Section 7 Freeze Cycle Suction Pressure High Checklist Possible Cause Check/Correct Improper installation See “Installation/Visual Inspection Checklist” Discharge pressure Discharge pressure is too high, and is affecting low side (See “Freeze Cycle Discharge Pressure High Checklist” ) Improper refrigerant charge Overcharged Wrong type of refrigerant Other Non-Manitowoc components in system Harvest valve stuck open TXV flooding (check bulb mounting) Defective compressor Freeze Cycle Suction Pressure Low Checklist Possible Cause Check/Correct Improper installation See “Installation/Visual Inspection Checklist” Discharge pressure Discharge pressure is too low, and is affecting low side (See “Freeze Cycle Discharge Pressure Low Checklist”) Improper refrigerant charge Undercharged Wrong type of refrigerant Other Non-Manitowoc components in system Improper water supply over evaporator (See “Water System Checklist” ) Loss of heat transfer from tubing on back side of evaporator Restricted/plugged liquid line drier Restricted/plugged tubing in suction side of refrigeration system TXV starving NOTE: Do not limit your diagnosis to only the items listed in the checklists. 7-14 Part Number 80-1634-3
Section 7 Refrigeration System HARVEST VALVE TEMPERATURE CHECK General NOTE: This procedure requires checking both harvest valves. A harvest valve requires a critical orifice size. This meters the amount of hot gas flowing into the evaporator during the harvest cycle. If the orifice is even slightly too large or too small, long harvest cycles will result. A too-large orifice causes refrigerant to condense to liquid in the evaporator during the harvest cycle. This liquid will cause compressor damage. A too-small orifice does not allow enough hot gas into the evaporator. This causes low suction pressure, and insufficient heat for a harvest cycle. Refer to the Parts Manual for proper valve application. If replacement is necessary, Use only “original” Manitowoc replacement parts. Harvest Valve Analysis Symptoms of a harvest valve remaining partially open during the freeze cycle can be similar to symptoms of either an expansion valve or compressor problem. The best way to diagnose a harvest valve is by using Manitowoc’s Ice Machine Refrigeration System Operational Analysis Table. Use the following procedure and table to help determine if a harvest valve is remaining partially open during the freeze cycle. 1. Wait five minutes into the freeze cycle. 2. Feel the inlet of the harvest valve(s). Important Feeling the harvest valve outlet or across the harvest valve itself will not work for this comparison. The harvest valve outlet is on the suction side (cool refrigerant). It may be cool enough to touch even if the valve is leaking. 3. Feel the compressor discharge line. ! Warning The inlet of the harvest valve and the compressor discharge line could be hot enough to burn your hand. Just touch them momentarily. 4. Compare the temperature of the inlet of the harvest valves to the temperature of the compressor discharge line. Findings Comments The inlet of the harvest valve is cool enough to touch and the compressor discharge line is hot. The inlet of the harvest valve is hot and approaches the temperature of a hot compressor discharge line. Both the inlet of the harvest valve and the compressor discharge line are cool enough to touch. This is normal as the discharge line should always be too hot to touch and the harvest valve inlet, although too hot to touch during harvest, should be cool enough to touch after 5 minutes into the freeze cycle. This is an indication something is wrong, as the harvest valve inlet did not cool down during the freeze cycle. If the compressor dome is also entirely hot, the problem is not a harvest valve leaking, but rather something causing the compressor (and the entire ice machine) to get hot. This is an indication something is wrong, causing the compressor discharge line to be cool to the touch. This is not caused by a harvest valve leaking. Part Number 80-1634-3 7-15
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Page 59 and 60: Section 6 Electrical System General
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Page 65 and 66: Section 6 Electrical System Diagnos
Page 67 and 68: Section 7 Refrigeration System Sequ
Page 69 and 70: Section 7 Refrigeration System S180
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Page 87 and 88: Section 7 Refrigeration System Refr
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Page 97 and 98: Section 7 Refrigeration System HFC
Page 100: Attend A Manitowoc Factory Service
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S1800 Marine Model Ice Machines – Service Manual - Manitowoc Ice

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