HOT GAS VALVE
General
The hot gas valve is an electrically operated valve that opens when energized, and closes when de-energized.
NORMAL OPERATION
The valve is de-energized (closed) during the freeze cycle and energized (open) during the harvest cycle. The valve is positioned between the compressor and the evaporator and performs two functions:
1. Prevents refrigerant from entering the evaporator during the freeze cycle.
The hot gas valve is de-energized (closed) preventing refrigerant flow from the receiver into the evaporator.
2. Allows refrigerant vapor to enter the evaporator in the harvest cycle.
During the harvest cycle, the hot gas valve is energized (open) allowing refrigerant gas from the discharge line of the compressor to flow into the evaporator. The heat is absorbed by the evaporator and allows release of the ice slab.
Exact pressures vary according to ambient temperature and ice machine model. Harvest pressures can be found in the “Ice Production Pressure Chart” in this manual.
Hot Gas Valve Analysis
The valve can fail in two positions:
• Valve will not open in the harvest cycle.
• Valve remains open during the freeze cycle.
VALVE WILL NOT OPEN IN THE HARVEST CYCLE:
Although the control board has initiated the harvest cycle, the evaporator temperature remains unchanged from the freeze cycle.
Part Number: 040006847 12/19 77
VALVE REMAINS OPEN IN THE FREEZE CYCLE:
Symptoms of a hot gas valve remaining partially open during the freeze cycle can be similar to symptoms of an expansion valve, capillary tube or compressor problem.
Symptoms are dependent on the amount of leakage in the freeze cycle.
A small amount of leakage will cause increased freeze times and the ice formation pattern on the top of the evaporator will be too thin, but a complete ice cube will eventually form.
Refer to the Parts Manual for proper valve application.
If replacement is necessary, use only “original” Welbilt replacement solenoid valves.
Use the following procedure to help determine if a harvest valve is remaining partially open during the freeze cycle:
1. Wait 5 minutes into the freeze cycle.
2. Feel the inlet of the hot gas valve.
Important
Feeling the hot gas valve outlet or across the hot gas valve itself will not work for this comparison. The hot gas 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.
78 Part Number: 040006847 12/19
4. Compare the temperature of the inlet of the hot gas valve to the temperature of the compressor discharge line.
Findings
The inlet of the hot gas valve is cool enough to touch and the compressor discharge line is hot.
The inlet of the hot gas valve is hot and approaches the temperature of a hot compressor discharge line.
Both the inlet of the hot gas valve and the compressor discharge line are cool enough to touch.
Comments
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 that 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: 040006847 12/19 79
PAGE INTENTIONALLY LEFT BLANK
80 Part Number 040006847 12/19
Flammable Refrigerant Procedures
Servicing Requirements
• It is recommended that only technicians specifically trained in handling flammable refrigerants, service or dispose of equipment containing hydrocarbon refrigerants.
• Color-coded red process tubes indicate use of a flammable refrigerant - Process tubes must be replaced after brazing or other service procedures.
• An accessible fire extinguisher is required when brazing.
• A combustible gas leak detector with a minimum sensitivity of 8 grams per cubic meter is required. The meter must be on while servicing the equipment.
Place the detector on the floor and set the detector to beep at approximately heart beat rate.
• Equipment using hydrocarbon refrigerants have fittings unique to flammable refrigerants.
• Work in well-ventilated, open spaces - A ventilation fan can be used to disperse any residual refrigerant. Place the fan a minimum of 10’ (3m) away from the work area.
• Eliminate all ignition sources.
• The filter drier must be replaced whenever the system is opened to the atmosphere.
Important
• Remove piercing valves after charging.
• Unit is critically charged. Nitrogen must be purged through the system while brazing to prevent build up of copper oxide in the refrigeration system.
• Manifold gauge set must be removed properly to ensure that no refrigerant contamination or loss occurs. A quick disconnect is required for the high side connection.
Part Number: 040006847 12/19 81
