Manitowoc UG Series, Technician'S Handbook

Page: 77 / 128

Part Number: 040006847 12/19 77
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.