Operation; Initial Start-Up Or Start-Up After Automatic Shut-Off; Freeze Sequence - Manitowoc Q270 Technician's Handbook

INITIAL START-UP OR START-UP AFTER
AUTOMATIC SHUT-OFF
1. Pressure Equalization
Before the compressor starts the hot gas valve is
energized for 15 seconds to equalize pressures during
the initial refrigeration system start-up.
2. Refrigeration System Start-up
The compressor starts after the 15-second pressure
equalization, and remains on throughout the entire
Freeze and Harvest Sequences. The hot gas valve
remains on for 5 seconds during initial compressor
start-up and then shuts off.
At the same time the compressor starts, the
condenser fan motor (air-cooled models) is supplied
with power throughout the entire Freeze and Harvest
Sequences. The fan motor is wired through a fan cycle
pressure control, therefore it may cycle on and off.
(The compressor and condenser fan motor are wired
through the relay. As a result, any time the relay coil is
energized, the compressor and fan motor are supplied
with power.)

FREEZE SEQUENCE

3. Prechill
The compressor is on for 30 seconds prior to water
flow to prechill the evaporator.
4. Freeze
The water pump starts after the 30-second prechill. An
even flow of water is directed across the evaporator
and into each cube cell, where it freezes.
When sufficient ice has formed, the water flow (not the
ice) contacts the ice thickness probe. After
approximately 7 seconds of continual water contact,
the Harvest Sequence is initiated. The ice machine
cannot initiate a Harvest Sequence until a 6-minute
freeze time has been surpassed.
Part Number STH039 8/13

Operation

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