Ice Production Check; Refrigeration Diagnostics - Manitowoc QM30A Installation, Use And Care, And Service Manual

Section 6

Ice Production Check

The QM 30 dice ice cube formation is slightly different from
our previous models. Manitowoc ice machines have a unique
cube shape. It is normal to have a dimple in the ice cube (a
concave indentation in the cube). Ice cubes from the QM 30
may appear to have a slightly larger dimple than other
Manitowoc dice cube machines. Therefore, cube size for the
QM 30 is determined by measuring the slab weight (the
combined weight of all cubes from one harvest cycle). To
determine proper slab weight, follow the instructions listed
below.
1. Ensure the air filter, front, and back panels are installed
properly and close the bin door.
2. During the third harvest cycle open the bin door and
catch the entire slab of ice.
3. Weigh the ice slab. The combined weight of all cubes
from one harvest should weigh between 7 - 9-oz (200 -
270g). If the slab weight is within this range, the ice
machine is working properly and no further action is
needed. If the slab weight is not within this range or you
desire a slightly thicker or thinner cube, continue to step
four.
Disconnect electric power to the ice machine at the
electric switch box before proceeding.
4. Remove the air filter.
5. Remove the two screws holding the front panel in place
and remove the front cover.
6. Locate the ice thickness control dial on the control board
(see figure). Turn the dial clockwise for a thicker cube or
counter clockwise for a thinner cube.
7. Assure all of the panels and air filter are reinstalled
properly and the bin door is closed. Repeat steps one
through three.
WARNING
Ice
Thickness
Control
Dial

Refrigeration Diagnostics

The QM 30 ice machines have a very small refrigerant charge,
5.78 oz. (165 grams) and we do not recommend diagnosing
the ice machine using refrigerant pressures. For this reason
we have not included refrigeration access fittings.
Verify that your water flow is even across the entire
evaporator before diagnosing the refrigeration system.
Mineral build-up on the evaporator assembly can cause water
tracking and an erratic ice fill pattern. Clean with Manitowoc
Ice Machine cleaner to remove any mineral build-up before
entering the refrigeration system.
The following can be used for diagnostics:
Capillary Tube failures or low refrigerant charge will always
result in a starving evaporator.
Assume 86°F (30°C) air temperature 68°F (20°C) water
temperature.
Suction line temperature at the compressor will range from
86°F (30°C) three minutes into the cycle to 8°F (-13°C) at the
end of the freeze cycle. An obstructed capillary tube or low
refrigerant charge will have a suction line temperature higher
than normal.
Discharge line temperature at the compressor will range from
168°F (76°C) to140°F (60°C) through the freeze cycle. An
obstructed capillary tube or low refrigerant charge will have a
lower discharge line temperature than normal.
Suction line temperature at the compressor will range from
64°F (18°C) to 111°F (44°C) through the harvest cycle. An
obstructed capillary tube will not affect suction line
temperature range during the harvest cycle. Low refrigerant
charge will have a lower temperature than normal.
Discharge line temperature at the compressor will range from
180°F (82°C) to 150°F (60°C) through the harvest cycle. An
obstructed capillary tube will not affect discharge line
temperature range during the harvest cycle. Low refrigerant
charge will have a lower temperature than normal.
Ice fill pattern will vary depending on severity of the
obstruction or refrigeration loss. Ice fill patterns will range
from no ice on the entire evaporator to thin only at the
evaporator outlet (thin at the bottom, thick at the top of the
evaporator).
Service
6-11