McQuay ACZ 045A, Installation, Operation And Maintenance Manual

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44 IOMM ACZ/AGZ-1
Filter Driers
Each refrigerant circuit is furnished with a full flow filter drier or an optional replaceable core type
filter-drier. The core assembly of the replaceable core drier consists of a filter core held tightly in the
shell in a manner that allows full flow without bypass.
Pressure drop across the filter drier at full load conditions must not exceed 10 psig. If pressure drop is
more than 10 psig, then replace the filter drier. See Table 58 for maximum pressure drop at other load
points.
CAUTION
Pump out refrigerant before removing end flange for replacement of core(s).
A condenser liquid line service valve is provided for isolating the charge in the condenser, but also
serves as the point from which the liquid line can be pumped out. With the line free of liquid, the filter-
drier core(s) can be easily replaced.
System Adjustment
To maintain peak performance at full load operation, the system superheat and liquid subcooling may
require adjustment. Read the following subsections closely to determine if adjustment is required.
Liquid Sightglass and Moisture Indicator
The color of the moisture indicator is an indication of the dryness of the system and is extremely
important when the system has been serviced. Immediately after the system has been opened for
service, the element may indicate a wet condition. It is recommended that the equipment operate for
about 12 hours to allow the system to reach equilibrium before deciding if the system requires a
change of drier cores.
Bubbles in the sightglass to expansion valve at constant full load conditions indicates a shortage of
refrigerant, a plugged filter-drier, or a restriction in the liquid line. However, it is not unusual to see
bubbles in the sightglass during changing load conditions.
Thermostatic Expansion Valve
The expansion valve performs one specific function. It keeps the evaporator supplied with the proper
amount of refrigerant to satisfy the load conditions.
The sensing bulb of the expansion valve is installed in the closest straight run of suction line from the
evaporator. The bulb is held on by clamps around the suction line and is insulated to reduce the
effect of surrounding ambient temperatures. In case the bulb must be removed, simply slit the
insulation on each side of the bulb, remove the clamps and then remove the capillary tubing that runs
along the suction line from the valve.
The power element is removable from the valve body without removing the valve from the line.
Note: The superheat is factory set and adjustment is not needed unless operation is outside
the 8°F to 12°F range.
CAUTION
Before adjusting superheat, check unit charge is correct and liquid line sightglass is full with
no bubbles.