Daikin McQuay AGZ-D Operating And Maintenance Manual page 69

Pressure drop across the filter drier at full load conditions must not exceed 10 psig at full load. See
page for maximum pressure drop at other load points. Replace the filter drier if the pressure drop
exceeds maximum.
Pump out refrigerant before removing end flange for replacement of core(s) to remove liquid
refrigerant and lower pressure to prevent accidental blow off of cover. EPA recovery regulations
apply to this procedure.
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 refrigerant, 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 Line Sight Glass
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 sight glass at constant full load 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 sight glass during
changing load conditions.
Refrigerant Charging
Liquid line subcooling at the liquid shut-off valve should be between 15 and 20 degrees F at full load.
If the unit is at steady full load operation and bubbles are visible in the sight glass, then check liquid
subcooling.
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.
NOTE: Before adjusting superheat, check that unit charge is correct and liquid line sight glass is full
with no bubbles and that the circuit is operating under stable, full load conditions.
The suction superheat for the suction leaving the evaporator is set at the factory for 8 to 12 degrees F at
full load. To have full rated unit performance, the superheat must be about 8 degrees F at 95°F outdoor
ambient temperature.
Crankcase Heaters
The scroll compressors are equipped with externally mounted band heaters located at the oil sump
level. The function of the heater is to keep the temperature in the crankcase high enough to prevent
refrigerant from migrating to the crankcase and condensing in the oil during off-cycle.
Power must be supplied to the heaters 8 hours before starting the compressors.
Evaporator
Models AGZ 025C through 130C
The evaporator is a compact, high efficiency, dual circuit, brazed, plate-to-plate type heat exchanger
consisting of parallel stainless steel plates.
OMM 1087
WARNING
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AGZ 025D through 190D 69