Operating instructions

VFD Low Ambient Control (Optional)
The optional VFD fan control is used for unit operation below 35°F (2°C) down to a minimum of
0°F (-17°C). The control looks at the saturated discharge temperature and varies the fan speed to
hold the temperature (pressure) at the “target” temperature. This temperature is established as an
input to a setpoint screen labeled “Sat Condenser Temp Target”.
Filter-Driers (AGZ-BM)
A full flow filter-drier (AGZ 026 – 070) or a replaceable core type filter-drier (AGZ 075 – 130) for
each refrigerant circuit is shipped loose for field mounting. The core assembly of the replaceable
core drier consists of a filter core held tightly in the shell to allow full flow without bypass.
Pressure drop across the filter-drier at full load conditions must not exceed 10 psig at full load. See
Table 38 for pressure drop at other load points. Replace the filter-drier if the pressure drop exceeds
maximum.
WARNING
Pump out refrigerant before removing end flange for replacement of core(s).
Lowering refrigerant pressure will help prevent accidental blow-off of cover
causing possible bodily injury. 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 can
require adjustment. Read the following subsections closely to determine if adjustment is required.
Liquid Line Sight Glass 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 can 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.
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.
62 ACZ / AGZ-BM IMM ACZ/AGZ-4