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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.
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 24 hours before starting the compressors.
Evaporator
Models AGZ 026 through 070
The evaporator is a compact, high efficiency, single or dual circuit, brazed plate-to-
plate type heat exchanger consisting of parallel stainless steel plates.
The evaporator is protected with an electric resistance heater and insulated with 3/4"
(19mm) thick closed-cell polyurethane insulation. This combination provides freeze
protection down to -20°F (-29°C) ambient air temperature.
The water side working pressure is 363 psig (2503 kPa). Evaporators are designed and
constructed according to, and listed by, Underwriters Laboratories (UL).
Models AGZ 075 through 130
The evaporator is direct expansion, shell-and-tube type with water flowing in the
baffled shell side and refrigerant flowing through the tubes.
Two independent
refrigerant circuits within the evaporator serve the unit's dual refrigerant circuits.
The evaporator is wrapped with an electric resistance heater cable and insulated with
3/4" (19mm) thick vinyl nitrate polymer sheet insulation, protecting against water
freeze-up at ambient air temperatures to -20°F (-29°C). An ambient air thermostat
controls the heater cable. The fitted and glued-in-place insulation has a K factor of
°F at 75°F.
2
0.28 Btu in/hr ft
The refrigerant (tube) side maximum working pressure is 300 psig (2068 kPa). The
water side working pressure is 152 psig (1048 kPa). Each evaporator is designed,
constructed, inspected, and stamped according to the requirements of the ASME Boiler
and Pressure Vessel Code. Double thickness insulation is available as an option.
IOMM AGZ-5
AGZ 026B through 130B
95
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