Operating instructions

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.
NOTE: 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, 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 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 has a carbon steel shell and seamless high efficiency copper tubes, roller expanded
into a carbon steel tube sheet.
3/8" (10mm) vent and drain plugs are provided on the top and bottom of the shell.
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 0.28 Btu in/hr ft
2
at 75°F.
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.
IMM ACZ/AGZ-4 ACZ / AGZ-BM 63