Product Manual ALR2-3 ALR 110F – 150F 5
Hot Gas Mufflers
Hot gas discharge line mufflers are installed in each refrigerant circuit to reduce the overall sound
levels.
Evaporator
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.
Refrigerant heads are carbon steel with multi-pass baffles to ensure oil return and are removable to
permit access to the tubes from either end. For water removal and venting, 1/2" (12.7mm) 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 thermostat controls the heater cable.
The insulation has a K factor of 0.28 at 75°F (23°C). The fitted and cemented in place insulation is
painted with a resilient vinyl base paint to resist cracking.
The tube side maximum working pressure is 315 psig (2170 kPa). The water side working pressure is
152 psig (1047 kPa). Each evaporator is designed, constructed, inspected, and stamped according to
the requirements of the ASME Boiler and Pressure Vessel Code.
NOTE: A chilled water pump starter interlock, water flow switch or both, must be field installed to
protect against evaporator freeze-up under low water flow conditions.
Electrical Control Center
Operating controls, safety controls, control transformer, and motor starting equipment is factory wired,
operationally tested, and ready for service. All centrally located controls are in a weatherproof,
hinged control center with key-locked doors. Panel access doors include steel rod door retainers to
secure the doors when open.
A fixed 5-minute, solid-state lockout timer delays compressor restart after a safety cutout, power
interruption, or thermostat cycling.
Power connection to the unit can be single-point or multiple-point. Single point is usually more
economical. Multiple point provides separate power for each of two compressor circuits plus a third
circuit for the fans and control power.
Part winding start is standard on 208 and 230 volt compressor motors. Across-the-line start is
standard on 380, 460 and 575 volts.
Circuit Breakers
Circuit breakers are factory installed, providing unit compressor short circuit protection.
Standard UNT Controller
This microprocessor based control accomplishes unit capacity control by staging compressors and by
cylinder unloading based on leaving chilled water temperature. Setpoint and control band are easily
field adjusted. Anti-cycling and stage delay timers are included. Safety controls include low
refrigerant pressure, low evaporator flow (field installed flow switch), low oil pressure, and sensor
failures. Outside air temperature sensor is standard. Reset options are; outside air, return water,
remote reset, demand limit, zone temperature reset. The optional Zone Terminal and Display control is
required to adjust the reset setpoints.
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