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Operating Theory
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Chill or Power Limit Mode: When the cool capacity is 100 percent (in the display), the controller
energizes the vapor injection valve continuously.
•
Compressor discharge temperature exceeds 138 C (280 F). Vapor injection stops when the compressor
discharge temperature decreases 6 C (10.7 F).
High Temperature Protection
If the discharge gas temperature rises above 148 C (298 F), the unit stops immediately. The controller
turns on the Alarm LED and records Alarm Code 56 (Compressor Temperature Too High). The controller
will restart the unit when the sensor temperature is below 90 C (194 F).
Power Limit Mode
The controller uses the total unit current and the condenser temperature to provide power limit control in
both the Chill and Frozen modes. When the unit is on water-cooled operation, power limit control is
based on the total unit current draw only.
Evaporator Fan Control
The controller determines evaporator fan motor speed based on the setpoint temperature and the mode
setting.
Chill Loads (Setpoints of -9.9 C [14.1 F] and Above)
When the Optimized Mode is set to ON, the evaporator fans operate on low and high speed as needed to
maintain the setpoint and save energy. Typically, the evaporator fans run in high speed during the initial
pull-down to setpoint, but the evaporator fans may run in low speed at times during pull-down as
determined by the controller. Once the setpoint has been reached, the evaporator fans usually run in low
speed as long as the temperature is near the setpoint. If the controller determines it is necessary, the
evaporator fans may shift back to high speed temporarily to bring the temperature back to setpoint or
increase air circulation.
When the Non-Optimized mode is set to On, the evaporator fans operate continuously on high speed.
Frozen Loads (Setpoint at -10.0 C [14.0 F] or Below)
When the Optimized mode is set to On, the evaporator fans operate on low speed on and off. The
evaporator fans run in low speed when the compressor is running. When the compressor is not running
the evaporator fans are usually off, but periodically run in low speed to circulate air to evaluate when to
start the compressor again.
When the Non-Optimized mode is set to On, the evaporator fans operate continuously on low speed.
Condenser Fan Control
The controller also uses a proportional-integral derivative algorithm to control the condenser temperature
and ensure a constant liquid pressure at the expansion valve. The condenser fan operates continuously in
high ambients. In low ambient conditions, the controller pulses the condenser fan on and off to maintain a
minimum condenser temperature. The controller maintains a minimum 30 C (86 F) condenser
temperature on Chill loads and a minimum 20 C (68 F) condenser temperature on Frozen loads.
To do this the condenser fan pulses.
Note: When the condenser fan is pulsing ON/OFF, the fan will come on just before the fan stops rotating.
Summary of Contents for 098203
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Page 3: ...MAGNUM TK 60275 4 MM Rev 3 08 15 Copyright 2012 Ingersoll Rand EMEIA Printed in Ireland...
Page 193: ...Refrigeration Maintenance 191 Figure 163 Filter Drier...
Page 200: ...Refrigeration Maintenance 198 Figure 169 Receiver Tank Figure 170 Water Cooled Condenser Tank...
Page 257: ...255 Schematic Diagram RELEASED 19 Sep 2013...
Page 258: ...256 Wiring Diagram Page 1 of 2 RELEASED 19 Sep 2013...
Page 259: ...257 Wiring Diagram Page 2 of 2 RELEASED 19 Sep 2013...
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