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Operating Theory
131
Cool with Modulation
•
Controller calls for the Cool mode whenever the Control Temperature Differential (based on supply
air temperature) is above setpoint.
•
Controller turns on the Compressor indicates when the compressor is operating.
•
Controller opens and closes Digital Control valve to control the compressor load. The duty cycle of
the Digital Control valve balances the unit cooling capacity against the actual load requirements.
•
Controller turns the In-range LED solid when the supply air sensor temperature is within 1.5 C (2.7 F)
of setpoint.
•
Controller turns on the Heat indicator whenever the heaters are pulsed on and off.
Heat
•
If the supply air temperature is too low and the Control Temperature Differential is below the setpoint,
the controller stops the compressor. The fans (low speed) are kept on to determine if fan heat is
sufficient to increase temperature to setpoint. If not, switch to high speed. If not sufficient heat -
increase with pulsating on the heaters until setpoint is reached.
Frozen Loads (Controller Setpoint at -10 C [14 F] and Below):
At setpoints of -10 C (14 F) and below, the controller locks out the Modulation and Heat modes. The
controller regulates compressor operation based the return air sensor and setpoint temperatures.
At setpoints of -10 C (14 F) and below, the controller operates the unit on:
•
Cool mode
•
Null mode
•
Defrost mode (electric heaters on, evaporator fans off)
•
Evaporator fans operate on low speed and continuously circulate air inside the container (except
during Defrost and in Null mode).
•
Controller display shows the return air sensor temperature.
•
Controller display shows the setpoint temperature.
•
Controller cycles a single-speed condenser fan on for 2 to 30 seconds every 30 seconds when the unit
is on air-cooled condenser operation. The amount of on time depends on the condenser coil, ambient
and compressor discharge temperatures.
•
Power limit is active during initial start-up and pull-down when the unit is cooling at return air
temperatures above -10 C (14 F).
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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