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Operating Theory
110
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 LED
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 on the In-range LED when
the supply air sensor temperature is within
1.5 C (2.7 F) of setpoint.
•
Supply air sensor control algorithm increases
temperature control accuracy and protection
against frost damage (see “Chill Loads” under
“General Theory of Operation” in this
chapter).
•
Controller turns on the Heat LED 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
and pulses the electric heaters on and off on a
60 second duty cycle to provide heat. The
controller pulses the electric heaters on and off
until the supply air temperature increases to
setpoint.
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; or when Economy
mode is on and the unit is in Null mode).
•
Controller LED display shows the return air
sensor temperature.
•
Controller LCD 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 098916
Page 5: ......
Page 11: ...Table of Contents 10...
Page 19: ...Service Guide 18...
Page 28: ...Specifications 27 Figure 2 Physical Specifications AMA313...
Page 41: ...Unit Description Features Options 40...
Page 105: ...Operating Instructions 104...
Page 155: ...Servicing The Unit 154...
Page 187: ...Index 186...
Page 189: ...Wiring and Schematic Diagrams Index 188...
Page 190: ...189 Wiring Schematic...
Page 191: ...190 Wiring Diagram Page 1 of 2...
Page 192: ...191 Wiring Diagram Page 2 of 2...