Thermo King 098916, Руководство по обслуживанию

Страница: 111 / 196

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).