4–3
T-340
NOTE
The controlling probe in perishable range is the SUPPLY air probe and the controlling probe in frozen
range is the RETURN air probe.
• SUPPLY - Yellow LED: Energized when the supply air probe is used for control. When this LED is illumi
-
nated, the temperature displayed in the AIR TEMPERATURE display is the reading at the supply air probe.
This LED will flash if dehumidification or humidification is enabled.
• RETURN - Yellow LED: Energized when the return air probe is used for control. When this LED is illumi
-
nated, the temperature displayed in the AIR TEMPERATURE display is the reading at the return air probe.
• ALARM - Red LED: Energized when an active or an inactive shutdown alarm in the alarm queue.
Figure 4.3 Display Module
4.1.3
Controller
CAUTION
!
Do not remove wire harnesses from controller modules unless you are grounded to the unit
frame with a static safe wrist strap.
CAUTION
!
Unplug all controller module wire harness connectors before performing arc welding on any
part of the container.
CAUTION
!
Do not attempt to use anML2i PC card in an ML3 equipped unit. The PC cards are physically
different and will result in damage to the controller.
NOTE
Do not attempt to service the controller modules. Breaking the seal will void the warranty.
The Micro-Link 3 controller (see
) is fitted with test points, harness connectors and a software card pro
-
gramming port.
4.2 Controller Software
The controller software is a custom designed program that is subdivided into configuration software and opera
-
tional software. The controller software performs the following functions:
• Control supply or return air temperature to required limits, provide modulated refrigeration operation, econo
-
mized operation, unloaded operation, electric heat control, and defrost. Defrost is performed to clear buildup
of frost and ice to ensure proper air flow across the evaporator coil.
• Provide default independent readouts of set point and supply or return air temperatures.
COOL
HEAT
DEFROST
IN RANGE
ALARM
SUPPLY RETURN
SETPOINT/Code
AIR TEMPERATURE/Data
