Carrier 69NT40-541-001, Operation And Service

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T-316 4–4
4.1.3 Controller
CAUTION
!
Do not remove wire harnesses from controller unless you are grounded to the unit frame with a
static safe wrist strap.
CAUTION
!
Unplug all controller wire harness connectors before performing arc welding on any part of the
container.
NOTICE
Do not attempt to service the controller. Breaking the seal will void the warranty.
CAUTION
!
Do not attempt to use an ML2i PC card in an ML3 equipped unit. The PC cards are physically
different and will result in damage to the controller.
The Micro-Link 3 controller is a single module microprocessor as shown in Figure 4.4 . It is fitted with test points,
harness connectors, and a software card programming port.
4.2 CONTROLLER SOFTWARE
The controller software is a custom designed program that is subdivided into the Configuration Software and the
Operational Software. The controller software performs the following functions:
a. Control supply or return air temperature to required limits, provide modulated refrigeration control, electric
heat control and defrost. Defrost is performed to clear build up of frost and ice from the coil to ensure contin-
uous conditioned air delivery to the load.
b. Provide default independent readouts of set point and supply or return air temperatures.
c. Provide ability to read and (if applicable) modify the Configuration Software Variables, Operating Software
Function Codes, and Alarm Code Indications.
d. Provide a Pre-Trip step-by-step checkout of refrigeration unit performance including: proper component
operation, electronic and refrigeration control operation, heater operation, probe calibration, pressure limit-
ing, and current limiting settings.
e. Provide battery powered ability to access or change selected codes and set point without AC power connected
f. Provide the ability to reprogram the software through the use of a memory card.
4.2.1 Configuration Software (Configuration Variables)
The Configuration Software is a variable listing of the components available for use by the Operational Software.
This software is factory installed in accordance with the equipment fitted and options listed on the original purchase
order. Changes to the Configuration Software are required only when the original software has been lost or a phys-
ical change has been made to the unit such as the addition or removal of an option. A Configuration Variable list is
provided in
Table 4–4 . Change to the factory installed Configuration Software is achieved via a configuration card.
4.2.2 Operational Software (Function Codes)
The Operational Software is the actual operation programming of the controller which activates or deactivates
components in accordance with current unit operation conditions and operator selected modes of operation.
The programming is divided into function codes. Some of the codes are read only while the remaining codes may
be user configured. The value of the user configurable codes can be assigned in accordance with user desired
mode of operation. A list of the function codes is provided in
Table 4–5 .