Control Logic And Temperature Control; Modes Of Operation; Introduction; Temperature Control Logic - Carrier Supra 950MT Operation & Service Manual
Truck refrigeration units with cab command controller
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Also See for Supra 950MT:
- Operation and service manual (92 pages) ,
- Operator's manual (42 pages)
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CONTROL LOGIC AND TEMPERATURE CONTROL
4.1
MODES OF OPERATION
4.1.1
Introduction
The operational software responds to various inputs. These inputs come from the temperature and pressure sen-
sors, the temperature set point, the settings of the configuration variables and the function code assignments. The
action taken by the operational software will change if any one of the inputs changes. Overall interaction of the
inputs is described as a "mode" of operation. Refer to
Refer to
Section 5.18
for a description of the microprocessor logic circuit.
4.1.2
Temperature Control Logic
There are three modes of operation - Cool, Heat, and Defrost. The microprocessor automatically selects the nec-
essary mode to maintain the refrigerated compartment temperature at set point.
There are two control ranges:
•
Frozen: Set point less than 10.4°F (-12°C)
•
Perishable: Set point greater than 10.4°F (-12°C)
In the frozen range, there are two control logics depending on whether or not heat is allowed.
There are also two operating modes:
•
Continuous
•
Start-Stop
a. Temperature Control/Continuous Mode
For DIESEL or STANDBY Modes: There are three possible states:
•
Cool
•
Heat
•
Null
See
Figure 4.2
and
Figure
b. Temperature Control/Start-Stop
When START-STOP mode is activated, there is an additional off-state that corresponds to unit shut-off when box
temperature is close to set point (see
c. Operation
COOL Mode: Default mode for the microprocessor
HEAT Mode: Microprocessor will energize MHR relay, which controls the Main Heat Valve and Receiver Tank heat
Valve (RPV).
Either the HGR 1 or 2 (or any combination of the relays) is energized depending on which compartment requires
heat. These control the hot gas valve in the evaporator.
Micro
N1
S2
Null
SECTION 4
4.4.
Figure 4.1
and
CR, HGR, EHR De-energized
Section 2.7.4
for a description on the refrigerant circuit.
Figure
4.3).
Relay
HGR1
HGR2
4-1
Valve
1HGV
2HGV
Not used
62-11863
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