Ingersoll-Rand 900829, Maintenance Manual

Page: 34 / 142

32
Operating Instructions
In truck-driven units, temperature control is based
on two values: The setting (Setpoint) of the
electronic thermostat and the evaporator return
temperature. The difference between these two
temperatures will determine the mode of
operation: cool, heat, or null.
Cool:
When the temperature in the load
compartment is higher than the setpoint, the unit
runs in cool mode to reduce the evaporator return
temperature.
Heat (If So Equipped):
When the temperature in
the load compartment is lower than the setpoint,
the unit changes to heat mode to raise the
evaporator return temperature.
Null:
Once the Setpoint Temperature has been
reached, and while the temperature remains
between X F/C above or below the setpoint, there
is no demand for transfer of heat or cold, and the
unit runs in null mode.
Defrost:
After a scheduled period of time in cool
mode, between 1 and 8 hours, the unit runs in this
fourth mode of operation to eliminate ice that has
accumulated in the evaporator coil. Defrost can be
initiated automatically or manually.
Figure 12: Thermostat Algorithm
Factory setting for X is 5 F (3 C). During unit
installation, this value can be adjusted by between
2 and 9 F (1 and 5 C) in increments of 1 F/C.
Units with R-134a refrigerant: Temperatures can
be controlled from -8 F to +71 F (-22 C to +22 C).
Units with R-404A refrigerant: Temperatures can
be controlled from -26 F to +71 F (-32 C to +22
C).
Unit Controls
WARNING: Never operate the unit unless you
completely understand the controls; otherwise
serious injury may occur.
Figure 13: In-Cab Control Box
Display, Keys and Symbols
Decrease in
Temperature
Temperature Setpoint
Increase in
temperature
X C/F above the setpoint
X C/F below the setpoint
COOL
HEAT
NULL
MODE
1. Display It is always active and backlit except
when the unit is disconnected (no
power) or when the unit is connected
but has been manually switched off
from the In-Cab Control Box. It
normally displays the return air
temperature.
2. On/Off
Key This key is used to start/stop the unit.
It is always lit except when the unit is
disconnected (no power), and thus
acts as an indicator of the presence of
power in the unit.
3. Select
Key Selects prompt screens and
information screens.
4. Up Key Is used to increase the setpoint
temperature.
5. Down Key Is used to reduce the setpoint
temperature.
6. Enter Key Is used to enter a new command such
as manual defrost, etc.
7. Buzzer It is energized when the vehicle
battery and the electric power supply
are connected simultaneously. It is
also energized if the doors are
opened while the refrigeration unit is
running.
8. Cool
Symbol (Thermometer with an arrow pointing
downward). The unit is cooling.
9. Heat
Symbol (Thermometer with an arrow pointing
upward). The unit is heating.
10. C/ F
Symbol Indicates whether the on-screen
temperature reading is in degrees
Celsius (C) or degrees Fahrenheit
(F).
11. Alarm
Symbol Indicates that there is an alarm in the
system.