2-3
T-312
5. To open or close the fresh air damper, press the
FRESH AIR button.
6. To read interior or exterior temperature, press the
TEMPERATURE button to illuminate the indicator
light and bring the display to the desired temperature
reading. After a short delay, the display will return to
the default set point or return air temperature read-
ing.
7. Setpoint may be changed by pressing the UP or
DOWN arrow button. The UP button will increase the
setpoint temperature and the DOWN button will de-
crease the setpoint temperature.
2.1.4 Activating Defrost
Windshield defrost is initiated and controlled with the
Defrost switch and the Heat switch (Figure 2-1). Moving
the switches to the high setting on both will deliver the
highest volume of warm air on the windshield.
Correspondingly, moving either or both of the two
switches to the low setting will decrease the volume of
air and the temperature of air delivered across the
windshield.
2.1.5 Active Alarm
During normal operation, the controller monitors system
operating parameters for out of tolerance conditions.
The display gets the controller alarm queue information
every 30 seconds. Alarms will be shown as an alarm
code. If an alarm is activated and the display is reading
temperature, the display will show the temperature and
the alarm code alternately in 1 second intervals.
2.1.6 Diagnostics (Check for Alarms)
If an alarm condition exists, diagnostics can be manually
initiated to isolate system fault(s) by simultaneously
pressing the Up and Down Selection keys continuously
for five seconds. Diagnostics should be accessed only
when the coach is not moving. When entering the
diagnostic mode, all LEDs for the key pad will be turned
off. All keys except the On/Off, Up (increase) Selection
and Auto keys will stop functioning. To scroll through
the diagnostic information press the UP key. Pressing
the O/I key at any time will exit this mode. To clear the
alarm message, scroll thru the alarms until ’------’
appears, then press the Auto Key for 5 seconds or until
’------’ disappears. Refer to section 3 for description of
diagnostics. Refer to Table 3-3 for definition of alarm
messages.
2.1.7 Diagnostics (Parameters)
To access the system parameters press the Up and
Down Selection keys continuously for five seconds. The
display will now be in the Diagnostics mode and may be
displaying alarms. Scroll thru the alarms(if present) until
’------’ appears. With ’------’ displayed on the read--out,
press the Up Selection key. The first parameter code
will be displayed. To scroll thru the parameters press the
Up Selection key. When showing parameters, the
display will first flash out the parameter identifier Pxx for
one second and then show the parameter value. To
return to normal operation press the On/Off key (see
Figure 2-1). Refer to Section 3 for for definitions of the
parameter codes.
2.1.8 Stopping
With the system operating, pressing the ON/OFF key
will stop the HVAC system operation and the display will
be blank.
2.2 PRE-TRIP INSPECTION
After starting system operation, allow system to
stabilize for ten to fifteen minutes and check for the
following:
a. Listen for abnormal noises in compressor or fan mo-
tors.
b. Check compressor oil level. (Refer to paragraph
4.12.4)
c. Check refrigerant level. (Refer to paragraph 4.7.1)
d. Ensure that self-test has been successfully per-
formed and that there are no errors or alarms indi-
cated. (Refer to paragraph 2.1.5 or 2.1.6)
2.3 SYSTEM DESCRIPTION
Refer to Section 5 for sample schematic diagrams of the
power and control circuits.
2.3.1 Pull Up and Pull Down Modes
At power up, the system will enter a pull up or pull down
mode to rapidly obtain desired temperatures within the
coach. During this mode, the system will run at
maximum heating or cooling capacity until the set point
(in the passenger zone) is reached for the first time. For
the driver zone, temperature control is controlled by the
two slide switches next to the controller (See
Figure 2-1).
1. Pullup/pulldown main evaporator fan speed is limit-
ed to a maximum of thirty minutes and can be put in
pullup/pulldown speed only once. When the control-
ler switches out of pullup/pulldown speed, pullup/
pulldown speed is prevented again by the controller
unless the controller is shut off and restarted. The
display cannot override the fan speed to pullup/pull-
down.
2. The minimum run time in pullup or pulldown for the
main evaporator fans is three minutes for automatic
control.
a. Capacity State Selection
The main controller automatically compares system
temperature with the controller set point and changes
system operating modes at certain temperature
deviations. Figure 2-4 shows various changes in
operating modes and controller actions at various
temperature deviations from controller set point. Upon
rising temperature, mode changes occur at values in
Figure 2-4 above controller set points, On a falling
temperature, mode changes occur when temperatures
are equal to those given in Figure 2-4 The system will
operate in these modes unless pressure overrides the
controller settings. If the controller detects that the
temperature setting is not being reached during a period
of time, it will slowly adjust the temperature at which
these modes are entered; this will allow the system to
always attempt to reach the controller temperature
setting.
