Section 22: HEATING AND AIR CONDITIONING
PA1562
4
1. HEATING AND AIR CONDITIONING
The coach’s interior is pressurized by its
Heating, Ventilation, Air Conditioning (HVAC)
units. Air flow and controls divide the vehicle in
two areas: driver’s area and passengers’ area.
The interior of vehicle should always be slightly
pressurized to prevent dust and moisture from
entering vehicle. Each section has its own fresh
air, returning air and discharge air ducting. The
exhaust is mainly done through the lavatory
ventilator and through normal air-tightness
losses.
2. AIR CIRCULATION
2.1 DRIVER’S AREA
Fresh air is taken from a plenum underneath the
front service compartment and enters the mixing
box through an ON/OFF damper. Return air is
taken through the base of the dashboard panel
utility compartments into the mixing box. Mixed
air goes through cooling and heating coils, fans
and discharge ducts.
Both right and left discharge ducts defrost one
half of the windshield. The driver can also divert
some air flow to the console, from which he can
direct air to his knees and/or upper body with
adjustable HVAC air registers and to his feet
with the appropriate button (see Fig. 1 and
Operator’s manual). The coach is also equipped
with a windshield upper section de-icing system.
One additional air register is located in the
driver’s area but supplied by the passengers’ air
ducting system. It is installed in the stepwell for
step de-icing.
FIGURE 1: DRIVER’S AIR CIRCULATION 22307
2.2 PASSENGERS’ AREA
Fresh air enters the vehicle on the L.H. side,
through the recirculation damper located inside
the evaporator compartment door (Fig. 2). The
damper can be fully opened for normal operation
or closed for extreme weather or highly polluted
areas (Refer to the X3 Operator's Manual for
more details). The recirculation REC button is
located on the HVAC control unit. Press down the
button to partially close the fresh air damper.
Return air is drawn from inside the vehicle
through the register duct located amidships on
L.H. side of vehicle (Fig. 3).
FIGURE 2: PASSENGERS' AREA RECIRCULATION
DAMPER
22302
A double blower fan unit, which is activated by the
evaporator motor, draws mixed air through an air
filter, cooling and heating coils, then forces this air
in the ventilation ducts along the walls, and finally
exhausts it just below side windows.
X3 coaches are also equipped with an overhead
compartment ventilation system, a three-position
rocker switch
(0FF - 1
st
speed - 2
nd
speed)
located on R.H. dashboard panel controls the
speed of both fans. Return air is drawn just below
the middle side windows through an air filter into
the overhead compartment fan; discharge air is
fed to the rotating registers through the ventilation
duct (Fig. 4).
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