13
INSTALLATION INSTRUCTIONS
Where the return air must be provided through louvers
or mesh screen, the FREE AREA percentage of the
material used shall be taken into consideration when
making this determination. An example of how to
determine FREE AREA is included in "3.2.2. Outside
Coil".
B. Grills (See FIG. 3.4)
Note: The return air grill must have the same square
surface as the return air duct.
1. For each system, there must be a return grill to
bring vehicle air back into the unit. There must also
be at least four discharge grills per unit.
2. Return grills must be mounted in front of the inside
coil. If this is not possible, make sure there is
nothing blocking the air flow from the grill to the
inside coil.
3. The unit must have a return filter between the grill
and the unit. This filter must be accessible for
periodic cleaning.
C. Discharge Air (See FIG. 3.4)
The air diffusion system, supplied by the installer,
must be sized to maintain a static pressure at the
blower outlet between 0.40 (minimum) and 1.20 (maxi-
mum) inches water column.
The installer has the options of side discharge or top
discharge and side return. The unit can be ordered
originally with the inside blower mounted to discharge
the air as required. If the installer needs to change the
direction of the discharge it is necessary to rotate the
inside blower housing 90 degrees.
All air handling ducts must be properly insulated to
prevent condensation forming on their surface during
operation. A vapor barrier must also be supplied on the
outer surface of the insulation to prevent moisture from
traveling through the insulation and condensing on the
cold duct work.
D. Condensate Drain
A condensate drain tube is located on bottom of the
base pan, under the return air opening.
1. The installer needs to install the condensate drain
into the base pan and ensure a snug fit.
2. A 3" diameter hole must be provided for installation
of the tube and clearance. See Figure 2.11.
Note: Condensate will not drain properly if drain
tube is not installed or missing.
The outside coil is a "draw-through" type. When the
face of the coil is positioned behind a louvered or other
type of restrictive opening, the FREE AREA of the
opening must be at least 648 square inches.
FIG. 3.3
8
8
2
2
2
1/2
1/2
1/2
1/2
36
64
EXAMPLE OF HOW TO DETERMINE FREE
AREA OR % OPEN AREA:
TOTAL AREA =
8 X 8
=
64
FREE AREA
=
2 X 2 X 9 openings
=
36
% OPEN AREA
=
=
56%
B. Free Area
Free area is the opening that remains in a grill or
louvered panel after the restrictions are taken away.
For example, an opening of 10 x 20 inches has 200
square inches. When this opening is covered with a
grill that is 56 percent open the FREE AREA is (200
x .56), 112 square inches. See FIG. 3.3.
Expanded and perforated metal grills in general vary
from 30 percent to 60 percent open. Be certain that
648 square inches of FREE AREA is available to the
face of the outside coil.
Note: Service access must always be supplied either
as clearance or as a defined access panel.
Do not install the unit where the fan will draw
air from the exhaust of the vehicle, a motor
generator set, transmission, road heat or
any other heat producing source.
CAUTION
3.2.3 MOUNTING
The Model 39626 Air conditioner and 39726 Heat Pump units
design are for installation below the floor. This unit should be
mounted in an angle-iron frame, designed and built for the
Model 39626 and 39726. Frame rails should not restrict the
condenser air discharge opening.
Important:
Do not mount the Units in a sealed com-
partment. Recirculation of hot condenser discharge air
will cause high system pressure and trip breakers.
3.2.4 CLEARANCES
A. The unit clearances depend on:
1. Inlet air access used;
2. Discharge air duct arrangement;
3. Return air duct;
Allow a minimum of eight (8) inches for the return air
duct. Access to the electrical connections must be
provided when making the installation.
3.2.5 INSIDE COIL SECTION
A. Return Air
The inside coil must have free access to room air. A
minimum of 135 square inches of FREE AREA
opening is required.
It is the responsibility of the installer to en-
sure that the drain tube is installed properly
and that it will not leak. Dometic Corporation
will not be liable for any structural damage
due to improperly installed, sealed or re-
stricted drain tube.
CAUTION
