Air Distribution System Sizing And Design - Dometic FreshJet 4 Series Installation Manual

General information
Tilt allowance
Model number
FreshJet 4 series
4 .7 .3 Planning the return air grille
location
The return air grille requires unobstructed airflow to
operate properly. Make sure the installation location
inside the RV is free of obstructions such as, door
openings, room dividers, curtains, ceiling fixtures, etc.
4 .7 .4 Planning the thermostat location
The proper location of the thermostat is important to
ensure the unit provides a comfortable RV temperature.
To determine where to place the thermostat, consider
these items:
• Locate the thermostat 54.0 in. (1.4 m) above the floor.
• Install the thermostat on a partition, not on an outside
wall.
• Never expose the thermostat to direct heat from
lamps, the sun, or other heat-producing items.
• Avoid locations close to doors that lead outside,
windows, or adjoining outside walls.
• Avoid locations close to supply registers and the air
from them.
For thermostats installed with an optional indoor
temperature sensor in all zones, consider these
additional items:
• The thermostat may be mounted anywhere in the RV
that is convenient.
• Avoid hard to reach and hard to see areas.
• See the instructions provided with the indoor
temperature sensor for installation details.
For multiple, single zone thermostats, consider these
additional items:
• Install each individual thermostat in the room that the
AC is responsible for cooling.
8
Maximum tilt (all directions)
15°
Rooftop air conditioner (FreshJet return air grille, wall thermostat controls)
• This configuration will prevent the air conditioners
from attempting to turn on at the same time and
overloading the breaker.
4 .8 Air distribution system sizing
and design
NOTICE: Make sure ductwork will not bend or collapse
during and after installation, and that it is correctly
insulated and sealed. Otherwise, damage to the roof
structure and ceiling could occur.
This section describes the sizing and design
requirements; and, a recommended configuration for
the air distribution ductwork.
4 .8 .1 Ductwork requirements
Return air grille kit
Roof cavity depth
Duct cross sectional area
Duct depth
Duct width
Duct total (short run)
Duct length total
Number registers required
Supply register free air area
Return register free air area
(including the filter)
Distance from duct end
Distance from elbow
Total system static air
pressure, blower at high
speed, filter and grille in
place
The following additional requirements must be met for
the unit to operate properly:
FRESHJET, RAG-
PLAIN PREM, WHT
9610003699
FRESHJET, RAG-PLAIN
PREM, WHT, LED
9610003700
1.5 in. (38 mm) —
6.0 in. (152 mm)
21.0 sq in. (53 cm)
minimum
1.5 in. (4 cm) —
2.5 in. (6 cm)
7.0 in. ( 18 cm) —
10.0 in. (25 cm)
One-third total duct length
15.0 ft ( 4.6 m) —
40.0 ft (12.2 m)
Four minimum
14 sq in. (36 sq cm)
40 sq in. (102 sq cm)
minimum
5.0 in. (13 cm) —
8.0 in. (20 cm)
15 in. (38 cm)
0.5 — 1.1 in. WC
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