Duo-Therm 39125 Service Manual Download Page 5

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Total System Pressure must be between the following:

0.55 to 0.90 in. W.C. for 579 Series
0.40 to 1.10 in. W.C. for 591, 595 & 630 Series
0.12 to 0.65 in. W. C. for 600 Series

This is determined with the air conditioner blower opera-
tion on high speed and return air filter and grille in place.

The Dometic Corporation recommends the basic configu-
ration shown below for installing this Air Conditioner Sys-
tem. We have found by testing that this configuration works
best in most applications of the Air Conditioner/Heat Pump
System.

It is the responsibility of the installer of this system to re-
view each RV floor plan and determine the following:

A. Duct Size
B. Duct Layout
C. Register Size
D. Register Locations
E. Thermostat Location

These items must be determined in conjunction with the
Air Distribution System Sizing and Design Requirements
listed.

Note:

Alternate configurations and methods may be used

which still allow the air conditioner to operate properly.
However, these alternate configurations and methods must
be approved by The Dometic Corporation in writing.

The following instructions are based upon the use of
Dometic Return Air Kit.

The electronic control kit has

mounting bolts supplied for use with this Kit. See FIG. A3.

Before preparing the ceiling opening, the type of system
options must be decided upon. If a remote sensor is to be
used, provisions must be made for it. If the load shed op-
tion (Energy Management System feature) is to be used,
wires must be run from the load shed control to the Dometic
A/C. If a furnace is to be connected, wires must be run
from the furnace to the Air Conditioner.

The 14-1/4" x 14-1/4" (±1/8") opening must be framed to
seal off the roof cavity. Holes used to route electrical wir-
ing should be sealed. The 14-1/4" x 14-1/4" (±1/8") open-

Section A - Installation, cont’d.

ing is part of the return air duct and must be finished in
accordance with NFPA Standard 501C, Standard for Rec-
reational Vehicles, Section 2-7.

The most commonly found installation problem is the im-
proper sealing of the 14-1/4" x 14-1/4" (±1/8") opening in
the roof cavity. The cooled discharge and warm return air
are mixed in the roof cavity and produce conditions that
are excellent for frost production.

Even the best framing job will not stop frost from occurring
if the cold air discharge is allowed to enter into the return
air portion of the 14-1/4" x 14-1/4" (±1/8") opening. See
FIG. A4.

FIG. A3

FIG. A4

Duo-Therm’s return air kits are designed to be installed
tightly to the bottom of the base pan and ceiling template.
Insulation supplied in the kit not only stops condensation
from forming on the divider plate, but prohibits air leaks as
well. The insulation
is purposely over-
sized to be at-
tached to the sides
of the 14-1/4" x 14-
1/4" (±1/8") open-
ing and the base of
the air conditioner
and ceiling tem-
plate. Make sure
the data plate does
not get covered
with insulation.
See FIG. A5.