Flexible Ducting; Air Flow Check; Furnace Installation; Sidewall Cutout - Dometic AFM Series Technical Installation Manual


Proper duct installation is critical to proper operation of the
furnace. When installing ducts, use materials rated for continuous
use at 200°F.

Each 4-inch duct opening provides 12 in
2
Provide an extra 12 in of non-closeable duct discharge area for
each closeable register used.

Ducting into dead air space with no return air, such as holding
tank areas, does not count toward achieving minimum discharge
requirements.

Adjust ducting installation to obtain an air temperature rise of
100°F-130°F. Also see air flow check section.

FLEXIBLE DUCTING


Follow ducting configurations shown.

Avoid sharp bends, deep sags or crushed ducts.

Stretch all ducts thoroughly and run them directly to outlets,
keeping number of angles of bends to a minimum.

Remove knockout plate from desired outlets. If a knockout is
removed accidently cover plates can be purchased.

Unused knockouts MUST be covered.

Attach a duct adapter by inserting flange over casing hole, locking
the tab into casing slot and turning adapter 90°

Attach and secure four-inch flexible duct to adapter(s)

Run duct(s) to desired location within RV, secure to register(s)

AIR FLOW CHECK


Appliance is tested to a temperature rise as specified on the
Rating Plate. After installation of the furnace and duct system is
completed, adjustment to obtain proper temperature rise should
be made.

The table below is a reference to maintain maximum operation of
the appliance when checking temperature rise is not possible.
Airflow measurements made at each registers the total reading
should not be less than what is shown in table below for each
BTU size.

If readings are below the table values airflow can be improved by
adding ducts or reducing/eliminating restrictions in the system.
2
of discharge area.
16,000 20,000
3000 fpm 3000 fpm
Total fpm= feet per minute readings

FURNACE INSTALLATION


Remove furnace from box

Remove vent assembly supplied with furnace

DO NOT mix assemblies with other units, each model has a
specific vent baffle size to operate correctly, see sticker on vent
assembly.

Remove knockouts in locations that will be used and install
adapters.

The furnace should always be installed level (front to back, side to
side) to prevent water build up into the interior of the vent area.

If units are installed using the small outside vent system, access
to the inside of the coach must be provided directly in front of the
unit to remove for servicing suggested opening size 17" wide by
8.5" height.

Secure unit with two brackets and screws provided at the rear of
the unit through holes provided.

Attach flexible ducting over duct adapters and secure.

Run ducting to locations keeping bends and excess ducting to a
minimum and secure to registers.

Connect wiring to furnace see wiring connection section.

Connect gas line see gas connection section.

SIDEWALL CUTOUT

Maximum exterior wall thickness 0" to 2-1/2". Optional vent kit can be
purchased to extend the vent to a 3" wall thickness on small vent
installations.
WALL CUTOUTS
(Standard door square corner and Flush Door requires 3/4" radius
corners)
Side Wall Cutout
Small Vent
Standard Door
(horizontal or 17" Max
vertical)
Flush Door
(horizontal or 18-1/4" Max
vertical)

DO NOT oversize hole – over sizing can result in water leakage.

Zero clearance around air intake cutout for best sealing condition.
4
25,000 30,000
3500 fpm 4000 fpm
A B
3-1/2" Dia.
- -
Max
7-1/2" Max
9-1/8" Max
35,000
5500 fpm
D