Required Discharge; Flexible Ducting; Air Flow Check; Furnace Installation - Atwood AFL Series Technical Installation Manual

 Horizontal Bottom Discharge: This installation is for horizontally
installed units and can be used with the addition of one duct any
location except the top two.
 Vertical Bottom Discharge: Installation of the furnace in a
vertical mounting position can be used with the addition of one
duct any location except the top two.

REQUIRED DISCHARGE

Models
AFL (35)(40)
Horizontal Bottom
Vertical Bottom
System AFLD35 AFLD40
4" Duct
3
Bottom plus
4x10
4"duct min
Vertical
5x9-3/4
Bottom
*Note the table is for minimum requirements and should in most
cases allow the unit to operate correctly. If the burner cycles on
and off on high temperature limit. Extra ducting can be used to
help correct this condition due to restriction or bends in duct
work.

Proper duct installation is critical to operation of 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 air rise of 100°F-130°F. Also
see air flow check section.
Required Discharge Area
2
36 in
2
48 in
2
48 in
AFLA35 AFLA40
3 3
4x10 4x10
5x9-3/4 5x9-3/4 5x9-3/4
2
of discharge area.

FLEXIBLE DUCTING

When designing flexible duct systems:

Follow ducting configuration shown

Avoid sharp bends or crushed ducts.

Stretch all ducts and run them directly to outlets, keeping quantity
and angles of bends to a minimum.

Remove knockout plate from desired outlets. If a knockout is
removed accidentally a cover plate can be purchased.

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
3
Rating Plate. After installation of the furnace and duct system is
completed, adjustment to obtain a temperature rise should be
4x10
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 reduce restrictions in the system.
Total fpm= feet per minute readings

FURNACE INSTALLATION


The furnace should always be installed level (front to back, side to
side) to prevent water intrusion into the interior.

Set aside venting and outer door parts for installing on the outside
of coach.

NOTE to assure sufficient return air to circulating blower maintain
specified clearances.

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 service suggested opening size 17" wide by 9-
1/2" height.

Remove knockouts from furnace and install duct adapters for side
discharge by inserting back flange over casing and inserting tab
into square notch, then twist adapter 90°.

Insert furnace into cabinet opening and secure with two screws
through casing legs to floor. Units are secured by door or vent
systems through the coach sidewall.

Attach flexible ducting over duct adapters and secure. All flex
ducting requires rating of 200°F.

Run ducting to locations keeping bends and excess ducting to a
minimum and secure to registers.

Connect wiring to located on the top of the furnace. See wiring
connection section.

Connect gas line to top or rear of furnace. See gas connection
section.

SIDEWALL CUTOUT

Maximum exterior wall thickness 0" to 2-1/2" an optional vent kit can be
purchased to extend the vent usage to 3" wall thickness for small vent
installations

WALL CUTOUT

(Flush Door requires 3/4" radius corners)
Flush Door (corner cut requires
3/4" radius) (horizontal or vertical)

DO NOT oversize hole – over sizing can result in water leakage.

Zero clearance around air intake cutout for best sealing condition.
4
35-40 DC 35-40 AC
4600 fpm 5000 fpm
A
18-1/4" 11 1/8"
B C
20"