Literature number 32471
hydro flame™
AFM Series Furnaces Models
AFMD16, AFMD20, AFMD25
AFMD30, AFMD35
1120 North Main Street • Elkhart, IN 46514
USA & Canada : 1-866-869-3118
Internet: http://www.atwoodmobile.com

Technical Installation Manual

English, Français (et Canada)
This instruction manual is for use by an authorized service technician
to install an Atwood – hydro flame™ furnace. Should you require
further information, contact your dealer or Atwood Mobile Products
LLC.
This furnace design has been certified for installation in recreation
vehicles as a MSP Category III furnace. Follow this installation
instruction to insure safe operation of the furnace. Failure to install
furnace according to this installation instruction nullifies the furnace
warranty.

Effective 8/15

WARNING
Installation of this appliance must be made in accordance with the
written instructions provided in this manual. No agent, representative
or employee of Atwood or other person has the authority to change,
modify or waive any provision of the instructions contained in this
manual.

WARNING
Avoid possible injury or death

TO THE INSTALLER: LEAVE THIS MANUAL WITH THE
APPLIANCE.

TO THE CONSUMER: RETAIN THIS MANUAL FOR
FUTURE REFERENCE.

Improper installation, adjustment, alteration, service or maintenance
can cause property damage, personal injury or loss of life. Refer to the
installation instructions and/or owner’s manual provided with this
appliance. A qualified installer, service agency or the gas supplier must
perform installation and service.

SAFETY ALERT SYMBOLS
Safety Symbols alerting you to potential personal safety
hazards obey all safety messages following these
symbols

WARNING
Avoid possible injury or
death

FOR YOUR SAFETY
Do not store or use gasoline or other flammable vapors and liquids in
the vicinity of this or any other appliance.

CAUTION
Avoid possible injury
and/or property damage

WARNING
Be sure the furnace and all ignition systems are “off” during any type of
refueling and while vehicle is in motion or being towed.

WARNING
FIRE OR EXPLOSION

CRITICAL INSTALLATION WARNINGS


If the information in this manual is not followed
exactly, a fire or explosion may result causing
property damage, personal injury or loss of life.

FOR YOUR SAFETY
WHAT TO DO IF YOU SMELL GAS:
 Extinguish any open flame.
 Evacuate all persons from the vehicle.
 Shut off the gas supply at the gas container
or source.
 Do not touch any electrical switch, or use
any phone or radio in the vehicle.
 Do not start the vehicle’s engine or electric
generator.
 Contact the nearest gas supplier or qualified
service technician for repairs.
 If you cannot reach a gas supplier or
qualified service technician, contact the
nearest fire department.
 Do not turn on the gas supply until the gas
leak(s) have been repaired.
A qualified Service Technician
Service Center or gas supplier must perform
installation and service.


















DO NOT install furnace on material that restricts return air, like
carpet or any soft material such as vinyl.
DO NOT install furnace where clearance to combustibles cannot be
maintained.
DO NOT modify furnace in any way.
DO NOT alter furnace for a positive grounding system.
DO NOT hi pot furnace unless electronic ignition system (circuit
board) has been disconnected.
DO NOT use a battery charger to supply power to a DC model
furnace even when testing.
DO NOT use 120-volt AC current with DC models.
DO NOT use furnace cabinet area as a storage compartment.
DO NOT vent furnace with venting system serving another
appliance.
DO NOT vent furnace to an outside enclosed porch area.
DO NOT use for temporary heating of buildings or structures under
construction.
Protect building materials from degrading from flue gas exhaust.
Protect furnace electrical components from water.
Compartment must be closed when operating unit.
Should the gas supply fail to shut off or if overheating occurs, shut
off the gas valve to the furnace before shutting off the electrical
supply.
DO NOT use this furnace if any part has been under water.
DO NOT use petroleum or citrus type cleaner on plastic parts, as
damage may occur.

CAUTION
PERSONAL INJURY
All sheet metal edges are sharp care should be taken when
handling or brushing up against them.

WIRING AND LADDER DIAGRAM ............................................ 8

WARNING

MODEL SPECIFICATIONS

CARBON MONOXIDE POISONING
Properly seal vent assembly to prevent carbon monoxide from entering
coach.
 DO NOT draw combustion air from living area.
 DO NOT vent exhaust air into the living area or an enclosed porch.

WARNING
CARBON MONOXIDE POISONING


Furnace must be installed and vented according to these
instructions.
 Improper installation, adjustment, alteration, service or
maintenance can cause injury or property damage.
Improper installation location may cause furnace to produce negative
pressure, affecting combustion air or venting of other appliances.

WARNING
CARBON MONOXIDE POISONING



Properly seal door to prevent carbon monoxide from entering
coach.
Properly adjust draft cap to prevent carbon monoxide from entering
coach.

MODEL NOMENCLATURE
AF

M

D

25

1

1

1

A

Atwood
Furnace
AF

Cabinet
Size
M=medium

Voltage

Input
Btu/hr

Gas
Type
1=LP

Gas
Location
1=door

Valve

Model
Rev
A

D=12
VDC

16K
20K
25K

1=Single

Models

AFMD16

AFMD20

AFMD25

AFMD30

AFMD35

Type of
Gas

LP
Propane

LP
Propane

LP
Propane

LP
Propane

LP
Propane

BTU Input
BTU
Output

16,000
12,160

20,000
15,200

25,000
19,000

30,000
22,800

34,000
25,840

Duct
Static
Pressure
Amperage
(AMPS)
Watts

.20” WC

.10” WC

.10” WC

.10” WC

.10” WC

4.2*

4.2*

7.5*

7.5*

11.1*

50

50

90

90

132

Power
Supply
(Volt DC)
Return Air

12

12

12

12

12

80 in2

80 in2

80 in2

80 in2

80 in2

Minimum
65 in2
65 in2
65 in2
Return Air
(WC = WATER COLUMN)
* 15 AMP DECATATED CIRCUIT FOR FURNACE

65 in2

65 in2

DIMENSIONS
Approx.
Width
Casing
16-1/2”
STD Door
19-1/4”
FLUSH
19-3/8”
DOOR
Vent LD
5-1/2”

2=LD (small
vent)
3=door w/
rear gas
fitting
4=door
w/pigtail
5=door w/
pigtail & rear
gas fitting

Height
7”
9-3/4”

Depth
20”
3/4”

10-1/4”

7/32”

5-1/2”

1-1/16”

Weight
Furnace
26lbs.
Boxed
29 lbs.

INSTALLATION AND SAFETY CODES

USA and Canada – follow all applicable state and local codes in
the absence of local codes or regulations, refer to current
35K
standards of:
Contents

ANSI/NFPA 1192 Recreational Vehicles Code and ANSI/RVIA LV
Low Voltage Systems in Conversion and Recreational Vehicles
MODEL NOMENCLATURE ....................................................... 2

CSA Z240.4, Gas-Equipped Recreational Vehicles and Mobile
MODEL SPECIFICATIONS ....................................................... 2
Housing

National Fuel Gas Code ANSI Z223.1 and/or CAN/CGA B149
DIMENSIONS ................................................................................... 2

This furnace must be installed in accordance with the
INSTALLATION AND SAFETY CODESError! Bookmark not defined.
manufacturer’s instructions and the manufactured Home
INSTALLATION CODES ................... Error! Bookmark not defined.
Construction and Safety Standard, Title 24 CFR, part 3280, or
when such standard is not applicable, the Standard for
GENERAL FURNACE INSTALLATIONS .................................. 2
Manufactured Home Installations. (Manufactured Home Sites,
CLEARANCE TO COMBUSTIBLES: ............................................... 3
Communities and Set-Ups), ANSI A255.1 and/or CAN/CSA-Z240
REQUIRED DUCTING ...................................................................... 3
MH Series M92 Canadian Standard for Mobile Homes.”
REQUIRED DISCHARGE ................................................................. 3

ANSI A 255.1 and/or CAN/CSA-Z240.6.2 MH Series, Mobile
FLEXIBLE DUCTING
4
Homes
AIR FLOW CHECK........................................................................... 4

Ground National Electrical Code ANSI/NFPA 70 and/or CSA
FURNACE INSTALLATION ....................................................... 4
C22.1, Part 1

Park Trailers ANSI 1195
SIDEWALL CUTOUT ....................................................................... 4
30K

SMALL VENT INSTALLATION ................................................. 5
STANDARD DOOR INSTALLATION ........................................ 5
FLUSH DOOR INSTALLATION ................................................ 6
HARD DUCT SYSTEMS ............................................................ 6

GENERAL FURNACE INSTALLATIONS


FLOOR DISCHARGE CUTOUTS ..................................................... 6




GAS CONNECTION .................................................................. 6
ELECTRICAL CONNECTIONS ................................................. 7
THERMOSTAT INSTALLATION ............................................... 7
OPERATING INSTRUCTIONS .................................................. 7




TO SHUT DOWN UNIT ..................................................................... 8

IGNITION CONTROL DIAGNOSTIC CODES ............................ 8

2

All models can be installed in either a horizontal or vertical
mounting position horizontal installed units have the gas line
positioned on top or rear, vertical installed units must have the
vent located at the floor and gas line at right side and rear.
Always install furnace through an exterior wall.
DO NOT install furnace near tilt-out rooms, slide-outs, doors or
other projection that could obstruct furnace exhaust.
Locate furnace near midpoint of coach for single furnace
applications.
Installation must provide accessibility if any repairs are necessary
to the furnace. Failure to meet this requirement will create
additional labor costs that will be the responsibility of the installer.













DO NOT install vent in areas where projection or door openings
come within 6” of vent opening.
DO NOT install furnace in an area where wires, pipes or other
objects will interfere with installation or operation of furnace.
DO NOT install furnace on material that restricts return air, such
as directly on carpet, or soft material (like vinyl). If you must install
furnace on carpet or soft material, install furnace on cleats, or on
a wood or metal panel extending the full width and depth of
furnace plus minimum clearance to combustibles.
DO NOT use petroleum or citrus type cleaner on plastic parts, as
damage may occur.
NOTE: The exhaust temperature of this furnace could discolor or
warp some materials. You should verify that the material used on
coach door, panel, or covers will not discolor, warp or burn from
the exhaust temperature whenever placed directly in front of vent.
CAUTION: Due to the differences in vinyl siding materials this
appliance should not be installed without first consulting with the
manufacturer of siding.
A gas-fired furnace for installation in a residential garage must be
installed so the burner(s) and the ignition source are located not
less than 18 in (457mm) above the floor and the furnace must be
located or protected to avoid physical damage by vehicles.





REQUIRED DUCTING
All ducts in the table are four-inch ducts except for bottom discharge as
noted. Two-inch ducts cannot be used in place of four inch. .
A bottom discharge requires no additional ducting; one additional duct
can be added if required. Vertically installed units can also be bottom
discharge when right side cover panel has been removed one
additional duct can be added if required.
FOR OPTIMAL PERFORMANCE use the following instructions for
ducting. (Two top ducts are only to be used in addition to the below
installations and are not allowed to be used until these requirements
have been met). Additional ducting added will reduce the air flow and
could cause poor heating.
 Horizontal or Vertical 4” Ducting: when using 4” ducting one
duct from each side must be used. When using side ducts,
utilizing rear duct openings as the other duct will yield the best
performance.
 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 casing top two ducts.

CLEARANCE TO COMBUSTIBLES:
Floorboards, walls & similar combustible building materials must be
provided the full length and width of unit. Spacing is based on installed
position when installed horizontally bottom is bottom. When installed
vertically bottom becomes right side.
clearances

Top

Sides

Rear

Bottom (to