Literature number 31970
hydro flame™
AFS Series Furnaces Models
AFSAD12
AFSD12, AFSD16, AFSD20
1120 North Main Street • Elkhart, IN 46514
USA & Canada : 1-866-869-3118
Internet: http://www.atwoodmobile.com

Technical Installation Manual

English, French (et Canada)

Effective 8/15

WARNING

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 is 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.

Installation of this appliance must be 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

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.

WITH THE APPLIANCE.
TO THE CONSUMER: RETAIN THIS MANUAL FOR
FUTURE REFERENCE.

SAFETY ALERT SYMBOLS
FOR YOUR SAFETY

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

WARNING
Avoid possible injury or
death

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

CAUTION

WARNING

Avoid possible injury
and/or property damage

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.

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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) has been repaired.
A qualified Service Technician
Service Center or gas supplier must perform
installation and service.

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1

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 or intake or exhaust vents 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 battery charger to supply power to 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 installation materials from degrading air and flue exhaust
systems.
Protect furnace electrical components from water.
Compartments must be closed when in operation.
Should the gas supply fail to shut off during operation or
overheating occurs, shut the gas valve off to the furnace before
shutting off 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.

TO SHUT DOWN UNIT ................................................................. 7

CAUTION

IGNITION CONTROL DIAGNOSTIC CODES ......................... 7

PERSONAL INJURY

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

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

MODEL NOMENCLATURE

WARNING
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.

AF

S

D

20

1

1

1

A

Atwood
Furnace

Cabinet
Size
S=small
SA=small
low amp

Voltage

Input
Btu/hr
12K
16K
18K

Gas
Type
1=LP

Style

Valve

Model
Rev
A

D=12
VDC

WARNING
CARBON MONOXIDE POISONING
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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.

AFSD12
AFSD16
Model #
Type of
LP
LP
Gas
Propane
Propane
BTU Input
12,000
16,000
BTU Output
9,120
12,160
Duct Static
0.10”WC
0.10”WC
Pressure
12 Volt
Amperage
3.4*
3.4*
(AMPS)
Power
Supply
12
12
(Volt DC)
Watts
41
41
Minimum
35 in2
35 in2
Return Air
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(WC = WATER COLUMN)
*
15 AMP DECATATED CIRCUIT for furnace

WARNING

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1=
single
stage

MODEL SPECIFICATIONS

CARBON MONOXIDE POISONING
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1=Door
2=LD
(small
vent)
3=door w/
rear gas
fitting
4=door
w/pigtail
5=door
w/pigtail &
rear gas
fitting

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

More information and installation information can be found on
top of furnace and inside front.

Contents

DIMENSION
Approx.
Dim.
Casing
Vent (LD)
Door
Interior Grill
Trim Ring

MODEL NOMENCLATURE .....................................................2
MODEL SPECIFICATIONS .....................................................2
DIMENSION .................................................................................. 2

INSTALLATION AND SAFETY CODES..................................2
INSTALLATION CODES ................ Error! Bookmark not defined.

GENERAL FURNACE INSTALLATIONS ................................ 2
CLEARANCE TO COMBUSTIBLES .......................................3
REQUIRED DUCTING .............................................................3
DISCHARGE AND DUCTING ..................................................3
FLEXIBLE DUCTING SYSTEMS.............................................4
AIR FLOW CHECK ..................................................................4
FURNACE INSTALLATION .....................................................4
SIDEWALL CUTOUT ............................................................... 4

AFSD20

AFSAD12

LP
Propane
18,000
13,680

LP
Propane
12,000
9,120
0.10”WC
0”WC front

0.10”WC
4.8*

2.4*

12

12

56

34

35 in2

35 in2

Height

Width

Depth

Weight

7”
5-1/2”
9-3/4”
12-1/2”
10-1/8”

12”
5-1/2”
14-3/4”
8-1/2”
14-1/8”

20”
1-1/6”
1/2”
1/2”
1/8”

Furnace 21
lbs.
Boxed
24 lbs.

INSTALLATION AND SAFETY CODES
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USA and Canada – follow all applicable state and local codes in
the absence of local codes or regulations, refer to current
standards of:
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ANSI/NFPA 1192 Recreational Vehicles Code and ANSI/RVIA LV
Low Voltage Systems in Conversion and Recreational Vehicles
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CSA Z240.4, Gas-Equipped Recreational Vehicles and Mobile
Housing
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National Fuel Gas Code ANSI Z223.1 and/or CAN/CGA B149
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This furnace must be installed in accordance with the
manufacturer’s instructions and the manufactured Home
Construction and Safety Standard, Title 24 CFR, part 3280, or
when such standard is not applicable, the Standard for
Manufactured Home Installations. (Manufactured Home Sites,
Communities and Set-Ups), ANSI A255.1 and/or CAN/CSA-Z240
MH Series M92 Canadian Standard for Mobile Homes.”
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ANSI A 255.1 and/or CAN/CSA-Z240.6.2 MH Series, Mobile
Homes
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Ground National Electrical Code ANSI/NFPA 70 and/or CSA
C22.1, Part 1
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Park Trailers ANSI 1195

WALL CUTOUTS .......................................................................... 4

SMALL VENT INSTALLATION ...............................................4
STANDARD DOOR INSTALLATION ......................................5
INTERIOR GRILL ....................................................................5
PROPANE GAS CONNECTION ..............................................6
ELECTRICAL CONNECTIONS ...............................................6
POWER SUPPLY ....................................................................6
CONDUCTOR SIZING ................................................................... 6

THERMOSTAT INSTALLATION .............................................7
OPERATING INSTRUCTIONS ................................................7

GENERAL FURNACE INSTALLATIONS

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All models can be installed in either a horizontal or vertical
position Horizontal installs must have the gas line positioned on
top, vertical installs must have vent located at the floor and gas
line on the right side.
Always install furnace exhaust system 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 removal for servicing 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 requirements.
DO NOT use petroleum or citrus base 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 the siding or cutting the siding away from the
area around the appliance vent.
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 and protected to avoid physical damage by vehicles.
DO NOT use petroleum or citrus type cleaner on plastic parts, as
damage may occur.

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Spacing of 1/4” to ducting within 3 feet of furnace must be
provided unless UL listed wire bound vinyl ducts are used. All
ducting material must be rated for continuous use at minimum of
200°F.
Clearances are specifically for plywood or similar building
materials surrounding the furnace (i.e. Furnace should not be
located under furniture or in a closet space where clothing or
other material could be located).
Furnace efficiency rating is a thermal rating determined under
continuous operating conditions, independent of any installation.
Efficiency rate is given at 76% minimum; actual efficiency rating
may be higher.
Return air is supplied through openings in and around the
furnace. All return air passages must be kept clear for furnace to
function properly.
The total unobstructed return air opening size must not be less
than specified in these instructions. Failure to meet minimum
return air requirements nullifies furnace warranty.
To install without the additional 16 in2 cutout on the blower side,
supply blower side of unit with 2” clearance full height length and
width of the unit.

REQUIRED DUCTING
CLEARANCE TO COMBUSTIBLES

All ducts in the table are four-inch ducts except for front discharge as
noted. Two-inch ducts cannot be used in place of one four. A front
discharge system using a five-inch duct requires no other ducts
maximum length 12”.
Optional five-inch to four-inch adapter ducting can be purchased to
allow four-inch duct in addition (1) four-inch or (2) two-inch ducts must