INSTALLATION
INSTRUCTIONS
DF Series Furnace
Models DFSAD12, DFSD12, DFSD16, DFSD20, DFMD16,
DFMD20, DFMD25, DFMD30, DFMD35, DFLD35,
DFLD40, DFLA35, DFLA40
USA & CANADA
SERVICE OFFICE
Dometic Corporation
1120 North Main Street
Elkhart, IN 46514
SERVICE CENTER &
DEALER LOCATIONS
Visit:
www.eDometic.com
Form No. 33400 09/17
©2017 Dometic Corporation
LaGrange, IN 46761
INTRODUCTION ............................................................................. 2
IMPORTANT SAFETY INSTRUCTIONS AND DOCUMENT SYMBOLS .................................... 2
GENERAL INFORMATION ...................................................................... 4
PRE-INSTALLATION ........................................................................... 6
INSTALLATION .............................................................................. 16
TESTING ................................................................................... 24
TROUBLESHOOTING ........................................................................25
REPLACEMENT PARTS ........................................................................ 25
Read these instructions carefully. These instructions MUST stay with this product.
WARNING:
FIRE OR EXPLOSION HAZARD
Failure to follow safety warnings exactly could result in serious
injury, death or property damage.
− Do not store or use gasoline or other flammable vapors and
liquids in the vicinity of this or any other appliance.
− WHAT TO DO IF YOU SMELL GAS
• 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.
− Installation and service must be performed by a qualified
installer, service agency, or the gas supplier.
2
INTRODUCTION
This manual is for use by an authorized service technician to install a Dometic DF Series Furnace. Should you require further
information, contact Dometic. The design of the DF Series Furnace (hereinaer referred to as “Furnace”) has been certified for
installation in a recreational vehicle (hereinaer referred to as “RV”) as an MSP Category III Furnace. Follow these instructions to
ensure the correct installation of the Furnace. Failure to install the Furnace according to these installation instructions nullifies the
Furnace warranty.
Dometic Corporation reserves the right to modify appearances and specifications without notice.
IMPORTANT SAFETY INSTRUCTIONS AND DOCUMENT SYMBOLS
This manual has safety information and instructions to help you eliminate or reduce the risk of accidents and injuries.
A. Recognize Safety Information
This is the safety alert symbol. It is used to alert you to potential physical injury hazards. Obey all safety messages that follow
this symbol to avoid possible injury or death.
B. Understand Signal Words
A signal word will identify safety messages and property damage messages, and will indicate the degree or level of hazard
seriousness.
indicates a hazardous situation that, if NOT avoided, could result in death or serious injury.
indicates a hazardous situation that, if NOT avoided, could result in minor or moderate injury.
is used to address practices NOT related to physical injury.
Indicates additional information that is not related to physical injury.
C. Supplemental Directives
Read and follow all safety information and instructions to avoid possible injury or death.
Read and understand these instructions before installation of this product.
Incorrect installation of this product can lead to serious injury or death.
The installation MUST comply with all applicable local or national codes, including the latest edition of the following standards:
U.S.A.
• ANSI/NFPA70, National Electrical Code (NEC)
• ANSI/RVIA LV, Low Voltage Systems in Conversion and
Recreational Vehicles
• ANSI/NFPA 1192, Recreational Vehicles Code
• ANSI Z223.1, NFPA 54 National Fuel Gas Code
• ANSI 1195, Park Trailers
CANADA
• CSA C22.1, Parts l & ll, Canadian Electrical Code
• CSA Z240 RV Series, Recreational Vehicles
• CAN/CGA B149, Natural Gas and Propane Installation
Code
FOR DFLA35 and DFLA40 Models Only
This Furnace is manufactured for use with Liquid Propane (LP) gas. A kit has been provided with the Furnace, so that a qualified
service technician can convert the Furnace for use with natural gas. Any conversion to natural gas must conform with local
codes, or in the absence of local codes, with the National Fuel Gas Code, ANSI Z223.1/NFPA 54 Natural Gas and Propane
Installation Code, in addition to the Standard for Recreational Vehicles NFPA1192 and CSA Z240 RV Recreational Vehicle Code.
3
IMPORTANT SAFETY INSTRUCTIONS AND DOCUMENT SYMBOLS
D. General Safety Messages
Failure to obey the following warnings could result in property damage, serious injury, or death:
• This Furnace MUST be installed by a qualified service technician.
• Do NOT modify this Furnace in any way. Modifi cation can be extremely hazardous.
• FIRE OR EXPLOSION HAZ ARD:
• Do NOT store gasoline, oil- or gasoline-soaked rags, or other flammable vapors and liq uids, inside storage compartment(s).
• BEFORE refueling or parking near a gas oline pump, make sure ALL LP gas appliances (vented to the outside of the RV) are
shut OFF. Oth erwise, fumes from gasoline pumps could come into contact with an LP gas appliance burner flame and ignite.
• Turn OFF LP gas supply at tank.
• Use only with the type of gas approved for the Furnace. Refer to the Furnace rating plate.
• Use only Dometic replacement parts and components, which are specifically approved for use with the Furnace.
• CRITICAL INSTALLATION WARNINGS:
• Do NOT install this Furnace if any part has been underwater.
• Sheet metal edges are sharp; take care when handling or touching edges.
• Protect Furnace electrical components from water.
• Protect building materials from degrading from vent assembly gas exhaust.
• Compartment MUST be closed when operating the Furnace.
• Do NOT install screens over the intake air or exhaust vents for any reason.
• CARBON MONOXIDE HAZARD:
• This Furnace can produce carbon monoxide, which has no odor and can be life-threatening. The burner and vent assembly
system MUST be kept clean.
• Doors MUST be properly sealed and the dra cap and assemblies MUST be adjusted and sealed correctly to prevent
carbon monoxide from entering the RV.
• Do NOT allow snow or any objects to block the exhaust system of the Furnace.
• Combustion products MUST be properly vented to the atmosphere and all combustion air supplied to the burner MUST be
drawn from the outside atmosphere.
• Use only Dometic replacement parts and components, which are specifically approved for use with the Furnace.
• ELECTRICAL SHOCK HAZARD:
• Make sure AC power is dis connected from the Furnace during installation.
• Furnaces with 12 VDC connection are for low-voltage battery or direct current only. DC Furnaces are designed for negative
ground 12 VDC only. Do NOT attempt to alter the Furnace for a positive ground system or connect the Furnace directly to
120 or 240 VAC.
• Do NOT use a battery charger to supply power to DC model Furnaces, even when testing.
• Use only Dometic replacement parts and components, which are specifically approved for use with the Furnace.
4
GENERAL INFORMATION
INCLUDED HARDWARE
(2) Mounting Bracket (2 to 3) Duct Adapter (depending on Furnace model)
Ventilation Assembly 15 Amp Breaker (DFMD35,DFLD35 & DFLD40 models only)
REQUIRED TOOLS AND MATERIALS
Manometer Gauge/U-Tube Volt-Ohm Meter (15+ amps)
Gas Leak Detector Liquid Wrenches
Safety Glasses RTV Type Sealant
Pipe Thread Sealing Compound Foil Tape (optional)
A. Model Specifications
DFSAD12, DFSD12, DFSD16, DFSD20 (Small Furnace Models)
MODELS
DFSAD12 DFSD12 DFSD16 DFSD20
TYPE OF GAS
LP Gas LP Gas LP Gas LP Gas
BTU INPUT
12,000 12,000 16,000 18,000
BTU OUTPUT
9,120 9,120 12,160 13,680
DUCT STATIC PRESSURE
0.10" WC, 0" WC front 0.10" WC 0.10" WC 0.10" WC
AMPERAGE (AMPS)
2.4* 3.4* 3.4* 4.8*
WATTS
34 41 56 34
POWER SUPPLY (VOLT DC)
12 12 12 12
MINIMUM RETURN AIR
35 in.
2
35 in.
2
35 in.
2
35 in.
2
WC = Water Column; *15 Amp dedicated circuit for Furnace
DFMD16,DFMD20, DFMD25, DFMD30, DFMD35 (Medium Furnace Models)
MODELS
DFMD16 DFMD20 DFMD25 DFMD30 DFMD35
TYPE OF GAS
LP Gas LP Gas LP Gas LP Gas LP Gas
BTU INPUT
16,000 20,000 25,000 30,000 35,000
BTU OUTPUT
12,160 15,200 19,000 22,800 25,840
DUCT STATIC PRESSURE
0.20" WC 0.10" WC 0.10" WC 0.10" WC 0.10" WC
AMPERAGE (AMPS)
4.2* 4.2* 7.5* 7.5* 11.1*
WATTS
50 50 90 90 132
POWER SUPPLY (VOLT DC)
12 12 12 12 12
RETURN AIR
80 in.
2
80 in.
2
80 in.
2
80 in.
2
80 in.
2
MINIMUM RETURN AIR
65 in.
2
65 in.
2
65 in.
2
65 in.
2
65 in.
2
WC = Water Column; *15 Amp dedicated circuit for Furnace
5
GENERAL INFORMATION
DFLD35, DFLD40, DFLA35, DFLA40 (Large Furnace Models)
MODELS
DFLD35 DFLD40 DFLA35 DFLA40
TYPE OF GAS
LP Gas LP Gas LP Gas & Natural Gas LP Gas & Natural Gas
BTU INPUT
35,000 40,000 35,000 40,000
BTU OUTPUT
26,600 30,400 26,600 30,400
DUCT STATIC PRESSURE
0.10" WC 0.10" WC 0.10" WC 0.10" WC
AMPERAGE (AMPS)
12.5** 12.5** 2.5* 2.5*
WATTS
138 138 154 154
POWER SUPPLY
12 VDC 12 VDC 12 VAC 12 VAC
RETURN AIR
80 in.
2
80 in.
2
80 in.
2
80 in.
2
MINIMUM RETURN AIR
65 in.
2
65 in.
2
65 in.
2
65 in.
2
WC = Water Column; *15 Amp dedicated circuit for Furnace; **20 Amp dedicated circuit for Furnace
B. Model Dimensions
DFSAD12, DFSD12, DFSD16, DFSD20 (Small Furnace Models)
COMPONENT WIDTH HEIGHT DEPTH WEIGHT
Casing 12" 7" 20"
Furnace 21 lbs.
Boxed 24 lbs.
Small Vent 4-7/16" 4-7/16" 1-1/16"
Door 14-3/4" 9-3/4" 1/2"
Interior Grill 8-1/2" 12-1/2" 1/2"
Trim Ring 14-1/8" 10-1/8" 1/8"
DFMD16,DFMD20, DFMD25, DFMD30, DFMD35 (Medium Furnace Models)
COMPONENT WIDTH HEIGHT DEPTH WEIGHT
Casing 16-1/2" 7" 20"
Furnace 26 lbs.
Boxed 29 lbs.
STD Door 19-1/16" 9-1/2" 7/16"
Flush Door 20-5/8" 11" 7/32"
Small Vent 4-7/16" 4-7/16" 1-1/16"
DFLD35, DFLD40, DFLA35, DFLA40 (Large Furnace Models)
COMPONENT WIDTH HEIGHT DEPTH WEIGHT
Casing 16-1/2" 9" 20"
Furnace 39 lbs.
Boxed 46 lbs.
Door 19-1/4" 9-1/4" 1/4"
Recess Bezel 20-9/16" 11-1/2" 3/8"
Small Vent 4-7/16" 4-7/16" 1-1/16"
6
PRE-INSTALLATION
A. Identifying The Furnace Location
Failure to obey the following warnings could result in property damage, serious injury, or death:
• Install the Furnace only in a location and position specified in these instructions.
• Provide adequate combustion and ventilation air to the Furnace space, as specified in these instructions.
• Combustion products must be discharged outdoors. Connect this Furnace to an approved vent system only, as specified in
these instructions.
• As specified in these instructions, always install the Furnace to operate within the Furnace’s intended temperature-rise
range, with a duct system that has an external static pressure within the allowable range. Refer to the furnace rating plate.
• Do NOT install the Furnace near tilt-out rooms, slide-outs, and doors (refer to local codes for clearances), in an area where
wires, pipes, or other objects will interfere with the installation or operation of the Furnace, or in an area that is less than 12"
above a water heater (unless a heat shield is installed above the water heater).
• Do NOT install the Furnace directly on combustible flooring that restricts return air. Examples of combustible flooring
include carpet, tile, so material (like vinyl), or other combustible materials other than wood flooring.
• Do NOT install the Furnace where clearance to combustibles cannot be maintained. Excessive exposure to contaminated
combustion air will result in safety and performance-related problems.
The Furnace must be accessible for repairs.
Determining The Installation Type And Clearances Required
• Locate the Furnace near the midpoint of the RV, at least 3' from the gas service regulator, for a single-Furnace application. The
Furnace must be installed through an exterior wall. Spacing of 1/4" to ducting, within 3' of Furnace, must be provided unless
UL-listed, wire-bound, vinyl ducts are used. All ducting material used must be rated for continuous use at a minimum of 200 °F.
• Determine if you are using a horizontal or vertical installation.
• Horizontal Installation: locate the Furnace so that the gas line is at the top or rear of the Furnace.
• Vertical Installation: the Furnace top becomes the right side of the Furnace. Locate the Furnace so that the vent is at the
floor and the gas line is at the right or rear side.
• Identify the clearances required between the Furnace and the building materials surrounding the Furnace to allow for proper
airflow. Use the “Minimum Clearance To Combustibles” and the “Proper Return-Air Inlet Clearance” sections as guidelines.
Minimum Clearance To Combustibles
The minimum clearances allowed between the surface of the Furnace and combustible objects (board, wall, floor, etc) are shown in
the table.
The Furnace CANNOT be enclosed completely using these minimum dimensions.
CLEARANCE TO COMBUSTIBLES* Top Sides Rear
Bottom
(To Screw Heads)
SM. & MED. VERTICAL/HORIZONTAL 1/2" 1/2" 1/2" 0"
LG. VERTICAL/HORIZONTAL 1/2" 1" 1/2" 0"
*Combustibles are carpet, vinyl, tile, plywood, or similar building materials.
7
PRE-INSTALLATION
Proper Return-Air Inlet Clearance
When a furnace is installed so that supply ducts carry air circulated by the furnace to areas outside the space
containing the furnace, the return air shall also be handled by duct(s) sealed to the furnace casing and terminating outside the space
containing the furnace. Failure to do so could result in property damage, serious injury, or death.
Furnaces MUST have at least the Minimum Return Air detailed in section “A. Model Specifications” on page 4 and
page 5.
FIG.1
(Horizontal installation)
(Vertical Installation)
Vertical Wall
(Either Side
Of Furnace)
Horizontal Wall
Vertical Wall
If one wall is close
to the Return-Air
Inlet, there MUST
be at least 2"
clearance from the
TOP or Inlet SIDE.
2"
2"
2"
2"
Horizontal Wall
FIG.2
(Horizontal Installation)
(Vertical Installation)
Vertical Wall
If 2 or more walls are
close to the Return-Air
Inlet, there MUST be at
least 3" clearance from
the TOP and Inlet SIDE.
3"
3"
3"
3"
3"
Horizontal Wall
Horizontal Wall
Vertical Wall
8
PRE-INSTALLATION
B. Determining A Door Installation Option And Cutout Sizing
• Determine whether the RV has a standard door, flush door, or small vent configuration.
• Cut an opening through the side wall to fit the door installation option.
Standard Door Installations
FIG.1
12.50"
to
12.63"
17.00
to
17.13"
FloorFloor
7.25"
to
7.38"
Small Standard
Door Cutout
Medium Standard
Door Cutout
Large Standard
Door Cutout
7.25"
to
7.38"
17.00
to
17.13"
9.25"
to
9.38"
Flush Door Installations
FIG.2
10.00"
to
10.13"
R 0.50" to 0.63"
R 0.50" to 0.63"
1.375"1.375"1.375"
R 0.50" to 0.63"
Small Flush
Door Cutout
Medium Flush
Door Cutout
Large Flush
Door Cutout
15.00
to
15.13"
19.75
to
19.88
19.75
to
19.88"
10.00"
to
10.13"
12.00"
to
12.13"
Floor Floor
Small Vent Installations
FIG.3
Wall Hole
3-1/2"
1-3/4"
2-1/8"
(RV Wall Panel)
Floor (Furnace Bottom)
• There is NO door cutout on the outside of the RV for the small vent installation. The cutout is a hole in the side of the RV used to
vent the Furnace outside of the RV.
Access must be provided directly in front of the Furnace on the inside of the RV, for removal of the Furnace during servicing.
9
PRE-INSTALLATION
C. Ducting
Failure to obey the following warnings could result in property damage, serious injury, or death:
• Do NOT install floor registers within 24" of return-air openings.
• Do NOT use undersized ducting, which can cause high-temperature limiting.
• Do NOT use oversized ducting, which can cause inadequate air flow from the registers. When hard ducting is 1-1/2" in
depth, additional flex ducts may be needed to maintain air flow requirements.
• Hard ducting MUST be sealed to the Furnace and the floor.
• Spacing of 1/4" to ducting, within 3' of the Furnace, must be provided unless UL-listed, wire-bound, vinyl ducts are used.
All ducting material used must be rated for continuous use at a minimum of 200 °F.
• Floor registers must NOT be installed directly below the thermostat.
Setting Up The Return-Air Pathways
Keep all return-air passages clear to allow the Furnace to function properly. Make sure the total return-air opening size(s) meet
the clearance requirements specified in “A. Model Specifications” on page 4 and page 5. Do NOT block the return
airflow path with ducting.
Furnace
FIG.1
RV Wall
Return-Air Vent
Identifying Duct Locations
FIG.1
Duct 1
Duct 2
Duct 1
Duct 2
Duct 8
Duct 9
Duct 7
Duct 6
Duct 3
Duct 3
Duct 4
Duct 8
Duct 5
Duct 9
Duct 4
Duct 5
(Medium and Large Furnace)
FIG.2
Bottom
Discharge
Vertical
Discharge
FIG.3
Duct 2
Duct 4
Duct 1
Front Discharge
(Small Furnace)
Duct 3
10
PRE-INSTALLATION
Air Discharge Configuration Examples
The following figures offer a visual representation of the detailed discharge requirements outlined in the “Air Discharge
Requirements” tables on page 11 and page 12. These examples show vertical and horizontal installations, using different
Furnace models and ducting options.
FIG.1
(Top View)
Hard Ducting
Register
Register
Medium or
Large Furnace
• Horizontal Furnace – Bottom exit into hard ducting
FIG.2
Hard Ducting
Register
Register
Medium or
Large Furnace
(Top View)
• Vertical Furnace – Bottom exit into hard ducting
FIG.3
Medium or Large
Furnace Only
4" Flex
Ducting
Hard Ducting
Register
Register
(Top View)
• 4" flex ducts into hard ducting
For medium and large Furnaces: ducts 8 and 9 are used for
additional ducting only, and are not used to calculate the
required discharge area shown at the bottom of page 11.
FIG.4
Small, Medium,
or Large Furnace
(Vertical Mount)
Small, Medium, or
Large Furnace
(Horizontal Mount)
4" Flex Ducting 4" Flex Ducting
Duct 4
Duct 5
Duct 4
Duct 3
Duct 5
Duct 3
(Top View) (Top View)
• Make sure to use at least the minimum number of 4" flex
ducts required for your model size. See “Air Discharge
Requirements” on page 11 and page 12.
FIG.5
Small
Furnace
Only
Interior Grill
Cabinet Cutout
Location
5" Flex
Ducting
(Top View)
• 5" ducting over 12" long must have an additional 4" duct
added to the system.
To aid in the removal of the Furnace through the grill
cutout for servicing, when using a front interior grill, orient
the grill to the direction of the Furnace: horizontal if the
Furnace is horizontal, vertical if the Furnace is vertical.
11
PRE-INSTALLATION
Air Discharge Requirements
HORIZONTAL BOTTOM
EXIT INTO HARD
FLOOR DUCT
VERTICAL
BOTTOM EXIT
INTO HARD
FLOOR DUCT
HORIZONTAL OR
VERTICAL – USE DUCTS
3, 4 & 5 INTO HARD
FLOOR DUCT
4" FLEX DUCTS
5" FRONT EXIT
FLEX DUCTS
LARGE
DFL40
Minimum CFM
220 175 165 215 N/A
DISCHARGE
REQ.
4" x 10" Bottom exit
PLUS 1- 4" flex duct
(for hard ducting
under 2.5" deep).
Duct 6 or 7 is recommended.
5" x 9-3/4" Bottom
exit does not require
additional ducts.
Horizontal or vertical.
Use ducts 3, 4, and 5.
Three ducts
MINIMUM.
Four ducts
recommended.
N/A
DFL35
Minimum CFM
200 175 165 215 N/A
DISCHARGE
REQ.
4" x 10" Bottom exit PLUS 1-
4" flex duct
(for hard ducting
under 2.5" deep).
Duct 6 or 7 is recommended.
5" x 9-3/4" Bottom
exit does not require
additional ducts.
Horizontal or vertical.
Use ducts 3, 4, and 5.
Three ducts
MINIMUM.
Four ducts
recommended.
N/A
HORIZONTAL BOTTOM
EXIT INTO HARD
FLOOR DUCT
VERTICAL
BOTTOM EXIT
INTO HARD
FLOOR DUCT
HORIZONTAL OR
VERTICAL – USE DUCTS
3, 4 & 5 INTO HARD
FLOOR DUCT
4" FLEX DUCTS
5" FRONT EXIT
FLEX DUCTS
MEDIUM
DFM35
Minimum CFM
225 155 155 285 N/A
DISCHARGE
REQ.
4" x 10" Bottom exit PLUS
1- 4" flex duct
(for hard ducting
under 2.5" deep).
Duct 6 or 7 is recommended.
5" x 9-3/4" Bottom
exit does not require
additional ducts.
Horizontal or vertical.
Use ducts 3, 4, and 5.
Four ducts
MINIMUM.
N/A
DFM30
Minimum CFM
210 150 155 220 N/A
DISCHARGE
REQ.
4" x 10" Bottom exit PLUS 1-
4" flex duct
(for hard ducting
under 2.5" deep).
Duct 6 or 7 is recommended.
5" x 9-3/4" Bottom
exit does not require
additional ducts.
Horizontal or vertical.
Use ducts 3, 4 and 5.
Three ducts
MINIMUM.
N/A
DFM25
Minimum CFM
175 160 160 190 N/A
DISCHARGE
REQ.
4" x 10" Bottom exit
(40 in.
2
).
5" x 9-3/4" Bottom
exit does not require
additional ducts.
Horizontal or vertical.
Use ducts 3, 4 and 5.
Three ducts
MINIMUM.
N/A
DFM20
Minimum CFM
135 85 115 132 N/A
DISCHARGE
REQ.
4" x 10" Bottom exit
(40 in.
2
).
5" x 9-3/4" Bottom
exit does not require
additional ducts.
Horizontal or vertical.
Use any two ducts:
3, 4 or 5.
Two ducts
MINIMUM.
N/A
DFM16
Minimum CFM
135 85 115 132 N/A
DISCHARGE
REQ.
4" x 10" Bottom exit
(40 in.
2
).
5" x 9-3/4" Bottom
exit does not require
additional ducts.
Horizontal or vertical
Use any two ducts:
3, 4 or 5.
Two ducts
MINIMUM.
N/A
12
PRE-INSTALLATION
HORIZONTAL OR VERTICAL USE
(DUCTS 3, 4, & 5) OR BOTTOM
EXIT INTO HARD FLOOR DUCT
4" FLEX DUCTS
5" FRONT EXIT
FLEX DUCTS
SMALL
DFS20
Minimum CFM
N/A
130 92
DISCHARGE
REQ.
N/A
Two 4" flex ducts –
one each from the left and right side, based
on horizontal or vertical mounting.
One 5" OR two 4" ducts
(5" can be reduced to 4"
if necessary)
DFS16
Minimum CFM
N/A
110 82
DISCHARGE
REQ.
N/A
Two 4" flex ducts –
one each from the left and right side, based
on horizontal or vertical mounting.
One 5" OR two 4" ducts
(5" can be reduced to 4"
if necessary)
DFS12
Minimum CFM
N/A
90 80
DISCHARGE
REQ.
N/A
Two 4" flex ducts –
one each from the left and right side, based
on horizontal or vertical mounting.
One 5" OR two 4" ducts
(5" can be reduced to 4"
if necessary)
DFSA12
(LOW AMP)
Minimum CFM
N/A N/A
60
DISCHARGE
REQ.
N/A N/A One 5" front duct ONLY
Air flow: shown in cubic feet-per-minute, taken with a cold system (Cold CFM).
Registers: 4" x 10" floor registers flow air better than 4" Round Plastic registers. Using 4" Round registers may require additional
ducting.
Required Discharge
MODELS REQUIRED DISCHARGE AREA
SMALL
DFSA12 Front Grill or 15 in.
2
DFS (12, 16, & 20) 24 in.
2
MEDIUM
DFM (16 & 20) 24 in.
2
with 4" flex
DFM (25 & 30) 36 in.
2
with 4" flex
DFM35 48 in.
2
with 4" flex
DFM (30 & 35) Horizontal Bottom 48 in.
2
(Bottom + 4" duct)
DFM (16, 20, & 25) Horizontal Bottom 40 in.
2
(Bottom only)
DFM Vertical Bottom 48 in.
2
(Bottom only)
LARGE
DFL (35 & 40) 36 in.
2
with 4" flex
DFL (35 & 40) Horizontal Bottom 48 in.
2
(Bottom + 4" duct)
DFL (35 & 40) Vertical Bottom 48 in.
2
(Bottom only)
13
PRE-INSTALLATION
Installing The Floor Discharge System
Read BEFORE proceeding:
• Each 4" duct opening provides 12 in.
2
of discharge area. For each closeable register, provide an extra 12 in.
2
of
noncloseable duct discharge area. Make sure that all clearances and temperature requirements are met and the seal is
airtight.
• Ducting into dead-air space with no return air, such as holding tank areas, does not count toward achieving minimum
discharge requirements.
• 2" ducts exiting into the return-air space count as part of the minimum discharge area and minimum CFM.
• As applicable, the medium and large Furnace can be installed as a bottom-discharge system in either a horizontal or
vertical position.
STEP1
Plenum
Plenum
Horizontal
Bottom
Discharge
Vertical
Bottom
Discharge
• Cut the opening for the floor discharge system in the floor of the RV.
• Standard Door: see “Standard Door Floor Discharge Installations” on page 14.
• Flush Door: see “Flush Door Floor Discharge Installations” on page 14.
• Small Vent: see “Small Vent Floor Discharge Installations” on page 14.
• Remove the bottom discharge plate or side.
• Fasten the plenum plate bend tabs over the floor cutout.
• Place the gasket on the plenum around the floor opening.
Plenum plates and gaskets are available for purchase through Dometic. If not using a Dometic gasket and plenum plate, seal the
Furnace to the hard ducting system using an approved foil tape, or use a gasket that has a 300° F minimum temperature rating
and a UL94-V0 rating.
Vertical Mount Furnace: Kit 30205
Horizontal Mount Furnace: Kit 30261
14
PRE-INSTALLATION
Standard Door Floor Discharge Installations
The dotted lines around the knockouts in the figures represent the floor-hole position.
FIG.1
2.2"
5" 5" 10"
RV Wall
(Top View)
Large Door
Vertical Install
Medium Door
Vertical Install
Medium & Large
Door Horizontal
Install
RV Wall RV Wall
1.2" 3.5"
9.5"
9.75" 9.75"
9.5"
15.1"
4"
Flush Door Floor Discharge Installations
FIG.2
3.5"5" 5" 10"
RV Wall
(Top View)
Large Door
Vertical Install
Medium Door
Vertical Install
Medium & Large
Door Horizontal
Install
RV Wall RV Wall
2.6" 4.9"
9.8"
9.75" 9.75"
9.8"
15.4"
4"
Small Vent Floor Discharge Installations
FIG.3
0.1" 5" 5"
0.9"
1.5"10"
RV Wall
(Top View)
Large Door
Vertical Install
Medium Door
Vertical Install
Medium & Large
Door Horizontal
Install
RV Wall
RV Wall
9.6"9.6"
9.75" 9.75"
15.2"
4"
15
PRE-INSTALLATION
Installing The Duct Adapters
STEP1
Knockout Location
• Remove the knockout plates from the desired outlets.
• Cover all unused knockouts.
If a knockout is removed accidentally, cover plates are
available for purchase through Dometic.
Cover Plate: 31361
STEP2
Knockout Location
Duct Adapter
Ducting
• Install the duct adapters (provided) by inserting the flange
over the casing hole and turning the duct adapter 90° to
lock the tab into the casing slot.
• Securely attach ducting to the duct adapter. If using screws
to secure the ducting, do not use screws longer than 1/2".
D. Installing the Furnace
• Proceed to the appropriate installation section to install the Furnace:
• Standard Door: See “A. Installing The Furnace Using A Standard Door Option” on page 16.
• Flush Door: See “B. Installing The Furnace Using A Flush Door Option” on page 17.
• Small Vent: See “C. Installing The Furnace Using The Small Vent Option” on page 18.
16
INSTALLATION
A. Installing The Furnace Using A Standard Door Option
STEP1
Sealant
(Or Butyl Tape)
Bezel
The standard door option requires that the rectangular
hole cut into the wall for the door opening has sharply cut
corners to match the Furnace. The Furnace must be able to
slide freely through the opening.
• Place the Furnace through the cutout approximately 1"–2"
from the wall.
• Apply RTV sealant or butyl tape to the entire back flange of
the bezel.
STEP2
RV Wall
Bezel
• Place the bezel over the tabs and flush with the front edge
of the casing. Be sure the edge of the bezel marked "TOP"
faces the top of the casing. Bend the casing tabs over the
bezel.
• Push the Furnace and bezel against the side wall. Secure
using six #6 or #8-18 Pan Head Type A screws (not
provided) placed through the bent tabs, bezel, and into
the RV wall.
• Place six more screws (three per side) to the le and right
side of the bezel. The bezel MUST fit tightly against the
wall. Remove excess sealant.
Do NOT deform the bezel during placement. The bezel
must fit tightly to maintain an airtight seal.
STEP3
Gas
Connection
Electrical Connection
• Connect the electrical wiring. Refer to “H. Connecting The
Electrical” on page 22.
• Connect the gas line to the valve. Refer to “F. Connecting
The Gas” on page 20.
STEP4
RV Wall
Mounting
Bracket
Door
Vent
Assembly
Bezel
• Align the door with the bezel.
• Secure the door using four #6-19x1/2" thread-forming
screws for plastic (not provided). Place the screws through
the door and into the bezel bosses.
• Insert the vent assembly (provided) through the hole in
the door, making sure the vent assembly goes into the
chamber tube. Make sure the vent assembly is aligned with
the Dometic text at the TOP.
• Secure the vent assembly to the door using four stainless
steel exhaust screws (provided with the door).
• To secure the Furnace to the floor of the RV, proceed to
“D. Installing The Mounting Brackets” on page 19.
17
INSTALLATION
B. Installing The Furnace Using A Flush Door Option
STEP1
Gas
Connection
Electrical Connection
Flush-mounted door systems require the Furnace to be
installed on a 1" high platform, so the door cutout is level
with the floor surface. Otherwise, the side wall must be
routed out across the bottom to the depth of the bezel, to
create a pocket area. The flush door option requires 1/2"
radius corners.
• Place the Furnace through the cutout.
• Connect the electrical wiring. Refer to “H. Connecting The
Electrical” on page 22.
• Connect the gas line to the valve. Refer to “F. Connecting
The Gas” on page 20.
STEP2
Furnace
Flush Mounting Brackets
RV Wall
Recessed Side
Wall Cutout
• Use three screws (not included) on each side of the Furnace
to secure the flush mounting brackets to the wall. Leave
5/16" of space from the bracket to the outside of the wall.
• Apply RTV sealant or butyl tape to the back of the bezel
and the back of the flanges on the recess pan, where it will
overlap with the wall.
• Pull the front edge of the Furnace out of the wall
approximately 2".
STEP3
RV Wall
Recess Pan
Flush Mounting
Bracket
Bezel
Recessed
Side Wall
Cutout
• Slide the recess pan over the Furnace and place the bezel
on the six mounting tabs.
• Push the recess pan and bezel forward until the six casing
tabs move through the slots in the bezel.
• Bend the casing tabs to the outside of the bezel.
• Align the top three holes on the bezel with the holes in the
recess pan, then place six (three on the top and three on
the bottom) #6 or #8 x1/2" Pan Head Type AB screws, or
self-drilling screws, (not provided) into the top and bottom
holes on the bezel. Tighten the screws to attach the bezel
to the recess pan.
• Secure the Furnace using six (three per side) #6 or #8 x1/2"
Pan Head Type AB screws, or self-drilling screws, (not
provided) placed through the bezel, the recess pan, and
into the flush mounting brackets. Remove excess sealant.
Do NOT deform the bezel during placement. The bezel
must fit tightly to maintain an airtight seal.
STEP4
RV Wall
Door
Vent
Assembly
Bezel
• Secure the door using four #6-19x3/8" thread-forming
screws for plastic (not provided). The door should be flush
with the RV wall.
• Insert the vent assembly (provided) through the hole in the
door, making sure the vent assembly goes into the chamber
tube with the Dometic text aligned at the TOP.
• Secure the vent assembly to the door using four stainless
steel exhaust screws (provided with the door).
• To secure the Furnace to the floor of the RV, proceed to
“D. Installing The Mounting Brackets” on page 19.
18
INSTALLATION
C. Installing The Furnace Using The Small Vent Option
Failure to obey this warning could result in property damage, serious injury, or death:
• Do NOT install vents where projection or door openings come within 6" of the vent opening. The RV door, panel, or cover material
may discolor, warp, or burn from the exhaust temperature.
• CARBON MONOXIDE HAZARD:
• Properly seal the vent assembly to prevent carbon monoxide from entering the RV. Do NOT vent exhaust air or draw
combustion air from the living area or an enclosed porch.
• Do NOT vent the Furnace with a venting system serving another appliance.
Access must be provided directly in front of the Furnace on the inside of the RV for removal of the Furnace during servicing.
STEP1
RV Wall
Wall Hole
Wall Hole
3-1/2"
Vent
Panel
• Locate the Furnace exhaust vent cutout location.
• Drill a 3-1/2" dia. hole through the wall for intake/exhaust.
The maximum exterior wall thickness is 2-1/2". Do NOT
exceed maximum wall thickness. Purchase an optional vent
kit to extend the vent to a 3" wall thickness, if necessary.
STEP2
RV Wall
Vent
Panel
Water Dam
Sealant
Vent Assembly
Vent Extension
• Apply butyl tape or RTV sealant to the back flange of the
vent extension before securing to the wall.
• Hold the vent extension with the printed “THIS SIDE UP”
text at the top, and the water dam at the bottom.
• Push the vent extension into the wall until it slides onto the
vent panel.
• Align the vent assembly (provided) over the vent extension
so that the Dometic text is at the TOP.
• Push the vent assembly into the chamber tube and secure
using four stainless steel exhaust screws (not provided).
Overlap the vent tube over the chamber tube by a
minimum of 1-1/2" for proper venting of exhaust fumes.
• Connect the electrical wiring. Refer to “H. Connecting The
Electrical” on page 22.
• Connect the gas line to the valve. Refer to “F. Connecting
The Gas” on page 20.
• Push the Furnace vent panel against the RV wall.
The Furnace vent panel MUST be pushed against the RV
wall before installing the mounting brackets.
• Proceed to “D. Installing The Mounting Brackets” on page 19.
19
INSTALLATION
D. Installing The Mounting Brackets
.
STEP1
Mounting
Bracket
• Make sure the mounting surface on the RV is flat and the
Furnace is positioned evenly (front-to-back, side-to-side).
• Fasten the two mounting brackets (provided) to the casing
by placing the brackets over any two of the three holes
at the rear of the Furnace. Secure using two #8-18x1/2"
screws (provided).
• Secure the Furnace mounting brackets to the RV using
screws (not provided).
Mounting brackets can be attached to the Furnace casing
by removing an existing casing screw, ONLY with prior
approval from Dometic. When securing the Furnace, it
MUST be accessible and easily removed for service.
E. Running the Ductwork
STEP1
Not Recommended
• Stretch out all of the ducts and run them directly to the
outlets. Keep the number of angles to a minimum and
avoid sharp bends, deep sags, or crushed ducts, as shown.
• Attach and secure the 4" flexible duct to the adapter(s).
STEP2
Ducting
Heat Register
RV Wall
• Run duct(s) to the desired location(s) within the RV.
• Secure the ducting to the register(s).
If the burner cycles ON and OFF at the high-temperature
limit, it may be due to a restriction or bend in the ductwork.
Add extra ducting to correct this condition.
• Adjust the Furnace to the proper temperature rise aer
installation of the Furnace and ducting is complete. The
Furnace is tested to the temperature rise specified on the
rating plate.
• If checking the temperature rise is not possible, measure the airflow
at each register. Airflow should meet or exceed the measurements
in the “Air Discharge Requirements” on page 11.
• Adjust the ducting installation to obtain an airflow rate total
from all living area vents (in CFM) of the Furnace, as specified
in the “Air Discharge Requirements” on page 11.
• If readings are below the table values, improve the airflow
by adding ducts or reducing/eliminating system restrictions.
Reference the “Air Discharge Configuration Examples” on
page 10 for guidance.
20
INSTALLATION
F. Connecting The Gas
FIRE OR EXPLOSION HAZ ARD. Failure to obey the following warnings could result in property damage, serious injury,
or death:
• Install gas connections in compliance with the applicable supplemental directives listed in this manual. Refer to
“C. Supplemental Directives” on page 2.
• NEVER use an open flame to check for gas leaks. Use a commercially available soap solution made specifically for the
detection of leaks to check all connections, as specified in these instructions.
• 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 put sealing compound on flare fittings.
FIG.1
Extended
Manifold
(Rear)
Gas Connection
Grommet
Plug
An extended manifold is used in this example; however,
the use of tubing or other variations to connect the gas is
acceptable.
• Treat all male pipe threads, other than flare fittings, with a
sealing compound resistant to a chemical reaction with LP
gas.
• Remove the grommet plug from the Furnace and install on
the gas line.
• Insert the gas line through the hole in the top of the casing.
• Connect the gas line to the fitting located on the valve. If
the Furnace is supplied with an extended manifold,
connect the gas line at the rear of the Furnace.
• Reinstall the grommet plug on the casing, as it is a required
air seal. DO NOT CUT.
• Use two wrenches to hold the valve and flare nut, and
tighten the flare nut over the gas line.
• Torque the fitting to 20–22 . lbs. Do NOT twist the valve
out of position when tightening the gas line.
For DFLA35 and DFLA40 models only, a gas conversion kit
is included with your Furnace. To convert the Furnace gas
type, proceed to “G. Converting The Furnace Gas Type” on
page 21.
LP Gas Pressure Test
Read BEFORE proceeding:
• Test all piping systems BEFORE connecting the
Furnace.
• Disconnect the Furnace and any individual shut-off
valves from the gas supply piping system when
pressure testing the system at pressures of more than
1/2" PSI.
• If local codes allow the use of a flexible gas appliance
connector, do NOT use a connector which has
previously serviced another gas appliance.
• For gas conversions only, a 1/8" NPT plug is provided
upstream of the gas connections for checking the gas
pressure.
• Perform an air pressure test on the piping system. The test
must maintain an air pressure of a least 6" of mercury or
3 PSI for at least 10 minutes.
• Adjust the piping system to maintain the minimum gas
supply pressure listed on the rating plate, when all
appliances are in operation.
• Test gas connections for leakage with a commercially
available soap solution made specifically for the detection
of leaks.
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aqua metro Contoil DFM 12ECO Mounting And Operating Instructions
