Desa GWN20TB Original instructions

MODELS
GWN20TB, GWP20TB, GWN30TB, GWP30TB, HDB20NT, HDB20PT,
HDB30NT, HDB30PT, MN20T, MP20T, MN30T, MP30T,
VN20BTB, VP20BTB, VN30BTB, VP30BTB WMN20A, WMP20A
UNVENTED (VENT-FREE) BLUE FLAME GAS HEATER
SAFETY INFORMATION AND INSTALLATION MANUAL
For more information, visit www.desatech.com
WARNING: If the information in this manual is not
followed exactly, a re or explosion may result causing
property damage, personal injury or loss of life.
— Do not store or use gasoline or other ammable
vapors and liquids in the vicinity of this or any other
appliance.
— WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any
phone in your building.
• Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions.
• If you cannot reach your gas supplier, call the re
department.
— Installation and service must be performed by a quali-
ed installer, service agency or the gas supplier.
INSTALLER: Leave this manual with the appliance.
CONSUMER: Retain this manual for future reference.

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SAFETY
This appliance may be in-
stalled in an aftermarket,*
permanently located,
manufactured (mobile)
home, where not prohib-
ited by local codes.
* Aftermarket: Completion of sale, not for
purpose of resale, from the manufacturer
WARNING: This product con-
tains and/or generates chemicals
known to the State of California
to cause cancer or birth defects
or other reproductive harm.
IMPORTANT: Read this owner’s
manual carefully and completely
before trying to assemble, operate
or service this heater. Improper
use of this heater can cause seri-
ous injury or death from burns, re,
explosion, electrical shock and
carbon monoxide poisoning.
DANGER: Carbon monoxide
poisoning may lead to death!
Carbon Monoxide Poisoning: Early signs
of carbon monoxide poisoning resemble the
u, with headaches, dizziness or nausea. If
you have these signs, the heater may not be
working properly. Get fresh air at once! Have
heater serviced. Some people are more af-
fected by carbon monoxide than others. These
include pregnant women, people with heart or
lung disease or anemia, those under the inu-
ence of alcohol and those at high altitudes.
WARNING: Improper
installation, adjustment,
alteration, service or main-
tenance can cause injury
or property damage. Refer
to this manual for correct
installation and operation-
al procedures. For assis-
tance or additional infor-
mation consult a qualied
installer, service agency or
the gas supplier.
WARNING: This is an
unvented gas-red heater.
It uses air (oxygen) from the
room in which it is installed.
Provisions for adequate
combustion and ventila-
tion air must be provided.
RefertoAir for Combustion
and Ventilation section on
page 5 of this manual.
This appliance is only for
use with the type of gas
indicated on the rating
plate. This appliance is
not convertible for use
with other gases.
TABLE OF CONTENTS
Safety .................................................................. 2
Local Codes......................................................... 4
Unpacking............................................................ 4
Product Identication ........................................... 4
Product Features ................................................. 4
Air For Combustion And Ventilation ..................... 5
Installation ........................................................... 7
Operation ........................................................... 15
Inspecting Heater .............................................. 17
Cleaning and Maintenance ................................ 18
Troubleshooting ................................................. 19
Specications .................................................... 23
Replacement Parts ............................................ 23
Parts .................................................................. 24
Accessories ....................................................... 26
Service Hints ..................................................... 26
Technical Service............................................... 26
Service Publications .......................................... 26
Parts Central...................................................... 27

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124002-01C 3
Natural and Propane/LP Gas: Natural and
propane/LP gases are fuel gases. Fuel gases
are odorless. An odor-making agent is added
to fuel gases. The odor helps you detect a fuel
gas leak. However, the odor added to fuel
gas can fade. Fuel gas may be present even
though no odor exists.
Make certain you read and understand all
warnings. Keep this manual for reference. It
is your guide to safe and proper operation of
this heater.
WARNING: Any change to
this heater or its controls can
be dangerous.
WARNING: Do not use a
blower insert, heat exchanger
insert or other accessory not ap-
proved for use with this heater.
Due to high temperatures, the
appliance should be located out
of trafc and away from furniture
and draperies.
Do not place clothing or other
ammable material on or near
the appliance. Never place any
objects on the heater.
Surface of heater becomes very
hot when running heater. Keep
children and adults away from
hot surface to avoid burns or
clothing ignition. Heater will
remain hot for a time after shut-
down. Allow surface to cool
before touching.
Carefully supervise young chil-
dren when they are in the same
room with heater.
Make sure grill guard is in place
before running heater.
Keep the appliance area clear
and free from combustible ma-
terials, gasoline and other am-
mable vapors and liquids.
1. This appliance is only for use with the type
of gas indicated on the rating plate. This
appliance is not convertible for use with
other gases.
2. Do not place propane/LP supply tank(s)
inside any structure. Locate propane/LP
supply tank(s) outdoors.
3. This heater shall not be installed in a
bedroom or bathroom.
4. If you smell gas
• shut off gas supply
• do not try to light any appliance
• do not touch any electrical switch; do not
use any phone in your building
• immediately call your gas supplier from
a neighbor’s phone. Follow the gas sup-
plier’s instructions
• if you cannot reach your gas supplier,
call the re department
5. This heater needs fresh, outside air ventila-
tion to run properly. This heater has an Oxy-
gen Depletion Sensing (ODS) safety shutoff
system. The ODS shuts down the heater if
not enough fresh air is available. See Air for
Combustion and Ventilation, page 5.
6. Keep all air openings in front and bottom
of heater clear and free of debris. This will
insure enough air for proper combustion.
7. If heater shuts off, do not relight until you
provide fresh, outside air. If heater keeps
shutting off, have it serviced.
8. Do not run heater
• where ammable liquids or vapors are
used or stored
• under dusty conditions
9. Before using furniture polish, wax, carpet
cleaner or similar products, turn heater off. If
heated, the vapors from these products may
create a white powder residue within burner
box or on adjacent walls or furniture.
10. Do not use heater if any part has been
under water. Immediately call a qualied
service technician to inspect the room
heater and to replace any part of the
control system and any gas control which
has been under water.
11. Turn off and let cool before servicing. Only
a qualied service person should service
and repair heater.
SAFETY
Continued

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12. Operating heater above elevations of
4,500 feet could cause pilot outage.
13. To prevent performance problems, do not
use propane/LP fuel tank of less than 100
lbs. capacity.
SAFETY
Continued
Figure 1 - Vent-Free Gas Heater
(actual heater may vary from illustration)
Ignitor Button
Control Knob
Heater
Cabinet
Front Panel
Glass Panel
Grill Guard
PRODUCT
IDENTIFICATION
PRODUCT FEATURES
SAFETY DEVICE
This heater has a pilot with an Oxygen Deple-
tion Sensing (ODS) safety shutoff system. The
ODS/pilot is a required feature for vent-free
room heaters. The ODS/pilot shuts off the
heater if there is not enough fresh air.
IGNITION SYSTEM
Some models are equipped with a piezo
ignitor that requires no matches, batteries or
other sources to light heater.
Other heaters are equipped with an electronic
ignitor to light heater fuel supply.
THERMOSTATIC HEAT CONTROL
Thermostat models have a thermostat sens-
ing bulb and a control valve. This results in the
greatest heater comfort. This can also result
in lower gas bills.
14. Provide adequate clearances around air
openings.
LOCAL CODES
Install and use heater with care. Follow all lo-
cal codes. In the absence of local codes, use
the latest edition of National Fuel Gas Code,
ANSI Z223.1/NFPA 54*.
*Available from:
American National Standards Institute, Inc.
1430 Broadway
New York, NY 10018
National Fire Protection Association, Inc.
Batterymarch Park
Quincy, MA 02269
State of Massachusetts: The installation
must be made by a licensed plumber or
gas tter in the Commonwealth of Mas-
sachusetts.
Sellers of unvented propane or natural
gas-red supplemental room heaters shall
provide to each purchaser a copy of 527
CMR 30 upon sale of the unit.
Vent-free gas products are prohibited for
bedroom and bathroom installation in the
Commonwealth of Massachusetts.
UNPACKING
1. Remove heater from carton.
2. Remove all protective packaging applied
to heater for shipment.
3. Check heater for any shipping damage.
If heater is damaged, promptly return to
dealer where you bought heater or call
DESA Heating, LLC at 1-866-672-6040.

www.desatech.com
124002-01C 5
AIR FOR COMBUSTION AND VENTILATION
Unusually Tight Construction
The air that leaks around doors and windows
may provide enough fresh air for combustion
and ventilation. However, in buildings of un-
usually tight construction, you must provide
additional fresh air.
Unusually tight construction is dened as
construction where:
a. walls and ceilings exposed to the outside
atmosphere have a continuous water
vapor retarder with a rating of one perm
(6x10-11 kg per pa-sec-m2) or less with
openings gasketed or sealed and
b. weather stripping has been added on
openable windows and doors and
c. caulking or sealants are applied to areas
such as joints around window and door
frames, between sole plates and oors,
between wall-ceiling joints, between
wall panels, at penetrations for plumb-
ing, electrical and gas lines and at other
openings.
If your home meets all of the three criteria
above, you must provide additional fresh air.
See Ventilation Air From Outdoors, page 7.
If your home does not meet all of the three
criteria above, proceed to Determining Fresh-
Air Flow For Heater Location, page 6.
Conned and Unconned Space
The National Fuel Gas Code, ANSI Z223.1/
NFPA 54 denes a conned space as a space
whose volume is less than 50 cubic feet per
1,000 Btu/hr (4.8 m3 per kw) of the aggregate
input rating of all appliances installed in that
space and an unconned space as a space
whose volume is not less than 50 cubic feet
per 1,000 Btu/hr (4.8 m3 per kw) of the ag-
gregate input rating of all appliances installed
in that space. Rooms communicating directly
with the space in which the appliances are
installed*, through openings not furnished
with doors, are considered a part of the un-
conned space.
* Adjoining rooms are communicating only if
there are doorless passageways or ventilation
grills between them.
WARNING: This heater shall
not be installed in a room or
space unless the required vol-
ume of indoor combustion air
is provided by the method de-
scribed in the National Fuel Gas
Code, ANSI Z223.1/NFPA 54, the
International Fuel Gas Code, or
applicable local codes. Read the
following instructions to insure
proper fresh air for this and
other fuel-burning appliances
in your home.
Today’s homes are built more energy efcient
than ever. New materials, increased insulation
and new construction methods help reduce
heat loss in homes. Home owners weather
strip and caulk around windows and doors to
keep the cold air out and the warm air in. Dur-
ing heating months, home owners want their
homes as airtight as possible.
While it is good to make your home energy
efcient, your home needs to breathe. Fresh
air must enter your home. All fuel-burning ap-
pliances need fresh air for proper combustion
and ventilation.
Exhaust fans, replaces, clothes dryers and
fuel burning appliances draw air from the
house to operate. You must provide adequate
fresh air for these appliances. This will insure
proper venting of vented fuel-burning appli-
ances.
PROVIDING ADEQUATE
VENTILATION
The following are excerpts from National Fuel
Gas Code, ANSI Z223.1/NFPA 54, Air for
Combustion and Ventilation.
All spaces in homes fall into one of the three
following ventilation classications:
1. Unusually Tight Construction
2. Unconned Space
3. Conned Space
The information on pages 5 through 7 will help
you classify your space and provide adequate
ventilation.

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AIR FOR COMBUSTION AND VENTILATION
Continued
DETERMINING FRESH-AIR FLOW
FOR HEATER LOCATION
Determining if You Have a Conned or
Unconned Space
Use this work sheet to determine if you have a
conned or unconned space.
Space: Includes the room in which you will install
heater plus any adjoining rooms with doorless
passageways or ventilation grills between the
rooms.
1. Determine the volume of the space (length
x width x height).
Length x Width x Height =__________cu. ft.
(volume of space)
Example: Space size 20 ft. (length) x 16 ft.
(width) x 8 ft. (ceiling height) = 2560 cu. ft.
(volume of space)
If additional ventilation to adjoining room
is supplied with grills or openings, add the
volume of these rooms to the total volume
of the space.
2. Multiply the space volume by 20 to determine
the maximum Btu/Hr the space can support.
______ (volume of space) x 20 = (Maximum
Btu/Hr the space can support)
Example: 2560 cu. ft. (volume of space) x
20 = 51,200 (maximum Btu/Hr the space
can support)
3. Add the Btu/Hr of all fuel burning appliances
in the space.
Vent-free heater ____________ Btu/Hr
Gas water heater* ____________ Btu/Hr
Gas furnace ____________ Btu/Hr
Vented gas heater ____________ Btu/Hr
Gas replace logs ____________ Btu/Hr
Other gas appliances* + ___________ Btu/Hr
Total = ___________ Btu/Hr
* Do not include direct-vent gas appliances.
Direct-vent draws combustion air from the
outdoors and vents to the outdoors.
Example:
Gas water heater ____________ Btu/Hr
Vent-free heater + ___________ Btu/Hr
Total = ___________ Btu/Hr
40,000
20,000
60,000
4. Compare the maximum Btu/Hr the space
can support with the actual amount of Btu/
Hr used.
_______ Btu/Hr (maximum can support)
_______ Btu/Hr (actual amount used)
Example:
51,200 Btu/Hr (maximum the space can
support)
60,000 Btu/Hr (actual amount of Btu/Hr
used)
The space in the above example is a conned
space because the actual Btu/Hr used is more
than the maximum Btu/Hr the space can sup-
port. You must provide additional fresh air. Your
options are as follows:
A. Rework worksheet, adding the space of an
adjoining room. If the extra space provides
an unconned space, remove door to adjoin-
ing room or add ventilation grills between
rooms. See Ventilation Air From Inside
Building, page 7.
B. Vent room directly to the outdoors. See
Ventilation Air From Outdoors, page 7.
C. Install a lower Btu/Hr heater, if lower Btu/Hr
size makes room unconned.
If the actual Btu/Hr used is less than the maximum
Btu/Hr the space can support, the space is an
unconned space. You will need no additional
fresh air ventilation.
WARNING:Iftheareainwhich
the heater may be operated does
not meet the required volume for
indoor combustion air, combus-
tion and ventilation air shall be
provided by one of the methods
described in the National Fuel
Gas Code,ANSI Z223.1/NFPA54,
theInternational Fuel Gas Code,
or applicable local codes.

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124002-01C 7
Figure 3 - Ventilation Air from Outdoors
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining
unconned space. When ventilating to an
adjoining unconned space, you must provide
two permanent openings: one within 12" of the
ceiling and one within 12" of the oor on the
wall connecting the two spaces (see options
1 and 2, Figure 2). You can also remove door
into adjoining room (see option 3, Figure 2).
Follow the National Fuel Gas Code, ANSI
Z223.1/NFPA 54, Air for Combustion and
Ventilation for required size of ventilation
grills or ducts.
Ventilation Air From Outdoors
Provide extra fresh air by using ventilation
grills or ducts. You must provide two perma-
nent openings: one within 12" of the ceiling
and one within 12" of the oor. Connect these
items directly to the outdoors or spaces open
to the outdoors. These spaces include attics
and crawl spaces. Follow the National Fuel
Gas Code, ANSI Z223.1/NFPA 54, Air for
Combustion and Ventilation for required size
of ventilation grills or ducts.
IMPORTANT: Do not provide openings for
inlet or outlet air into attic if attic has a thermo-
stat-controlled power vent. Heated air entering
the attic will activate the power vent.
Figure 2 - Ventilation Air from Inside
Building
Or
Remove
Door into
Adjoining
Room,
Option 3
Ventilation Grills
Into Adjoining Room,
Option 2
12"
12"
Ventilation
Grills into
Adjoining
Room,
Option 1
Outlet
Air
Ventilated
Attic
Outlet
A
ir
Inlet
Air
Inlet Air Ve ntilated
Crawl Space
T o
Crawl
Space
T o A ttic
AIR FOR COMBUSTION AND VENTILATION
Continued
INSTALLATION
NOTICE: This heater is intended
for use as supplemental heat.
Use this heater along with your
primary heating system. Do not
install this heater as your pri-
mary heat source. If you have a
central heating system, you may
run system’s circulating blower
while using heater. This will help
circulate the heat throughout the
house. In the event of a power
outage, you can use this heater
as your primary heat source.
WARNING: A qualied ser-
vice person must install heater.
Follow all local codes.
CHECK GAS TYPE
Use only the correct type of gas (natural or
propane/LP). If your gas supply is not the
correct gas type, do not install heater. Call
dealer where you bought heater for proper
type heater.
WARNING: This appliance is
equipped for either natural gas
or propane/LP gas but not both.
Gas type is indicated on the rat-
ing plate. Field conversion is not
permitted.

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INSTALLATION ITEMS
Before installing heater, make sure you have
the items listed below.
• for propane/LP gas, external regulator
(supplied by installer)
• piping (check local codes)
• sealant (resistant to propane/LP gas)
• equipment shutoff valve *
• ground joint union
• sediment trap
• tee joint
• pipe wrench
• for natural gas, test gauge connection*
• hardware packet (included)
- wall anchor (4) 095112-02
- red key (1) 095116-01
- pan head screw, black (4) 097403-02
- nylon spacer (2) 099064-02
- clamp (1) 099123-01
- Phillips head screw, silver (4) 100159-02
* A CSA design-certied equipment shutoff
valve with 1/8" NPT tap is an acceptable alter-
native to test gauge connection. The optional
CSA design-certied equipment shutoff valve
can be purchased from your dealer.
LOCATING HEATER
This heater is designed to be mounted on a wall.
WARNING: Maintain the
minimum clearances shown
in Figure 4. If you can, provide
greater clearances from oor,
ceiling and joining wall.
You can locate heater on oor, away from
a wall. An optional oor mounting stand is
needed. Purchase the oor mounting stand
from your dealer. See Accessories, page 26,
if stand is not included with your heater.
WARNING: Never install the
heater
• in a bedroom or bathroom
• in a recreational vehicle
• where curtains, furniture, cloth-
ing or other ammable objects
arelessthan36"fromthefront,
top or sides of heater
• as a replace insert
• in high trafc areas
• in windy or drafty areas Figure 4 - Mounting Clearances As
Viewed From Front of Heater
INSTALLATION
Continued
CAUTION:Thisheatercreates
warm air currents. These currents
move heat to wall surfaces next
to heater. Installing heater next
to vinyl or cloth wall coverings or
operating heater where impurities
(such as, but not limited to, to-
bacco smoke, aromatic candles,
cleaning uids, oil or kerosene
lamps, etc.) in the air exist, may
discolor walls or cause odors.
IMPORTANT: Vent-free heaters add moisture
to the air. Although this is benecial, installing
heater in rooms without enough ventilation
air may cause mildew to form from too much
moisture. See Air for Combustion and Ventila-
tion, page 5. If high humidity is experienced,
a dehumidier may be used to help lower the
water vapor content in the air.
CAUTION: If you install the
heater in a home garage
• heater pilot and burner must
be at least 18" above oor
• locate heater where moving
vehicle will not hit it
For convenience and efciency, install heater
• where there is easy access for operation,
inspection and service
• in coldest part of room
If not included with your heater, an optional fan
kit is available from your dealer. See Acces-
sories, page 26. If planning to use fan, locate
heater near an electrical outlet (see page 16).
Minimum
From
Sides Of
Heater
36"
2"
FLOOR
CEILING
Minimum
Minimum To
Top Surface
Of Carpeting,
Tile Or Other
Combustible
Material
Left
Side
Right
Side
6"
36"
(91.5 cm)

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124002-01C 9
INSTALLATION
Continued
THERMOSTAT SENSING BULB
(Thermostat Models Only)
The thermostat sensing bulb has been placed
below the heater.
1. Place clamp on thermostat sensing bulb
as shown in Figure 5. Clamp is provided
in hardware package.
2. Snap clamp into upper mounting hole as
shown in Figure 5. Mounting hole is located
on lower left edge on back of heater. Make
sure the thermostat sensing bulb is point-
ing up.
Figure 5 - Attaching Thermostat Sensing
Bulb
INSTALLING HEATER TO WALL
Mounting Bracket
Locate mounting bracket in heater carton. Re-
move mounting bracket from heater carton.
Figure 7 - Removing Front Panel Of Heater
(actual heater may vary from illustration)
Clamp
Thermostat
Sensing Bulb
Figure 6 - Mounting Bracket
Removing Front Panel Of Heater
1. Remove the four painted screws, two on
each side of front panel.
2. Pull bottom of front panel forward, then
out.
3. Remove any remaining packaging ma-
terials.
Methods For Attaching Mounting Bracket
To Wall
Only use last hole on each end of mounting
bracket to attach bracket to wall. These two
holes are 14" apart from their centers. Attach
mounting bracket to wall in one of two ways:
1. Attaching to wall stud
2. Attaching to wall anchor
Attaching to Wall Stud: This method pro-
vides the strongest hold. Insert mounting
screws through mounting bracket and into
wall studs.
Attaching to Wall Anchor: This method al-
lows you to attach mounting bracket to hollow
walls (wall areas between studs) or to solid
walls (concrete or masonry).
Decide which method better suits your needs.
Either method will provide a secure hold for
the mounting bracket.
Marking Screw Locations
1. Tape mounting bracket to wall where
heater will be located. Make sure mount-
ing bracket is level.
WARNING: Maintain mini-
mum clearances shown in Figure
8, page 10. If you can, provide
greater clearances from oor
and joining wall.
Screw
Front Panel

www.desatech.com 124002-01C10
16"
Min.
14"
12"
Min.
Adjoining Wall
14"
Adjoining Wall
Only Insert Mounting
Screws Through Last
Hole On Each End
Only Insert Mounting
Screws Through Last
Hole On Each End
Floor
Floor
19
3
/ 4 "
Min.
19
3
/ 4 "
Min.
INSTALLATION
Continued
20,000 Btu/Hr Models
30,000 Btu/Hr Models
Figure 8 - Mounting Bracket Clearances
Attaching Mounting Bracket To Wall
Note: Wall anchors, mounting screws and
spacers are in hardware package. The hard-
ware package is provided with heater.
Attaching To Wall Stud Method
For attaching mounting bracket to wall studs
1. Drill holes at marked locations using 9/64"
drill bit.
2. Place mounting bracket onto wall. Line
up last hole on each end of bracket with
holes drilled in wall.
3. Insert mounting screws through bracket
and into wall studs.
4. Tighten screws until mounting bracket is
rmly fastened to wall studs.
Figure 9 - Folding
Anchor
Figure 11 - Mounting Heater Onto
Mounting Bracket
Stand-
Out Tab
Figure 10 - Popping
Open Anchor Wings
For Thin Walls
Mounting Bracket
(attached to wall)
Horizontal Slots
Attaching To Wall Anchor Method
For attaching mounting bracket to hollow
walls (wall areas between studs) or solid walls
(concrete or masonry)
1. Drill holes at marked locations using
5/16" drill bit. For solid walls (concrete or
masonry), drill at least 1" deep.
2. Fold wall anchor as shown in Figure 9.
3. Insert wall anchor (wings rst) into hole.
Tap anchor ush to wall.
4. For thin walls (1/2" or less), insert red key
into wall anchor. Push red key to “pop” open
anchor wings. IMPORTANT: Do not ham-
mer key! For thick walls (over 1/2" thick) or
solid walls, do not pop open wings.
5. Place mounting bracket onto wall. Line up
last hole on each end of bracket with wall
anchors.
6. Insert mounting screws through bracket
and into wall anchors.
7. Tighten screws until mounting bracket is
rmly fastened to wall.
2. Mark screw locations on wall (see Figure 8).
Note: Only mark last hole on each end of
mounting bracket. Insert mounting screws
through these holes only.
3. Remove tape and mounting bracket from
wall.
Placing Heater On Mounting Bracket
1. Locate two horizontal slots on back panel
of heater.
2. Place heater onto mounting bracket. Slide
horizontal slots onto stand-out tabs on
mounting bracket.