Desa LSL18NT Original instructions

Save this manual for future reference.
For more information, visit www.desatech.com
WARNING: If the information in this manual is not fol-
lowed exactly, a fire or explosion may result causing
property damage, personal injury or loss of life.
— 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
• 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 fire
department.
— Installation and service must be performed by a quali-
fied installer, service agency or the gas supplier.
18,000 BTU THERMOSTAT MODELS
LSL18NT, LSL18PT, SL18NT, SL18PT, VSL18NT AND VSL18PT
UNVENTED (VENT-FREE) BLUE FLAME GAS HEATER
SAFETY INFORMATION AND INSTALLATION MANUAL

www.desatech.com 116292-01A
2
WARNING: Improper installation, adjustment, altera-
tion, service or maintenance can cause injury or prop-
erty damage. Refer to this manual for correct installation
and operational procedures. For assistance or addi-
tional information consult a qualified installer, service
agency or the gas supplier.
WARNING: This is an unvented gas-fired heater. It uses
air (oxygen) from the room in which it is installed. Provi-
sions for adequate combustion and ventilation air must
be provided. Refer to Air for Combustion and Ventilation
section on page 5 of this manual.
This appliance may be installed in an aftermarket,* per-
manently located, manufactured (mobile) home, where
not prohibited by local codes.
This appliance is only for use with the type of gas indi-
cated on the rating plate. This appliance is not convert-
ible for use with other gases.
* Aftermarket: Completion of sale, not for purpose of resale, from the manufacturer
State of Massachusetts: The installation must be made by a licensed plumber or gas fitter in the
Commonwealth of Massachusetts.
Sellers of unvented propane or natural gas-fired 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 Common-
wealth of Massachusetts.
TABLE OF CONTENTS
Safety Information ............................................... 3
Local Codes ........................................................ 4
Product Identification ........................................... 4
Unpacking ........................................................... 4
Product Features ................................................. 4
Air For Combustion And Ventilation ..................... 5
Installation ........................................................... 7
Operating Heater ............................................... 14
Inspecting Heater ............................................. 16
Cleaning and Maintenance ................................ 17
Troubleshooting ................................................. 18
Specifications .................................................... 22
Wiring Diagrams ................................................ 22
Accessories ....................................................... 23
Technical Service .............................................. 23
Service Publications .......................................... 23
Replacement Parts ............................................ 23
Service Hints ..................................................... 23
Illustrated Parts Breakdown and Parts List ....... 24
Parts Centrals .................................................... 26
Warranty Information ......................................... 28

www.desatech.com
116292-01A 3
SAFETY INFORMATION
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 serious injury or death
from burns, fire, 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 flu, with head-
aches, 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 affected by carbon monoxide than others.
These include pregnant women, people with heart
or lung disease or anemia, those under the influence
of alcohol and those at high altitudes.
Natural and Propane/LP Gas: Natural and
propane/LP gases are fuel gases. Fuel gases are
odorless. An odor-making agent are 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 warn-
ings. 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 traffic and away from furniture
and draperies.
Do not place clothing or other
flammable 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 flam-
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) in-
side any structure. Locate propane/LP supply
tank(s) outdoors.
3. This heater shall not be installed in a bathroom
or a bedroom.
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
neighborʼs phone. Follow the gas supplierʼs
instructions
• if you cannot reach your gas supplier, call
the fire department
5. This heater needs fresh, outside air ventilation
to run properly. This heater has an Oxygen
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.

www.desatech.com 116292-01A
4
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 flammable 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 qualified 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 qualified service person should service and
repair heater.
12. Operating heater above elevations of 4,500
feet (1,371 m) could cause pilot outage.
13. To prevent performance problems, do not use
propane/LP fuel tank of less than 100 lbs. (45 kg)
capacity.
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
SAFETY INFORMATION
Continued
Figure 1 - Vent-Free Gas Heater
Ignitor
Control Knob
(under door)
Heater Cabinet
Glass Panel
PRODUCT
IDENTIFICATION
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 inform dealer
where you bought heater.
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
This heater has either a piezo ignitor or electronic
ignitor to light heater fuel supply.
THERMOSTATIC HEAT CONTROL
Thermostat models have a thermostat sensing
bulb and a control valve. This results in the great-
est heater comfort. This can also result in lower
gas bills.

www.desatech.com
116292-01A 5
AIR FOR COMBUSTION
AND VENTILATION
WARNING: This heater shall
not be installed in a confined
space or unusually tight con-
struction unless provisions are
provided for adequate combus-
tion and ventilation air. Read the
following instructions to insure
proper fresh air for this and
other fuel-burning appliances
in your home.
Todayʼs homes are built more energy efficient
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. During heating months, home
owners want their homes as airtight as possible.
While it is good to make your home energy effi-
cient, your home needs to breathe. Fresh air must
enter your home. All fuel-burning appliances need
fresh air for proper combustion and ventilation.
Exhaust fans, fireplaces, 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 appliances.
PROVIDING ADEQUATE
VENTILATION
The following are excerpts from National Fuel
Gas Code, ANSI Z223.1/NFPA 54, Section 5.3,
Air for Combustion and Ventilation.
All spaces in homes fall into one of the three fol-
lowing ventilation classifications:
1. Unusually Tight Construction
2. Unconfined Space
3. Confined Space
The information on pages 5 through 7 will help
you classify your space and provide adequate
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 unusually
tight construction, you must provide additional
fresh air.
Unusually tight construction is defined as
construction where:
a. walls and ceilings exposed to the out-
side 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 floors, between wall-ceiling joints,
between wall panels, at penetrations
for plumbing, 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 Determin-
ing Fresh-Air Flow For Heater Location,
page 6.
Confined and Unconfined Space
The National Fuel Gas Code, ANSI Z223.1/NFPA
54 defines a confined space as a space whose
volume is less than 50 cubic feet per 1,000 Btu
per hour (4.8 m3 per kw) of the aggregate input
rating of all appliances installed in that space and
an unconfined space as a space whose volume is
not less than 50 cubic feet per 1,000 Btu per hour
(4.8 m3 per kw) of the aggregate input rating of
all appliances installed in that space. Rooms com-
municating directly with the space in which the
appliances are installed*, through openings not
furnished with doors, are considered a part of the
unconfined space.
* Adjoining rooms are communicating only if
there are doorless passageways or ventilation grills
between them.

www.desatech.com 116292-01A
6
AIR FOR COMBUSTION
AND VENTILATION
Continued
DETERMINING FRESH-AIR FLOW
FOR HEATER LOCATION
Determining if You Have a Confined or
Unconfined Space
Use this work sheet to determine if you have a con-
fined or unconfined space.
Space: Includes the room in which you will install
heater plus any adjoining rooms with doorless pas-
sageways 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. (6.1 m) (length) x 16
ft. (4.88 m)(width) x 8 ft. (2.44 m) (ceiling height)
= 2560 cu. ft. (72.49 m3) (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. (72.49 m3) (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 fireplace logs ___________ Btu/Hr
Other gas appliances* + __________ Btu/Hr
Total = __________ Btu/Hr
* Do not include direct-vent gas appliances. Di-
rect-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
18,000
58,000
4. Compare the maximum Btu/Hr the space can
support with the actual amount of Btu/Hr used.
_________ Btu/Hr (maximum the space can support)
_________ Btu/Hr (actual amount of Btu/Hr used)
Example: 51,200 Btu/Hr (maximum the space
can support)
58,000 Btu/Hr (actual amount of
Btu/Hr used)
The space in the above example is a confined space
because the actual Btu/Hr used is more than the maxi-
mum Btu/Hr the space can support. You must provide
additional fresh air. Your options are as follows:
A. Rework worksheet, adding the space of an adjoin-
ing room. If the extra space provides an unconfined
space, remove door to adjoining room or add
ventilation grills between rooms. See Ventilation
Air From Inside Building, page 7.
B. Vent room directly to the outdoors. See Ventila-
tion Air From Outdoors, page 7.
C. Install a lower Btu/Hr heater, if lower Btu/Hr size
makes room unconfined.
If the actual Btu/Hr used is less than the maximum
Btu/Hr the space can support, the space is an uncon-
fined space. You will need no additional fresh air
ventilation.
WARNING: If the area in
which the heater may be oper-
ated is smaller than that defined
as an unconfined space or if the
building is of unusually tight
construction, provide adequate
combustion and ventilation air
by one of the methods described
in the National Fuel Gas Code,
ANSI Z223.1/NFPA 54 Section 5.3
or applicable local codes.

www.desatech.com
116292-01A 7
Figure 3 - Ventilation Air from Outdoors
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining un-
confined space. When ventilating to an adjoining
unconfined space, you must provide two perma-
nent openings: one within 12" (30.4 cm) of the
ceiling and one within 12" (30.4 cm) of the floor
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,
Section 5.3, Air for Combustion and Ventilation for
required size of ventilation grills or ducts.
Figure 2 - Ventilation Air from Inside
Building
Or
Remove
Door into
Adjoining
Room,
Option 3
Ventilation Grills
Into Adjoining Room,
Option 2
12"
(30.4 cm)
Ventilation
Grills
into Adjoining
Room,
Option 1
12"
(30.4 cm)
Outlet
Air
Ventilated
Attic
Outlet
A
ir
Inlet
Air
Inlet Air Ventilated
Crawl Space
To
Crawl
Space
To Attic
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 qualified ser-
vice person must install heater.
Follow all local codes.
CHECK GAS TYPE
Use only the correct type of gas (natural or pro-
pane/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 (natural or pro-
pane/LP) gas. Field conversion
is not permitted.
Ventilation Air From Outdoors
Provide extra fresh air by using ventilation grills
or ducts. You must provide two permanent open-
ings: one within 12" (30.4 cm) of the ceiling and
one within 12" (30.4 cm) of the floor. 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, Section 5.3, 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 thermostat-
controlled power vent. Heated air entering the attic
will activate the power vent.

www.desatech.com 116292-01A
8
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*
* A CSA design-certified equipment shutoff valve
with 1/8" NPT tap is an acceptable alternative to
test gauge connection. The optional CSA design-
certified equipment shutoff valve can be purchased
from your dealer. See Accessories, page 23.
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 floor,
ceiling and joining wall.
WARNING: Never install the
heater
• in a bathroom or a bedroom
• in a recreational vehicle
• where curtains, furniture,
clothing or other flammable
objects are less than 36 inches
(92 cm) from the front, top or
sides of the heater
• as a fireplace insert
• in high traffic areas
• in windy or drafty areas
Figure 4 - Mounting Clearances As
Viewed From Front of Heater
INSTALLATION
Continued CAUTION: This heater cre-
ates warm air currents. These
currents move heat to wall sur-
faces next to heater. Installing
heater next to vinyl or cloth wall
coverings or operating heater
where impurities (such as, but
not limited to, tobacco smoke,
aromatic candles, cleaning flu-
ids, 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 beneficial, installing heater
in rooms without enough ventilation air may cause
mildew to form from too much moisture. See Air
for Combustion and Ventilation, page 5. If high hu-
midity is experienced, a dehumidifier 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 inches (45.7 cm)
above floor
• locate heater where moving
vehicle will not hit it
For convenience and efficiency, install heater
• where there is easy access for operation, inspec-
tion and service
• in coldest part of room
Locate heater near a 120V 60Hz electrical outlet
(normal household voltage).
Minimum
From
Sides Of
Heater
36"
(91.4 cm)
Minimum
2" (5.1 cm)
FLOOR
CEILING
Minimum To
Top Surface
Of Carpeting,
Tile Or Other
Combustible
Material
Left
Side
Right
Side
6" (15.2 cm)

www.desatech.com
116292-01A 9
INSTALLATION
Continued
INSTALLING HEATER TO WALL
Mounting Bracket
Locate mounting bracket in heater carton. Remove
mounting bracket from heater carton.
Figure 7 - Installing Glass Panel
Figure 5 - Mounting Bracket
Removing Front Panel Of Heater
1. Remove the four screws, two on each side of
front panel.
2. Pull front panel forward from the bottom, only
2 to 3 inches (5 to 7.6 cm).
3. Reach into lower right corner of heater and
disconnect ignitor wire.
4. Lift panel up to remove, set aside.
5. Remove any remaining packaging materials.
4. Turn front panel face down. Gently press onto
a hard surface to snap bushing into hole. Turn
panel back over, face up.
5. Place spacers over 4 holes on front panel as
shown in Figure 7.
6. Position glass on top of spacers, aligning holes.
Note: If glass gets scratched or marred from
normal use, it may be reversed on heater.
7. Place 4 retaining clips on glass over holes.
8. Install screws in each hole, but do not tighten
at this time.
9. Square glass up with top front surface of front
panel. Tighten screws.
10. Snap screw covers over retaining clips.
Glass Panel
Screw Cover
Front
Panel
Spacer
Screw
Retainer Clip
Installing Glass Panel
Items needed from hardware packet:
1 - Bushing
4 - Black spacers
4 - Retaining clips
4 - 1.5" long screws
4 - Screw covers
1. Locate hardware packet and dark acrylic glass.
2.
Peel protective coating from both sides of glass.
3. Snap bushing into center front hole of front
panel (see Figure 7).
Figure 6 - Removing Front Panel Of Heater
Screw
Front Panel
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 centers are
13 inches (33 cm) apart. 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 provides the
strongest hold. Insert mounting screws through
mounting bracket and into wall studs.
Attaching to Wall Anchor: This method allows 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 mounting bracket
is level.
Ignitor
Wire
Bushing

www.desatech.com 116292-01A
10
INSTALLATION
Continued
Figure 9 - Folding Anchor
Figure 11 - Mounting Heater Onto
Mounting Bracket
Figure 10 - Popping Open Anchor Wings
For Thin Walls
Mounting Bracket
(attached to wall)
Horizontal Slots
Stand-Out Tab
WARNING: Maintain mini-
mum clearances shown in Figure
8. If you can, provide greater
clearances from floor and join-
ing 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.
Attaching Mounting Bracket To Wall
Note: Wall anchors, mounting screws and spacers
are in hardware package. The hardware 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
firmly fastened to wall studs.
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.
13" (33 cm)
11"
(27.9 cm)
Min.
12"
(30.4
cm)
Min.
Adjoining Wall
Only Insert Mounting
Screws Through Last
Hole On Each End
Floor
Figure 8 - Mounting Bracket Clearances
3. Insert wall anchor (wings first) into hole. Tap
anchor flush to wall.
4. For thin walls [1/2" (1.3 cm) or less], insert red
key into wall anchor. Push red key to “pop” open
anchor wings. IMPORTANT: Do not hammer
key! For thick walls [over 1/2" (1.3 cm) 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
firmly fastened to 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 mount-
ing bracket.

www.desatech.com
116292-01A 11
Side View
Front View
Figure 12 - Installing Bottom Mounting
Screws
Wall
Spacer
Heater
Installing Bottom Mounting Screws
1. Locate two bottom mounting holes. These
holes are near bottom on back panel of heater
(see Figure 12).
2. Mark screw locations on wall.
3. Remove heater from mounting bracket.
4. If installing bottom mounting screws into
hollow or solid wall, install wall anchors.
Follow steps 1 through 4 under Attaching To
Wall Anchor Method, page 10.
If installing bottom mounting screw into wall
stud, drill holes at marked locations using
9/64" drill bit.
5. Replace heater onto mounting bracket.
6. Place spacers between bottom mounting holes
and wall anchor or drilled hole.
7. Hold spacer in place with one hand. With other
hand, insert mounting screw through bottom
mounting hole and spacer. Place tip of screw
in opening of wall anchor or drilled hole.
8. Tighten both screws until heater is firmly
secured to wall. Do not over tighten.
Note: Do not replace front panel at this time.
Replace front panel after making gas connec-
tions and checking for leaks.
INSTALLATION
Continued
CONNECTING TO GAS SUPPLY
WARNING: This appliance
requires a 3/8" NPT (National
Pipe Thread) inlet connection to
the pressure regulator.
WARNING: A qualified service
person must connect heater to gas
supply. Follow all local codes.
WARNING: For natural
gas, never connect heater to
private (non-utility) gas wells.
This gas is commonly known
as wellhead gas.
IMPORTANT: For natural gas, check gas line
pressure before connecting heater to gas line. Gas
line pressure must be no greater than 10.5 inches of
water. If gas line pressure is higher, heater regula-
tor damage could occur.
CAUTION: For propane/LP
gas, never connect heater di-
rectly to the propane/LP supply.
This heater requires an external
regulator (not supplied). Install
the external regulator between the
heater and propane/LP supply.
For propane/LP gas, the installer must supply an
external regulator. The external regulator will
reduce incoming gas pressure. You must reduce
incoming gas pressure to between 11 and 14 inches
of water. If you do not reduce incoming gas pres-
sure, heater regulator damage could occur. Install
the external regulator with the vent pointing down
as shown in Figure 13. Pointing the vent down
protects it from freezing rain or sleet.
Figure 13 - External Regulator With Vent
Pointing Down
External
Regulator
Propane/LP
Supply Tank
Vent
Pointing
Down

www.desatech.com 116292-01A
12
Tee Joint
Reducer
Bushing to
1/8" NPT
1/8" NPT
Plug Tap
Test Gauge Connection*
3/8" NPT
Pipe Nipple
Heater
Cabinet
Equipment
Shutoff
Valve *
3"
(7.6 cm)
Min. Natural Gas
From Gas Meter (4" W.C.
to 10.5" W.C. Pressure)
Propane/LP
From External Regulator
(11" W.C. to 14" W.C.
Pressure)
Ground Joint
Union
Tee Joint
Pipe
Nipple
Cap
Sediment Trap
Figure 14 - Gas Connection
INSTALLATION
Continued
Pressure
Regulator
* A CSA design-certified equipment shutoff valve
with 1/8" NPT tap is an acceptable alternative to
test gauge connection. Purchase the optional CSA
design-certified equipment shutoff valve from your
dealer. See Accessories, page 23.
CAUTION: Use only new,
black iron or steel pipe. Inter-
nally-tinned copper tubing may
be used in certain areas. Check
your local codes. Use pipe of
large enough diameter to allow
proper gas volume to heater. If
pipe is too small, undue loss of
volume will occur.
Typical Inlet Pipe Diameter - 3/8" (9.5 mm)
or greater
Installation must include equipment shutoff valve,
union and plugged 1/8" NPT tap. Locate NPT tap
within reach for test gauge hook up. NPT tap must
be upstream from heater (see Figure 14).
IMPORTANT: Install an equipment shutoff valve
in an accessible location. The equipment shutoff
valve is for turning on or shutting off the gas to
the appliance.
Apply pipe joint sealant lightly to male NPT
threads. This will prevent excess sealant from
going into pipe. Excess sealant in pipe could result
in clogged heater valves.
WARNING: Use pipe joint
sealant that is resistant to liquid
petroleum (LP) gas.
Install sediment trap in supply line as shown in
Figure 14. Locate sediment trap where it is within
reach for cleaning. Locate sediment trap where
trapped matter is not likely to freeze. A sediment
trap traps moisture and contaminants. This keeps
them from going into heater controls. If sediment
trap is not installed or is installed wrong, heater
may not run properly.
IMPORTANT: Hold the pressure regulator with
wrench when connecting it to gas piping and/or
fittings. Do not over tighten pipe connection to
regulator. The regulator body could be damaged.
CHECKING GAS CONNECTIONS
WARNING: Test all gas piping
and connections, internal and
external to unit, for leaks after
installing or servicing. Correct
all leaks at once.
WARNING: Never use an
open flame to check for a leak.
Apply a noncorrosive leak detec-
tion fluid to all joints. Bubbles
forming show a leak. Correct all
leaks at once.
CAUTION: For propane/LP
gas, make sure external regula-
tor has been installed between
propane/LP supply and heater.
See guidelines under Connect-
ing to Gas Supply, page 11.

www.desatech.com
116292-01A 13
PRESSURE TESTING GAS SUPPLY
PIPING SYSTEM
Test Pressures In Excess Of 1/2 PSIG
(3.5 kPa)
1. Disconnect appliance with its appliance main
gas valve (control valve) and equipment
shutoff valve from gas supply piping system.
Pressures in excess of 1/2 psig will damage
heater regulator.
2. Cap off open end of gas pipe where equipment
shutoff valve was connected.
3. Pressurize supply piping system by either
opening propane/LP supply tank valve for
propane/LP gas or opening main gas valve
located on or near gas meter for natural gas
or using compressed air.
4. Check all joints of gas supply piping system.
Apply a noncorrosive leak detection fluid to
all joints. Bubbles forming show a leak.
5. Correct all leaks at once.
6. Reconnect heater and equipment shutoff
valve to gas supply. Check reconnected fit-
tings for leaks.
Test Pressures Equal To or Less Than 1/2
PSIG (3.5 kPa)
1. Close equipment shutoff valve (see Figure 15).
2. Pressurize supply piping system by either
opening propane/LP supply tank valve for
propane/LP gas or opening main gas valve
located on or near gas meter for natural gas
or using compressed air.
3. Check all joints from gas meter for natural gas
(see Figure 16) or propane/LP supply tank for
propane/LP gas, to equipment shutoff valve
(see Figure 17). Apply a noncorrosive leak
detection fluid to all joints. Bubbles forming
show a leak.
4. Correct all leaks at once.
PRESSURE TESTING HEATER GAS
CONNECTIONS
1. Open equipment shutoff valve (see Figure 15).
2. For natural gas open main gas valve located
on or near gas meter. For propane/LP gas open
propane/LP supply tank valve.
3. Make sure control knob of heater is in the OFF
position.
4. Check all joints from equipment shutoff valve
to thermostat gas valve (see Figure 16 or 17).
Apply a noncorrosive leak detection fluid to
all joints. Bubbles forming show a leak.
Figure 17 - Checking Gas Joints for
Propane/LP Gas
Propane/LP
Supply Tank
Figure 16 - Checking Gas Joints for
Natural Gas
Equipment
Shutoff Valve
Gas
Meter
INSTALLATION
Continued
5. Correct all leaks at once.
6. Light heater (see Operating Heater, page 14).
Check all other internal joints for leaks.
7. Turn off heater (see To Turn Off Gas to Appli-
ance, page 15).
8. Replace front panel.
Figure 15 - Equipment Shutoff Valve
Open
Closed
Equipment
Shutoff Valve
Equipment
Shutoff Valve

www.desatech.com 116292-01A
14
OPERATING HEATER
FOR YOUR SAFETY READ
BEFORE LIGHTING
WARNING: If you do not fol-
low these instructions exactly,
a fire or explosion may result
causing property damage, per-
sonal injury or loss of life.
A. This appliance has a pilot which must be
lighted by hand. When lighting the pilot,
follow these instructions exactly.
B. BEFORE LIGHTING smell all around the
appliance area for gas. Be sure to smell next
to the floor because some gas is heavier than
air and will settle on the floor.
WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electric switch; do not
use any phone in your building.
• Immediately call your gas supplier from
a neighborʼs phone. Follow the gas
supplierʼs instructions.
• If you cannot reach your gas supplier,
call the fire department.
C. Use only your hand to push in or turn the
gas control knob. Never use tools. If the
knob will not push in or turn by hand,
donʼt try to repair it, call a qualified service
technician. Force or attempted repair may
result in a fire or explosion.
D. Do not use this appliance if any part has
been under water. Immediately call a
qualified service technician to inspect the
appliance and to replace any part of the
control system and any gas control which
has been under water.
INSTALLATION
Continued
CONNECTING TO ELECTRICAL
SUPPLY
WARNING: Fan accessory
must be grounded. Fan comes
with a three-prong, grounding
plug as shown in Figure 18. The
plug is your protection against
electrical shock. Plug it into a
standard, three-hole, grounded,
outlet. If cord needs replacing,
use only a cord with a three-
prong, grounding plug.
CAUTION: Label all wires
prior to disconnection when
servicing controls. Wiring errors
can cause improper and danger-
ous operation (see page 22).
Grounding Plug
Grounded Outlet
Figure 18 - Grounding Plug
EXTENSION CORD
Use extension cord if needed. The cord must have
a three-prong, grounding plug and a three-hole re-
ceptacle. Make sure cord is in good shape. It must
be heavy enough to carry the current needed. An
undersized cord will cause a drop in line voltage.
This will result in loss of power and overheating.
Use a No. 16 AWG cord for lengths less than 50
feet (15.24 m) .
CAUTION: Verify proper op-
eration after servicing.
Operating Fan
The blower is connected to a thermostat. When unit
heats up, the fan will operate. A few minutes after
unit cycles off or is turned off, the fan will shut
off. The fan will cycle on and off in this manner.
Note: If you have a heater with a thermostat, the
heater and fan will not turn off and on at exactly
the same time. Fan cycle times will vary with the
heat setting selected.

www.desatech.com
116292-01A 15
LIGHTING
INSTRUCTIONS
1. STOP! Read the safety information, page 14.
2. Make sure equipment shutoff valve is fully
open.
3. Turn off any electric power to the appliance
if service is to be performed.
4. Turn control knob clockwise to the
OFF position.
5. Wait five minutes to clear out any gas. Then
smell for gas, including near the floor. If you
smell gas, STOP! Follow “B” in the safety
information, page 14. If you donʼt smell gas,
go to the next step.
6. Turn control knob counterclockwise
to the PILOT position. Press in control
knob for five (5) seconds.
7. With control knob pressed in, push down and
release ignitor button. This will light pilot.
The pilot is attached to the front of burner.
Note: You may be running this heater for the
first time after hooking up to gas supply. If so,
you may need to press in control knob for 30
seconds or more. This will allow air to bleed
from the gas system. If needed, keep pressing
ignitor button until pilot lights. If ignitor does
not light pilot, refer to Troubleshooting, page
18 or contact a qualified service person or gas
supplier for repairs. Until repairs are made,
light pilot with match. To light pilot with match,
see Manual Lighting Procedure, page 16.
8. Keep control knob pressed in for 30 seconds
after lighting pilot. After 30 seconds, release
control knob.
• If control knob does not pop up when re-
leased, contact a qualified service person
or gas supplier for repairs.
Note: If pilot goes out, repeat steps 4 thru 7.
Thermostat models have a safety interlock
system. Wait one (1) minute before lighting
pilot again.
9. Turn control knob counterclockwise
to desired heating level. The main burner
should light.
WARNING: Always operate
manual control heaters at the
locked positions. Operation
between these positions may
create a possible health hazard
if used in a poorly ventilated
room. Read owner’s manual for
complete instructions.
O
F
F
P
I
L
O
T
Figure 19 - Control Knob In The OFF
Position
Piezo Ignitor
Figure 21 - Pilot (actual pilot may vary)
OPERATING HEATER
Continued
Ignitor Electrode
Pilot Burner
Thermocouple
TO TURN OFF GAS
TO APPLIANCE
Shutting Off Heater
1. Turn control knob clockwise to the
OFF position.
2. Turn off all electric power to the appliance
if service is to be performed.
Shutting Off Burner Only (pilot stays lit)
Turn control knob clockwise to the
PILOT position.
THERMOSTAT CONTROL
OPERATION
The thermostatic control used on these models
differs from standard thermostats. Standard
thermostats simply turn on and off the burner.
The thermostat used on this heater senses the
room temperature. The thermostat adjusts the
amount of gas flow to the burner. This increases
or decreases the burner flame height. At times
the room may exceed the set temperature. If so,
the burner will shut off. The burner will cycle
back on when room temperature drops below the
set temperature. The control knob can be set to
any heat level between 1 and 5. Selecting the 5
setting will cause the burner to remain fully on
without modulating down in most cases.
OFF
O
F
F
P
I
L
O
T
Electronic Ignitor
Figure 20 - Ignitor Buttons
CAUTION: Do not try to ad-
just heating levels by using the
equipment shutoff valve.

www.desatech.com 116292-01A
16
Figure 24 - Correct Burner Flame Pattern
Yellow
Tipping
Figure 25 - Incorrect Burner Flame
Pattern
1/2
Deflector
Height
Blue
Flame
1/2
Deflector
Height
Note: The thermostat sensing bulb measures
the temperature of air near the heater cabinet.
This may not always agree with room tem-
perature (depending on housing construction,
installation location, room size, open air tem-
peratures, etc.). Frequent use of your heater will
let you determine your own comfort levels.
MANUAL LIGHTING
PROCEDURE
1. Remove front panel (see Figure 6, page 9).
2. Follow steps 1 through 7 under Lighting
Instructions, page 15.
3. With control knob pressed in, strike match.
Hold match to pilot until pilot lights.
4. Keep control knob pressed in for 30 seconds
after lighting pilot. After 30 seconds, release
control knob. Now follow step 9, under
Lighting Instructions, page 15.
5. Replace front panel.
INSPECTING HEATER
Check pilot flame pattern and burner flame pat-
tern often.
PILOT FLAME PATTERN
Figure 22 shows a correct pilot flame pattern.
Figure 23 shows an incorrect pilot flame pattern.
The incorrect pilot flame is not touching the
thermocouple. This will cause the thermocouple
to cool. When the thermocouple cools, the heater
will shut down.
If pilot flame pattern is incorrect, as shown in
Figure 23
•
turn heater off (see To Turn Off Gas to Appliance,
page 15)
• see Troubleshooting, page 18
Note: The pilot flame on natural gas units will
have a slight curve, but flame should be blue and
have no yellow or orange color.
Figure 24 - Incorrect Pilot Flame Pattern
Figure 23 - Correct Pilot Flame Pattern
Thermocouple
Pilot
Burner
Thermocouple
Blue Flame
Yellow Flame
Pilot
Burner
OPERATING HEATER
Continued
BURNER FLAME PATTERN
WARNING: If yellow tipping
occurs, your heater could pro-
duce increased levels of carbon
monoxide.
NOTICE: Do not mistake orange
flames with yellow tipping. Dirt
or other fine particles enter the
heater and burn causing brief
patches of orange flame.
Figure 24 shows a correct burner flame pattern.
Figure 25 shows an incorrect burner flame pattern.
The incorrect burner flame pattern shows yellow
tipping of the flame. It also shows the flame higher
than 1/2 the deflector panel height.
If burner flame pattern is incorrect, as shown in
Figure 25
• turn heater off (see To Turn Off Gas To Appli-
ance, page 15)
• see Troubleshooting, page 18

www.desatech.com
116292-01A 17
CLEANING AND
MAINTENANCE
WARNING: Turn off heater
and let cool before cleaning.
CAUTION: You must keep
control areas, burner and circu-
lating air passageways of heater
clean. Inspect these areas of
heater before each use. Have
heater inspected yearly by a
qualified service person. Heater
may need more frequent clean-
ing due to excessive lint from
carpeting, bedding material, pet
hair, etc.
WARNING: Failure to keep
the primary air opening(s) of
the burner(s) clean may result in
sooting and property damage.
ODS/PILOT AND BURNER
Use a vacuum cleaner, pressurized air or small,
soft bristled brush to clean.
BURNER PILOT AIR INLET
The primary air inlet holes allow the proper
amount of air to mix with the gas. This provides a
clean burning flame. Keep these holes clear of dust,
dirt and lint. Clean these air inlet holes prior to each
heating season. Blocked air holes will create soot.
We recommend that you clean the unit every three
months during operation and have heater inspected
yearly by a qualified service person.
We also recommend that you keep the burner
tube and pilot assembly clean and free of dust and
dirt. To clean these parts we recommend using
compressed air no greater than 30 PSI. Your local
computer store, hardware store or home center
may carry compressed air in a can. You can use a
vacuum cleaner in the blow position. If using com-
pressed air in a can, please follow the directions on
the can. If you don't follow directions on the can,
you could damage the pilot assembly.
Figure 26 - Pilot Inlet Air - Propane/LP
Pilot Shown (Actual Pilot May Vary from
Illustration)
Pilot Air Inlet
1. Shut off the unit, including the pilot. Allow
the unit to cool for at least thirty minutes.
2. Inspect burner, pilot for dust and dirt.
3. Blow air through the ports/slots and holes in
the burner.
4. Never insert objects into the pilot tube.
Clean the pilot assembly also. A yellow tip on the
pilot flame indicates dust and dirt in the pilot as-
sembly. There is a small pilot air inlet about two
inches from where the pilot flame comes out of
the pilot assembly (see Figure 26). With the unit
off, lightly blow air through the air inlet. You may
blow through a drinking straw if compressed air
is not available.
Pilot Assembly
CABINET
Air Passageways
Use a vacuum cleaner or pressurized air to clean.
Exterior and Dark Acrylic Front Glass
Use a soft cloth dampened with a mild soap and
water mixture. Wipe the cabinet to remove dust.

www.desatech.com 116292-01A
18
TROUBLESHOOTING
WARNING: Turn off and unplug heater and let cool before servicing.
Only a qualified service person should service and repair heater.
CAUTION: Never use a wire, needle or similar object to clean
ODS/pilot. This can damage ODS/pilot unit.
Note: All troubleshooting items are listed in order of operation.
POSSIBLE CAUSE
1. Ignitor electrode positioned
wrong
2. Ignitor electrode broken
3. Ignitor electrode not con-
nected to ignitor cable
4. Ignitor cable pinched or wet
5. Broken ignitor cable
6. Bad piezo ignitor
1. Gas supply turned off or equip-
ment shutoff valve closed
2. Control knob not in PILOT
position
3. Control knob not pressed in
while in PILOT position
4. Air in gas lines when in-
stalled
5. Depleted gas supply (propane/
LP gas only)
6. ODS/pilot is clogged
7. Gas regulator setting is not
correct
OBSERVED PROBLEM
When ignitor button is pressed,
there is no spark at ODS/pilot
When ignitor button is pressed,
there is spark at ODS/pilot but
no ignition
REMEDY
1. Replace pilot assembly
2. Replace pilot assembly
3. Reconnect ignitor cable
4. Free ignitor cable if pinched
by any metal or tubing. Keep
ignitor cable dry
5. Replace ignitor cable
6. Replace piezo ignitor
1. Turn on gas supply or open
equipment shutoff valve
2. Turn control knob to PILOT
position
3. Press in control knob while in
PILOT position
4. Continue holding down con-
trol knob. Repeat igniting op-
eration until air is removed
5. Contact local propane/LP gas
company
6. Clean ODS/pilot (see Cleaning
and Maintenance, page 17) or
replace ODS/pilot assembly
7. Replace gas regulator

www.desatech.com
116292-01A 19
OBSERVED PROBLEM
ODS/pilot lights but flame
goes out when control knob is
released
Burner does not light after
ODS/pilot is lit
Delayed ignition of burner
Burner backfiring during com-
bustion
REMEDY
1. Press in control knob fully
2. After ODS/pilot lights, keep
control knob pressed in 30
seconds
3. Wait one minute for safety in-
terlock system to reset. Repeat
ignition operation
4. Fully open equipment shutoff
valve
5. Hand tighten until snug, then
tighten 1/4 turn more
6. A) Contact local natural or
propane/LP gas company
B) Clean ODS/pilot (see
Cleaning and Maintenance,
page 17) or replace ODS/pilot
assembly
7. Replace pilot assembly
8. Replace control valve
1. Clean burner (see Cleaning
and Maintenance, page 17)
or replace burner orifice
2. Contact local natural or pro-
pane/LP gas company
1. Contact local natural or pro-
pane/LP gas company
2. Clean burner (see Cleaning
and Maintenance, page 17)
or replace burner orifice
1. Clean burner (see Cleaning
and Maintenance, page 17)
or replace burner orifice
2. Replace burner
3. Replace gas regulator
POSSIBLE CAUSE
1. Control knob not fully pressed in
2. Control knob not pressed in
long enough
3. Safety interlock system has
been triggered
4. Equipment shutoff valve not
fully open
5. Thermocouple connection
loose at control valve
6. Pilot flame not touching ther-
mocouple, which allows ther-
mocouple to cool, causing
pilot flame to go out. This
problem could be caused by
one or both of the following:
A) Low gas pressure
B) Dirty or partially clogged
ODS/pilot
7. Thermocouple damaged
8. Control valve damaged
1. Burner orifice is clogged
2. Inlet gas pressure is too low
1. Manifold pressure is too low
2. Burner orifice is clogged
1. Burner orifice is clogged or
damaged
2. Burner damaged
3. Gas regulator defective
TROUBLESHOOTING
Continued

www.desatech.com 116292-01A
20
TROUBLESHOOTING
Continued
OBSERVED PROBLEM
Yellow flame during burner
combustion
Slight smoke or odor during
initial operation
Heater produces a whistling
noise when burner is lit
White powder residue forming
within burner box or on adjacent
walls or furniture
Blower fan does not come on
Heater produces a clicking/tick-
ing noise just after burner is lit
or shut off
POSSIBLE CAUSE
1. Not enough air
2. Gas regulator defective
3. Clogged or dirty burner
1. Residues from manufacturing
processes
1. Turning control knob to 5
position when burner is cold
2. Air in gas line
3. Air passageways on heater
blocked
4. Dirty or partially clogged
burner orifice
1. When heated, vapors from
furniture polish, wax, carpet
cleaners, etc. may turn into
white powder residue
1. Power cord not connected
2. No power to electric outlet
3. Time delay for thermal switch
to warm up
4. Bad switch
5. Loose wire connection
1. Metal expanding while heat-
ing or contracting while
cooling
REMEDY
1. Check burner for dirt and
debris. If found, clean burner
(see Cleaning and Mainte-
nance, page 17)
2. Replace gas regulator
3. Clean burner (see Cleaning
and Maintenance, page 17)
1. Problem will stop after a few
hours of operation
1. Turn control knob to 1 posi-
tion and let warm up for a
minute
2. Operate burner until air is
removed from line. Have gas
line checked by local natural
or propane/LP gas company
3. Observe minimum installation
clearances (see Figure 4, page 8)
4. Clean burner (see Cleaning
and Maintenance, page 17)
or replace burner orifice
1. Turn heater off when using
furniture polish, wax, carpet
cleaners or similar products
1. Connect power cord to 120V
60Hz outlet
2. Have a qualified service per-
son check for power at outlet
3. Wait 4 to 5 minutes with the
burner on
4. Replace switch
5. Reconnect wires
1. This is common with most heat-
ers. If noise is excessive, contact
qualified service person