Desa LSL18NT Original instructions

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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

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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

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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.

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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.

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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.

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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.

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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.

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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)

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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

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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.