Monessen Hearth Magnum Unvented Vent-Free Fireboxes MCUF42D... User manual

For use with a listed gas-fired
unvented decorative room heater
not to exceed 40,000 BTU/hr. Do
not build a wood fire.
READ AND SAVE THESE INSTRUCTIONS
WARNINGS
If the information in this manual is not followed exactly,
a fire or explosion may result causing property damage,
personal injury or loss of life.
– 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.
• Immediatelycallyourgassupplierfromaneighbor'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 qualified installer, service agency or the gas
supplier.
MODELS:
MCUF36D and MCUF42D SERIES
MAGNUM
UNVENTED
VENT-FREE
FIREBOXES
INSTALLATION AND
OPERATING INSTRUCTIONS
Carefully review the instructions
supplied with the decorative type
unventedroomheaterforthemini-
mum fireplace size requirement.
DO NOT INSTALLANAPPLIANCE
IN THIS FIREBOX UNLESS THIS
FIREBOX MEETS THE MINIMUM
DIMENSIONS REQUIRED FOR
THE INSTALLATION.
WARNINGS
If the information in this manual is not followed
exactly, a fire or explosion may result causing
property damage, personal injury or loss of life.
– 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 qualified installer, service agency or the gas
supplier.
WARNINGS

2 26D4720
CONTENTS
Important Safety Information ................................. 3
Product Features......................................................5
Before You Start.....................................................5
General Installation Information .............................6
Firebox Dimensions ...............................................6
Minimum Hearth Dimensions.................................7
Location of Firebox..................................................7
Clearances and Height Requirements....................8
Fireplace Framing...................................................10
Gas Line Installation ..............................................12
Canopy Installation ................................................13
Optional Equipment ...............................................14
Forced Air Kit .......................................................14
Brass or Chrome Trim..........................................14
Optional Wide Canopy.........................................14
Illustrated Parts Breakdown..................................15
Using Optional Outside Air Kit..............................16
Warranty..................................................Back Cover

26D4720 3
9. The installation must conform with local codes or, in
the absence of local codes, with the National Fuel Gas
Code, ANSI Z223.l/NFPA54.
10. This unit complies with ANSI Z21.91.2001 ventless fire-
box enclosures for gas-fired unvented decorative room
heaters.
11. Do not install heater in a bathroom or bedroom.
12. Correct installation of the ceramic fiber logs, proper
location of the heater, and annual cleaning are necessary
to avoid potential problems with sooting. Sooting,
resulting from improper installation or operation,
can settle on surfaces outside the fireplace. See log
placement instructions for proper installation.
13. Avoid any drafts that alter burner flame patterns. Do not
allow fans to blow directly into fireplace. Do not place
a blower inside burn area of firebox. Ceiling fans may
create drafts that alter burner flame patterns. Sooting
and improper burning will occur.
14. Caution: Candles, incense, oil lamps, etc. produce
combustion byproducts including soot. Vent-free appli-
ances will not filter or clean soot produced by these types
of products. In addition, the smoke and/or aromatics
(scents) may be reburnt in the vent-free appliance which
can produce odors. It is recommended to minimize the
use of candles, incense, etc. while the vent-free appliance
is in operation.
15. An unvented gas-fired heater uses air (oxygen) from the
room in which it is installed. Provisions for adequate
combustion and ventilation air must be provided. See
installation guidelines.
INSTALLER
Please leave these instructions with the appliance.
OWNER
Please retain these instructions for future reference .
IMPORTANT
Read these instructions carefully before installing or trying to operate a vent-free gas heater in this firebox.
IMPORTANT SAFETY INFORMATION
1. Due to high temperatures, the appliance should
be located out of traffic and away from furniture
and draperies.
2. Children and adults should be alerted to the hazard
of high surface temperature and should stay away
to avoid burns or clothing ignition.
3. Young children should be carefully supervised
when they are in the same room with the appli-
ance.
4. Do not place clothing or other flammable material
on or near the appliance.
5. Any safety screen or guard removed for servicing
an appliance, must be replaced prior to operating
the heater.
6. Installation and repair should be done by a qualified
service person.
7. To prevent malfunction and/or sooting, an unvented
gas heater should be cleaned before use at least
annually by a professional service person. More
frequent cleaning may be required due to exces-
sive lint from carpeting, bedding material, etc. It is
imperative that control compartments, burners and
circulating air passageways be kept clean.
8. CARBON MONOXIDE POISONING: Early signs of
carbon monoxide poisoning are similar to the flu with
headaches, dizziness and/or nausea. If you have these
signs, obtain fresh air immediately. Have the heater
serviced as it may not be operating properly. Continued on page 4
• Any change to this heater or its controls can be dangerous.
• Improper installation or use of the heater can cause serious injury or death from fire,
burns, explosion or carbon monoxide poisoning.
• Do not allow fans to blow directly into the fireplace. Avoid any drafts that alter burner
flame patterns.
• Do not use a blower insert, heat exchanger insert or other accessory, not approved for
use with this heater where applicable.
WARNING

4 26D4720
IMPORTANT SAFETY INFORMATION
Continued from page 3
16. Keep room area clear and free from combustible materi-
als, gasoline and other flammable vapors and liquids.
17. Unvented gas heaters are a supplemental zone heater.
They are not intended to be a primary heating appli-
ance.
18. Unvented gas heaters emit moisture into the living area.
In most homes of average construction, this does not pose
a problem. In houses of extremely tight construction,
additional mechanical ventilation is recommended.
19. During manufacturing, fabricating and shipping, various
components of this appliance are treated with certain
oils, films or bonding agents. These chemicals are not
harmful but may produce annoying smoke and smells
as they are burned off during the initial operation of the
appliance; possibly causing headaches, or eye or lung
irritation. This is a normal and temporary occurrence.
The initial break-in operation should last two to three
hours with the burner at the highest setting. Provide
maximum ventilation by opening windows or doors to
allow odors to dissipate. Any odors remaining after this
initial break-in period will be slight and will disappear
with continued use.
20. Input ratings are shown in BTU per hour and are for
elevations up to 2,000 feet. For elevations above 2,000
feet, input ratings should be reduced 4 percent for each
1,000 feet above sea level. Refer to the National Fuel
Gas Code.
21. The appliance and its appliance main gas valve must be
disconnected from the gas supply piping system during
any pressure testing of that system at test pressures in
excess of 1/2 psig (3.5 kPa).
22. The appliance must be isolated from the gas supply
piping system by closing its equipment shutoff valve
during any pressure testing of the gas supply piping
system at test pressures equal to or less than 1/2 psig
(3.5 kPa).
23. Do not use this room 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.
24. Never burn solid fuels in a fireplace where a unvented
room heater is installed.
25. Always have a fireplace screen in place when the appli-
ance is in operation, and unless other provisions for
combustion air are provided, the screen shall have an
opening(s) for induction of combustion air.
26. Do not fill spaces around the firebox with insulation or
other materials. These spaces must be maintained to pre-
vent the firebox from coming in contact with combustible
materials.
www.nficertified.org
We suggest that our gas hearth
products be installed and
serviced by professionals who
are certified in the U.S. by the
National Fireplace Institute®
(NFI) as Gas Specialists.
Never connect unit to private
(non-utility) gas wells. This
gas is commonly known as
wellhead gas.
WARNING

26D4720 5
The MCUF36D and MCUF42D Series are vent-free fireboxes. They feature a self contained heat-circulating system.
This installation manual will enable you to obtain a safe, efficient and dependable installation of your vent-free firebox.
Do not alter or modify the firebox or its components under any circumstances. Any modification or alteration of the firebox
system, including but not limited to the firebox and accessories, may void the warranty, listings and approvals of this system
and could result in an unsafe and potentially dangerous installation.
BEFORE YOU START
Carefully inspect the contents for shipping damage. If any parts are missing or damaged, immediately inform the dealer
from whom you purchased the appliance. Do not attempt to install any part of the appliance unless you have all the parts in
good condition.
MAKE SURE YOU HAVE RECEIVED ALL PARTS
Check your packing list to verify that all listed parts have been received. You should have the following:
1. Vent-Free Gas Firebox 4. Five (5) sheet metal screws for canopy
2. Canopy
3. Installation and Operating Instructions
WHAT YOU WILL NEED FOR INSTALLATION
TOOLS BUILDING SUPPLIES
• Phillips screwdriver • Square • Framing materials
• Hammer •
Piping complying with local codes • Wall finishing materials
• Saw and / or sabersaw • Tee joint • Caulking material (noncombustible)
• Level • Pipe wrench • Fireplace surround materials (noncombustible)
• Measuring tape • Pliers
• Electric drill and bits • Pipe sealant approved for use with propane/L.P.G. (resistant to sulfur compounds)
Refer to the installation instructions provided with the log sets for items required for log set installation.
PRODUCT FEATURES
Do not attempt to burn solid wood fuels, vented gas log sets, or any other combustible
in this unvented firebox. Also, do not install a vent-free gas log set in this firebox if
the minimum clearance and height requirements of the log set are too large for the
firebox.
WARNING
Illustrations shown in this manual reflect “typical” installations with nominal dimensions
and are for design and framing reference only. Actual installations may vary due to
individual design preferences. However, always maintain minimum clearances to
combustible materials and do not violate any specific installation requirements.
NOTICE

6 26D4720
D
F
E
H
C
5.25"
32.125"
2.50" 2.50"
B26.25"
9.75"
8.25"
37.375"
6"
A
In planning the installation for the appliance it is necessary to determine where the unit is to be installed and whether optional
accessories are desired. Gas supply piping should also be planned. The following steps represent the normal sequence of
installation. Each installation is unique, however, and might require a different sequence.
1. Position firebox prior to framing or into prepared framing.
2. Field wire main power supply to models with fan kit. (Electrical connections should only be performed by an experi-
enced, licensed /certified tradesman).
3. Plumb gas line. (Gas connections should only be performed by an experienced, licensed/certified tradesman).
4. Install vent-free gas log heater per the instructions provided with the vent-free gas log heater.
5. Complete finish wall material, surround and optional hearth extension to your individual taste.
FIREBOX DIMENSIONS
GENERAL INSTALLATION INFORMATION
Figure 1 - Firebox Dimensions
MCUF36D MCUF42D
A 411/4" 47"
B 36" 42"
C 181/4" 181/4"
D 32" 38"
E 203/4" 203/4"
F 271/4" 331/4"
H337/8" 397/8"

26D4720 7
MINIMUM HEARTH DIMENSIONS
GENERAL INSTALLATION INFORMATION AND LOCATION OF FIREBOX
Figure 2 - Minimum Hearth Dimensions
LOCATION OF FIREBOX
Carefully select the best location for installation of your
vent-free firebox. The following factors should be taken
into consideration:
• Clearance to side wall, ceiling, woodwork and
windows. See “Clearances/Height Requirements on
page 8. Minimum clearances to combustibles must
be maintained.
• Location must not be affected by drafts caused by
kitchen exhaust fans, ceiling fans, return air registers
for forced air furnaces / air conditioners, windows
or doors.
• Installation must provide adequate ventilation and
combustion air.
• DO NOT INSTALL THIS FIREBOX IN A
BEDROOM OR BATHROOM.
• Location should be out of high traffic or windy or
drafty areas.
• DO NOT INSTALL WHERE CURTAINS, FURNITURE, CLOTHING OR OTHER FLAMMABLE OBJECTS
ARE LESS THAN 42" FROM FRONT OF HEATER.
• Never obstruct the front opening of the vent-free firebox or restrict the flow of combustion and ventilation air.
• Minimize modifications to existing construction. Refer to Figure 3 below for location suggestions.
• Do not install in the vicinity where gasoline or other flammable liquids may be stored. The vent-free firebox must be
kept clear and free from these combustible materials.
Figure 3 - Location of Firebox
MCUF36D-F MCUF36D-R MCUF42D-F MCUF42D-R
A 261/4" 253/4" 321/4" 313/4"
B 15" 143/4"15" 143/4"
C 325/8" 321/8" 385/8" 381/8"
D 25" 25" 25" 25"
E201/2"201/2" 201/2" 201/2"

8 26D4720
6"
Minimum
42"
Minimum
6"
Minimum
Ensure that minimum clearances shown in Figures 4 through 7 are
maintained. Left and right clearances are determined when facing the
front of the firebox.
Follow these instructions carefully to ensure safe installation. Failure
to follow these requirements may create a fire hazard.
1. Sidewall clearances: The clearance from the inside of the
appliance to any combustible wall should not be less than 6".
See Figure 4.
2. Ceiling clearance: The ceiling must be at least 42” from the
top of the firebox opening. See Figure 4.
3. Back wall clearance: The appliance may be placed against a
combustible back wall.
Figure 4 - Clearance and Height
Requirements
4. Floor clearance: This inner chamber firebox floor must be installed at least 6" above any combustible flooring mate-
rial, such as carpeting or asphalt tile, which is closer than 14" to the base of the firebox. See Figure 5.
Or
The inner chamber firebox floor may be installed nearer to the floor if a minimum of 14" of noncombustible material
such as slate or marble is installed between the base of the firebox and the combustible flooring. See Figure 6.
Figure 5 - Minimum Clearance above
Combustible Flooring
Figure 6 - Minimum Clearance above Combustible
Flooring with Non-Combustible Material Installed at
Base of Fireplace
Combustible
Material
6" Minimum
14" Minimum
Can Be
Less than 6" Non-Combustible
Material
CLEARANCES AND HEIGHT REQUIREMENTS

26D4720 9
12"
10"
8"
6"
21/2"
12"
16"
19"
21"
23"
CLEARANCES AND HEIGHT REQUIREMENTS
5. Mantel clearances: The canopy supplied with the unit must be installed. If a combustible mantel is installed, it must
meet the clearance requirements as shown in Figure 7A. However, if lower mantel height is desired, see page 15 and
Figure 7B.
Figure 7A - Mantel Clearances Figure 7B - Mantel Clearances for Wide Profile
Canopy Only.
FIREPLACE
WALL
COMBUSTIBLE
MATERIAL AREA
HOOD
TOP VIEW
Figure 8- Mantel Clearances

10 26D4720
H
G
D
F
E
A
C
B
A
81/4"
1/2"-5/8"
C
A
G
C
G
A½"-⅝"
FIREPLACE FRAMING
Firebox framing can be built before or after the appliance is set in place. Construct firebox framing following Figures 9
through 12 and the chart below for your specific installation requirements. See Figure 1 on Page 6 for firebox dimensions.
The framing headers may rest on the top of the firebox standoffs.
The firebox may be installed directly on a combustible floor or raised on a platform of an appropriate height. When the
firebox is installed directly on carpeting, tile, or other combustible material, other than wood flooring, the firebox shall be
installed on a metal or wood panel extending the full width and depth of the enclosure.
MCUF36D MCUF42D
A 411/4" 471/4"
B 373/4" 373/4"
C 32" 38"
D 163/8" 193/8"
E 687/8" 747/8"
F 341/2" 371/2"
G 173/4" 173/4"
H 483/4" 53"
Figure 9 - Corner Installation
Figure 11 - Stud Location
Figure 10 - Inside Chase
Installation
Figure 12 - Recessed Installation
Do not fill spaces around firebox with
insulation or other materials. This
could cause a fire.
WARNING
Combustibles may not come any closer to the top of the
enclosure than the standoffs will allow.

26D4720 11
K
J
FIREPLACE FRAMING
MCUF36D MCUF42D
with Trim with Trim
K42" 473/4"
J381/8" 381/8"
1. Bend out the nailing flanges located on each side of the firebox.
2. Slide the firebox into prepared framing or position firebox in its final position and frame later.
3. Level the firebox by checking the top edge of the firebox. Shim if necessary.
4. Anchor firebox to the side framing members using 8d nails or other suitable fasteners. See Figure 14.
5. The canopy must be installed for safe operation of the heater. See page 13 for canopy installation details.
When finishing a custom cabinet, mantel, or other built-in enclosure,
the opening size to accommodate the fireplace with trim installed
is as follows:
Figure 13 - Custom Cabinet
Figure 14 - Location of Nailing Flanges
Nail Sides
Through Nailing
Flanges
The fireplace must be installed giving
full consideration to the clearance and
height requirements identified in this
manual.
WARNING

12 26D4720
GAS LINE INSTALLATION
Consult all local codes. All gas piping must be installed to comply with local codes, or in the absence of local codes, with
the latest edition of the National Fuel Gas Code ANSI Z223.1/NFPA54.
Remove the baseplate for ease of gas line installation. Remove three (3) screws along the front edge of the baseplate.
Remove four (4) screws which secure the baseplate to the combustion casing (two at rear and one along each side).
Replace baseplate prior to connecting gas line to heater. Consult heater installation and operating instructions for correct
installation of the heater into the firebox.
The 1/2" gas line may enter either from the left side or right side of the firebox. Gas access holes are provided on
both sides of the firebox.
A listed manual shutoff valve must be installed upstream of the appliance. A union tee and plugged 1/8" NPT pressure tap-
ping point should be installed upstream of hte appliance.
IMPORTANT: Install main gas valve (equipment shutoff valve) in an accessible location. The main gas valve is for turning
on or shutting off the gas to the fireplace.
A sediment trap may be upstream of the heater to prevent moisture and contaminants from passing through trap to the heater
controls and burners. Failure to do so could prevent the heater from operating reliably. Consult applicable codes.
An external regulator must be used on all propane / L.P.G. heaters, in addition to the regulator fitted to the heater,
to reduce the supply tank pressure to 13" w.c. (maximum). Any copper tubing used to supply propane / L.P.G. from
the tank must be internally tinned.
Note: When connecting propane / L.P.G. vent-free room heaters, you must use pipe sealant resistant to
propane / L.P.G.
Important: Hold heater regulator with a wrench to prevent movement when connecting to inlet piping.
Check gas type: The gas supply must be the same as stated on the heater’s rating plate. If the gas supply
is different, DO NOT INSTALL THE HEATER. Contact your dealer for the correct model.
After completing connection, test all gas joints from the gas meter to the gas heater regulator for leaks. Using soap and
water solution or a gas sniffer. DO NOT USE AN OPEN FLAME.
Plumbing connections should only be performed by a qualified, licensed plumber. Main
gas supply must be off when plumbing gas line to fireplace or performing service.
WARNING
Connecting directly to an unregulated
propane / L.P.G. tank can cause an
explosion.
WARNING
Do not connect directly to natural gas 1/2 PSI or 2 PSI systems. Always make sure
natural gas pressure is regulated 10.5 w.c. (maximum before operating the unit).
WARNING

26D4720 13
CANOPY INSTALLATION
INSTALLING CANOPY
A canopy is furnished with each firebox and MUST be installed for safe operation. See Figure 15.
1. Remove the three (3) screws from the top front frame assembly. Also remove the two (2) screws on the side frames.
See Figure 15.
2. Align the canopy with the holes in the top frame.
3. Replace the screws previously removed.
4. Tighten side screws. Make sure the canopy is level and
secure.
The firebox canopy must not be
modified or replaced with a canopy
that maybe provided withthe unvented
decorative room heater.
WARNING
Close fireplace screen panel before
operating a decorative type unvented
room heater.
WARNING
Figure 15 - Installing Canopy

14 26D4720
Thermostat
Control
Fan Switch
OFF
ON
Black
White
Green
110/115
V.A.C. Black
Blower
Motor
OPTIONAL EQUIPMENT
FORCED AIR KIT (BLOTMC)
If you are installing the forced air kit, Model BLOTMC, on MCUF36D or MCUF42D models, see the installation instructions
provided with the kit for electrical wiring requirements, or the blower installation section. The firebox must be connected
to main power supply at time of firebox installation. The blower must be installed prior to the installation of the vent-free
heater. The electrical connections must be made before the firebox is framed and enclosed in the finished walls.
Electrical connections should only be performed by a qualified, licensed electrician,
main power must be off when connecting to main electrical power supply or performing
service.
The blower when installed, must be electrically grounded in accordance with local
codes or in the absence of local codes, with the National Electrical CodeANSI Z..223.1/
NFPA 70.
WARNING
Any of the original wire as supplied with the fireplace must
be replaced. Contact dealer for proper replacement wiring
harness. (see parts list for part number). 120 volts, 60Hz,
1 amps.
Electrical power cord (plug) can be routed to exit the
MCUF36D/MCUF42D on either the left side or the right side.
Remove cord protector from side of unit, route power cord
through hole opposite side. Reinstall cord protector.
This fireplace has a three-prong, grounded electrical plug. This plug helps protect
you against electrical shock. Only connect plug to a properly grounded, three-prong
receptacle. Do not cut or remove the grounded prong from this plug.
WARNING
Never attempt to service heater while it
is plugged in, operating, or hot. Burns
and/or electrical shock could result.
WARNING
Figure 16 - BLOTMC Wiring Diagram
IMPORTANT: Always check local building
codes. The installation must comply with local
regulations as well as the national electric codes.
BRASS OR CHROME TRIM
Optional brass trim kits can be used with unit when installed as a free standing fireplace with wood surround.
OPTIONAL WIDE CANOPY
The optional wide canopy can be installed. See installation instructions provided with kit.

26D4720 15
1
4
5Ê
2
3
*Not illustrated, see following page.
ILLUSTRATED PARTS LIST
ITEM DESCRIPTION QTY MCUF36D MCUF42D
1 Canopy 1 71D0500 71D1000
2 Screen Panel 2 26D4562 26D45622
3 Screen Rod 2 26D0132K 26D0133K
ACCESSORIES IN KITS
1 Standard Brass Canopy 1 BRCU36 BRCU42
1 Wide Brass Canopy 1 BRC36 BRC42
4 Blower w/ Rheostat 1 BLOTMC BLOTMC
5 Brass Trim Curved Design 1 BRTKM36 BRTKM42
5 Pewter Trim Curved Design 1 PWTKM36 PWTKM42
5
Black Trim Curved Design 1 BLTKM36 BLTKM42
6 Outside Air Kit* 1 AK-4 AK-4

16 26D4720
USING OPTIONAL AK-4 OUTSIDE AIR KIT
8'max.
COMBUSTION AIR
1. Locate combustion air assembly at an exterior location which is not likely to be accidentally blocked in any manner.
Locate assembly a min. of 12" above the snow line to prevent blockage by snow accumulation.
2. Never mount the combustion air inlet assembly in a garage or storage area where combustible fumes such as gasoline
might be drawn into the fireplace.
3. Combustion air can be drawn from the crawl space under a house when an adequate supply of air is provided by open
ventilation.
4. CAUTION: Do not take combustion air from attic space or garage space.
5. Locate air supply inlet at least 3' away from any appliance vent terminal.
6. Avoid extremely long runs and numerous turns in the duct leading from the fireplace to the combustion air assembly.
These conditions increase the resistance to the free flow of air through the duct. See Figures 17 through 20 for methods
of installing the outside air for combustion assemblies.
Figure 17 - Basement Installation Figure 18 - Concrete Slab Installation
(Optional Outside Air Runs)
Above
Snow
Level
Ground
Level
Basement
Wall
Firestop Spacer
Inlet Grill in
Soffit
(Overhang)
Figure 20 - 45° Corner Installation on
Slab Floor
Figure 19 - Installation Above Basement or
Crawl Space
Inside Wall
Outside
Wall
Duct Extended
to Miss Joist
To Outside Wall
Note: Fireplace model in illustrations may not be representative of your appliance.

26D4720 17
USING OPTIONAL AK-4 OUTSIDE AIR KIT
The use of outside air for combustion is optional unless required by building codes. It is only necessary to supply outside
combustion air to one side of the fireplace. Use the model AK4 combustion air kit.
MODEL AK-4 COMBUSTION AIR ASSEMBLY
1. Remove the cover plate from the 4" outlet opening location on the left or
right outside of the fireplace.
2. Place the insulation ring between the AK-4 starting collar and fire-
place wall.
3. Place the starting collar (4") into the hole on the side of fireplace. Fasten it in place with the four sheet metal screws
provided. See Figures 21 and 22.
Note: The air starting collar extends through the fireplace outer wrap. When the air starting collar is
securely attached, it will form a seal against the fireplace wall.
4. Attach outside duct to starting collar with duct clamp or screws. See Figure 22.
DO NOT remove the
cover if the outside air
will not be connected.
WARNING
Figure 21 - Attaching Outside Air Starting Collar
and Insulation Ring to Left Side of Fireplace
Figure 22- Attaching Outside Duct
to Starting Collar
Insulation Ring
AK-4 Starting
Collar
Sheet
Meal
Screws
Left Side of
Fireplace
Shorter End
of Air Starting
Collar
Air Starting
Collar
Duct
Screws
Left Side of
Fireplace
5. Cut a 6-inch diameter opening for modelAK-4 in the outside
wall covering where the outside vent is to be located. See
Figure 23.
6. Select and cut a piece of duct long enough to attach to the
fireplace and stick out at least 3" beyond the face of the wall
to which theAK-4 inlet air vent will be attached. See Figure
22.
Figure 23 - Combustion Air Assembly for
Model No. AK-4
Nail
Holes
UseFP-4Uductformaximumefficiency
and safety. Do not use a combustible
duct. Always use UL Listed Class 0 or
1 duct material.
WARNING
6" Diameter
Hole
Duct
Extending
3"min.
AK-4 Inlet
Air Vent
Screw
Screws
Continued

18 26D4720
MODEL AK-4 COMBUSTION AIR ASSEMBLY (CONTINUED)
7. If the duct is the insulated type, push the insulation back from one end of
the duct approximately 2". See Figure 24.
8. Slip the exposed end of the duct over the starting collar on the fireplace.
9. Using the sheet metal screws provided, secure the duct end to the collar
attached to the fireplace.
10. Nail or screw the combustion air assembly to the surface of the wall.
Note: If the wall covering is brick or stone, use appropriate
masonry fasteners. If necessary, splice the duct. Use a model
403-duct connector to splice duct sections.
INSTALLING MODEL 403 DUCT CONNECTOR
1. Push insulation back approximately 2" from the end of each duct.
2. Slip each duct over duct connector until an equal length of connector extends into each duct.
3. Place duct clamp over the end of each duct. Tighten duct clamp down snuggly.
4. Push insulation back into place and over duct clamp.
Figure 24 - Installing Duct
Connector 403
Approximately
2"
Insulation
Duct
Connector
Duct Clamp
USING OPTIONAL AK-4 OUTSIDE AIR KIT

26D4720 19
NOTES

JUNE 2008 P/N 26D4720 • Rev. 7
MONESSEN HEARTH SYSTEMS
LIMITED LIFETIME WARRANTY POLICY
The following components are warranted for life to the original owner, subject of proof of purchase: Firebox,
Combustion Chamber, Heat Exchanger, Grate, and Stainless Steel Burners.
FIVE YEAR WARRANTY
The following components are warranted for 5 years to the original owner, subject of proof of purchase: Vent Free
Ceramic Fiber Logs, Catalytic Filter and Aluminized Burners.
BASIC WARRANTY
Monessen Hearth Systems (MHS) warrants the components and materials in your gas appliance to be free from
manufacturing and material defects for a period of two years from date of installation. After installation, if any of
the components manufactured by MHS in the appliance are found to be defective in materials or workmanship,
MHS will, at its option, replace or repair the defective components at no charge to the original owner. MHS will
also pay for reasonable labor costs incurred in replacing or repairing such components for a period of two years
from the date of installation. Any products presented for warranty repair must be accompanied by a dated proof
of purchase.
This Limited Lifetime Warranty will be void if the appliance is not installed by a qualified installer in accordance
with the installation instructions. The Limited Lifetime Warranty will also be void if the appliance is not operated
and maintained according to the operating instructions supplied with the appliance, and does not extend to (1)
firebox/burner assembly damage by accident, neglect, misuse, abuse, alteration, negligence of others, including
the installation thereof by unqualified installers, (2) the costs of removal, reinstallation or transportation of
defective parts on the appliance, or (3) incidental or consequential damage. All service work must be performed
by an authorized service representative.
This warranty is expressly in lieu of other warranties, express or implied, including the warranty of merchantability
of fitness for purpose and of all other obligations or liabilities. Monessen Hearth Systems, Inc. does not
assume for it any other obligations or liability in connection with the sale or use of the appliance. In states
that do not allow limitations on how long an implied warranty lasts, or do not allow exclusion of indirect
damage, those limitations of exclusions may not apply to you. You may also have additional rights not covered
in this Limited Lifetime Warranty.
MHS reserves the right to investigate any and all claims against the Limited Lifetime Warranty and decide
upon method of settlement.
For information about this warranty, contact:
Technical Services
Monessen Hearth Systems
149 Cleveland Drive
Paris, Kentucky 40361