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.