Monessen Hearth GCUF Series User manual

710530
GCUF cover
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.
WARNINGS
– Do not store or use gasoline or other
ammable vapors and liquids in the
vicinity of this or any other appliance.
– WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do
not use any phone in your building.
• Immediately call your gas supplier
from a neighbor's phone. Follow the
gas supplier's instructions.
• If you cannot reach your gas supplier,
call the re department.
– Installation and service must be
performed by a qualified installer,
service agency or the gas supplier.
For use with a listed gas-red unvented
decorative room heater not to exceed
40,000 BTU/hr. Do Not Build a Wood Fire.
Carefully review the instructions supplied
with the decorative type unvented room
heater for the minimum fireplace size
requirement.
DO NOT INSTALL AN APPLIANCE IN THIS
FIREBOX UNLESS THIS FIREBOX MEETS
THE MINIMUM DIMENSIONS REQUIRED
FOR THE INSTALLATION.
INSTALLER: Leave this manual with the appliance.
CONSUMER: Retain this manual for future reference.
Unvented Fireboxes
Installation and Operating Instructions
Models: GCUF, GRUF
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev F • 05/19

2
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
CONTENTS
PLEASE READ THE INSTALLATION & OPERATING INSTRUCTIONS BEFORE USING APPLIANCE.
Thank you and congratulations on your purchase of a Monessen vent free rebox.
IMPORTANT: Read all instructions and warnings carefully before starting installation. Failure to follow these
instructions may result in a possible re hazard and will void the warranty.
Important Safety Information .....................................3
General Installation Information ................................5
Before You Start......................................................5
What You Will Need for Installation.........................5
Firebox and Framing Dimensions..............................6
Hearth Dimensions......................................................7
Firebox Location..........................................................7
Minimum Clearances...................................................8
Firebox Framing ..........................................................9
Fireplace Installation.................................................10
Canopy Installation ...................................................10
Gas Line Installation ................................................. 11
Combustion Air..........................................................12
Optional AK4 Outside Air Kit .................................13
Model 403 Duct Connector ...................................14
Optional Equipment ..................................................15
Service Parts .............................................................16
Warranty .....................................................................19
►

3
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
13. Correct installationoftheceramicberlogs,proper
location of the heater, and annual cleaning are neces-
sary to avoid potential problems with sooting. Sooting,
resulting from improper installation or operation, can
settleonsurfacesoutsidethereplace.Seelogplace-
ment instructions for proper installation.
14. Avoidanydraftsthatalterburneramepatterns.Donot
allowfanstoblowdirectlyintoreplace.Donotplace
ablowerinsideburnareaofrebox.Ceilingfansmay
createdraftsthatalterburneramepatterns.Sooting
and improper burning will occur.
15. CAUTION: Candles, incense, oil lamps, etc. produce
combustion byproducts including soot. Vent-free
appliances will not lter or clean soot produced by
these types of products. In addition, the smoke and/
or aromatics (scents) may be re-burnt 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.
16. Anunventedgas-red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.
17. Keep room area clear and free from combustible
materials,gasolineandotherammablevaporsand
liquids.
18. Unvented gas heaters are a supplemental zone heater.
They are not intended to be a primary heating appli-
ance.
19. 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.
20. During manufacturing, fabricating and shipping, various
components of this appliance are treated with certain
oils,lmsorbondingagents.Thesechemicalsarenot
harmful but may produce annoying smoke and smells
astheyareburnedo󰀨duringtheinitialoperationofthe
appliance; possibly causing headaches, or eye or lung
irritation. This is a normal and temporary occurrence.
IMPORTANT SAFETY INFORMATION
8. CARBON MONOXIDE POISONING: Early signs of
carbonmonoxidepoisoningaresimilartotheu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.
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ventlessrebox
enclosures for gas-red unvented decorative room
heaters.
11. Do not install the unvented heater in a bathroom.
12. Do not install the unvented heater in a bedroom unless
the maximum input rating is equal to or less than
10,000 Btu/hr.
Continued on page 4
INSTALLER
Please leave these instructions with the appliance.
OWNER
Please retain these instructions for future reference .
WARNING!
• 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 re, burns, explosion or
carbon monoxide poisoning.
• Do not allow fans to blow directly into the replace. Avoid any drafts that alter burner ame patterns.
• Do not use a blower insert, heat exchanger insert or other accessory, not approved for use with this heater
where applicable.
1. Due to high temperatures, the rebox should be
locatedoutoftra󰀩c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rebox.
4. Donotplaceclothingorotherammablematerial
nearthereplacewhenthereboxisinuse.
5. Any safety screen or guard removed for servicing,
must be replaced prior to operating a heater within
therebox.
6. Installationandrepairshouldbedonebyaqualied
service person.
7. To prevent malfunction and/or sooting, an unvented
gasheater/reboxshouldbecleanedatleastannu-
ally by a professional service person. More frequent
cleaning may be required due to excessive lint from
carpeting, etc. It is imperative that control compart-
ments, burners and circulating air passageways be
kept clean.

4
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
IMPORTANT SAFETY INFORMATION
Continued from page 3
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.
21. 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.
22. 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 pres-
sures in excess of 1/2 psig (3.5 kPa).
23. The appliance must be isolated from the gas supply
pipingsystembyclosingitsequipmentshuto󰀨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).
24. Do not use this room heater if any part has been under
water.Immediatelycallaqualiedservicetechnician
to inspect the room heater and to replace any part of
the control system and any gas control which has been
under water.
25. Neverburnsolidfuelsinareplacewhereaunvented
room heater is installed.
26. Always have a replace screen in place when the
appliance is in operation, and unless other provisions
for combustion air are provided, the screen shall have
an opening(s) for induction of combustion air.
27. Donotllspacesaroundthereboxwithinsulationor
other materials. These spaces must be maintained to
preventthereboxfromcomingincontactwithcom-
bustible materials.
Nous recommandons que nos
appareils de chauffage au gaz
soient installés et entretenus par
des professionnels qui ont été
accrédités aux È.U. par le National
Fireplace Institute ® (NFI) comme
étant des spécialistes du NFI en
matièred’appareils de chauffage
au gaz.
WARNING!
Do not attempt to burn solid wood fuels, vented
gas log sets, or any other combustible in this
unvented rebox. Also, do not install a vent-
free gas log set in this rebox if the minimum
clearance and height requirements of the log
set are too large for the rebox.
Notice: Illustrations shown in this manual reect
“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 specic installation requirements.
WARNING: This product and the
fuels used to operate this product (liquid
propane or natural gas), and the products
of combustion of such fuels, can expose
you to chemicals including benzene, which
is known to the State of California to cause
cancer and reproductive harm. For more
information go to: www.P65Warnings.
ca.gov.

5
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
GENERAL INSTALLATION INFORMATION
ThenewGCUFandGRUFSeriesarevent-freereboxes.
They feature a self contained heat-circulating system.
This installation manual will enable you to obtain a safe,
e󰀩cient and dependable installation of your vent-free
replacesystem.
Donotalterormodifythereboxoritscomponentsunder
anycircumstances.Anymodicationoralterationofthe
reboxsystem,includingbutnotlimitedtotherebox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 that all listed parts have been received. You should
have the following:
1. Vent-Free Gas Firebox
2. Canopy
3. Installation and Operating Instructions
4. Five (5) sheet metal screws for canopy
WHAT YOU WILL NEED FOR INSTALLATION
TOOLS and BUILDING SUPPLIES
•Phillips screwdriver •Square
•Framing materials •Hammer
•Saw and / or saber saw •Tee joint
•Level •Pipe wrench
•Measuring tape •Pliers
•Electric drill and bits
•Fireplace surround materials (noncombustible)
•Caulking material (noncombustible)
• Wallnishingmaterials
• Piping complying with local codes
•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.
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, how-
ever,andmightrequireadi󰀨erentsequence.
1. Positionreboxpriortoframingorintopreparedfram-
ing.
2. Field wire main power supply to models with fan kit.
(Electrical connections should only be performed by an
experienced,licensed/certiedtradesman).
3. Plumb gas line. (Gas connections should only be per-
formed by an experienced, licensed/certied trades-
man).
4. Install vent-free gas log heater per the instructions
provided with the vent-free gas log heater.
5. Complete nish wall material, surround and optional
hearth extension to your individual taste.

6
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
FIREBOX DIMENSIONS
2¹⁄₂”B
2¹⁄₂”
A
Rough
Opening
Height
D
F
C
Rough
Opening
Depth
M - Rough Opening Width 1/2” - 5/8”
O
Q
P
P
R
710530
GCUF dims
I
1¹⁄₄”
6”
1⁵⁄₁₆”
5⁷⁄₁₆”
N21³⁄₄”
E
H
J
L
G
K
34³⁄₄”
Ref. GCUF32C/GRUF32C GCUF36C/GRUF36C GCUF42C/GRF42C
A 37" 41" 47"
B 32" 36" 42"
C 16" 18" 18"
D 29" 32" 38"
E 185⁄8" 205⁄8" 205⁄8"
F 233⁄8" 273⁄8" 333⁄8"
G 131⁄4" 153⁄4" 153⁄4"
H 18" 175⁄8" 175⁄8"
I 297⁄8" 34" 40"
J 71⁄8" 93⁄4" 93⁄4"
K 8" 81⁄4" 81⁄4"
L 23⁄4" 21⁄4" 21⁄4"
M 371⁄4" 411⁄4" 471⁄4"
N 35" 35" 35"
O 151⁄2" 171⁄2" 171⁄2"
P 433⁄4" 483⁄4" 53"
Q 613⁄4" 687⁄8" 747⁄8"
R 307⁄8" 341⁄2" 371⁄2"
Figure 1 -
Firebox and Framing Dimensions

7
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
HEARTH DIMENSIONS and FIREBOX LOCATION
A
B
C
DE
FP2901
hearth dims
Ref. GCUF/GFRUF32C GCUF/GRUF36C GCUF/GRUF42C
A 297⁄8" 34" 40"
B 131⁄4" 153⁄4" 153⁄4"
C 233⁄8" 273⁄8" 333⁄8"
D 217⁄8" 217⁄8" 217⁄8"
E 18" 175⁄8" 175⁄8"
Figure 2 -
Minimum Hearth Dimensions
LOCATION OF FIREBOX
Carefully select the best location for installation of your
vent-free rebox. 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 main-
tained.
• Location must not be a󰀨ected 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 com-
bustion air.
• Locationshouldbeoutofhightra󰀩c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rebox
orrestricttheowofcombustionandventilationair.
• Minimizemodicationstoexistingconstruction.Refer
to Figure 3 below for location suggestions.
• Do not install in the vicinity where gasoline or other
ammableliquidsmaybestored.Thevent-freerebox
must be kept clear and free from these combustible
materials.
FP2440
fireplace locations
Figure 3 -
Location of Firebox
FP2440

8
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
Ensure that minimum clearances shown in Figures 4
through 8 are maintained. Left and right clearances are
determinedwhenfacingthefrontoftherebox.
Follow these instructions carefully to ensure safe instal-
lation. Failure to follow these requirements may create a
rehazard.
1. Sidewall clearances: The clearance from the inside
of the appliance to any combustible wall should not be
less than 9". Figure 4
2. Ceiling clearance: The ceiling must be at least 42"
fromthetopofthereboxopening.Figure 4
3. Back wall clearance: The appliance may be placed
against a combustible back wall.
MINIMUM CLEARANCES
9"
Minimum
42"
Minimum
9"
Minimum
FP2687
minimum clearances
FP2687
Figure 4 -
Clearance and Height Requirements
4. 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 5. However, if lower mantel height is desired,
refer to Page 14, Figure 6.
NOTE: The Monessen Barrington Cabinet Mantel Model
series BWC300, BWC400 and BWC500 are specially
designed to comply with all mantel temperature require-
ments. Any custom-built mantel must comply with all
clearance requirements shown in this instruction manual.
12”
10”
8”
6”
2¹⁄₂”
12”
16”
19”
21”
23”
FP2690
Mantel clearances
Combustible
Material Can
Contact Top
of Fireplace
FP2690
Noncombustible Material
Only if Needed to Cover
Radiant Top Face
Figure 5 -
Mantel Clearances
12”
8”
8”
14”
FP2691
mantel clear wide canopy
FP2691
Figure 6 -
Mantel Heights for Wide Prole Canopy
45°
1”
2¹⁄₂”
3”
5”
6”
1¹⁄₂”
3¹⁄₂”
4¹⁄₂”
FP2692
mantel leg clearance
6”
7¹⁄₂”
7¹⁄₂”
9”
Finish Wall
Combustible
Material Area
FP2692
Figure 5a -
Mantel Leg Clearance

9
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
FP2688
min floor combustible
5" Minimum
Combustible
Material
FP2688
Figure 7 -
Minimum Clearance Above
Combustible Flooring
MINIMUM CLEARANCES and FRAMING
14” Minimum
FP2689
min floor clear noncomb
Can be Less
Than 5" Noncombustible
Material
FP2689
Figure 8 -
Minimum Clearance above Combustible Flooring with
Noncombustible Material Installed at Base of Fireplace
FIREBOX FRAMING
Firebox framing can be built before or after the appliance
issetinplace.ConstructreboxframingfollowingFigure
1foryourspecicinstallationrequirements.See Figure 1
on Page 6 forreboxdimensions.Theframingheaders
mayrestonthetopoftherebox.
Thereboxmaybeinstalleddirectlyonacombustibleoor
or raised on a platform of an appropriate height. When
thereboxisinstalleddirectlyoncarpeting,tile,orother
combustiblematerial,otherthanwoodooring,therebox
shall be installed on a metal or wood panel extending the
full width and depth of the enclosure.
Theclassication"noncombustiblematerial"includes,but
is not limited to: stone, brick, and mortar. Noncombustibles
are safe to overlay the black-painted metal face, including
radiantplates,anddonotposearehazard.Anynoncom-
bustiblenishmaterialmustnotextendpastorinterfere
withthereplaceopening.
Theclassication"combustiblematerial"includes,butis
not limited to: plywood, drywall, and particle board. Com-
bustible materials may contact the sides, bottom, or back
oftherebox.Donotoverlaytheblackpaintedfacewith
combustible materials.
WARNING!
Do not ll spaces around rebox with insulation
or other materials. This could cause a re.
WARNING!
The fireplace must be installed giving full
consideration to the clearance and height
requirements identied in this manual.
5. Floor clearance: Thisinnerchamberreboxoormust
beinstalledatleast5"aboveanycombustibleooring
material, such as carpeting or asphalt tile, which is
closerthan14"tothebaseoftherebox.Figure 7
OR
Theinnerchamberreboxoormaybeinstallednearerto
theoorifaminimumof14"ofnoncombustiblematerial
such as slate or marble is installed between the base of
thereboxandthecombustibleooring. Figure 8

10
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
FIREPLACE and CANOPY INSTALLATION
Whennishingacustomcabinet,mantel,orotherbuilt-in
enclosure,theopeningsizetoaccommodatethereplace
with trim installed is as follows:
Figure 10 -
Custom Cabinet
A
B
FP2694
custom cabinet
GCUF32C GCUF36C GCUF42C
Ref. w/Trim w/Trim w/Trim
A 377⁄8" 417⁄8" 477/8"
B 357⁄8" 357⁄8" 357⁄8"
INSTALLING CANOPY
A canopy is furnished with each rebox and MUST be
installed for safe operation. Figure 11
1. Align the canopy with the holes in the top frame.
2. Secure the screws as shown.
3. Tighten side screws. Make sure the canopy is level and
secure.
Figure 11 -
Installing Canopy
FP2451
install canopy
Screws
Canopy FP2451
WARNING!
The rebox canopy must not be modied or
replaced with a canopy that may be provided
with the unvented decorative room heater.
WARNING!
Close replace screen panel before operating a
decorative type unvented room heater.
1. Bendoutthenailingangeslocatedoneachsideofthe
rebox.
2. Slidethereboxintopreparedframingorpositionrebox
initsnalpositionandframelater.
3. Levelthereboxbycheckingthetopedgeoftherebox.
Shim if necessary.
4. Anchorreboxtothesideframingmembersusing8d
nails or other suitable fasteners. Figure 9.
5. The canopy must be installed for safe operation of the
heater.
FP2902
nailing flanges
Nail Sides Through
Nailing Flanges
FP2902
Figure 9 -
Location of Nailing Flanges

11
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
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.
The 1/2" gas line may enter either from the left side or right
sideoftherebox.Gasaccessholesareprovidedonboth
sidesoftherebox.
Alistedmanualshuto󰀨valvemustbeinstalledupstreamof
the appliance. A union tee and plugged 1/8" NPT pressure
tapping point should be installed upstream of the appliance.
IMPORTANT: Install main gas valve (equipment shuto󰀨
valve) in an accessible location. The main gas valve is
for turning on or shutting o󰀨 the gas to the replace.
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 appli-
cable codes.
An external regulator must be used on all propane/L.P.G.
heaters,inadditiontotheregulatortted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 di󰀨erent, 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sni󰀨er. DONOTUSE
AN OPEN FLAME.
WARNING!
Plumbing connections should only be performed
by a qualified, licensed plumber. Main gas
supply must be o󰀨 when plumbing gas line to
replace 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).

12
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
COMBUSTION AIR
COMBUSTION AIR
1. Locate combustion air assembly at an exterior location
which is not likely to be accidentally blocked in any man-
ner. 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replace.
3. Combustion air can be drawn from the crawl space un-
der 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 ap-
pliance vent terminal.
6. Avoid extremely long runs and numerous turns in the
ductleadingfromthereplace to the combustion air
assembly. These conditions increase the resistance to
thefreeowofairthroughtheduct.Refer to Figures
12 through 15 for methods of installing the outside air
for combustion assemblies.
FP2459
OA basement install
Above
Snow
Level
Ground
Level FP2459
Figure 12 -
Basement Installation
15' Max.
FP2460
OA slab install
Inlet Grille
inSo󰀩t
(Overhang)
FP2460
Figure 13 -
Concrete Slab Installation
(Optional Outside Air Runs)
FP2461
above basement
Duct
Extended
to Miss
Joist
FP2461
Figure 14 -
Installation Above Basement or
Crawl Space
To Outside Wall
FP2462
OA corner install
Outside
Wall
Inside Wall
FP2462
Figure 15 -
45° Corner Installation
on Slab Floor
NOTE: Fireplace model in illustrations may not be
representative of your appliance.

13
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
COMBUSTION AIR
WARNING!
DO NOT remove the cover if the outside air
will not be connected.
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replace.Usethe
model AK4 combustion air kit.
MODEL AK4 COMBUSTION AIR ASSEMBLY
1. Remove the cover plate from the 4" outlet opening
locationontheleftorrightoutsideofthereplace.
2. Place the insulation ring between the AK4 starting collar
andreplacewall.
3. Place the starting collar (4") into the hole on the side
ofreplace.Fastenitinplacewiththefoursheetmetal
screws provided. Figures 16 and 17
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
replace wall.
FP1900
OA start collar
8/08
Figure 16 -
Attach Outside Air Starting Collar and Insulation
Ring to Left Side of Fireplace
Insulation
Ring
AK4 Starting
Collar
Sheet Meal
Screws
Left Side of
Fireplace
Shorter End
of Air Starting
Collar
4. Attach outside duct to starting collar with duct clamp or
screws. Figure 17
5. Cut a 6-inch diameter opening for model AK4 in the
outside wall covering where the outside vent is to be
located. Figure 18
6. Select and cut a piece of duct long enough to attach to
thereplaceandstickoutatleast3"beyondthefaceof
the wall to which the AK4 inlet air vent will be attached.
Cut duct with a standard pocket knife. Figure 17
FP2700
OA duct
Screws
Air Starting
Collar
Duct
Left Side of
Fireplace
FP2700
Figure 17 -
Attach Outside Duct to Starting Collar
FP1904
AK4 install
8/08
6"
Diameter
Hole
Duct
Extending
3" Min.
Screws
Nail
Hole
Screws
AK4 Inlet Air
Vent
Figure 18 -
Combustion Air Assembly for Model
AK4
FP1904
WARNING!
Use FP-4 U duct for maximum e󰀩ciency and
safety. Do not use a combustible duct. Always
use UL Listed Class 0 or 1 duct material.

14
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
COMBUSTION AIR
7. If the duct is the insulated type, push the insulation back
from one end of the duct approximately 2". Figure 19
8. Slip the exposed end of the duct over the starting collar
onthereplace.
9. Using the sheet metal screws provided, secure the duct
endtothecollarattachedtothereplace.
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.
INSTALL 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.
FP1907
Duct connector
8/08
Approximately
2”
Figure 19 -
Install Duct Connector 403
Insulation
Duct
Connector
Duct Clamp
Duct
FP1907

15
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
OPTIONAL EQUIPMENT
FORCED AIR KIT (BLOTMC)
If you are installing the forced air kit on GCUF or GRUF models, see the installation instruc-
tions provided with the kit for electrical wiring requirements, or the blower installation section.
Thereboxmustbeconnectedtomainpowersupplyattimeofreboxinstallation.Theblower
must be installed prior to the installation of the vent-free heater. The electrical connections
mustbemadebeforethereboxisframedandenclosedinthenishedwalls.
BRASS OR PEWTER LOUVERS AND FILIGREE
Optional brass or pewter louver kits may be installed in place of the factory installed black
louvers. Refer to installation instructions provided with the brass or pewter louvers.
OPTIONAL TRIM
Optionaltrimkitscan be usedwithunitwheninstalledas afreestandingreplacewith
wood surround.
FIREBRICK
Optionalrebrickkitscanbeinstalled.Seeinstallationinstructionsprovidedwithkit.
OPTIONAL WIDE CANOPY
The optional wide canopy can be installed. See installation instructions provided with kit.
WARNING!
Electrical connections should only be
performed by a qualied, licensed electrician,
main power must be o󰀨 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 Code ANSI/NFPA 70.

16
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
SERVICE PARTS
Service Parts GCUF32C-F / -R, GRUF32C-F / -R
Beginning Manufacturing Date: N/A
Ending Manufacturing Date: Active
IMPORTANT: THIS IS DATED INFORMATION. Parts must be ordered from a dealer or distributor.
Hearth and Home Technologies does not sell directly to consumers. Provide model number
and serial number when requesting service parts from your dealer or distributor.
Stocked
at Depot
ITEM DESCRIPTION COMMENTS PART NUMBER
1 Canopy Black Paint 71D0023K
Texture Paint 71D0023TK
2 Screen Panel Qty 2 req SRV61D0001
3 Screen Rod Qty 2 req 26D0138K
4 Black Louver Assembly (GCUF Only) Top 54D0900TK
Bottom 54D0901TK
Accessories
5 Blower w/Rheostat BLOTMC
6Black Trim Curved Design BLTK32C
Black Trim Kit BLMTK32C
7.1 Refractory, Right 71D0045K Y
Cottage Clay 71D0042K
7.2 Refractory, Left 71D0044K Y
Cottage Clay 71D0041K Y
7.3 Refractory, Back 71D0043K
Cottage Clay 71D0040K Y
Outside Air Kit AK4
5/19
1
2
4
7.1
6
4
3
7.3
7.2 5

17
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
SERVICE PARTS
Service Parts GCUF36C-F / -R, GRUF36C-F / -R
Beginning Manufacturing Date: N/A
Ending Manufacturing Date: Active
IMPORTANT: THIS IS DATED INFORMATION. Parts must be ordered from a dealer or distributor.
Hearth and Home Technologies does not sell directly to consumers. Provide model number
and serial number when requesting service parts from your dealer or distributor.
Stocked
at Depot
ITEM DESCRIPTION COMMENTS PART NUMBER
1 Canopy Black Paint 71D0011K
Texture Paint 71D0011TK
2 Screen Panel Qty 2 req SRV61D0001
3 Screen Rod Qty 2 req 26D0132K
4 Black Louver Assembly (GCUF Only) Top 54D0902TK
Bottom 54D0903TK
Accessories
5 Blower w/Rheostat BLOTMC
6Black Trim Curved Design BLTK36C
Black Trim Kit BLMTK36C
7.1 Refractory, Right 71D0518K Y
Cottage Clay 71D0521K Y
7.2 Refractory, Left 71D0517K Y
Cottage Clay 71D0520K
7.3 Refractory, Back 71D0516K Y
Cottage Clay 71D0519K
Outside Air Kit AK4
5/19
1
2
4
7.1
6
4
3
7.3
7.2 5

18
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
SERVICE PARTS
Service Parts GCUF42C-F / -R, GRUF42C-F / -R
Beginning Manufacturing Date: N/A
Ending Manufacturing Date: Active
IMPORTANT: THIS IS DATED INFORMATION. Parts must be ordered from a dealer or distributor.
Hearth and Home Technologies does not sell directly to consumers. Provide model number
and serial number when requesting service parts from your dealer or distributor.
Stocked
at Depot
ITEM DESCRIPTION COMMENTS PART NUMBER
1 Canopy Black Paint 71D1000K
Texture Paint 71D1000TK
2 Screen Panel Qty 2 req SRV61D0003
3 Screen Rod Qty 2 req 26D0133K
4 Black Louver Assembly (GCUF Only) To p 54D0904TK
Bottom 54D0905TK
Accessories
5 Blower w/Rheostat BLOTMC
6Black Trim Curved Design No longer available BLTK42C
Black Trim Kit BLMTK42C
7.1 Refractory, Right 71D0518K Y
Cottage Clay 71D0521K Y
7.2 Refractory, Left 71D0517K Y
Cottage Clay 71D0520K
7.3 Refractory, Back 71D1016K Y
Cottage Clay 71D1017K
Outside Air Kit AK4
5/19
1
2
4
7.1
6
4
3
7.3
7.2 5

19
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
Hearth & Home Technologies
LIMITED LIFETIME WARRANTY
Hearth & Home Technologies, on behalf of its hearth brands (“HHT”), extends the following warranty for HHT gas, wood, pellet and
electric hearth appliances that are purchased from an HHT authorized dealer.
WARRANTY COVERAGE:
HHT warrants to the original owner of the HHT appliance at the site of installaƟon, and to any transferee taking ownership of the
appliance at the site of installaƟon within two years following the date of original purchase, that the HHT appliance will be free from
defects in materials and workmanship at the Ɵme of manufacture. AŌer installaƟon, if covered components manufactured by HHT
are found to be defecƟve in materials or workmanship during the applicable warranty period, HHT will, at its opƟon, repair or replace
the covered components. HHT, at its own discreƟon, may fully discharge all of its obligaƟons under such warranƟes by replacing the
product itself or refunding the veried purchase price of the product itself. The maximum amount recoverable under this warranty
is limited to the purchase price of the product. This warranty is subject to condiƟons, exclusions and limitaƟons as described below.
WARRANTY PERIOD:
Warranty coverage for consumers begins at the date of installaƟon. In the case of new home construcƟon, warranty coverage begins
on the date of rst occupancy of the dwelling or six months aŌer the sale of the product by an independent, authorized HHT dealer/
distributor, whichever occurs earlier. However, the warranty shall commence no later than 24 months following the date of product
shipment from HHT, regardless of the installaƟon or occupancy date. The warranty period for parts and labor for covered components
is produced in the following table.
The term “Limited LifeƟme” in the table below is dened as: 20 years from the beginning date of warranty coverage for gas appliances,
and 10 years from the beginning date of warranty coverage for wood and pellet appliances. These Ɵme periods reect the minimum
expected useful lives of the designated components under normal operaƟng condiƟons.
Page 1 of 2
4021-645K 1/20
Parts Labor Gas Pellet Wood Electric Venting Components Covered
XX Igniters, Auger Motors, Electronic Components, and
Glass
X
Electrical components limited to modules, remotes/wall
switches, valves, pilots, blowers, junction boxes, wire
harnesses, transformers and lights (excluding light bulbs)
XX Molded Refractory Panels, Glass Liners
XVent Free Burners, Vent Free Logs
XX Castings, Medallions and Baffles
6 years 3 years XCatalyst - Limitations Listed
7 years 3 years XX Manifold tubes, HHT Chimney and Terminations
10 years 1 year XBurners, logs and refractory
Limited
Lifetime 3 years XXX Firebox and heat exchanger, FlexBurn®System
(engine, inner cover,access cover and fireback)
1 Year None XXXXXAll replacement parts beyond warranty period
Warranty Period HHT Manufactured Appliances and Venting
All parts including handles, external enamaled
components and other material except as covered by
Conditions, Exclusions, and Limitations listed
2 years
3 years X
x1 Year X X X X
5 years 1 year
Firepots, burnpots, mechanical feeders/auger
assemblies
See conditions, exclusions and limitations on the next page
►

20
GCUF/GRUF Vent-Free Fireboxes
Monessen • GCUF/GRUF Owner Manual • 71D0530 • Rev G • 01/20
WARRANTY CONDITIONS:
• This warranty only covers HHT appliances that are purchased through an HHT authorized dealer or distributor. A list of HHT
authorized dealers is available on the HHT branded websites.
• This warranty is only valid while the HHT appliance remains at the site of original installaon.
• This warranty is only valid in the country in which the HHT authorized dealer or distributor that sold the appliance resides.
• Contact your installing dealer for warranty service. If the installing dealer or distributor is unable to provide necessary parts,
contact the nearest HHT authorized dealer or supplier. Addional service fees may apply if you are seeking warranty service from
a dealer other than the dealer from whom you originally purchased the product.
• Check with your dealer in advance for any costs to you when arranging a warranty call. Travel and shipping charges for parts are not
covered by this warranty.
• Limited Catalyst Warranty
o For wood burning products containing a catalyst, the catalyst will be warranted for a six-year period to the original purchaser at
the site of original installaon. The purchaser must provide the name, address, and telephone number of the locaon where
the product is installed, proof of original purchase date, date of failure, and any relevant informaon regarding the failure of the
catalyst.
WARRANTY EXCLUSIONS:
This warranty does not cover the following:
• Changes in surface nishes as a result of normal use. As a heang appliance, some changes in color of interior and exterior surface
nishes may occur. This is not a aw and is not covered under warranty.
• Damage to printed, plated, or enameled surfaces caused by ngerprints, accidents, misuse, scratches, melted items, or other
external sources and residues leon the plated surfaces from the use of abrasive cleaners or polishes.
• Repair or replacement of parts that are subject to normal wear and tear during the warranty period are not covered. These parts
include: paint, wood and pellet gaskets, rebricks, grates, ame guides, baeries and the discoloraon of glass.
• Expansion, contracon, or movement of certain parts causing noise. These condions are normal and complaints related to this
noise are not covered by this warranty.
• Damages resulng from: (1) failure to install, operate, or maintain the appliance in accordance with the installaon instrucons,
operang instrucons, and lisng agent idencaon label furnished with the appliance; (2) failure to install the appliance in
accordance with local building codes; (3) shipping or improper handling; (4) improper operaon, abuse, misuse, connued operaon
with damaged, corroded or failed components, accident, or improperly/incorrectly performed repairs (5) environmental condions,
inadequate venlaon, negave pressure, or draing caused by ghtly sealed construcons, insucient make-up air supply, or
handling devices such as exhaust fans or forced air furnaces or other such causes; (6) use of fuels other than those specied in
the operaon instrucons; (7) installaon or use of components not supplied with the appliance or any other components not
expressly authorized and approved by HHT; (8) modicaon of the appliance not expressly authorized and approved by HHT in
wring; and/or (9) interrupons or uctuaons of electrical power supply to the appliance.
• Non-HHT venng components, hearth connecons or other accessories used in conjuncon with the appliance.
• Any part of a pre-exisng replace system in which an insert or a decorave gas appliance is installed.
• HHT’s obligaon under this warranty does not extend to the appliance’s capability to heat the desired space. Informaon is provided
to assist the consumer and the dealer in selecng the proper appliance for the applicaon. Consideraon must be given to the
appliance locaon and conguraon, environmental condions, insulaon and air ghtness of the structure.
This warranty is void if:
• The appliance has been over-red, operated in atmospheres contaminated by chlorine, uorine, or other damaging chemicals.
Over-ring can be idened by, but not limited to, warped plates or tubes, deformaon/warping of interior cast iron structure or
components, rust colored cast iron, bubbling, cracking and discoloraon of steel or enamel nishes.
• The appliance is subjected to prolonged periods of dampness or condensaon.
• There is any damage to the appliance or other components due to water or weather damage which is the result of, but not limited
to, improper chimney or venng installaon.
LIMITATIONS OF LIABILITY
• The owner’s exclusive remedy and HHT’s sole obligaon under this warranty, under any other warranty, express or implied, or in
contract, tort or otherwise, shall be limited to replacement, repair, or refund, as specied above. In no event will HHT be liable for
any incidental or consequenal damages caused by defects in the appliance. Some states do not allow exclusions or limitaon of
incidental or consequenal damages, so these limitaons may not apply to you. This warranty gives you specic rights; you may also
have other rights, which vary from state to state. EXCEPT TO THE EXTENT PROVIDED BY LAW, HHT MAKES NO EXPRESS WARRANTIES
OTHER THAN THE WARRANTY SPECIFICED HEREIN. THE DURATION OF ANY IMPLIED WARRANTY IS LIMITED TO DURATION OF THE
EXPRESSED WARRANTY SPECIFIED ABOVE.
Page 2 of 2
4021-645K 1/20