Monessen Hearth NB18, NB18SCR, NB24, NB24SCR Installation And Operating Instructions Manual
Vented/Unvented Gas Log Set
Installation and Operating Instructions
Models: NB18, NB24, NB18SCR, NB24SCR
WARNING
If the information in this manual is not followed
exactly, a re or explosion may result causing
property damage, personal injury or loss of life.
– 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 qualied installer, service
agency or the gas supplier.
This appliance may be installed in
an aftermarket, permanently located,
manufactured (mobile) home, where not
prohibited by local codes.
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.
This is an unvented gas-red heater. It uses
air (oxygen) from the room in which it is
installed. Provisions for adequate
combustion and ventilation air must be
provided. Refer to page 4.
INSTALLER: Leave this manual with the appliance.
CONSUMER: Retain this manual for future reference.
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
CONTENTS
NB18/NB24 Gas Log Set
Thank you and congratulations on your purchase of a Monessen log set
IMPORTANT: Please read the installation and operation instructions and all warning before installing or using the
appliance! Failure to follow these instructions may result in a possible re hazard and will void the warranty.
Important Safety Information ......................................3
Codes ..........................................................................4
Product Features and Specications ........................5
Check Parts .................................................................5
Items Needed for Installation ......................................5
Gas Pressures ............................................................5
Gas Specications ......................................................5
Millivolt Ignition Controls ............................................5
Signature Command Controls .....................................5
Pilot/ODS ....................................................................5
Thermal Generator ......................................................5
Fireplace and Hearth Dimensions ..............................6
Placement in a Fireplace with Restrictive Barrier
Adequate Combustion Ventilation Air
►
Clearances and Height Requirements .......................8
Floor Clearance .........................................................11
Fireplace Preparation ................................................12
Before Fully Installing the Unit ..................................12
Vented Application Installation —
NB, NBSC Models ....................................................12
Before Installing the Appliance ..................................12
Damper Stop Installation ...........................................12
Vented Application Installation .................................13
Assembly ...................................................................13
Gas and Valve Connection .......................................14
Gas Line Connection .................................................14
Millivolt Valve Control ................................................14
Electrical Wiring — Millivolt ......................................15
Connect Optional Wall Switch or Thermostat ............15
Connect Remote Receiver ........................................16
Check System Operation ..........................................16
Grate and Log Installation .........................................17
Before You Begin .....................................................17
Cast Iron Grate Installation .......................................17
Rock Wool Placement ...............................................18
Berkley Oak Log Placement .....................................18
Place the Decorative Rock ........................................19
Highland Oak Log Placement ..................................20
Stony Creek Log Placement .....................................21
Kentucky Wildwood Log Placement ..........................23
Beachcomber and Riverwood Log Placement ..........25
Flame Appearance ......................................................26
Check the Pilot Flame ...............................................26
Operating Instructions ...............................................26
............................7
...........6
Operating Instructions — Millivolt ............................27
For Your Safety Read Before Lighting .......................27
Millivolt Control Lighting Instructions .........................28
To Turn Off Gas to Heater .........................................28
Match Lighting Instructions .......................................29
Check Gas Pressure .................................................30
Electrical Installation—
Signature Command System .................................30
Electrical Wiring ........................................................30
Command Center Wall Installation ............................30
Wall Switch Installation ..............................................30
Wiring Diagram — Signature Command System ......31
Operating Instructions —
Signature Command System .................................32
For Your Safety Read Before Lighting .......................32
Operating Instructions ...............................................33
To Turn Off Gas to Appliance ....................................33
Features ....................................................................34
Battery Installation .....................................................34
System Conguration and Setup ..............................34
Remote Transmitter Learn Function ..........................35
Key Combinations for System Settings .....................35
Functions/Operations from the Command Center ....36
Touch Screen Remote Control Operation .................. 37
Function Areas of the LCD Display ............................. 37
Initializaiton and Set Up .............................................. 37
Functions and Operations ........................................... 38
Safety Features ........................................................... 40
Using the Mounting Base ............................................ 41
Cleaning & Servicing..................................................42
Troubleshooting .........................................................43
Millivolt Control System .............................................43
Signature Command System ....................................44
►
Service Parts and Accessories .................................46
Burner Assembly — Millivolt Models .........................46
Burner Assembly — Signature Command System ...48
Berkeley Oak Refractory Logs ..................................52
Highland Oak Refractory Log ....................................55
Stony Creek Refractory Logs ....................................58
Kentucky Wildwood Logs ..........................................61
Beachcomber and Riverwood Refractory Log ..........64
Hi/Lo Accessory Kit ...................................................67
Massachusetts Residents Only.................................68
Warranty ......................................................................69
NOTE: Monessen vent ree gas logs are hand painted for
ultimate beauty and realism. As a result, some variation
in color and shading will occur from set to set. This is
intentional and designed to make each product unique,
as found in nature.
2
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
NB18/NB24 Gas Log Set
IMPORTANT SAFETY INFORMATION
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 this vent-free gas heater.
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 appliance should be
located out of trafc 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 appliance.
4. Do not place clothing or other ammable 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 qualied
service person.
7. To prevent malfunction and/or sooting, an unvented
gas heater should be cleaned before use and at least
annually by a professional service person. More frequent cleaning may be required due to excessive 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 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. The NB(18,24) and NB(18,24)SC units comply with
ANSI Z21.11.2 Unvented Heaters, latest edition and
also complies with ANSI Z21.60 Decorative Vented
Appliances for Solid Fuel Burning Fireplaces, latest
edition. The NB(18,24)SCR units comply with ANSI
Z21.11.2 Unvented Heaters, latest edition ONLY.
State and local codes may only allow operation of
this appliance in a vented conguration. Check your
state or local codes. For vented operation, see “Vented
Instructions” in this manual.
11. Do not install the heaters in a bathroom or bedroom.
12. Correct installation of the 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 replace. See log placement
instructions for proper installation.
13. 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.
14. Caution: Candles, incense, oil lamps, etc. produce
combustion by-products 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 reburned 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. This is an unvented gas-fired heater. It uses air
(oxygen) from the room in which it is installed. Provisions for adequate combustion and ventilation air must
be provided.
16. This heater shall not be installed in a room or space
unless the required volume of indoor combustion air is
provided by the method described in the National Fuel
Gas Code, ANSI Z223.1/NFPA 54, the International
Fuel Gas Code or applicable local codes.
17. Keep room area clear and free from combustible mate-
rials, gasoline and other ammable vapors and liquids.
.
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
3
IMPORTANT SAFETY INFORMATION
NB18/NB24 Gas Log Set
18. Unvented gas heaters are a supplemental zone heater.
They are not intended to be the primary heating appliance.
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 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 four hours to
properly cure logs and rock wool, 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
pressures 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 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).
24. Do not use this room heater if any part has been under
water. Immediately call a qualied 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. This appliance must not be used with glass doors in
the closed position. This can lead to pilot outages and
severe sooting outside the replace.
26. Never burn solid fuels in a replace where a unvented
room heater is installed.
27. Always have a replace screen in place when the
appliance is in operation and, unless other provisions
for combustion air are provided, the screen must have
an opening(s) for induction of combustion air.
MASSACHUSSETTS RESIDENTS ONLY:
Refer to page 47 for additional information.
WARNING
Never connect unit to private (non-utility) gas wells.
This gas is commonly known as wellhead gas.
NB18, NB18SC, NB24, NB24SC
Certied to ANSI Z21.11.2 Latest Edition
Unvented Heaters & Z21.60 Latest Edition;
CSA 2.26 Latest Edition
NB18SCR, NB24SCR
Certied to ANSI Z21.11.2, Latest Edition
Unvented Heaters
WARNING
If the area in which the heater may be operated does
not meet the required volume for indoor combustion
air, combustion and ventilation air shall be provided
by one of the methods described in the National Fuel
Gas Code, ANSI Z223.1/NFPA 54, the International
Fuel Gas Code or applicable local codes.
CODES
Adhere to all local codes or, in their absence, the latest
edition of THE NATIONAL FUEL GAS CODE ANSI Z223.1
or NFPA54 which can be obtained from…
American National Standards Institute, Inc.
1430 Broadway
New York, NY 10018
or
National Fire Protection Association, Inc.
Batterymarch Park
Quincy, MA 02269
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.
4
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
NB18/NB24 Gas Log Set
PRODUCT FEATURES
CHECK PARTS:
Verify contents to ensure you have received all parts. You
should have the following:
NB Models
• Unvented gas log burner assembly
• Two (2) bags of crushed volcanic rock
• Installation/operating instructions
• Two (2) Anchoring Screws
• Ceramic ber or refractory logs
• Rock wool
• Grate assembly
• On/off log switch assembly (MV models only)
• Thermostat remote control (SCR models only)
• Double A batteries (SC models only)
The following options may be used with the millivolt con-
trolled heater. These options are not packaged with the
log set.
• Hand-held remote with receiver (MV)
• Wall thermostat with 15' wire
• Wall switch with 15' wire
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 parts in good condition.
ITEMS NEEDED FOR INSTALLATION:
You should have the following items available before proceeding with installation:
• External regulator (for propane/LPG and 1/2 psi
natural gas systems only)
• Piping which complies with local codes
• Sediment trap (recommended)
• Screwdriver
• Tee joint.
• Pipe sealant approved for use with propane/LPG
(Resistant to sulfur compounds)
• Drill with 5/32 masonry bit
• Pipe wrench or appropriate size crescent wrench
set
• Manual shutoff valve
Gloves are recommended when handling
ceramic ber logs to prevent skin irritation
from loose bers. Logs are fragile; handle
with care.
CAUTION
GAS PRESSURES
Natural Propane (LP)
Inlet Minimum 5.0" w.c. 11.0" w.c.
Inlet Maximum 10.5" w.c. 13.0" w.c.
Regulator Pressure
Setting
Pilot Regulator 3.5" w.c. n/a
GAS SPECIFICATIONS
Model Fuel BTU/h BTU/h
NB18 Natural 28,000 19,000
NB24 Natural 37,000 25,000
NB18 LP 27,000 22,000
NB24 LP 36,000 28,000
NATURAL GAS: An external regulator is required to reduce
supply pressure to a maximum of 10
systems operating at higher pressure.
PROPANE/LPG: An external regulator is required to reduce
supply pressure to a maximum of 13" w.c.
3.5" w.c. 11.0" w.c.
Gas Rate
Max. Input Min. Input
1
⁄2" w.c. on natural gas
MILLIVOLT IGNITION CONTROLS
The piezo ignitor allows ignition of the pilot without the use
of matches or batteries.
Millivolt control has four (4) positions:
OFF:All gas to the gas logs is shut off at the valve.
IGN : Valve position to light/maintain a standing pilot.
ON: Valve position to turn ON/OFF log set with remote
switch/thermostat.
LOW/HI: Variable position to control ame height (heat
output).
SIGNATURE COMMAND CONTROLS
Refer to page 28.
PILOT/ODS
The gas log heater is tted with a specially designed safety
pilot (ODS assembly) which senses the amount of oxygen
available in the room and shuts the gas log heater off if the
oxygen level begins to drop below a satisfactory level. The
pilot can only be relit when adequate fresh air is available.
THERMAL GENERATOR
The millivolt gas log pilot is tted with a millivolt (thermopile)
generator to provide power for remote activation.
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
5
FIREPLACE AND HEARTH DIMENSIONS
NB18/NB24 Gas Log Set
WARNING
This appliance is for installation only in a solid-fuel
burning masonry or UL127 factory-built replace,
vent free appliance, or in listed ventless rebox
enclosure. It has been design certied for these
installations.
Exception: DO NOT install this appliance in a factorybuilt replace that includes instructions stating
it has not been tested or should not be used with
unvented gas logs.
Use manufacturer's installation and clearance requirements as dened in their manual.
The NB and NBSC/SCR series unvented room heaters
are approved for installation into the following unvented
reboxes: MCUF 36/42, LCUF36, GCUF, GRUF or BUF
The NB and NBSC/SCR Series unvented room heaters
may also be installed into a Ventless Firebox Enclosure for
Gas Fired Decorative Type Unvented Room Heaters per
ANSI Z21.91 (typically referred to as a "universal rebox"),
as long as rebox hearth dimensions meet the minimum
hearth dimensions shown below.
C
PLACEMENT IN FIREPLACE WITH A
RESTRICTIVE BARRIER
The following are guidelines for placing a gas log set in a
replace that has a restrictive barrier along the bottom front
opening of the replace. Some examples of barriers are
glass/screen door frames and sunken/recessed replaces.
Height of Restriction
(x)
No Restriction 13"
1
0" to 1
Greater than 1
⁄2" 16"
1
⁄2" to 3" 16"
Greater than 3" *
*Any barrier greater than 3" placed in front of the gas log set is not
recommended by the manufacturer.
NOTE: Non-combustible material such as refractory brick
may be used to line the oor of the replace in order to
raise the height of the gas log set in relation to a restrictive
barrier. If the unit is raised, the minimum height dimension
listed in the homeowner’s manual must not be exceeded.
NOTE: If the log set is equipped with a remote receiver, a
restrictive barrier may reduce the battery life by increasing
the ambient temperature inside the replace. Placement
of the receiver outside of the replace will extend the
battery life.
Minimum Depth of
Fireplace/Firebox
D
A
B
Model A B C D
NB18 w/18" Log 26" 13" 18" 17"
NB24 w/24" Log 29" 13" 22
NB24 w/30" Log 33" 13" 25
NB18SC,SCR w/18" Log 28
1
⁄2" 13" 201⁄4" 17"
NB24SC/SCR w/24" Log 31" 13" 25
NB24SC/SCR w/30" Log 35" 13" 25
Figure 1 Minimum Hearth Dimensions
1
⁄4" 17"
1
⁄4" 17"
1
⁄4" 17"
1
⁄4" 17"
WARNING
Barriers such as the bottom of a glass door frame
placed in front of a gas log set can change the air
ow characteristics of the replace which in turn can
cause the unit to overheat and malfunction.
Height of restrictive barrier caused by glass
door frames, recessed replaces, etc. from
the base or bottom surface of the unit.
(Refer to table)
Glass door frames with adjustable louvers
should have the louvers fully open while
the unit is in operation
Figure 2 Reference Drawing of a Natural Flame Log Set in an Enclosure
The log set should be placed against
or as near as possible to the rear
wall of the replace/rebox.
Depth of replace/rebox
(Refer to table)
6
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
NB18/NB24 Gas Log Set
►
ADEQUATE COMBUSTION VENTILATION
AIR
This heater shall not be installed in a conned space or
unusually tight construction unless provisions are provided
for adequate combustion and ventilation air.
The National Fuel Gas Code, (ANSI Z223.1/NFPA54),
denes a conned space as a space whose volume is less
than 50 cubic feet per 1,000 BTU per hour (4.8m
of the aggregate input rating of all appliances installed in
that space, and an unconned 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 communicating
directly with the space in which the appliances are installed,
through openings not furnished with doors, are considered
a part of a conned space.
Unusually tight construction is dened as construction
where:
a. Walls and ceilings exposed to the outside atmosphere
have a continuous water vapor retarder with a rating of
1 perm (6 x 10
gasketed or sealed, and
b. Weather stripping has been added to windows and
doors, and
c. Caulking or sealants are applied to areas such as joints
around window and door frames, between sole plates
and oors, between wall-ceiling joints, between wall
panels, at penetrations for plumbing, electrical and gas
lines and other openings.
11
kg per pa/sec-m2) or less with openings
3
per kw)
Counter
Figure 3
If the area in which the heater may be
operated does not meet the required volume
for indoor combustion air, combustion and
ventilation air shall be provided by one
of the methods described in the National
Fuel Gas Code, ANSI Z223.1/NFPA 54, the
WARNING
International Fuel Gas Code or applicable
local codes.
Fireplace
H
W
The following formula can be used to determine the maxi-
mum heater rating per the denition of unconned space:
BTU/Hr = (L1 + L2) Ft x (W) Ft x (H) Ft
50
Consider two connecting rooms with an open area between, with the following dimensions:
L1 = 151/2 Ft., L2 = 12 Ft., W = 12 Ft., H = 8 Ft.
BTU/Hr = (151/2 + 12) x (12) x (8)
50
If there were a door between the two rooms the calculation
would be based only on the room with the heater.
BTU/Hr = (151/2) x (12) x (8)
50
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
7
CLEARANCES AND HEIGHT REQUIREMENTS
NB18/NB24 Gas Log Set
WARNING
The dimensions shown in Figures 4 through 12 and
dened in the replace manufacturer's instructions
are minimum clearances to maintain when installing
this heater. Left and right clearances are determined
when facing the front of the heater.
When heater is installed into a ventless rebox,
minimum clearances, as specied by the ventless
rebox manufacturer, must be met.
Follow these instructions carefully to ensure safe
installation. Failure to follow instructions exactly
can create a re hazard.
Sidewall and ceiling clearances: The sides of the re-
place opening must be at least 16" from any combustible
wall. The ceiling must be at least 42" from the top of the
replace opening.
42"
Heat resistant material (minimum requirements) with
no wooden mantel or other combustible projection:
To install the gas logs into a replace with no wooden
mantel, shelf or other combustible projection above the
replace opening, measure the heat resistant material
height, according to Figure 5 and TABLE A.
Heat resistant materials such as slate and marble must be
at least 1/2" thick. Sheet metal should not be installed
onto combustible material.
IMPORTANT: If you cannot meet these minimum clear-
ances you must operate the heater with chimney ue
damper open. Refer to “Installing Vented Applications”
found on page 12.
Heat resistant
Material
Measure
This
Distance
16"
Heater in
Fireplace/
Firebox
FP2253
FP2254
Figure 4 Sidewall and Ceiling Clearances
Table A — Heat Resistant Material Requirements with No Mantel or Combustible Projection
Heat Resistant Material
Measurement
NB18 NB24
12" or more Hood not required Hood not required
8" or less than 12" Hood not required Extend heat resistant material to 12" or install hood. Figure 4
Less than 8" Extend heat resistant Extend heat resistant material to 8" AND install hood Figure 5.
8
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
Figure 5 Measure Heat Resistant Material
Requirements for Safe Installation
OR Extend heat resistant material to a height of at least 12".
NB18/NB24 Gas Log Set
Heat resistant material (minimum requirements) with
wooden mantel or other combustible projection:
To install the heater with a wooden mantel, shelf or other
combustible projection above, first measure the heat
resistant material shown in Figure 6, then refer to Table B.
CLEARANCES AND HEIGHT REQUIREMENTS
8" or More
Hood
Heater in Fireplace
or Firebox
of Heat
Resistant
Material
Figure 6 Measuring Heat Resistant Material for Mantel
Table B - Heat Resistant Material Requirements Height and Mantel Location
Heat Resistant
Material
Measurement
Requirements for Safe Installation with Wooden Mantel, Shelf or other Combustible
Projection
NB18 NB24
12" or more Hood not required. Observe proles (side
elevations) shown in Figure 6.
8" or less than 12" Install hood and observe proles shown in
Figure 7. OR Extend heat resistant material
to at least 12" and observe proles and
observe proles shown in Figure 8.
Less than 8" Extend heat resistant to at least 8", install
hood and observe proles shown in Figure
7. OR Extend heat resistant material to at
least 12" and observe proles shown in
Figure 6.
Hood not required. Observe prole (side
elevations shown in Figure 8.
Install hood and observe proles shown in
Figure 7. OR Extend heat resistant material
to at least 12" and observe proles shown in
Figure 8.
Extend heat resistant material to least 8",
install install hood and observe proles
shown in Figure 7. OR Extend heat resistant
material to at least 12" and observe proles
shown in Figure 6.
FP2255
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
9
CLEARANCES AND HEIGHT REQUIREMENTS
NB18/NB24 Gas Log Set
10"
8"
6"
2¹⁄₂"
Heat
Resistant
Material
8" 14" 20¹⁄₂" 24⁵⁄₈" 28"
Heater in
Fireplace or
Firebox
FP2256
Figure 7 Minimum Mantel Clearance with No Hood — NB18
10" or less
Heat
Resistant
Material
28"
12" min.
Heater in
Fireplace or
Firebox
Figure 9 Minimum Mantel Clearance with No Hood — NB24
Example: A mantel may project from the wall a maximum
of 21⁄2" at a minimum of 14" above the opening, and a
maximum of 6" at a minimum of 201⁄2" above the opening.
12"
10"
8"
6"
Heat
Resistant
Material
2¹⁄₂"
8" 14¹⁄₂" 18⁵⁄₈" 22¹⁄₂" 26"
Hood
Heater in
Fireplace or
Firebox
Figure 8 Minimum Mantel Clearance with Hood — All Models
Example: A mantel may project from the wall a maximum
of 21⁄2" at a minimum of 8" above the opening, and a
maximum of 6" at a minimum of 141⁄2" above the opening.
Example: The bottom of the mantel may project from the
wall a maximum of 10" at a minimum of 28" above the
opening.
7"
6"
Mantel
Minimum
of 8" Heat
Resistant
Material
2¹⁄₂"
14¹⁄₂"
4"
8"
Hood
Figure 10 - Minimum Mantel Clearance with Hood — NB24
(Example of Unsafe Installation)
Figure 9 is an example of an unsafe mantel installation.
This mantel projects 4" at 8" above the opening, exceeding
the maximum acceptable depth of 2
1
⁄2" The mantel also
projects 7" at 141⁄2" above the opening, exceeding the
maximum acceptable depth of 6".
If your mantel prole is unsafe, you may either raise the
mantel to an acceptable height OR remove the mantel
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Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
NB18/NB24 Gas Log Set
The gas log heater must be installed at least 13⁄8" above
any combustible ooring material, such as carpeting or
tile, which is closer than 14" to the base of the replace.
The minimum distance must be maintained from the top
surface of carpeting, tile, etc. Figure 11
OR
The gas log heater 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 replace and
the combustible ooring. Figure 12
FLOOR CLEARANCE
Heater in Fireplace
or Firebox
Combustible
Material
3
⁄8" Minimum
1
FP2261
Figure 11 Minimum Clearance above Combustible Flooring
Heater in Fireplace
or Firebox
This Distance
May Now be
Less Than 1
3
⁄8"
FP2262
14” Minimum
Figure 12 Minimum Clearance above Combustible Flooring with
Noncombustible Material Installed at Base of Fireplace
Combustible
Material
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
11
FIREPLACE PREPARATION
NB18/NB24 Gas Log Set
WARNING
Before installing in a solid fuel burning replace,
The chimney ue and rebox must be cleaned of
soot, creosote, ashes and loose paint by a qualied
chimney cleaner.
WARNING
This appliance is for installation only in a solid
fuel burning fireplace (masonry fireplace or
manufactured replace) with a working ue and
constructed of noncombustible material.
Exception: DO NOT install this appliance in a factorybuilt replace that includes instructions stating that
it has not been tested or should not be used with
unvented gas logs. This log set may be installed as
a vented log set.
BEFORE FULLY INSTALLING THE UNIT:
Turn OFF the gas supply to the replace or rebox.
•
• Seal any fresh air vents and/or ash clean-out doors
located on the oor or wall of the replace. If left
unsealed, drafting may cause pilot outage or sooting. Use a heat resistant sealant. Do not seal the
chimney ue damper.
VENTED APPLICATION INSTALLATIONS —
NB & NBSC ONLY
Manual and millivolt controlled gas logs may be installed as
a vented decorative log set in compliance with ANSI Z21.60
and National Fuel Gas Code, Section 6.6. Since, the gas
logs are operated with the damper open, non-combustible material and minimum mantel requirements
do not apply.
Before installing the appliance:
• Turn off gas supply to replace or rebox.
• Have the replace oor and chimney professionally
cleaned to remove ashes, soot, creosote or other
obstructions. Have this cleaning performed annually
after installation.
• Seal any fresh air vents or ash clean-out doors
located on oor or wall of replace. If not, drafting
may cause pilot outage or sooting. Use a heat-resistant sealant.
Install and operate the appliance as directed in this
manual.
DAMPER STOP INSTALLATION
A damper stop must be provided with the unit. Contact your
dealer to obtain one. The damper stop must be installed as
shown in Figure 13 to prevent full closure of the replace
damper blade and provide a minimum 29 square inch ue
opening.
Damper Stop
Damper
FP2263
Figure 13 Damper Stop Installation.
NOTE: The use of a thermostat is prohibited in vented log
applications.
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NB18/NB24 Gas Log Set
VENTED APPLICATION INSTALLATION / SECURE APPLIANCE
WARNING
The replace and gas logs function as a system. If
the replace is spilling into the room (check with
a match or a smoke stick), reposition the damper
clamp until a positive draft is obtained by opening
the damper. If negative pressure in home prevents
having a positive draft, contact your dealer for
assistance.
ASSEMBLY PROCEDURE
1. Center the gas log unit on the replace or rebox. Make
certain the front of the burner sits inside the front edge
of the replace or rebox.
2. Anchor holes are located on the right and left sides of
the unit. After centering the burner correctly, mark the
hole positions on the replace/rebox oor. Drill two (2)
5/32" diameter holes approximately 11⁄2" deep.
3. Anchor the grate to the replace/rebox oor using the
screws provided. Figure 14
Proper installation of the grate is essential to prevent
any movement of the gas logs and controls during
operation.
WARNING
You must secure the gas log heater to the replace
oor. If not, the entire unit may move when you
adjust the controls. Movement of unit may cause
shifting of the gas logs which leads to sooting and
improper burning. Grate movement could cause a
gas leak.
Special care is required if you are installing the unit
into a sunken replace. You must raise the replace
oor to allow access to gas log controls. This will
insure adequate air ow and guard against sooting.
Raise the fireplace floor using noncombustible
materials, as described in Placement in a Fireplace
with Restrictive Barrier on Page 6.
Screw
Figure 14 Securing Heater to Floor of Fireplace/Firebox
Screw
FP2264
Anchor Hole
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
13
GAS AND VALVE CONNECTION
NB18/NB24 Gas Log Set
WARNING
Use new black iron or steel pipe. Internally tinned
copper or copper tubing can be used per National
Fuel Code, section 2.6.3, providing gas meets
hydrogen sulde limits, and where permitted by local
codes. Gas piping system must be sized to provide
minimum inlet pressure (Listed on Data Plate) at the
maximum ow rate (BTU/hr). Undue pressure loss
will occur if the pipe is too small.
A manual shutoff valve must be installed upstream
of the appliance. Union tee and plugged 1/8" NPT
pressure tapping point should be installed upstream
of the appliance. Figure 15
GAS LINE CONNECTION
NOTICE: A qualied gas appliance installer must connect
the heater to the gas supply. Consult all local codes.
IMPORTANT: Hold heater valve rmly with a wrench to
prevent movement when connecting to inlet pipe.
Always use an external regulator for all propane/LPG
heaters and high pressure one to two-pound systems
only, to reduce the supply tank pressure to a maximum of
13" w.c. This is in addition to the internal regulator in the
heater valve.
To Heater
Valve
WARNING
Connecting directly to an unregulated propane/
LPG tank can cause an explosion.
The heater gas inlet connection is a 3/8" NPT at the valve.
On all control type units, the inlet connection is on the right
side of unit. To connect from the opposite side, route the
pipe around the back portion of the unit.
When tightening up the joint to the valve, hold the valve
securely to prevent movement.
Test all gas joints from the gas meter to the heater valve for
leaks using a gas analyzer or soap and water solution after
completing connection. DO NOT USE AN OPEN FLAME.
Check the gas pressure with the appliance burning and
the control set to HIGH.
MILLIVOLT VALVE CONTROL
Figure 16
The valve regulator controls the burner pressure which
should be checked at the pressure test point.
Turn captured screw counter clockwise two or three turns
and then place tubing to pressure gauge over test point
(Use test point “OUT” closest to control knob). After taking
pressure reading, be sure and turn captured screw clock-
wise rmly to re-seal. Do not over torque. Check for gas
leaks.
Locations
Pipe Coupling
Pipe
Stainless
Flexible Tube
Manual Shutoff
Valve
Figure 15 Gas Connection
that the
Pressure
Tapping
Point May Be
Installed
Gas
Supply
Inlet
FP2265
WARNING
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.
Test Port “OUT”
FP2266
Figure 16 Pressure Test Point Location
Millivolt Control
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Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
NB18/NB24 Gas Log Set
Label all wires prior to disconnection when
servicing controls. Wiring errors can cause
improper and dangerous operation. Verify
proper operation after servicing.
CAUTION
The millivolt valve is a self-powered combination gas control THAT DOES NOT REQUIRE 110 VAC TO OPERATE.
ELECTRICAL WIRING - MILLIVOLT
►
CONNECT OPTIONAL WALL SWITCH
OR THERMOSTAT (VENT FREE
APPLICATIONS ONLY)
1. Use 18 awg, two-wire cable, 15 feet maximum length.
2. At one end of the cable, connect both wires to the wall
switch or thermostat. At the other end, connect one
wire to TP/TH and one wire to TH, or connect the wall
switch/thermostat to the two male (0.25") terminals on
the left side of the unit. The color of the wires does not
matter.
ODS Pilot
ODS
On/Off Switch
or Optional Wall
Switch, Remote
or T-Stat
TH = 3
TP = 1
TP/TH = 2
Log Switch
Figure 17 Wiring Diagram
NOTE: Log switch wires are not factory connected. Connect log switch wires to the TH/TP and TH valve terminals as
shown.
Pilot
Millivolt
Valve
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
15
ELECTRICAL WIRING - MILLIVOLT
TH = 3
NB18/NB24 Gas Log Set
CONNECT REMOTE RECEIVER
1. Set remote receiver. See instructions included in
receiver kit.
2. Connect the two (2) 1/4" female connectors to the TP/
TH and TH terminals on the control valve.
A. Complete Millivolt System Check
(“A” Reading - Thermostat contacts CLOSED -
Control Knob “ON” - Main burner should turn
ON)
a. If the reading is more than 175 millivolts and the
automatic valve still does not come on, replace the
NOTE: Do not allow wires touch grate or burner.
NOTE: Heat reduces battery life. You can protect the
receiver and extend battery life by mounting receiver
in wall or other location outside the replace.
CHECK SYSTEM OPERATION
The millivolt system and individual components may be
checked with a millivolt meter having a 0-1000 mV range.
Conduct each check shown in chart below by connection
meter test leads to terminals as indicated.
control.
b. If the closed circuit reading (“A” reading) is less than
175 millivolts, determine cause for low reading, proceed to Section B below.
B. Thermopile Output Reading Check
(“B” Reading - Thermostat contacts OPEN - Main
burner OFF)
1. Check gas pressure to the unit. If gas pressure is
within minimum and maximum on data plate, then
check pilot voltage, 500 millivolts minimum. If the
minimum millivolt reading is not obtainable, replace
pilot.
Check
Test To Test
Connect Meter Leads
to Terminals
Switch to Thermostat
Contacts Meter Should Read
A Complete System 2 and 3 Closed Minimum 175
B Thermopile Output 1 and 2 Open Minimum 500
Figure 18 Installing Remote Receiver
Remote Wire
Connectors
TP/TH = 2
TP = 1
Remote Wire
Connectors
FP2268
Valve
Remote Receiver
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Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
NB18/NB24 Gas Log Set
GRATE AND LOG INSTALLATION
WARNING
The positioning of the logs is critical to the safe and
clean operation of this heater. Sooting and other
problems may result if the logs are not properly
and rmly positioned in the appliance. Never add
additional logs or embellishments such as pine
cones, vermiculite or rock wool to the heater. Only
use the logs and 2G-RW rock wool (for NB18), or
3G-RW rock wool (for NB24) supplied with the unit.
Failure to position the parts in accordance with
diagrams below or to use only parts specically
approved for this heater may result in property
damage or personal injury.
A.
BEFORE YOU BEGIN
This unit is supplied with seven (7) ceramic ber logs. Do
not handle these logs with your bare hands. Always wear
gloves to prevent skin irritation from ceramic bers.
After handling the logs, wash your hands gently with soap
and water to remove any traces of bers.
CAST IRON GRATE INSTALLATION
Install the cast iron grate by inserting screw head on back
of right side of grate into the “I” shaped slot on front right
corner of unit. After moving screw head to the bottom of the
“I” slot, insert the screw head on the back of the left side of
grate into the keyhole slot on the left front of unit. Figure 19
B.
Key
Hole Slot
Cast Iron Grate
Figure 19 Install Cast Iron Grate
Cast Iron Grate
I Slot
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
17
GRATE AND LOG INSTALLATION
NB18/NB24 Gas Log Set
ROCK WOOL PLACEMENT
Before installing logs, place rockwool in dime size pieces
evenly over small burner ports starting in the rear of the
burner going towards the front. Avoid placing rock wool on
slots on each side of rear burner and on large yellow ame
ports on front of burner. After covering small burner ports,
discard any excess rock wool.
Wash hands after placing rock wool. Itching may occur.
NOTE: Installation instructions are the same for 18",
24", and 30" log sets. Pictures used in this manual
illustrate the 24" set. Some variation may exist between
the images and the set included with this manual.
WARNING
• Use only rock wool provided with log set.
• Do not add additional rock wool.
Right Front
Log #2
Figure 22 Place Right Front Log #2
3. Place right rear log (#3) on pin located on rear support
bracket and rest left side of log on front right log. Figure
23.
Right Rear
Log #3
Dime-sized pieces
of rock wool
Figure 20 Place Rock Wool
INSTALL 18", 24" AND 30" (F, R) BERKLEY
OAK LOGS ON NATURAL BLAZE BURNER
1. Place the #1 log (the “chunk”) on the grate bar right side
of the burner adjacent to the controls. Figure 21
2. Place front right log (#2) on right pin located on burner
and right grate bar. Figure 21. slide Log #1 forward so
that it is tight against log #2.
Ember Chunk
Log #1
LG620
Figure 23 Place Right Rear Log #3
4. Place left rear log (#4) on pin located on rear support
bracket on left side. Figure 24
Left Rear
Log #4
Figure 21 Place Ember Chunk Log #1
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Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
Figure 24 Place Left Rear Log #4
NB18/NB24 Gas Log Set
GRATE AND LOG INSTALLATION
5. Place left front log (#5) on left pin located on burner and
left grate bar. Rest top right portion of log on right front
log. Figure 25
Left Front Log #5
Figure 25 Place Left Front Log #5
6. Place top left log (#6) on unit by placing grooved portion
of log onto left grate bar with bark facing outward. Rest
front part of log in groove on left front log. Figure 26
Middle Left
Log #6
8. Place right top log (#8) onto right rear (#3) and right
front (#2) logs using locator on bottom of right top log.
Figure 28
Left Top
Log #7
Figure 28 Place Right Top Log #8
Right Top
Log #8
Figure 26 Place Middle Left Log #6
7. Place left top log (#7) on left rear log (#4) and left front
log (#5) using locating grooves on bottom of #7 and
locating blocks on logs #4 and #5. Figure 27
Left Top Log #7
PLACE THE DECORATIVE ROCK
Optional volanic rock may be placed around the unit on
the oor of the rebox. Be sure to avoid any areas on
the burner itself.
DO NOT sprinkle volcanic rock on the logs,
around the pilot, or on or near burners. This
may cause sooting. Place volcanic rock only
on the oor of the replace.
During initial operation of the new heater,
new burning logs and/or rock wool will give
CAUTION
off a paper burning smell and orange ames
will be present. Simply open the windows for
a few hours to vent the odor.
Figure 27 - Place Left Top Log #7
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
19
GRATE AND LOG INSTALLATION
NB18/NB24 Gas Log Set
INSTALL 18", 24" AND 30" (F,R) HIGHLAND
OAK LOGS ON NATURAL BLAZE BURNER
1. Place the #1 log (the “chunk”) on the grate bar right side
of the burner adjacent to the controls. Figure 29
Ember Chunk
Log #1
Figure 29
2. Place front right log (#2) on right pin located on burner
and right grate bar. Figure 30. After placing front right
log, ensure log is fully upright and tilting towards the
back of the burner.
Right Front Log #2
4. Place left rear log (#4) on pin located on rear support
bracket on left side and left grate bar. Figure 32
Left Rear Log #4
Figure 32
5. Place left front log (#5) on left pin located on burner and
left grate bar. Rest top right portion of log on right front
log. Figure 33
Figure 30
3. Place right rear log (#3) on pin located on rear support
bracket and rest left side of log on front right log. Figure
31. After placing right rear log, ensure log is fully upright
and does not tilt forward. Slide #1 log ember chunk back
to contact right rear log.
Right Rear Log #3
Left Front Log #5
Figure 33
Figure 31
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Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
NB18/NB24 Gas Log Set
GRATE AND LOG INSTALLATION
6. Place top left log (#6) on left rear log (#4) and left front
log (#5) using locating grooves on bottom of #6 and
locating blocks on logs #4 and #5. Figure 34
7. Place right top log (#7) on right rear log (#3) and right
front log (#2) using locators on the bottom of log #7 and
locators on logs #2 and #3. Figure 34
Left Top Log #6
Figure 34
Right Top Log #7
8. Place small right front top log (#8) on log #7 and log
#2 using locating grooves on the bottom of log #8 and
locating blocks on log #7 and log #2. Figure 35
PLACE THE DECORATIVE ROCK
Optional volanic rock may be placed around the unit on
the oor of the rebox. Be sure to avoid any areas on the
burner itself.
DO NOT sprinkle volcanic rock on the logs,
around the pilot, or on or near burners. This
may cause sooting. Place volcanic rock only
on the oor of the replace.
During initial operation of the new heater,
new burning logs and/or rock wool will give
CAUTION
off a paper burning smell and orange ames
will be present. Simply open the windows for
a few hours to vent the odor.
STONY CREEK SC18/24/30-R LOGS
PLACEMENT
1. Place bottom log (#1) on two (2) pins on rear of grate
assembly and push towards rear as far as possible.
Figure 36
Bottom Rear Log #1
Figure 35
Right Front
Top Log #8
Figure 36
2. Place the ember chunk (#2) with notch on both ends
on the grate bar right side of the burner adjacent to the
controls. Push towards rear as far as possible. Figure
37
3. Place the ember chunk (#3) with notch on one end on
the grate bar left side of the burner with notch towards
rear. Push towards rear as far as possible. Figure 37
Ember Chunk Log #2
Ember Chunk
Log #3
(Notch on
one end)
(Notch on both ends)
Figure 37
Monessen • NB18/24 Gas Log Set Installation/Owner's Manual • 81D0107 • Rev I • 01/19
21
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