Monessen Hearth NBST27NV-B Operating instructions

1
Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/2020
NBST27
cover
Models:
Installation/Owner’s Manual
Appliance Setup, Care and Operation
NOTICE: DO NOT discard this manual!
In the Commonwealth of Massachusetts installation must be
performed by a licensed plumber or gas tter.
See appliance installation manual for additional
Commonwealth of Massachusetts requirements.
INSTALLER: Leave this manual with party responsible for use and operation.
OWNER: Retain this manual for future reference.
Contact your dealer with questions regarding installation, operation or service.
• DO NOT store or use gasoline or other am-
mable 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.
- Leave the building immediately.
- Immediately call your gas supplier from
a neighbor’s phone. Follow the gas sup-
plier’s instructions.
- If you cannot reach your gas supplier, call
the re department.
• Installation and service must be performed
by a qualied installer, service agency, or the
gas supplier.
WARNING:
FIRE OR EXPLOSION HAZARD
Failure to follow safety warnings exactly
could result in serious injury, death, or
property damage.
NBST27NV-B
NBST27PV-B
• DO NOT install this unit in a bedroom or
bathroom.

Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/20202
Safety Alert Key:
• DANGER! Indicates a hazardous situation which, if not avoided will result in death or serious injury.
• WARNING! Indicates a hazardous situation which, if not avoided could result in death or serious injury.
• CAUTION! Indicates a hazardous situation which, if not avoided, could result in minor or moderate injury.
• NOTICE: Used to address practices not related to personal injury.
Table of Contents
Installation Standard Work Checklist ....................3
1 Product Specic & Important Safety Information
A. Appliance Certication ............................4
B. BTU Specications ...............................4
C. High Altitude Installations ..........................4
D. Non-Combustible Materials Specication. . . . . . . . . . . . . . 4
2 Getting Started
A. Design and Installation Considerations ...............5
B. Tools and Supplies Needed ........................5
C. Inspect Appliance and Components .................. 5
D. Check Parts ....................................6
E. Installation Information ............................6
F. Pilot/ODS ......................................7
G. Adequate Combustion Ventilation Air .................8
3 Clearances & Height Requirements
A. ..............................................9
4 Gas Information
A. Gas Line Connection ............................14
B. Millivolt Valve Controls ...........................14
C. Fuel Type .....................................15
D. Gas Pressure .................................. 15
E. Gas Service Access .............................15
F. Connect Optional Wall Switch or Thermostat ..........16
G. Connect Remote Receiver ........................17
H. Check System Operation ......................... 17
I. Rock Wool Placement ...........................18
5 Gas Log Sets
A. Log Placement .................................19
B. Place the Decorative Rock ........................21
C. Flame Appearance ..............................21
D. Operating Instructions ...........................21
6 Owner’s Manual
A. Congratulations ................................22
B. Limited Lifetime Warranty .........................24
7 Important Safety & Operating Information
A. Appliance Safety ...............................26
B. General Operating Parts .........................28
C. Fuel Specications ..............................28
D. Before Lighting Appliance. . . . . . . . . . . . . . . . . . . . . . . . . 28
8 Product Specication Information
A. Application Certication ..........................29
B. BTU Specications ..............................29
9 Lighting Instructions
A. .............................................30
10 Maintenance & Service
A. Maintenance: Frequency & Tasks .................33
B. Maintenance Tasks: Qualied Service Technician ..... 33
C. Burner Ignition & Operation .......................33
D. Cleaning & Servicing ............................34
11 Troubleshooting
A. .............................................35
12 Service Parts & Accessories
A. Service Parts ..................................37
B. Accessories ...................................39
C. Contact Information .............................41
NOTE: Monessen vent free 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.
►

3
Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/2020
Installation Standard Work Checklist
Gas Section 4 (Pg 14)
Proper appliance for fuel type.
Leak check performed and inlet pressure verified.
Verified proper air shutter setting for installation type.
Customer:
Lot/Address:
Model (circle one): NBST27NV-B, NBST27PV-B
Date Installed:
Location of Fireplace:
Installer:
Dealer/Distributor Phone #
Serial #:
Comments: Further description of the issues, who is responsible (Installer/ Builder/ Other Trades, etc) and corrective
action needed _____________________________________________________________________________________
Comments Communicated to party responsible ____________________ by ______________________on ___________
(Builder / Gen. Contractor/) (Installer) (Date)
?YHW , ON F I SEY
___________________________
___________________________
___________________________
___________________________
___________________________
Gas Log Install Sections 2 and 4 (Pg. 5 & 20)
Verified that the chimney has been cleaned. (pg. 13)
Verifi ed clearances to combustibles.
Gas Logs are level ed and secured.
See page 8 for adequate provisions for combustion and ventilation
air have been verified.
___________________________
___________________________
___________________________
___________________________
___________________________
Finishing Section 3 (Pg 9)
Verifi ed all clearances meet installation manual requirements.
Mantels and wall projections comply with installation manual requirements.
___________________________
___________________________
___________________________
___________________________
___________________________
Manual bag and all of its contents are removed and the log set
given to party responsible for use and operation.
Started log set and veried no gas leaks exist.
___________________________
___________________________
4615-901A 07/18
 = Contains updated information.
Hearth & Home Technologies recommends the following:
• Photographing the installation and copying this checklist for your file.
• That this checklist remain visible at all times on the appliance until the installation is complete.
This standard work checklist is to be used by the installer in conjunction with, not instead of, the instructions contained in this
installation manual.
WARNING! Risk of Fire or Explosion! Failure to install appliance according to these instructions could
lead to a fire or explosion.
ATTENTION INSTALLER:
Follow this Standard Work Checklist
Embers & Logs Section 5 (Pg 19-21)
All packaging and protective materials removed (inside & outside of appliance).
Embers and logs installed correctly.
Accessories installed properly.
Electrical Section 4 (Pg 17)
Switch wires properly installed.

Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/20204
This product is listed to ANSI standards for "Unvented
Room Heaters” and applicable sections of "Gas Burning
Heating Appliances for Manufactured Homes" and "Gas
Fired Appliances for Use at High Altitude."
A. Appliance Certication
D. Non-Combustible Materials Specication
Material which will not ignite and burn. Such materials are
those consisting entirely of steel, iron, brick, tile, concrete,
slate, glass or plasters, or any combination thereof.
Materials that are reported as passing ASTM E 136,
Standard Test Method for Behavior of Materials in
a Vertical Tube Furnace at 750 ºC shall be considered
non-combustible materials.
NOT INTENDED FOR USE AS A PRIMARY HEAT SOURCE.
This appliance is tested and approved as either supplemen-
tal room heater or as a decorative appliance. It should not
be factored as primary heat in residential heating calcula-
tions.
NOTICE: This installation must conform with local codes.
In the absence of local codes you must comply with the
National Fuel Gas Code, ANSI Z223.1-latest edition in
the U.S.A.
1 Product Specic and Important Safety Information
B. BTU Specications
C. High Altitude Installations
NOTICE: If the heating value of the gas has been reduced,
these rules do not apply. Check with your local gas utility
or authorities having jurisdiction.
When installing above 4500 feet elevation: Reduce input
rate 4% for each 1000 feet above 4500 feet.
Check with your local gas utility to determine proper
orice size.
MODEL: NBST27NV-B, NBST27PV-B
LABORATORY: CSA
TYPE: Unvented Room Heater
STANDARD: ANSI Z21.11.2-2016 (Unvented Application)
ANSI Z21.60-2012/CSA2.26-2012 (Vented
Application)
Models
Maximum
Input
BTU/h
Minimum
Input
BTU/h
Orice
NBST27NV-B (0-4500 FT) 39,000 26,000
NBST27PV-B (0-4500 FT) 39,000 30,000
GAS PRESSURES
NOTE: For LP models an external regulator is required
to reduce supply pressure to a maximum of 13" w.c.
NATURAL PROPANE (LP)
Inlet Minimum 5.0" w.c. 11.0" w.c.
Inlet Maximum 10.5" w.c. 13.0" w.c.
Gas Valve Manifold
Pressure Setting
3.5" w.c. 10" w.c.
Pilot Regulator 3.5" w.c. —
NATURAL GAS: An external regulator is required to reduce
supply pressure to a maximum of 101⁄2" w.c. on natural gas
systems operating at higher pressure.
PROPANE/LPG: An external regulator is required to reduce
supply pressure to a maximum of 13" w.c.
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).
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.

5
Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/2020
2 Getting Started
A. Design and Installation Considerations
Installation MUST comply with local, regional, state and
national codes and regulations. Consult insurance carrier,
local building inspector, re ofcials or authorities having
jurisdiction over restrictions, installation inspection and
permits.
Before installing, determine the following:
• Where burner assembly and log set are to be installed.
• Gas supply piping.
• Whether optional accessories—devices such as a wall
switch or remote control—are desired.
• Approved wood burning masonry replace or vent-free
replace.
Improper installation, adjustment, alteration, service or
maintenance can cause injury or property damage. For
assistance or additional information, consult a qualied
service technician, service agency or your dealer.
Installation and service of this appliance should
be performed by qualied personnel. Hearth
& Home Technologies recommends HHT
Factory Trained or NFI certied professionals.
C. Inspect Appliance and Components
• Carefully remove the appliance and components from
the packaging.
• Logs are packaged and sold separately.
• Report to your dealer any parts damaged in shipment.
•Read all of the instructions before starting the instal-
B. Tools and Supplies Needed
Before beginning the installation be sure that the following
tools and building supplies are available.
• Tape measure
• Gloves
• Voltmeter
• Manometer
• Phillips screwdriver
• Safety glasses
• Flat blade screwdriver
• Soapy water solution for gas leak testing
• Electric drill and bits (1/4 in. magnetic)
• External regulator (for propane/LPG only & 1/2 psi
Natural gas system)
• Piping which complies with local codes
• Pipe sealant approved for use with propane/LPG
(Resistant to sulfur compounds)
Hearth & Home Technologies disclaims any responsibility
for, and the warranty will be voided by, the following actions:
• Installation and use of any damaged appliance.
• Modication of the appliance.
• Installation other than as instructed by Hearth & Home
Technologies.
• Installation and/or use of any component part not approved
by Hearth & Home Technologies.
Any such action may cause a re hazard.
WARNING! Risk of Fire, Explosion or Electric Shock!
DO NOT use this appliance if any part has been under
water. Call a qualied service technician to inspect the
appliance and to replace any part of the control system
and/or gas control which has been under water.
• Manual shutoff valve
• Sediment trap
• Tee joint
• Pipe wrench
lation. Follow these instructions carefully during the
installation to ensure maximum safety and benet.
WARNING! Risk of Fire or Explosion! Damaged parts
could impair safe operation. DO NOT install damaged, in-
complete or substitute components. Keep appliance dry.
Gloves are recommended when handling
refractory to prevent skin irritation from
loose bers. Logs are fragile; handle with
care.
CAUTION

Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/20206
E. Installation Information
Use manufacturer's installation and clearance require-
ments as dened in their manual.
The NBST27-B unvented room heater is approved for
installation into the following unvented rebox: LSTF36-B.
The NBST27-B unvented room heater 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.
This appliance is for installation only in a solid-fuel
burning masonry or UL127 factory-built replace
or in listed ventless rebox enclosure. It has been
design certied for these installations.
Exception: DO NOT install this appliance in a factory-
built replace that includes instructions stating
it has not been tested or should not be used with
unvented gas logs.
WARNING
D. Check Parts
Verify contents to ensure you have received all parts. You
should have the following:
Models
• Unvented gas log burner assembly
• Three (3) bags of crushed volcanic rock
• Installation/operating instructions
• Two (2) anchoring brackets
• Two (2) anchoring screws
• Two (2) sheet metal screws
• Ceramic Fiber logs (packaged and sold separately)
• Two (2) bags of rock wool
• On/off log switch assembly
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 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.
32”
21½”
19”
Figure 2.1 - Hearth Minimum Dimensions for Solid Fuel
Burning Fireplaces and UL127 Factory Built Fireplaces

7
Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/2020
Do not install the heater:
•Where curtains, furniture, clothing, or
other ammable objects are less than
36" from the front of the heater.
• In high trafc areas.
•In windy or drafty areas.
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 when
installed as a vented log set.
WARNING
DO NOT INSTALL ANY GLASS OR BARRIERS ON A
VENTLESS FIREBOX
WARNING
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.
F. Pilot/ODS
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)
Minimum Depth of
Fireplace/Firebox
No Restriction 211⁄2”"
0" to 11⁄2"251⁄4"
Greater than 11⁄2" to 3" 271⁄4"
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.
FP2362
fireplace barrier
X
Glass door frames
with adjustable
louvers should have
the louvers fully
open while the unit
is in operation
Height of restrictive barrier
caused by glass door frames,
recessed replaces, etc. from the
base or bottom surface of the unit.
(Refer to Table)
Refer to
Table
Figure 2.2 - Reference Drawing of NBST27 Log Set in an
Enclosure

Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/20208
G. Adequate Combustion Ventilation Air
This heater shall not be installed in a conned space or
unusually tight construction unless provisions are provided
for adequate combustion and ventilation air.
The National Fuel Gas Code, (ANSI Z223.1/NFPA54),
denes a conned space as a space whose volume is less
than 50 cubic feet per 1,000 BTU per hour (4.8m3per kw)
of the aggregate input rating of all appliances installed in
that space, and an unconned space as a space whose
volume is not less than 50 cubic feet per 1,000 BTU per
hour (4.8 m3per 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 conned space.
Unusually tight construction is dened 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 1011 kg per pa/sec-m2) or less with openings
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.
The following formula can be used to determine the maxi-
mum heater rating per the denition of unconned 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
W
H
Counter
Fireplace
Figure 2.3
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
International Fuel Gas Code or applicable
local codes.
WARNING

9
Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/2020
3 Clearances and Height Requirements
Sidewall and ceiling clearances: The sides of the re-
place opening must be at least 6" from any combustible
wall. The ceiling must be at least 42" from the top of the
replace opening. The wall parallel to the side of heater
must be at least 36" from the side of the heater. Refer to
your rebox owner’s manual for more information.
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 3.2 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 13.
The dimensions shown in Figures 3.1 through
3.7 and defined in the fireplace 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 specied 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.
WARNING
42” 36”
36”
6”
FP2363
clearances
Figure 3.1 - Sidewall and Ceiling Clearances
IMPORTANT:
1. If installing unit into an unvented rebox, minimum
required clearances listed in the rebox installation
manual must be met.
2. If installing unit into a vented rebox with a working
damper, minimum clearances shown in Figures 3.1
through 3.7 must be met
3. If installing unit into a vented rebox with a damper that
is always open, no minimum clearances are required.
Heat Resistant
Material Mea-
surement Requirements for Safe Installation
12" or more Hood not required
8" to less than 12" Extend heat resistant material to 12" or
install hood. Figure 3.2
Less than 8" Extend heat resistant material to at
least 8" and install hood. Figure 3.2
OR extend heat resistant material to a
height of at least 12"
FP2364
Heat resist matl
Measure this Distance
Heat Resistant
Material
Heater in Fireplace or
Firebox
Figure 3.2 - Measure Heat Resistant Material

Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/202010
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, rst measure the heat resis-
tant material shown in Figure 3.3, then refer to Table B.
FP2365
heat resist w/hood
8" or More of
Heat Resistant
Material
Hood
Heater in Fireplace or Firebox
Figure 3.3 - Measure Heat Resistant Material for Mantel
Table B - Heat Resistant Material Heights and Mantel Loca-
tion
Heat Resistant
Material Mea-
surement Requirements for Safe Installation
12" or more Hood not required. Observe prole
(side elevations) shown in Figure 6.
8" to less than 12" Install hood and observer proles
shown in Figure 7; OR extend heat
resistant material to at least 12" and
observe proles shown in Figure 6.
Less than 8" Extend heat resistant material to at
least 8", install hood and observe pro-
les shown in Figure 7; OR extend heat
resistant material to at least 12" and
observe proles shown in Figure 6.
FP2366
mantel clear no hood
12"
Min.
28"
10" or Less
Heat Resistant
Material
Heater in
Fireplace
or Firebox
Example:
The bottom of the mantel may project from the wall a maxi-
mum of 10" at a minimum of 28" above the rebox.
Figure 3.4 - Minimum Mantel Clearance with No Hood
2 1/2"
12"
13"
24"
FP2367
mantel clearance with hood
Heat Resistant
Material
Heater in Fireplace or
Firebox
Hood
Example:
A mantel may project from the wall a maximum of 21⁄2" at a
minimum of 13" above the opening, and a maximum of 12" at
a minimum of 24" above the opening.
Figure 3.5 - Minimum Mantel Clearance with Hood

11
Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/2020
The gas log heater must be installed at least 3/4" 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 3.6.
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 3.7
3/4"
Combustible
Material
Heater in Fireplace
or Firebox
Figure 3.6 - Minimum Clearance above Combustible Floor-
ing
14" Min.
FP2369
comb floor
Heater in Fireplace
or Firebox
Combustible
Material
This distance may now
be less than 3/4"
Figure 3.7 - Minimum Clearance above Combustible
Flooring with Noncombustible Material Installed at Base
of Fireplace

Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/202012
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 soot-
ing. Use a heat resistant sealant. Do not seal the
chimney ue damper.
Vented Application Installations
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 3.9 to prevent full closure of the replace
damper blade and provide a minimum 29 square inch ue
opening.
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 qualied
chimney cleaner.
WARNING
This log set can be installed in a solid fuel burning
fireplace (masonry fireplace or manufactured
replace) with a working ue and constructed of
non combustible material or in a vent-free rebox.
Exception: DO NOT install this appliance in a factory-
built 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.
WARNING
The use of thermostat is not allowed on vented log
application. It is only allowed on unvented room
heater classication.
WARNING
When this log set is installed in a vented application,
the damper must be clamped to be fully open.
WARNING
FP2370
damper
Damper Stop
Damper
Figure 3.8 - Damper Stop Installation
(Refer to WARNING at top of page)

13
Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/2020
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 7.
WARNING
Figure 3.9 - Secure Burner
FP2375
secure burner
Piezo Ignitor
(Original Location)
Place and Secure Appliance
1. Center the gas log unit in the replace or rebox. Make
certain the front feet of the grate sit 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 grate correctly, mark the
hole locations on the replace/rebox oor. Drill two (2)
5/32” diameter holes approximately 11⁄4” deep.
3. Anchor the unit to the replace/rebox oor using the
screws provided. Figure 3.9
Proper installation of the grate is essential to prevent
any movement of the logs and controls during opera-
tion.

Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/202014
4 Gas Information
A. Gas Line Connection
NOTICE: A qualied 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.
The heater gas inlet connection is a female 3/8" NPT at
the valve. The inlet connection is on the right side of unit.
To connect from the opposite side, rotate unit 180° or route
the pipe under the rear 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.
B. Millivolt Valve Control
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.
Repeat process for “IN” port. Check “IN” port with unit set
on high with any other gas appliances in the house on or
cycling on. Pressure gauge readings should match max/
min requirements on data plate.
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 sulde 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.
WARNING
Connecting directly to an unregulated propane/
LPG tank can cause an explosion.
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.
WARNING
Figure 4.1 Gas Connection

15
Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/2020
C. Fuel Type
• This appliance is equipped for either natural or propane
gas. Field conversion is not permitted.
• Make sure the appliance is compatible with available gas
types.
D. Gas Pressure
• Optimum appliance performance requires proper input
pressures.
• Gas line sizing requirements will be determined in ANSI
Z223.1 National Fuel Gas Code in the USA.
• Pressure requirements are:
Note: Have the gas supply line installed in accordance with
local codes, if any. If not, follow ANSI 223.1. Installation
should be done by a qualied installer approved and/or
licensed as required by the locality. (In the Commonwealth
of Massachusetts installation must be performed by a
licensed plumber or gas tter).
Fire Risk.
Explosion Hazard.
High pressure will damage valve.
• Disconnect gas supply piping BEFORE
pressure testing gas line at test pressures
above 1/2 psig.
• Close the manual shutoff valve BEFORE
pressure testing gas line at test pressures
equal to or less than 1/2 psig.
WARNING
WARNING! Risk of Fire or Explosion! High pressure
will damage valve. Low pressure could cause explosion.
• Verify inlet pressures. Verify minimum pressures when
other household gas appliances are operating.
• Install regulator upstream of valve if line pressure is
greater than 1/2 psig.
• Valve pressure taps are accessible prior to installing log
set.
Depending upon local code, a manual gas shutoff, in
a readily accessible area may be required and located
upstream from the appliance.
E. Gas Service Access
NATURAL PROPANE (LP)
Inlet Minimum 5.0" w.c. 11.0" w.c.
Inlet Maximum 10.5" w.c. 13.0" w.c.
Gas Valve Manifold
Pressure Setting
3.5" w.c. 10" w.c.
Pilot Regulator 3.5" w.c. —
FP2266
valve
Figure 4.2 - Pressure Test Point Location Millivolt Control
Test Port “OUT”

Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/202016
The millivolt valve is a self-powered combination gas con-
trol THAT DOES NOT REQUIRE 110 VAC TO OPERATE.
F. Connect Optional Wall Switch or
Thermostat (vent free application 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, using fork terminal
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.
Figure 4.3 - Wiring Diagram
NOTE: Log switch wires are not factory connected. Connect log switch wires to the TH/TP and TH valve terminals as shown.
FP2267
wiring diagram
Log Switch
On/Off Switch
or Optional Wall
Switch, Remote
or T-Stat
ODS Pilot
Millivolt
Valve
TH = 3
TP = 1
TP/TH = 2
ODS
Pilot
CAUTION
Label all wires prior to disconnection when
servicing controls. Wiring errors can cause
improper and dangerous operation. Verify
proper operation after servicing.

17
Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/2020
G. Connect Remote Receiver
1. Set remote receiver. See instructions included in
receiver kit.
2. Unplug the two terminals for the log switch from the
valve, connect the piggy back terminal of the receiver
to the TH and TP/TH on the valve. Slide the terminal
of the log switch onto the piggy back terminal on the
receiver
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.
H. 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.
1. 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
control.
b. If the closed circuit reading (“A” reading) is less than
175 millivolts, determine cause for low reading, pro-
ceed to Section B below.
2. 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.
Figure 4.4 - Installing Remote Receiver
Check
Test To Test
Connect Meter Leads
to Terminals
Switch or Thermostat
Contacts Meter Should Read
A Complete System 2 and 3 Closed Minimum 175
BThermopile Output 1 and 2 Open Minimum 500
FP2376
remote switch
Remote
Wires
Remote
Receiver
Remote Wire
Connectors
Valve

Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/202018
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 supplied with
the unit.
Failure to position the parts in accordance with
diagrams below or to use only parts specically
approved for this heater may result in property
damage or personal injury.
WARNING
I. Rock Wool Placement
Place dime size pieces of rock wool evenly over small
burner ports starting at pilot and down each side of burn-
er. Avoid placing rock wool on slots on either side of burn-
er between the air defectors. Figure 16. Wash hands after
placing rock wool. Skin irritation may occur.
Figure 4.5 - Place Rock Wool
LG648
NBST rockwool
Pilot
Rockwool
Rock Wool
Horizontal
Grate Bar
Grate Tine
Grate Tines
Horizontal Grate Bar
Before You Begin
NBST27-B logs are sold separately. Do not handle these
logs with your bare hands. Always wear gloves to pre-
vent skin irritation from ceramic bers. After handling
the logs, wash your hands gently with soap and water to
remove any traces of bers.

19
Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/2020
5 Gas Log Sets
• Gloves are recommended when handling logs to
prevent skin irritation from loose bers. Logs
are fragile - handle with care.
• Use only rock wool provided with log set.
• DO NOT ADD ADDITIONAL ROCK WOOL.
WARNING
Wash hands after placing rock wool. Itching may occur.
A. Log Placement
Begin on Side A, valve on left as you face the replace.
1. Place log #1 on burner by aligning two (2) holes on
bottom of log with two (2) pins on burner. The tallest
part of the log is on the valve side of burner. Gently
push log down until it comes in contact with burner sur-
face. Figure 5.1
LG650
NBST log 1
Log 1
Control
Valve
Figure 5.1 - Place Log #1
2. Place log #2 on left grate tines by aligning the ‘V’
notches in the log with grate tines. The groove on the
bottom of the log should be rmly seated on the grate
bar. Figure 5.2
LG651
NBST log 2
Log #2
Figure 5.2 - Place Log #2
LG653
NBST Log 4
Log #4
Figure 5.4 - Place Log #4
3. Place log #3 on farthest right grate tine by aligning the
‘V’ notch in log with grate tine. The groove in the bot-
tom of the log should sit on the ller bracket surround-
ing the pilot assembly. Figure 5.3
LG652
NBST Log 3
Log #3
Figure 5.3 - Place Log #3
4. Place log #4 by aligning the ‘V’ notch on bottom of log
with horizontal grate bar between tines as shown in
Figure 20. Place the rectangular notch on bottom of
log onto the matching rectangular protrusion on log #1.
Figure 5.4
5. Place log #5 by placing rectangular notch on bottom
of log onto matching rectangular protrusion on log #2.
Make sure ember or ‘burnt’ portion of log is facing cen-
ter of burner. Figure 5.5
LG654
NBST log 5
Log #5
Figure 5.5 - Place Log #5

Monessen • NBST27-B Gas Log Set Owner’s /Installation Manual • 4615-900 Rev. D • 01/202020
Continue on Side B, valve on right as you face the
replace.
6. Place log #6 on pilot end of burner by aligning the ‘V’
notch in bottom of log with the ller bracket surround-
ing the pilot. Place the rectangular notch in the bottom
of the log onto the rectangular protrusion on the end of
log #1. Figure 5.6
7. Place log #7 on left two (2) grate tines by aligning the
‘V’ notch in log with grate tines. Make sure groove on
bottom of log is rmly seated on grate bar. Figure 5.7
LG655
NBST log 6
Log #6
Log #1
Control Valve
Figure 5.6 - Place Log #6
8. Place log #8 by aligning ‘V’ notch in bottom of log with
the horizontal grate bar between tines as shown in Fig-
ure 24. Place the rectangular notch on bottom of log
onto rectangular protrusion on middle of log #1. Figure
5.8
LG656
NBST log 7
Log #7
Figure 5.7 - Place Log #7
9. Place log #9 on farthest right grate tine by aligning ‘V’
notch in bottom of log with grate tine. Place rectangu-
lar notch in bottom of log onto rectangular protrusion
on log #8. Figure 5.9
LG657
NBST Log 8
Log #8
Figure 5.8 - Place Log #8
LG658
NBST log 9
Log #9
Figure 5.9 - Place Log #9
LG659
NBST Log 10
Log #10
Figure 5.10 - Place Log #10
10. Place log #10 by aligning two (2) rectangular notches
on bottom of log with rectangular protrusions on logs
#6 & #7. Make sure the ember or ‘burnt’ area of log is
facing center of burner. Figure 5.10