Vermont Castings NBST27 User manual

81D3032 10/15 Rev. 7
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. Refer to page 4.
Vented/Unvented Gas Log Set
Installation and Operating Instructions
Models: NBST27
INSTALLER: Leave this manual with the appliance.
CONSUMER: Retain this manual for future reference.
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.
If theinformationin thismanual is notfollowed
exactly, a fire or explosion may result causing
property damage, personal injury or loss of
life.
– Do not store or use gasoline or other
flammable vapors and liquids in the
vicinity of this or any other appliance.
– WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do
not use any phone in your building.
• Immediately call your gas supplier from
a neighbor's phone. Follow the gas
supplier's instructions.
• If you cannot reach your gas supplier,
call the fire department.
– Installation and service must be
performed by a qualified installer, service
agency or the gas supplier.
WARNING

281D3032
NBST27 Unvented Gas Log Set CONTENTS
Important Safety Information .............................3
Codes.............................................................4
Features and Specifications...............................5
Check Parts....................................................5
Items Needed for INstallation.........................5
Gas Pressures................................................5
Gas Specifications..........................................5
Pilot/ODS........................................................5
Thermal Generator.........................................5
Product Features and Specifications ...............5
Gas Pressures................................................5
Gas Specifications..........................................5
Ignition Controls..............................................5
Pilot/ODS........................................................5
Thermal Generator.........................................5
Fireplace and Hearth Dimensions .....................6
Placement in Fireplace with a Restrictive
Barrier.............................................................6
Clearances and Height Requirements ..............7
Floor Clearances ................................................9
Fireplace Preparation .......................................10
Before Fully Installing the Unit......................10
Installing in Vented Applications ...................10
Before Installing the Appliance .....................10
Damper Stop Installation..............................10
Place and Secure Appliance.............................11
Gas and Valve Connection ...............................12
Millivolt Valve Control....................................12
Electrical Wiring (Millivolt)................................13
Connecting Optional Wall Switch
or Thermostat ...............................................13
Connect Remote Receiver ...........................14
Checking System Operation.........................14
Log Placement...................................................15
Rockwool Placement....................................15
Log Placement..............................................15
Flame Appearance.............................................17
Check the Pilot Flame ..................................17
Check Burner Flame Appearance ................17
Operating Instructions......................................18
For Your Safety Read Before Lighting..........18
Millivolt Control Lighting Instructions............19
To Turn Off Gas to Heater.............................19
Match Lighting Instructions...........................20
Maintenance.......................................................20
Cleaning and Servicing.................................20
Troubleshooting ................................................21
Replacement Parts............................................23
Accessories .......................................................24
Requirements in Massachusetts......................25
Warranty.............................................Back Cover

3
81D3032
NBST27 Unvented Gas Log Set
IMPORTANT SAFETY INFORMATION
1. Due to high temperatures, the appliance should be
located out of traffic and away from furniture and
draperies.
2. Children and adults should be alerted to the hazard
of high surface temperature and should stay away
to avoid burns or clothing ignition.
3. Youngchildrenshould be carefully supervisedwhen
they are in the same room with the appliance.
4. Do not place clothing or other flammable material
on or near the appliance.
5. Any safety screen or guard removed for servicing
an appliance, must be replaced prior to operating
the heater.
6. Installationand repair shouldbe done by a qualified
service person.
7. To preventmalfunction 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
excessivelint from carpeting,bedding material, etc.
It is imperative that control compartments, burners
and circulating air passageways be kept clean.
8. CARBON MONOXIDE POISONING: Early signs of
carbon monoxide poisoning are similar to the flu with
headaches,dizzinessand/ornausea.Ifyouhavethese
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. Thisunit complies withANSIZ21.11.2 Unvented Heat-
ers, latest edition and also complies withANSI Z21.60
Decorative Vented Appliances for Solid Fuel Burning
Fireplaces, latest edition. State and local codes may
only allow operation of this appliance in a vented con-
figuration.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 ceramic fiber logs, proper
location of the heater, and annual cleaning are neces-
saryto avoid potential problems with sooting. Sooting,
resulting from improper installation or operation, can
settleon surfaces outside the fireplace.See log place-
ment instructions for proper installation.
13. Avoidanydraftsthatalterburnerflamepatterns.Donot
allow fans to blow directly into fireplace. Do not place
a blower inside burn area of firebox. Ceiling fans may
create drafts that alter burner flame patterns. Sooting
and improper burning will occur.
14. Caution: Candles, incense, oil lamps, etc. produce
combustion by-products including soot. Vent-free
appliances will not filter or clean soot produced by
these types of products. In addition, the smoke and/or
aromatics (scents) may be reburnt in the vent-free
appliancewhichcanproduceodors.Itisrecommended
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. Provi-
sionsforadequate combustion and ventilationair must
be provided. Refer to Page 5
16. This heater shall not be installed in a room or space
unlessthe required volume of indoor combustion air is
providedby 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
materials, gasoline and other flammable vapors and
liquids.
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.
• Any change to this heater or its controls can be dangerous.
• Improper installation or use of the heater can cause serious injury or death from fire, burns,
explosion or carbon monoxide poisoning.
• Do not allow fans to blow directly into the fireplace. Avoid any drafts that alter burner flame
patterns.
• Do not use a blower insert, heat exchanger insert or other accessory, not approved for use with
this heater where applicable.
WARNING:

481D3032
NBST27 Unvented Gas Log Set
18. Unventedgasheatersareasupplemental zone heater.
They are not intended to be the 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. Duringmanufacturing,fabricatingandshipping,various
components of this appliance are treated with certain
oils, films or bonding agents. These chemicals are not
harmful but may produce annoying smoke and smells
asthey are burnedoffduringthe 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
elevationsupto2,000 feet. For elevationsabove2,000
feet,inputratingsshouldbereduced 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
duringany pressure testingof that system at testpres-
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 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. Donot use this room heaterif any part has beenunder
water. Immediately call a qualified service technician
to inspect the room heater and to replace any part of
thecontrolsystem and any gascontrolwhich 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 fireplace.
26. Never burn solid fuels in a fireplace where a unvented
room heater is installed.
27. Always have a fireplace 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.
IMPORTANT SAFETY INFORMATION
NBST27 is certified to ANSI Z21.11.2
Latest Edition Unvented Heaters
& Z21.60 Latest Edition;
CSA 2.26 Latest Edition
CODES
Adhere to all local codes or, in their absence, the latest
editionofTHENATIONALFUELGAS CODEANSIZ223.1
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
Never connect unit to private (non-utility) gas wells.
This gas is commonly known as wellhead gas.
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.
WARNING
MASSACHUSSETTS RESIDENTS ONLY:
Refer to page 25 for additional information.

5
81D3032
NBST27 Unvented Gas Log Set
FEATURES AND SPECIFICATIONS
CHECK PARTS:
Verify contents to ensure you have received all parts. You
should have the following:
•Unvented Gas Log Burner Assembly
• Crushed Volcanic Rock, 3 bags
•Anchoring Screws, 2
•Ceramic Fiber Logs
•Rock wool
•Flickering Bright Embers, 1 bag
•On/Off Log SwitchAssembly
• Installation/Operating Instructions
The following options may be used with the milli-volt con-
trolled heater. These options are not packaged with the
log set.
• Hand Held Remote with Receiver
• Wall Thermostat with 15' Wire
• Wall Switch with 15' Wire
• Hand held Thermostat Remote with Receiver
• Andirons
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 pro-
ceeding with installation:
• External regulator (for propane/LPG and 1/2 lb.
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 fiber logs to prevent skin irritation
from loose fibers. 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 3.5" w.c. 11.0" w.c.
Pilot Regulator 3.5" w.c. n/a
NATURALGAS:Anexternalregulatorisrequiredtoreduce
supplypressure to a maximum of 101⁄2" w.c.on natural gas
systems operating at higher pressure.
PROPANE/LPG:Anexternalregulatoris required to reduce
supply pressure to a maximum of 13" w.c.
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 flame height (heat
output).
PILOT/ODS
Thegas log heateris fitted with a specially designedsafety
pilot (ODS assembly) which senses the amount of oxygen
available in the room and shuts the gas log heater off if the
oxygenlevel begins to drop below a satisfactory level.The
pilot can only be relit when adequate fresh air is available.
THERMAL GENERATOR
Themillivoltgaslog pilot is fitted with a millivolt(thermopile)
generator to provide power for remote activation.
GAS SPECIFICATIONS
Gas Rate
Max. Input Min. Input
Model Fuel BTU/h BTU/h
NBST27NV Natural 39,000 26,000
NBST27PV LP 39,000 30,000

681D3032
NBST27 Unvented Gas Log Set FIREPLACE AND HEARTH DIMENSIONS
Use the fireplace manufacturer's installation and clear-
ance requirements as defined in their manual.
TheNBST27unventedroomheaterisapprovedforinstalla-
tionintothe following unventedfireboxes:LSTF36, LPF36,
LRF36, LLF36
The NBST27 unvented room heater may also be installed
intoaVentless FireboxEnclosurefor Gas FiredDecorative
Type Unvented Room Heaters per IAS Requirement No.
2-97ANSI Z21.91-2001 (typically referred to as a "Univer-
sal Firebox"), as long as firebox hearth dimensions meet
the minimum hearth dimensions shown below.
32”
2156O”
2156O”
Figure 1 -
Hearth Minimum Dimensions for Solid Fuel Burning Fire-
places and UL127 Factory Built Fireplaces
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 fireplaces, etc. from the
base or bottom surface of the unit.
(Refer to Table)
Refer to
Table
Figure 2 -
Reference Drawing of NBST27 Log Set in an Enclosure
Barriers such as the bottom of a glass door frame
placed in front of a gas log set can change the air
flowcharacteristicsofthefireplacewhich in turn can
cause the unit to overheat and malfunction.
WARNING
This appliance is for installation only in a solid-fuel
burning masonry or UL127 factory-built fireplace,
vent free appliance, or in listed ventless firebox
enclosure. It has been design certified for these
installations.
Exception:DONOTinstallthisapplianceinafactory-
built fireplace that includes instructions stating
it has not been tested or should not be used with
unvented gas logs.
WARNING PLACEMENT IN FIREPLACE WITH A
RESTRICTIVE BARRIER
The following are guidelines for placing a gas log set in a
fireplacethathasa restrictive barrier alongthe bottom front
opening of the fireplace. Some examples of barriers are
glass/screendoorframes and sunken/recessed fireplaces.
Height of Restriction
(x) Minimum Depth of Fireplace/Firebox
No Restriction 211⁄2”"
0" to 11⁄2"25
1⁄4"
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 floor of the fireplace 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 fireplace. Placement
of the receiver outside of the fireplace will extend the
battery life.

7
81D3032
NBST27 Unvented Gas Log Set
CLEARANCE AND HEIGHT REQUIREMENTS
Sidewall and ceiling clearances: The sides of the fire-
place opening must be at least 13⁄4"from any combustible
wall. The ceiling must be at least 42" from the top of the
fireplaceopening.Thewallparallelto the sideof the heater
must be at least 36" from the side of the heater. Refer to
your firebox owners manual for more information.
42” 36”
36”
16M”
Figure 3 -
Sidewall and Ceiling Clearances
IMPORTANT:
1. If installing unit into an unvented firebox, minimum
required clearances listed in the firebox installation
manual must be met.
2. If installing unit into a vented firebox with a working
damper,minimumclearancesshowninFigure8through
10 must be met
3. If installing unit into a vented firebox with a damper that
is always open, no minimum clearances are required.
Heat resistant material (minimum requirements) with
no wooden mantel or other combustible projection:
To install the gas logs into a fireplace with no wooden
mantel, shelf or other combustible projection above the
fireplace opening, measure the heat resistant material
height, per Figure 4, then see 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 the unit is installed in a vented fireplace
and cannot meet these minimum clearances you must
operate the heater with chimney flue damper open. Refer
to “Installing Vented Applications” on Page 11.
Measure this Distance
Heat Resistant
Material
Heater in Fireplace or
Firebox
Figure 4 -
Measure Heat Resistant Material
Table A — Heat Resistant Material Requirements
with no Mantel or Combustible Projection
The dimensions shown in Figures 3 through 9 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 firebox,
minimum clearances, as specified by the ventless
firebox manufacturer, must be met.
Follow these instructions carefully to ensure safe
installation. Failure to follow instructions exactly
can create a fire hazard.
WARNING
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 4
Less than 8" Extend heat resistant material to at
least 8" and install hood. Figure 4 OR
extend heat resistant material to a
height of at least 12"

881D3032
NBST27 Unvented Gas Log Set CLEARANCE AND HEIGHT REQUIREMENTS
Heat resistant material (minimum requirements) with
wooden mantel or other combustible projection:
To install the heater with a wooden mantel, shelf or other
combustibleprojection above, firstmeasurethe heat resis-
tant material shown in Figure 5, then refer to Table B.
8" or More of
Heat Resistant
Material
Hood
Heater in Fireplace or Firebox
Figure 5 -
Measure Heat Resistant Material for Mantel
Table B -
Heat Resistant Material Heights and Mantel Location
12"
Min.
28"
10" or Less
Heat Resistant
Material
Heater in
Fireplace
or Firebox
FP2366
Example:
The bottom of the mantel may project from the wall a maximum
of 10" at a minimum of 28" above the firebox.
Figure 6 -
Minimum Mantel Clearance with No Hood
2 1/2"
12"
13"
24"
Heat Resistant
Material
Heater in Fireplace or
Firebox
Hood
Example:
A mantel may project from the wall a maximum of 21⁄2" at a min-
imum of 13" above the opening, and a maximum of 12" at a
minimum of 24" above the opening.
Figure 7 -
Minimum Mantel Clearance with Hood
Heat Resistant
Material Mea-
surement Requirements for Safe Installation
12" or more Hood not required. Observe profile
(side elevations) shown in Figure 6.
8" to less than 12" Install hood and observer profiles
shown in Figure 7; OR extend heat
resistant material to at least 12" and
observe profiles shown in Figure 6.
Less than 8" Extend heat resistant material to at
least 8", install hood and observe pro-
files shown in Figure 7; OR extend heat
resistant material to at least 12" and
observe profiles shown in Figure 6.

9
81D3032
NBST27 Unvented Gas Log SetFLOOR CLEARANCES
The gas log heater must be installed at least 3/4" above
any combustible flooring material, such as carpeting or
tile, which is closer than 14" to the base of the fireplace.
The minimum distance must be maintained from the top
surface of carpeting, tile, etc. Figure 8
OR
The gas log heater may be installed nearer to the floor if a
minimum of 14" of noncombustible material such as slate
ormarble is installed betweenthe base ofthe fireplace and
the combustible flooring. Figure 9
3/4"
Combustible
Material
Heater in Fireplace
or Firebox
Figure 8 -
Minimum Clearance above Combustible Flooring
14" Min.
Heater in Fireplace
or Firebox
Combustible
Material
This distance may now
be less than 3/4"
Figure 9 -
Minimum Clearance above Combustible Flooring with Noncombus-
tible Material Installed at Base of Fireplace

10 81D3032
NBST27 Unvented Gas Log Set FIREPLACE PREPARATION
BEFORE FULLY INSTALLING THE UNIT:
•Turn OFF the gas supply to the fireplace or firebox.
•Seal any fresh air vents and/or ash clean-out doors
located on the floor or wall of the fireplace. If left
unsealed, drafting may cause pilot outage or sooting.
Usea heat resistant sealant. Do not seal the chimney
flue damper.
INSTALLING IN VENTED APPLICATIONS
Milli-volt controlled gas logs may be installed as a vented
decorative log set in compliance with ANSI Z21.60 and
NationalFuel Gas Code, Section 6.6. Since, the gas logs
are operated with the damper open, noncombustible
material and minimum mantel requirements do not
apply.
Damper Stop
Damper
FP2370
Figure 10 -
Damper Stop Installation
(Refer to WARNING at top of page)
BEFORE INSTALLING THE APPLIANCE:
• Turn off gas supply to fireplace or firebox.
• Have the fireplace floor 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 floor or wall of fireplace. If not, drafting may cause
pilot outage or sooting. Use a heat-resistant sealant.
Do not seal chimney flue damper.
Install and operate the appliance as directed in this
manual.
DAMPER STOP INSTALLATION:
A damper stop must be provided with the unit when used
for vented applications. Contact your dealer to obtain one.
The damper stop must be installed as shown in Figure 10
to prevent full closure of the fireplace damper blade and
provide a minimum 29 square inch flue opening.
Refer to Page 27 for installations in the Commonwealth
of Massachusetts.
Before installing in a solid fuel burning fireplace,
The chimney flue and firebox must be cleaned of
soot, creosote, ashes and loose paint by a qualified
chimney cleaner.
WARNING
This appliance is for installation only in a solid
fuel burning fireplace (masonry fireplace or
manufactured fireplace) with a working flue and
constructed of noncombustible material.
Exception:DONOTinstallthisapplianceinafactory-
built fireplace 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