HearthStone Green Mountain Insert 90 User manual

Green Mountain Insert 90 (Model 8460)
Manual: 6400-41422
R: 11/2//22
Green Mountain Insert 90
(Model 8460)
Woodstove
OWNER'S MANUAL
Installation And
Operating Instructions
SAVE THIS OWNER’S MANUAL FOR FUTURE REFERENCE
PLEASE READ THIS ENTIRE OWNER’S MANUAL BEFORE YOU INSTALL AND
USE YOUR NEW GREEN MOUNTAIN INSERT 90 WOOD STOVE.
Ce manuel est disponible en français sur hearthstonetech.com
If this room heater is not properly installed, a house fire may result.
To reduce the risk of fire, follow the installation instructions.
Failure to follow these instructions can result in property damage, bodily injury, or even death.
Conforms to UL Std. 1482 & 737
Certified to ULC Std. S628
WARNING: This product can expose you to
chemicals including glass wool fiber and carbon
monoxide which are known to the State of California to
cause cancer, birth defects or other reproductive harm.
For more information go to www.P65Warnings.ca.gov
California Prop 65
CONTACT LOCAL AUTHORITIES WITH
JURISDICTION (BUILDING
DEPARTMENT or FIRE OFFICIALS),
ABOUT PERMITS REQUIRED,
RESTRICTIONS AND INSTALLATION
INSPECTION IN YOUR AREA.
Safety tested according to ULC S628,
UL 737 and UL 1482 Standards
by an accredited laboratory

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
2
NOTES ON STOVE OPERATION AND EFFICIENCY
Rating:
You have purchased a Hearthstone Green Mountain Insert 90 tested to EPA Alt 125 emissions testing where applicable.
This stove is certified to comply with the U.S. Environmental Protection Agency 2020 particulate emissions standard using
cord wood. It is certified at 1.14 gr/hr. emission rate and under specific test conditions has been shown to deliver heat at
rates ranging from 14,200 to 48,200 Btu (output).
This wood heater has a manufacturer-set minimum allowable low burn rate that must not be altered. It is against federal
regulations to alter this setting or otherwise operate this wood heater in a manner inconsistent with operating instructions in
this manual.
Please refer to the Warranty section of this manual for registration instructions. In case of warranty claims, please contact
the point of original sale or the nearest authorized Hearthstone dealer. Our dealer network processes all warranty claims.
Authorized Hearthstone dealers can be located at www.hearthstonestoves.com.
This heater is designed to burn natural wood only. Higher efficiencies and lower emissions generally result when burning
air-dried seasoned hardwoods, as compared to softwoods or to green or freshly cut hardwoods. DO NOT BURN: Garbage,
lawn clippings, material containing rubber (including tires), materials containing plastic, waste petroleum products paints or
paint thinners, asphalt products, materials containing asbestos, construction or demolition debris, railroad ties, pressure
treated wood, manure or animal remains, salt water driftwood or other previously salt-water saturated materials, unseasoned
wood, paper products, cardboard, plywood, or particleboard. This prohibition against burning these materials does not
prohibit the use of fire starters made from paper, cardboard, sawdust, wax, and similar substances for the purpose of starting
a fire in an affected wood heater. Burning these materials may result in a release toxic fume or render the heater ineffective
and cause smoke.
Following the maintenance guidelines set forth in this manual will help ensure the efficient use of your wood heater and
minimize visible emissions. Having your stove inspected by a trained professional on a regular basis will greatly increase the
potential for recognizing potential impacts to efficiency.
Proper draft is important to the efficient operation of your heater. Refer to the Normal Operation section of this manual for
information regarding adequate draft. Both excessive and sub-minimum draft can affect the efficiency of your wood heater.
Excessive draft can lead to over-consumption of fuel, lower overall heating capacity of the stove and potential over firing.
Low draft can result in inefficient burns, low heat output, expulsion of smoke into the living area when stove doors are
opened and an increased potential for build-up of flammable materials in the flue.
Efficiency:
Efficiency was measured and weighted using CSA B415.1-10 methodology. A weighted average was used to calculate the
overall efficiency across all the 4 burn rate categories using the higher heating value (HHV). The weighted average efficiency
is 68% (HHV).
To maximize the efficiency of your wood stove, make sure it is sized properly for the space you plan to heat. An oversized
stove will often be forced to burn at a lower and dirtier burn rate. Consult with your dealer for sizing and correctly placing the
stove in your home. An incorrectly placed stove can greatly reduce efficiency. Maximizing the efficiency of your stove will
heat your house quickly, burn cleaner and use less wood.
Refer to the Choosing Firewood section of this manual for appropriate fuel selection. Seasoned firewood is typically at or
near 20% moisture content. This can be measured with any number of hand-held moisture meters available through your
local hearth shop. Follow instructions included in the meter you purchase to measure fuel wood moisture content. Burn only
dry, seasoned wood as using wet wood will greatly reduce your efficiency.
CO Emissions:
The Green Mountain Insert 90 has an average CO emission rate over all burn categories of 53 g/hr. Wet wood or
unapproved fuel described above can greatly affect the emissions of a wood burning stove.
Smoke/Fire/CO Detectors:
It is highly recommended that smoke and CO detectors be installed throughout the heated space when a wood burning
heater is installed. Be certain to install these devices not only in the area where the wood appliance is located, but also in
bedrooms, hallways leading to other areas of the house and all common areas of the heated space. Check the batteries in
these devices and assure operation by performing whatever test operations are recommended by the manufacturer.

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
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TABLE OF CONTENTS
NOTES ON STOVE OPERATION AND EFFICIENCY ....................................................................................................... 2
TABLE OF CONTENTS .............................................................................................................................................. 3
INTRODUCTION ....................................................................................................................................................... 4
CODES ................................................................................................................................................................... 5
SAFETY INFORMATION ............................................................................................................................................ 5
PERIODIC CHECKLIST ............................................................................................................................................. 6
EMERGENCY PROCEDURES .................................................................................................................................... 6
SPECIFICATIONS ..................................................................................................................................................... 7
INSTALLATION ......................................................................................................................................................... 8
UNPACKING ............................................................................................................................................................ 8
PACK LIST .............................................................................................................................................................. 8
INSTALLING YOUR STOVE ....................................................................................................................................... 8
HEARTH REQUIREMENTS & FLOOR PROTECTION...................................................................................................... 9
COMBUSTIBLE SURFACE REQUIRED CLEARANCES ................................................................................................... 9
CHIMNEY CONNECTOR SYSTEMS AND CLEARANCES FROM COMBUSTIBLE WALLS FOR RESIDENTIAL HEATING
APPLIANCES ......................................................................................................................................................... 11
OUTSIDE AIR SUPPLY ........................................................................................................................................... 12
VENTING COMPONENTS & CONFIGURATION REQUIREMENTS ................................................................................... 12
MASONRY CHIMNEY WALL CONSTRUCTION: ............................................................................................................ 14
FLUE LINER OPTIONS: ........................................................................................................................................... 14
INTERIOR CHIMNEY REQUIREMENTS: ...................................................................................................................... 14
EXTERIOR CHIMNEY REQUIREMENTS: ..................................................................................................................... 14
CHIMNEY HEIGHT REQUIREMENTS (SEE FIGURE 8): ................................................................................................ 14
OPERATION ...................................................................................................................................................... 16
CONTROLS AND FEATURES ................................................................................................................................... 17
CHOOSING FIREWOOD .......................................................................................................................................... 17
BUILDING A FIRE .................................................................................................................................................. 19
BREAKING IN YOUR WOOD STOVE ........................................................................................................................ 19
NORMAL OPERATION ............................................................................................................................................ 20
OVER-FIRE CAUTION ............................................................................................................................................ 20
MAINTENANCE ...................................................................................................................................................... 22
GLASS REPLACEMENT PROCEDURES .................................................................................................................... 22
CREOSOTE FORMATION & REMOVAL ..................................................................................................................... 22
PREVENTION ........................................................................................................................................................ 22
CLEANING ............................................................................................................................................................ 22
GASKETS ............................................................................................................................................................. 23
GLASS ................................................................................................................................................................. 23
APPENDIX 1: INSTALLING THE OPTIONAL FIRE SCREEN ........................................................... 24
APPENDIX 2: INSTALLING THE OPTIONAL FRESH AIR INTAKE KIT ............................................. 25
APPENDIX 3: BLOWER INSTALLATION / REPLACEMENT ............................................................ 26
APPENDIX 4: INSTALLATION OF SECONDARY AIR TUBES AND BAFFLE ..................................... 28
APPENDIX 5: REMOVAL INSTRUCTIONS ................................................................................... 30
APPENDIX 6: EXPLODED DIAGRAM AND PARTS LIST ................................................................ 31
TROUBLESHOOTING .............................................................................................................................................. 33
TROUBLESHOOTING GUIDE ................................................................................................................................... 34
REPLACEMENT PARTS & OPTIONAL ACCESSORIES ................................................................................................. 35
SAFETY LABEL ..................................................................................................................................................... 36
LIMITED WARRANTY ............................................................................................................................................. 37

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
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INTRODUCTION
Thank you for purchasing a Green Mountain Insert 90
woodstove from Hearthstone Quality Home Heating
Products. This stove will provide years of comfortable
heat. The Green Mountain Insert 90 blends modern
technology with the unique beauty and qualities of
cast iron and Soapstone. We trust that you will
appreciate the quality of this handcrafted product.
Your Green Mountain Insert 90 woodstove burns very
efficiently, and produces a large amount of heat.
However, you should not consider your Green
Mountain Insert 90 the primary heat source for your
home. The Green Mountain Insert 90’s large glass
window allows you to enjoy the fire from a variety of
locations in the room.
Please read this manual in its entirety. Its purpose is
to familiarize you with your stove's safe installation,
proper break-in, operation, and maintenance. It
contains extremely important information so keep it
handy and refer to it often.
A qualified heating technician may need this owner’s
manual as a reference when installing this stove in
your home. There are national, state, and local
building codes that direct the technician on how to
install your stove. These codes stipulate the
dimension of stovepipe and clearances to walls,
ceilings, hearth, and other combustible surfaces. The
codes exist to reduce the risk of fire. Failure to follow
these instructions can result in fire, property damage,
bodily injury, and even death.
It is extremely important to install this stove with the
proper clearance from combustible surfaces. You can
purchase special wall coverings as specified by this
manual and the NFPA 211 code to protect
combustible surfaces. As a general rule, keep
furniture, drapes, curtains, wood, paper, and other
combustibles at least 36 inches (92 cm) away from
the stove. Never install the stove in or near a storage
location for gasoline, kerosene, charcoal lighter fluid
or any other flammable liquids.
Install the stove in your central living area to allow
heat to radiate naturally to distant rooms. Do not
install your stove in a poorly insulated area. This is
inefficient and would likely result in higher fuel
usage.
 SAFETY NOTICE:
AN IMPROPERLY INSTALLED STOVE CAN RESULT
IN A HOUSE FIRE. FOR YOUR SAFETY,
CAREFULLY FOLLOW THE INSTALLATION
DIRECTIONS. CONTACT LOCAL BUILDING OR
FIRE OFFICIALS ABOUT RESTRICTIONS AND
INSTALLATION INSPECTION IN YOUR AREA.
The safety of your stove will depend on many factors,
some of which include: distance to combustible
objects, correct venting, and adequate chimney
maintenance. Should you have any questions, do not
hesitate to contact your dealer for additional
information.
Contact your dealer for any necessary warranty
service.
This Green Mountain Insert 90 Model 8460 stove is
warranted by:
Hearthstone Quality Home Heating Products, Inc®
317 Stafford Ave.
Morrisville, Vermont 05661, USA
www.Hearthstonestoves.com

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
5
CODES
When you install your Green Mountain Insert 90
woodstove, it is imperative that you adhere to all
Federal and local codes. Obtain these codes from
either of the following sources:
American National Standards Institute, Inc. (ANSI)
1430 Broadway
New York, NY 10018
www.ansi.org
National Fire Protection Association, Inc. (NFPA)
Battery March Park
Quincy, MA 02269
www.nfpa.org
SAFETY INFORMATION
Read and understand this Owner's Manual
thoroughly before installing and using this stove.
Make sure to install your stove:
 According to the manufacturer's
recommendations
 In accordance with all applicable codes
 With the proper sized chimney
When using your stove, follow these safety
precautions:
 Never modify this stove in any way.
 Never burn kiln dried, painted or treated wood in
this stove.
 DO NOT BURN GARBAGE. Never burn garbage
or trash, colored or glossy paper, solvents,
plywood, artificial logs, cardboard, or driftwood, in
this stove.
 Never burn coal in this stove.
 DO NOT BURN FLAMMABLE FLUIDS.
 DO NOT USE CHEMICALS OR FLUIDS TO
START THE FIRE. Never use gasoline,
kerosene, charcoal lighter fluid, or other
flammable fluids to start or invigorate the fire.
These fuels will cause dangerous burning
conditions in the stove. Keep all such materials
away from the stove.
 Never use a wood grate or other device to
elevate the fire.
 Never allow logs in the firebox to hit the glass
when the door is closed.
 Never slam the door or use the door to force
wood in to the stove.
 Never over-fire your stove.
 Never put articles of clothing or candles on a hot
stove.
 Never connect the stove to a flue used by another
appliance.
Other safety guidelines:
 Keep all combustible items such as furniture,
drapes, clothing, and other items, at least 36"
(0.92 m) from the stove (See page 9)
 Install a smoke detector, preferably in an area
away from your wood stove.
 Keep a fire extinguisher handy. We recommend
the type rated "A B C."
 Dispose of ashes properly.
 Keep children and pets away from the stove when
it is burning; they could be seriously injured by
touching a hot stove.
 Clean your chimney system as needed.
 Outside combustion air may be required if:
1. This solid-fuel-fired appliance does not
draw steadily, smoke rollout occurs, fuel
burns poorly, or back-drafts occur whether
or not there is combustion present.
2. Existing fuel-fired equipment in the house,
such as fireplaces or other heating
appliances, smell, do not operate properly,
suffer smoke roll-out when opened, or
back-draft whether or not there is
combustion present.
3. Opening a window slightly on a calm
(windless) day alleviates any of the above
symptoms.
4. The house is equipped with a well-sealed
vapor barrier and tight-fitting windows
and/or has any powered devices that
exhaust house air.
5. There is excessive condensation on
windows in the winter.
6. A ventilation system is installed in the
house.
If these or other indications suggest that infiltration air
is inadequate, additional combustion air should be
provided from the outdoors. Outside combustion air
can be provided to the appliance by using the optional
outside air kit #94-53600

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
6
PERIODIC CHECKLIST
Perform each of these tasks at the specified
intervals.
At the End of Every Week:
 Empty ashes from the firebox, sooner if the
firebox is full.
At the Beginning of Every Other Month:
 Depending upon your use of the stove, visually
inspect the chimney connector and chimney for
creosote.
 Check door seals using the "dollar bill test." -
When the stove is cool, shut the door on a dollar
bill. If the bill pulls out without any resistance,
then your stove’s door is not sealing properly. To
tighten the seal, adjust the door latch
mechanism or change the door gasket.
At the End of Every Season:
 Dismantle the chimney connector and clean it
thoroughly. Replace any pieces that show signs
of rust or deterioration.
 Inspect and, if necessary, clean your chimney.
 Clean out the inside of the stove thoroughly.
 Inspect all door gasket material and replace if
worn, frayed, cracked or extremely hard.
EMERGENCY PROCEDURES
If you have a stovepipe or chimney fire, follow these
instructions:
1. If the fire is too threatening, leave the area and
call the fire department immediately! If not,
perform the next three steps.
2. Close the primary air control.
3. Close the stovepipe damper (if present).
4. Keep the stove front door closed!
 WARNING: DO NOT ATTEMPT TO PUT OUT A
STOVEPIPE OR CHIMNEY FIRE BY THROWING
WATER ONTO THE STOVE, STOVEPIPE, OR
CHIMNEY. THE EXTREMELY HIGH
TEMPERATURE OF SUCH FIRES CAN CAUSE
INSTANTANEOUS STEAM AND SERIOUS BODILY
HARM.
Once the chimney fire expires, leave the primary air
control closed and let the fire in the stove die out
completely. Inspect the stove, liner, and chimney
thoroughly for any sign of damage before firing the
stove again. You must correct any damage before
using your stove again.
Establish a routine for the fuel, wood burner and
firing technique. Check daily for creosote build-up
until experience shows how often you need to clean
to be safe. Be aware that the hotter the fire the less
creosote is deposited, and weekly cleaning may be
necessary in mild weather even though monthly
cleaning may be enough in the coldest months.
Contact your local municipal or provincial fire
authority for information on how to handle a chimney
fire. Have a clearly understood plan to handle a
chimney fire.

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
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SPECIFICATIONS
Maximum Heat Output:
80,000 BTUs per hour of cordwood max.
Floor Size of Heated Area:
Up to a maximum of 2,200 square feet. Factors
unique to your home can reduce the square
footage the stove will heat. Home insulation
value, number and efficiency of windows, floor
plan, stove placement, quality of the fuel and
other conditions may limit the heating ability of
the stove.
Firebox Capacity:
2.5 cubic feet.
Maximum Log Length: Up To 20” (50.8 cm).
Emissions: 1.14 g/hr.
Burn Time: HeatLife Up to 9+ hrs. Note: The
amount and weight of wood contained per cubic
foot of firebox volume can vary from 10 to 25
lbs. per cubic foot depending on type of wood,
moisture content, packing density and other
factors.
Stove Dimensions:
Height: 28 3/4” (73.0cm)
Width: 38 1/2" (97.8cm)
Depth: 24 7/8" (63.2cm)
Weight: 440 lbs. (200 kg)
Connector Size: 6" (152 mm) diameter
Metal Chimney: 6" (152 mm) inside diameter
Masonry Chimney: 6” (152 mm) inside diameter
(round flue), 8” x 8” (203 x 203 mm) (square
flue)
Crate Dimensions: H-34” W-30” L-36” or
86.4x76.2x 91.4cm
Optional Equipment:
Outside Air Kit 94-53600
Steel Surround 94-5960010
Surround Extension 94-5960110
Fire Screen Insert 94-69600
Figure 1 – Green Mountain Insert 90 Dimensions

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
8
INSTALLATION
UNPACKING
Hearthstone packages your Green Mountain Insert
90 woodstove with the greatest care so that it ships
safely. Under certain circumstances, however,
damage may occur during transit and handling. When
you receive the Green Mountain Insert 90, carefully
unpack and inspect the stove and all accompanying
parts. Ensure that all parts are included inside the
stove. If any parts are damaged or missing, please
contact your authorized Hearthstone dealer
immediately.
Be sure to remove the packaging material in the flue
collar and above the baffle before installing the
chimney.
PACK LIST
Green Mountain Insert 90 Model 8460 Woodstove
Owner’s Manual
Three boxes of refractory stone
The safety label is attached by a cable in the bottom
of the stove, behind the ash lip assembly. Be careful
not to destroy label when assembling or removing
blower. Make sure safety label is secured in clip
when you are before closing off this area by
reinstalling the ash lip.
Figure 2 – Safety Label Location
INSTALLING YOUR STOVE
Inspect this location to make sure that the stove and
liner will have the required clearance from
combustible materials that are near the stove.
Combustibles include walls, floor, ceiling, and
chimney chase. You must carefully consider the
clearances to all of these combustibles before
actually connecting your stove.
If the floor in front of the insert is made of combustible
material, then a non-combustible floor protector is
required out to the dimensions indicated in the
clearances section of this manual. An example of a
non-combustible floor protector is a hearth
constructed with a continuous layer of tile, brick, slate,
glass or another non-combustible facing. There is no
R-value requirement.
Check the listing of your pipe with UL for the correct
clearances.
The diagrams in this manual represent typical
installations, but are specific to the Simpson Dura-
Vent brand.
Clearances to NFPA Code 211 Protected Surfaces
You can reduce the clearances to combustible
surfaces by using any National Fire Protection
Agency (NFPA) approved wall protection system with
additional approval of the regulatory authority having
jurisdiction in your area. Please refer to NFPA Code
211 for specifications and complete details. You can
obtain this information directly from the NFPA.
National Fire Protection Agency
Batterymarch Park
Quincy, MA 02269
1-800-344-3555
1-617-770-3000
www.nfpa.org

HEARTH REQUIREMENTS & FLOOR PROTECTION
Ensure you protect combustible flooring with a covering of noncombustible material. The Green Mountain Insert
90 does not require an insulated hearth pad. The minimum floor protection must be met under the stove and
extend beyond the stove as follows:
The minimum floor protection for US installations is 41-1/2in x 16in.
The minimum floor protection for installations in Canada is 48in x 18in.
Figure 3 Trim and Mantle and Floor Protection Clearances
Installing the stove in a room with Luxury Vinyl Plank (LVP) or Luxury Vinyl Tile (LVT) flooring requires extra
consideration from the stove to the LVP or LVT flooring. Some LVP and LVT flooring begins to warp at 110°
Fahrenheit. Each installation and flooring specification is different. Consult the flooring manufacturer for
maximum temperature recommendations. Additional shielding to prevent warping may be necessary
depending on the flooring used.
Additional Floor Protection – Raised Installation Additional Floor Protection – Not Raised Installation
41 -1/2” US
48” CAN

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
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COMBUSTIBLE SURFACE REQUIRED CLEARANCES
Note: Dimensions shown in the following figures are from the body of the stove unless otherwise indicated.
It is very important to follow minimum clearances for chimney connectors to combustibles such as walls and
ceilings when installing the stove near combustible surfaces.
Figure 4 – Clearance to Combustibles

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
11
CHIMNEY CONNECTOR SYSTEMS AND
CLEARANCES FROM COMBUSTIBLE WALLS
FOR RESIDENTIAL HEATING APPLIANCES
A. Minimum 3.5in thick brick masonry all framed
into combustible wall with a minimum of 12in.
brick separation from clay liner to combustibles.
The fire clay liner shall run from outer surface of
brick wall to, but not beyond, the inner surface
of chimney flue liner and shall be firmly
cemented in place.
B. Solid-insulated, listed factory-built chimney
length of the same inside diameter as the
chimney connector and having 1in. or more of
insulation with a minimum 9in. air space
between the outer wall of the chimney length
and combustibles.
C. Solid insulated, listed factory-built chimney
length with an inside diameter 2in. larger than
the chimney connector and having 1in. or more
of insulation, serving as a pass-through for a
single wall sheet steel chimney connector of
minimum 24 gauge thickness, with a minimum
2in. air space between the outer wall of
chimney section and combustibles. Minimum
length of chimney section shall be 12in.
chimney section spaced 1in. away from
connector using sheet steel support plates on
both ends of chimney section. Opening shall be
covered, and chimney section supported on
both sides with sheet steel supports securely
fastened to wall surfaces of minimum 24-gauge
thickness. Fasteners used to secure chimney
section shall not penetrate chimney flue liner.

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
12
OUTSIDE AIR SUPPLY
(Optional Kit #94-53600)
You can connect an outside air source directly to this
stove using an optional outside air kit. The advantage
of providing outside air directly to the stove is that the
air used by the stove for combustion is taken from
outside the residence rather than from within the
room where the stove is located.
The outside air kit for this stove allows for the direct
connection of the stove's air intake to a minimum 3"
(76 mm) diameter duct (supplied by others) * which
leads to the outside of the house. When considering
placement of the duct from the outside of the house
to the hearth, keep in mind the need to avoid
structural members of the house. The outside air kit
attaches to the side of the stove. Refer to the
instructions provided with the kit for installation.
*An adaptor for 4” duct is available if needed. KIT #90-
53308
When using an outside air kit in Canada, the stove
must be attached to your home’s floor. Use the
shipping clips that came with the stove and fasteners
long enough to attach securely to the subfloor. (The
clips and fastener heads may be painted to minimize
visibility).
Figure 5 – Outside Air Kit Detail
The International Residential Code (IRC) does not
allow the outside air duct to terminate higher than the
appliance. Some building officials restrict vertical rise
in the duct’s termination. Hearthstone recommends
the termination be at the same level, or lower than the
air intake on the stove.
Locate the termination of the duct on the outside wall
of the home in such a manner to avoid the possibility
of obstruction by snow, leaves or other material.
Screen the termination using ¼” x ¼” mesh rodent
screen and cover it with a rain/wind proof hood (flex
pipe, outside termination, mesh, and hood supplied
by others) Contact your dealer for availability.
VENTING COMPONENTS &
CONFIGURATION REQUIREMENTS
 NOT APPROVED FOR MOBILE HOME
INSTALLATION
 DO NOT CONNECT THIS UNIT TO A CHIMNEY
FLUE USED BY ANOTHER APPLIANCE
 Connect the insert to a listed 6” stainless steel
flexible connector that connects to a listed 6”
stainless steel liner extending the full length of
the chimney.
 In all cases, a sealed block off plate, or a plug of
other noncombustible material such as unfaced
fiberglass insulation, must be installed at the
damper area of the existing fireplace to seal the
chimney from the room air
 The fireplace insert must be installed with a
continuous chimney liner with a minimum
diameter of 6” extending from the fireplace insert
to the top of the chimney. The chimney liner
must conform to the class 3 requirements of
chimney liner standards ULC-S635 or ULC-
S640, or UL1777.
 Be sure to follow the manufacturer’s instructions
to maintain an effective vapor barrier at the
location where the chimney of other component
penetrates the exterior of the structure
 It is very important to follow minimum clearances
for chimney connectors to combustibles Check
the specifications from the manufacturer of
your connector.

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
13
COMPONENTS OF A VENTING SYSTEM
The complete venting system consists of several
components: chimney connector, flue liner, and
chimeny. It is absolutely necessary that you install all
of these components and maintain the clearances to
combustibles discussed earlier to ensure a safe stove
installation.
To protect against the possibility of a house fire, you
must properly install and constantly maintain the
venting system in good condition. Be sure to inspect
the chimney and chimney connector and keep it clean.
Upon inspection, immediately replace rusted,
cracked, or broken components. Failure to follow
these instructions and specified components or using
make-shift compromises can result in fire, property
damage, bodily injury, and even death.
 The chimney connector is the stovepipe from the
woodstove to the chimney. The chimney
connector stovepipe is 6" (152 mm) diameter, 24
stainless steel connector pipe. Do not use mild
steel, aluminum or galvanized steel pipe - they
cannot withstand the extreme temperatures of a
wood fire.
 Only install this stove to a lined masonry chimney
or an approved high temperature prefabricated
residential type building heating appliance
chimney. Do not connect this stove to a chimney
serving another appliance; you will compromise
the safe operation of both the wood stove and the
connected appliance.
 A liner is the UL 1777 or ULC S635 (for factory
built fireplace or masonry) chimney.
You must connect your stove to a chimney
comparable to those recommended in this manual.
Do not use stovepipe as a chimney. Use stovepipe for
installations only to connect the stove to a proper
chimney.
 WARNING: DO NOT CONNECT THIS APPLIANCE
TO ANY AIR DISTRIBUTION DUCT OR SYSTEM.
INSTALLING A VENTING SYSTEM
Attach stovepipe section to the flue collar and to each
other with the crimped end toward the stove. If
creosote builds up, this allows the creosote to run into
the stove and not on the outside of the stovepipe or
onto the stove.
Secure all joints, including attaching the stovepipe to
the stove's flue collar, with three sheet metal screws.
Install #10 x 1/2" (3 mm x 13 mm) sheet metal screws
into the holes pre-drilled in the flue collar.
Disregarding the screws can cause joints to separate
from the vibrations that result from a creosote
chimney fire.
In general, you do not need to install a stovepipe
damper with the Green Mountain Insert 90. Some
installations, however, could benefit from a stovepipe
damper, such as a tall chimney which can create a
higher than normal draft. In such cases, a damper can
help regulate the draft. The Green Mountain Insert 90
requires a draft between 0.06" and 0.1" WC. For
drafts above 0.1" WC, install a stovepipe damper.
Check the draft at stove installation time.
Remember, the NFPA recommends minimum
clearances for chimney connectors to combustibles
such as walls and ceilings. Once the stove is installed
at safe distances from these combustible surfaces, it
is also important to maintain these connector
clearances for the remainder of the installation.
CONNECTING THE STOVE TO A CHIMNEY
You can install your Green Mountain Insert 90 to a
prefabricated metal chimney, or to a masonry
chimney.
This room heater must be connected to (1) a listed
Type HT (2100° F) chimney per UL 103 or ULC S629,
or (2) a code-approved masonry chimney with a flue
liner. The chimney size should not be less than the
flue collar, or more than three times greater than the
cross-sectional area of the flue collar.
Ensure the size of the chimney’s flue is appropriate
for the GMI90. The GMI90 requires a 6" (152 mm)
inside diameter flue for new installations. A 6”
diameter flue provides adequate draft and
performance. You can use an 8" (203 mm) diameter
existing flue with a reducer. An oversized flue
contributes to creosote accumulation. (In this case,
bigger is NOT better.)
An interior installation where the chimney passes
inside the residence through the ceiling and roof. • An
exterior installation where the chimney passes
through the wall behind the Fireplace Insert then up
the outside of the residence. Whenever possible,
choose an interior chimney. An interior chimney heats
quickly and retains its heat; thus promotes a better
draft and discourages the formation of creosote. An
exterior chimney does not benefit from the
surrounding warmth of the building, so it typically
operates at lower flue temperatures than an interior
chimney. An exterior chimney’s draft is not as strong
and may experience increased creosote
accumulation.

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• REMOVE THE DAMPER OR LOCK IT OPEN
We recommend installing a cleanout tee where
possible to simplify chimney cleaning and
maintenance.
Connecting to a Prefabricated Metal Chimney
Before installing the stove in a prefabricated metal
chimney, the fireplace must have the following
characteristics:
1) Listed per UL 127 or ULC S610.
2) Include a full height listed chimney liner meeting
ULC-S635 or ULC-S640 standards.
3) The means to prevent room air passage to the
chimney cavity of the fireplace.
4) Does not disturb the airflow in or within the fireplace
when installed (louvers, or cooling air inlet or outlet
ports must not be blocked).
5) Not be altered in any way, except for the following:
a) External trim pieces which do not affect the
operation of the fireplace can be removed, providing
they are stored on or within the fireplace for re-
assembly if the insert is removed. b) The chimney
damper can be removed to install the chimney liner.
6) Must not have blocked circulating chambers (if
available).
7) The means for removing the insert to clean the
chimney flue.
8) Have a permanent metal warning label (provided
with the GMI90—see following illustration) attached
to the fireplace by riveting it to the outside wall, stating
that the fireplace must be restored to its original
condition for safe use without the insert.
Connection to a Masonry Chimney
Consider two primary elements when connecting your
stove to a masonry chimney: the chimney itself and
the thimble where the stovepipe connects to the
chimney. Use only code approved masonry
chimneys containing a proper flue liner.
Before connecting to a masonry chimney, hire a
professional to examine the chimney for cracks, loose
mortar, and other signs of deterioration and blockage.
If the chimney needs repair, complete them before
installing and using your stove. Do not install your
stove until the chimney is safe for use.
Ensure the chimney’s cleanout is complete and
working properly. To avoid a loss of draft, the cleanout
door must close completely and provide a tight seal.
If the cleanout door leaks, the chimney will cool, your
stove will perform poorly, and creosote can form.
Ensure the size of the chimney’s flue is appropriate
for this stove and that it is not too large. Use a
masonry chimney with a maximum 6” Diameter or 8"
x 8" (203 mm x 203 mm) tile size for best results. An
oversized flue contributes to the accumulation of
creosote.
Use the following checklist to ensure that your
masonry chimney meets these minimum
requirements:
MASONRY CHIMNEY WALL CONSTRUCTION:
 Mortared brick or modular block at least 4" (102
mm) thick – must use liner
 A mortared rubble or stone wall – must use liner
FLUE LINER OPTIONS:
 Tile - minimum wall thickness of 5/8" (16 mm),
installed with refractory mortar, and with at least
1" (25 mm) air space around the liner
 Stainless steel - UL listed 6” diameter, insulated
or wrapped liner, or the space around the liner
filled with vermiculite or suitable material (these
keep the liner warmer for better performance)
 Ensure any equivalent flue liner is a listed
chimney liner system meeting type HT
requirements or other approved material.
INTERIOR CHIMNEY REQUIREMENTS:
 Must have at least 2" (51 mm) clearance to
combustible materials
 Must install fire stops at the spaces where the
chimney passes through floors and/or ceiling
 Any insulation material must be at least 2" (51
mm) from the chimney
EXTERIOR CHIMNEY REQUIREMENTS:
 At least 1" (25 mm) clearance to combustible
materials
CHIMNEY HEIGHT REQUIREMENTS (SEE FIGURE 8):
 At least 3 feet (0.9 m) higher than the highest
part of the roof opening through which it passes.
 At least 2 feet (0.6 m) higher than any part of the
roof within 10 feet (3 m) measured horizontally
from the top of the chimney.
The recommended minimum chimney height is 10
feet (3 m) off the floor. The recommended maximum
chimney height is 30 feet (9m). The Green Mountain
Insert 90 requires a draft between 0.06” and 0.1”
water column. Ensure your chimney is long enough
to provide the minimum draft, and use a damper if

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
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your installation has a required chimney height that
provides too much draft.
Figure 6 - Installation of Chimney Liner

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
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Figure 7 - Chimney Height Requirements

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
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OPERATION
Once your Green Mountain Insert 90 is installed, you
are ready to light a fire.
Every installation, season’s firewood, and operator’s
technique varies. Learn how to use your stove most
efficiently for your installation. We can give you the
basic principles, but only you can ensure maximizing
the potential of your stove while also operating it
safely.
 WARNING: HOT WHILE IN OPERATION! KEEP
CHILDREN, PETS, CLOTHING AND FURNITURE
AWAY. CONTACT MAY CAUSE SKIN BURNS.
Read this entire chapter before lighting your first fire.
It explains the controls and features of your wood
stove, how to choose firewood, and how to use your
stove on a daily basis.
CONTROLS AND FEATURES
Before lighting any fires, become familiar with the
location and operation of your stove's controls and
features and learn how to use them (See Figure 10).
For your own safety, do not modify these features in
any way. We recommend you use fireplace gloves
when the stove is in operation and hot.
Figure 8 - Controls & Features
FRONT DOOR HANDLE: The firebox door allows
you to load wood into your stove; a wood handle
operates the door. To open the door, pull up on the
handle and swing the door away from the stove. To
latch the door, push the door tightly towards the
firebox then continue to push the handle in and down
until it latches shut. Gently pull on the door handle to
make sure it is properly latched.
PRIMARY AIR CONTROL: The primary air control
lever is located under the ash lip. The primary air
control allows you to regulate the amount of air
entering the firebox. Generally, the more air allowed
into the firebox, the faster the rate of burn and the
higher the heat output; conversely, less air creates a
slower burn, with lower heat output. For maximum
airflow, pull the lever left as far as possible; move the
lever right as far as possible for minimum airflow
(does not close completely).
Figure 9 – Air Control
CHOOSING FIREWOOD
Burn only natural firewood (known as cordwood) in
the Green Mountain Insert 90 Model 8460 Wood
Heater. This stove is not designed to burn other fuels.
 CAUTION: DO NOT USE CHEMICALS OR
FLAMMABLE FLUIDS TO START THE FIRE. DO
NOT USE CHARCOAL, PELLETS, COAL,
ARTIFICIAL LOGS OR ANY OTHER MATERIALS AS
FUEL; THEY ARE NOT SAFE. DO NOT BURN
GARBAGE OR FLAMMABLE FLUIDS.
 THE USE OF UNAUTHORIZED FUEL SUCH AS
COAL COULD PRODUCE HIGH LEVELS OF
CARBON DIOXIDE IN THE LIVING SPACE. AT HIGH
LEVELS CARBON DIOXIDE COULD RESULT IN
PERSONAL INJURY OR DEATH.
The quality of your firewood directly affects heat
output, duration of burn and performance of your
stove. Softwoods generally burn hotter and faster,
while hardwoods burn longer and produce better
coals. Density and moisture content are two critical
factors to consider when purchasing wood.

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The following is a list of some wood species and their
relative BTU (British Thermal Unit) content. The
higher the BTU content, the longer the burn. Firewood
with higher BTUs is generally ideal for a wood stove.
Burn untreated wood only. Other materials such as
wood preservatives, metal foils, coal, plastic,
garbage, sulphur, or oil may damage the catalysts.
Wood Heat Value: Sorted By Btu Content
Common Name Lb/ cord MBTU/ cord
High
Osage Orange (Hedge) 4,728 32.9
Hickory, Shagbark 4,327 27.7
Hop Hornbeam (Ironwood) 4,267 27.3
Beech, Blue (Ironwood) 3,890 26.8
Birch, Black 3,890 26.8
Locust, Black 3,890 26.8
Hickory, Bitternut 3,832 26.7
Locust, Honey 3,832 26.7
Apple 4,100 26.5
Mulberry 3,712 25.8
Oak, White 4,012 25.7
Medium High
Beech, European 3,757 24
Maple, Sugar 3,757 24
Oak, Red 3,757 24
Ash, White 3,689 23.6
Birch, Yellow 3,689 23.6
Medium
Juniper, Rocky Mtn 3,150 21.8
Elm, Red 3,112 21.6
Coffee tree, Kentucky 3.112 21.6
Hackberry 3,247 20.8
Tamarack 3,247 20.8
Birch, Gray 3,179 20.3
Birch, White (Paper) 3,179 20.3
Walnut, Black 3,192 20.2
Cherry 3,120 20
Ash, Green 2,880 19.9
Cherry, Black 2,880 19.9
Elm, American 3,052 19.5
Elm, White 3,052 19.5
Sycamore 2,808 19.5
Ash, Black 2,992 19.1
Maple, Red 2,924 18.7
Fir, Douglas 2,900 18.1
Medium Low
Boxelder 2,797 17.9
Alder, Red 2,710 17.2
Pine, Jack 2,669 17.1
Pine, Norway (Red Pine) 2,669 17.1
Pine, Pitch 2,669 17.1
Catalpa 2,360 16.4
Hemlock 2,482 15.9
Spruce, Black 2,482 15.9
Pine, Ponderosa 2,380 15.2
Low
Aspen, American 2,290 14.7
Butternut (Walnut, White) 2,100 14.5
Spruce 2,100 14.5
Willow 2,100 14.5
Fir, Balsam 2,236 14.3
Pine, White (Eastern,
Western)
2,236 14.3
Fir, Concolor (White) 2,104 14.1
Basswood (Linden) 2,108 13.8
Buckeye, Ohio 1,984 13.8
Cottonwood 2,108 13.5
Cedar, White 1,913 12.2
Moisture content also plays a key role in the
performance of your stove. Wood freshly cut from a
living tree (green wood) contains a great deal of
moisture. As you might expect, green wood burns
poorly. You must season green wood before using it
in your wood stove. To season green wood properly,
split, stack, and allow it to air dry for a period of one
year. Green wood may provide less than 2000 Btu per
pound, whereas dry wood can provide up to 7000 Btu
per pound.
Stack the firewood on skids or blocks to keep it off the
ground, cover only the top of the stack. Plastic or
tarps that cover the sides of the woodpile trap
moisture and prevent the wood from drying. As for
stacking, an old Vermonter said, "The spaces
between the logs should be large enough for a mouse
to get through, but not for the cat that's chasing it."
 CAUTION: DO NOT STORE FIREWOOD WITHIN
THE STOVE'S SPECIFIED CLEARANCES TO
COMBUSTIBLE MATERIALS.

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
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BUILDING A FIRE
Once you understand the controls of your wood stove
and have the appropriate firewood, you are ready to
start a fire.
 WARNING: NEVER USE GASOLINE, GASOLINE-
TYPE LANTERN FUEL, KEROSENE, CHARCOAL
LIGHTER FLUID, OR SIMILAR LIQUIDS TO START
OR 'FRESHEN UP' A FIRE IN THIS HEATER. KEEP
ALL SUCH LIQUIDS WELL AWAY FROM THE
HEATER WHILE IT IS IN USE.
BREAKING IN YOUR WOOD STOVE
It is imperative that your stove is "broken in" gradually.
Soapstone must be "seasoned"; over-firing a new
stove may cause soapstone to crack or may damage
other stove parts. Natural moisture in the freshly
quarried soapstone must be driven out slowly to
minimize the “shock” to the stone of its first exposure
to high firebox temperatures. In addition, the
asbestos-free furnace cement must be cured slowly
to ensure adequate sealing and bonding.
When you light your first fires, the woodstove will emit
some smoke and fumes. This is normal “off-gassing”
of the paints and oils used when manufacturing the
woodstove. If you find it necessary, open a few
windows to vent your room. The smoke and fumes
will usually subside after 10 to 20 minutes of
operation. The odor and smoke will end once the
stove is “cured”.
The first few fires of the season may produce other
odors from impurities that exist in the area
immediately surrounding the stove. Some potential
impurities are cleaning solvents, paint solvents,
cigarette smoke, and soot from scented candles, pet
hair, dust, adhesives, a new carpet, and new textiles.
These odors will dissipate over time. You can
alleviate these odors by opening a few windows or
otherwise creating additional ventilation around your
stove. If any odor persists, contact your dealer or an
authorized service technician.
If you adhere to the operating procedures in this
manual, the steel, cast iron, and soapstone
components of your stove will give you many years of
trouble-free use. With use, the color of the soapstone
may change and small fractures may appear on the
surface. These changes do not affect the function of
the stove. If a panel breaks completely, it must be
replaced
Avoid the following conditions that can cause the
glass, soapstone, steel or cast iron pieces to break:
 Do not throw wood into the stove.
 Do not use the door as a lever to force wood into
the stove.
 Do not load wood encrusted with ice into a
burning stove - the thermal shock can cause
damage.
 Do not use a manufactured log grate or otherwise
support the fuel. Burn the fire directly on the floor
of the firebox.
BUILDING A BREAK IN FIRE
1) Open the front door and place five or six double
sheets of tightly twisted newspaper in the center
of the firebox. Arrange kindling in a crisscross
pattern over the newspaper. Kindling should be
approximately ten pieces, 1/2" (13 mm) in
diameter and 10" to 16" (254 mm to 457 mm)
long.
2) Fully open the primary air control by pulling the
control handle towards you, away from the
firebox.
3) Light the paper under the kindling. Leave the
door slightly ajar momentarily until the kindling
has started to burn and draft begins to pull.
4) Close the door and allow the fire to burn. Keep
the door closed while the stove is in use.
5) KEEP A WATCHFUL EYE ON YOUR STOVE to
maintain a steady, low-heat fire. Your first fire
should make the stove warm but not hot to the
touch. Visible steam, or boiling moisture and
hissing indicate the soapstone is too hot. At most,
a few small chunks of wood should be added to
the fire to reach safe break-in temperatures.
6) Once the stove is warm but not hot to the touch,
close the primary air control by pushing it fully
inward toward the stove to allow the fire to die out
completely.
7) Let the stove return to room temperature.
Your first fire and first fire each season thereafter
should be built and maintained as outlined above.
Your patience will be rewarded by a properly
seasoned stove.
 NOTE: The cool flue gas temperatures
present during the break-in procedure may
cause rapid creosote build-up. The door
glass may also get dirty. A good hot fire will
clean it. We recommend a visual inspection
(and cleaning if necessary) of your stovepipe
and chimney once the break-in procedure is
completed.

Hearthstone Quality Home Heating Products, Inc ® Green Mountain Insert 90 (Model 8460)
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NORMAL OPERATION
BUILDING A FIRE FOR EVERYDAY USE
1) Open the front door and place five or six double
sheets of tightly twisted newspaper in the center
of the firebox. Arrange kindling in a tee-pee
configuration over the newspaper. Use
approximately 10 pieces of kindling, 1/2" (13 mm)
in diameter and 10" to 16" (254 mm to 406 mm)
long.
2) Fully open the primary air control by pulling the
lever completely left.
3) Light the paper under the kindling. Leave the front
door slightly ajar momentarily until the kindling
begins to burn and draft begins to pull.
4) Close the door and allow the fire to burn.
5) Once the kindling is burning, open the front door
and add logs, small at first, to build the fire up.
Ensure you keep the logs away from the glass in
front in order for the air-wash system to work
properly. Keep the front door closed while the
stove is in use.
CAUTION: DO NOT BUILD THE FIRE TOO CLOSE
TO THE GLASS. KEEPING THE FIRE TOWARDS
THE CENTER OF THE FIRE BOX WILL KEEP
COALS FROM BUILDING UP AGAINST THE GLASS
DURING RELOADING.
6) Use the primary air control to regulate the desired
rate of burn. Pull the handle left for a higher burn
rate, and pull the handle right for a lower burn
rate. The air control does not close completely.
Note: When opening the front door to reload or re-
arrange logs, it is advisable to open the door just a
crack, pause for a moment then open the door
completely. This procedure allows the firebox to clear
of smoke before the door is open fully. In addition,
reloading on a bed of hot, red coals reduces smoking
time and brings fresh fuel up to a high temperature
rapidly. During the refueling and rekindling of a cool
fire, or a fire that has burned down to the charcoal
phase, operate the stove at a medium to high firing
rate for about 10 minutes When reloading the stove,
try to keep an open path behind the Lower Primary
Air Opening (LPAO). It is helpful to leave a small
valley in the coal bed behind the LPAO to insure
faster re-lighting.
BURN RATE
This wood heater has a manufacturer-set
minimum low burn rate that must not be altered.
It is against federal regulations to alter this
setting or otherwise operate this wood heater in
a manner inconsistent with operating
instructions in this manual
LOW BURN: Move the air control lever all the way to
the right. (See figure 10). This closes the air shutter
to its minimum opening. A low burn rate over
extended periods is not advisable as it can promote
the accumulation of creosote. Inspect the venting
system frequently if using low burn rates consistently.
MEDIUM LOW BURN: With the primary air control in
the low position, pull the air control left (a little less
than 1/2”). A medium-low burn rate is the typical
setting and is preferable if the stove is unattended. At
this burn rate, a little goes a long way.
MEDIUM HIGH BURN: With the primary air control in
the low position, pull the air control left (a little less
than 1”)
HIGH BURN: Completely open the primary air control
by moving it all the way left. Fully load the firebox with
wood on a bed of hot coals or on an actively flaming
fire. To minimize creosote accumulation, run the
stove on high once or twice daily for 35 to 45 minutes
to fully heat the stovepipe and chimney.
CAUTION: Do not burn fuel other than cordwood in
your stove.
OVER-FIRE CAUTION
Over-firing means the stove is operating at
temperatures above normal temperatures reached
during High Burns outlined in the BURN RATE
section. Carefully avoid over-firing, as it will damage
the stove. Symptoms of chronic over-firing can
include warped components, short burn times, a
roaring sound in the stove or stovepipe, and
discoloration of the stovepipe. A properly installed
stove using fuel and following operating procedures
as outlined in this manual should not over-fire.
Excessive draft, inappropriate fuel, and operator error
can cause over-firing. Correct an over-fire situation as
follows:
 EXCESSIVE DRAFT: Contact your local dealer
to have a draft reading taken. Any draft in excess
of 0.1 WC requires a damper in the stovepipe.
Some installations may require more than one
damper.
 INAPPROPRIATE FUEL: Do not burn coal; kiln
dried lumber, wax logs, compressed wood, highly
volatile fuels or combustibles, or anything other
than natural cordwood.