Large-Capacity Soapstone-Lined Wood Heat for Your Existing Fireplace

The Green Mountain Insert 90 (GMi90, Model 8460) is HearthStone's large non-catalytic wood fireplace insert with a flush cast iron front, 2.5 cu. ft. soapstone-lined firebox, and factory-installed blower.

Key Features

• Large soapstone-lined firebox — a 2.5 cu. ft. firebox lined with natural soapstone accepts logs up to 20 inches and radiates steady warmth as the fire burns down.
• Flush cast iron design — the insert sits flush with the fireplace facing for a built-in look, with a cast iron front in Black Matte or Brown Enamel.
• Non-catalytic secondary combustion — secondary air tubes and a baffle burn off gases released by the wood; a single-lever primary air control sets the burn rate.
• EPA 2020 certified using cordwood — certified at 1.14 g/hr particulate emissions with a 68% (HHV) weighted average efficiency, per the current owner's manual.
• Maximum cordwood heat output of 80,000 BTU/hr — with heating coverage of up to 2,200 square feet, depending on home layout, insulation, and operating conditions.
• Included convection blower — the unit ships complete with a factory-installed blower offering automatic heat-sensing operation, a manual mode, and variable speed.
• HeatLife up to 9+ hours — per the current owner's manual, soapstone extends usable heat well after the active flames decline.

Product Features

Large Soapstone-Lined Firebox

The firebox is lined with natural soapstone panels over a steel firebox body. Soapstone absorbs heat during the burn and releases it gradually, moderating temperature swings and extending comfortable warmth. The firebox capacity is 2.5 cu. ft., with a maximum log length of up to 20 inches, and the manual notes the insert is intended to supplement rather than serve as the primary heat source for a home.

Non-Catalytic Secondary Combustion

A single primary air control lever under the ash lip regulates the burn rate from high to low (the control does not close completely). Secondary air tubes beneath the baffle at the top of the firebox supply air to burn gases released by the wood, and an air-wash system helps keep the ceramic glass clear for viewing the fire. The glass is a clear ceramic material capable of operating at temperatures up to 2300°F.

Included Convection Blower

A blower is factory installed behind the faceplate at the bottom of the insert to move room air through the convection air jacket. A rocker switch selects automatic or manual mode and a rheostat sets the blower speed. In automatic mode the blower starts when the insert is warm and stops as it cools; in manual mode it runs until switched off. A 90-degree connector is supplied for optional hardwiring through the rear of the insert. The current dealer sheet confirms the unit ships complete with the blower.

Cast Iron Flush Design

The GMi90 is designed to sit flush with the fireplace facing, framing the fire with a cast iron front and door. An optional three-piece steel surround attaches behind the cast iron faceplate to trim the transition to the fireplace opening; current HearthStone materials list surround coverage of approximately 50 inches wide by 34-1/2 inches tall.

Flexible Fireplace Fit

The GMi90 is designed for installation in a compliant masonry fireplace and chimney, or in a qualifying listed factory-built fireplace system that meets every condition in the current Model 8460 manual, including listing to UL 127 or ULC S610 and a full-height listed chimney liner. An optional surround extension lets the insert project farther into the room, reducing the minimum fireplace depth per the manual. The GMi90 is not approved for mobile home installation and is not a freestanding stove.

Full-Length 6-Inch Liner Requirement

The GMi90 must be connected to a listed 6-inch stainless steel flexible connector and a continuous listed 6-inch stainless steel liner extending from the insert to the top of the chimney, using liners meeting UL 1777, ULC S635, or ULC S640 as applicable. A sealed block-off plate or noncombustible plug is required at the existing fireplace damper area, the fireplace damper must be removed or locked open, and the insert must never share a flue with another appliance or connect to any air-distribution duct. The manual requires a draft between 0.06 and 0.10 inches of water column, with a stovepipe damper installed where draft exceeds 0.10 inches.

Available Finishes and Configurations

The GMi90 is a single base model available in two finishes. Pricing varies by finish.

Specifications

Fireplace Opening, Clearances and Hearth Requirements

The GMi90 must be installed with a continuous 6-inch listed stainless steel chimney liner to the top of the chimney. Masonry fireplaces must have a code-approved lined chimney, and factory-built fireplaces must be listed to UL 127 or ULC S610, include a full-height listed liner, keep room air out of the chimney cavity, retain unblocked cooling-air and circulating chambers, remain unaltered except as the manual permits, and carry the permanent warning label supplied with the GMi90. Do not connect the insert to a chimney flue serving another appliance. The GMi90 is not approved for mobile home installation.

Where a fresh-air intake is required, HearthStone recommends adding at least 4 inches to the minimum fireplace-opening width. The optional surround extension permits the shallower installation depths by allowing the insert to project into the room when installed according to the current manual.

The current manual does not require an insulated hearth pad for the GMi90; combustible flooring in front of the insert must be covered with noncombustible material to the dimensions above. For raised and non-raised installations, and where the insert projects into the room, any additional floor protection is determined using the manual's floor-protection figures and the projection dimensions of the installation. Some luxury vinyl plank and tile flooring may begin to warp at approximately 110°F; consult the flooring manufacturer for maximum temperature limits, as additional shielding may be needed depending on the flooring used. The current owner's manual governs every installation; review it with your installer and local building official for complete requirements.

Included Equipment

• Green Mountain Insert 90 Model 8460 wood fireplace insert
• Factory-installed convection blower (the unit ships complete with the blower)
• Three boxes of refractory stone firebox lining (two rear, two side-rear, and two side-front stones)
• Side stone retainer brackets
• Leg leveling bolts (quantity 2)
• 90-degree Romex connector for optional blower hardwiring
• Rear valence cover bracket (installed or packed with the insert)
• Safety label (attached to the insert)
• Owner's manual

Compatible Accessories

All accessories are sold separately and installed per their instructions and the current manual.

Warranty

The GMi90 is covered by HearthStone's limited warranty as published in the current owner's manual, where Limited Lifetime is defined as ten years. In summary, the applicable schedule covers stone, cast iron components not listed elsewhere, and the clean-burning air-supply system for the Limited Lifetime period; door handles, latches, steel components, and the firebox for five years; appliance electrical components, refractory, vermiculite panels, and baffles for two years; and enamel finish, glass, accessories, and components not otherwise listed for one year. Warranty labor is covered in the first year through an authorized dealer when the appliance is dealer installed, and parts shipping is covered for the first 90 days under the written terms. Coverage extends to the original purchaser and is not transferable; wear parts and conditions and exclusions apply. See the current written warranty for complete terms.

About HearthStone

HearthStone Quality Home Heating Products of Morrisville, Vermont has built stoves prized for long-lasting, comfortable heat for more than four decades. The Green Mountain Insert 90 brings HearthStone's signature soapstone lining to a large flush-fitting wood fireplace insert offered through authorized dealers.

Cozy Glow Stoves is an authorized HearthStone dealer. Visit our Logan, Ohio showroom to see HearthStone products in person, or contact us with questions about the GMi90, current pricing, and installation planning.