Built-In Wood Heat on a Grand Scale from HearthStone's Largest Zero-Clearance Fireplace

The WFP-100 (Model 8420) is HearthStone's largest EPA-certified zero-clearance wood fireplace, combining a 4.28 cu. ft. firebox, double cast-iron-framed glass doors, and an included convection blower.

Key Features

• Large 4.28 cu. ft. firebox — accepts logs up to 25" loaded east-west, with a 16" north-south log length recommended by the current owner's manual.
• Maximum heat output up to 95,000 BTU/hr — per current HearthStone specifications, with a recommended heating area of 1,000 to 2,800 sq. ft. depending on home layout, insulation, and operating conditions.
• EPA 2020 certified using cordwood — certified at 1.6 g/hr particulate emissions, with an EPA tested heat output of 16,610–43,021 BTU/hr under specific test conditions and a 64% (HHV) average overall efficiency.
• Non-catalytic double combustion — a self-regulating system pairing a primary combustion control with four secondary-air tubes beneath a C-Cast baffle.
• Maximum burn time up to 10 hours — per the current owner's manual.
• Included convection blower — rated up to 176 CFM to move warmed air into the living space.
• Double ceramic-glass doors with cast-iron frames — a wide view of the fire framed by a textured cast-iron facade in Matte Black or Brown Enamel.
• Zero-clearance construction — engineered for framed new-construction and remodeling installations with a dedicated 8" chimney system; the specified clearances, framing, facing, and hearth protection in the current manual still apply.

Product Features

Large Zero-Clearance Fireplace Design

The WFP-100 is a built-in wood-burning fireplace designed to be framed into new construction or a remodel, without the mass and footprint of a site-built masonry fireplace. The fireplace enclosure permits 0" clearance at the back, sides, and floor under the fireplace, while every other published clearance, framing, facing, and hearth requirement in the current Model 8420 manual applies. The decorative cast-iron facade measures 50-3/4" wide, with an arched face of approximately 45-1/4" wide by 41-1/2" tall per the current HearthStone catalog, and a straight-wall framing depth reference of 26-7/8".

4.28 Cu. Ft. Firebox

The 4.28 cu. ft. firebox burns dry, seasoned cordwood and accepts logs up to 25" long loaded east-west. The current owner's manual recommends 16" logs loaded north-south for everyday burning. Published maximum burn time is up to 10 hours, depending on wood, draft, and operating conditions.

Non-Catalytic Double Combustion

A self-regulating double-combustion system burns the wood and then the gases it releases. A primary combustion control regulates the burn, while four secondary-air tubes beneath the C-Cast baffle supply air to complete combustion before the exhaust enters the chimney. The system is certified to the EPA 2020 particulate standard using cordwood at 1.6 g/hr, with a 64% (HHV) average overall efficiency per current HearthStone specifications (63.9% as printed in the current manual) and an optimum efficiency of 69.7% (LHV) at a specific burn rate.

Included Convection Blower

A convection blower rated up to 176 CFM is included with the fireplace, drawing room air around the firebox and returning warmed air to the living space.

Double Cast-Iron-Framed Glass Doors

Two ceramic-glass doors with cast-iron frames give the WFP-100 the wide, open sightline of a traditional hearth. The door opening measures approximately 33" wide by 12-3/4" tall per the current manual's dimensional drawing, behind a hand-textured cast-iron facade.

Refractory Ceramic Interior

The firebox is lined with molded refractory ceramic panels in a stacked-stone texture, reflecting heat back into the fire for cleaner combustion and giving the firebox a finished masonry appearance.

Flexible Heat Distribution Options

Beyond the included blower, the optional Forced Hot Air Kit (94-57200) can move heat to another room up to 50 ft away, and the optional Hot Air Circulation Kit (94-99200) adds passive convection vents. Fresh-air connector components — a 5" adapter, an air-inlet block-off plate, and four screws — are included with the fireplace for installations that connect outside combustion air.

Dedicated 8-Inch Chimney System

The WFP-100 uses a dedicated 8" chimney system listed to UL 103 HT (2100°F) or CAN/ULC S629, beginning with the appropriate listed 8" anchor plate. The minimum straight system height is 15 ft from the bottom of the unit to the chimney cap, and the fireplace must never share a flue with any other appliance.

Available Finishes and Configurations

The WFP-100 is a single base model available in two finishes. Pricing varies by finish.

Specifications

Installation, Clearances and Hearth Requirements

"Zero clearance" describes this class of built-in fireplace, not an absence of requirements. The current Model 8420 manual permits 0" enclosure clearance at the back, sides, and floor under the fireplace, and at the same time requires the combustible clearances, noncombustible facing, hearth protection, and chimney clearance below. The current owner's manual and its drawings govern every installation; review them with your installer and local building official.

The current manual publishes five hearth and floor-protection configurations. All five are reproduced below; do not rely on a single simplified R-value statement.

In every configuration, the hearth protection must be at least 49" wide in total, extending at least 8" beyond each side of the door opening, with a 2" sheet-metal joint-protection detail where the manual specifies it. The current Model 8420 manual is internally inconsistent at the 8" and 12" height boundaries. Its later minimum-hearth summary describes Option 4 as more than 8" but less than 12" and Option 5 as 12" or more, while the detailed option headings use different boundary wording, and the Option 3 and Option 4 height descriptions overlap above 8". Do not infer the required hearth construction for an installation exactly 8" or exactly 12" high from this summary alone; confirm the applicable configuration using the current Model 8420 manual, HearthStone and installer guidance, local code, and the authority having jurisdiction.

Framing and facing requirements include the following. These reference values do not replace the manual's complete installation drawings, and allowances may need to increase for the fresh-air kit, the forced-air kit, or the finish materials used.

The chimney is a dedicated listed 8" system (UL 103 HT or CAN/ULC S629) beginning with the appropriate listed 8" anchor plate and components. The minimum system height for a straight installation is 15 ft from the bottom of the unit to the chimney cap, and an installation at the minimum height requires optimal conditions. Where offsets are used, the manual calls for a minimum 18" rise before the first offset, a 15 ft minimum system height with two elbows, and a 17 ft minimum with four elbows. The chimney must terminate at least 3 ft above its point of contact with the roof and at least 2 ft higher than any wall, roof, or building within 10 ft, must be braced if it extends more than 5 ft above the roof, and must maintain 2" clearance to combustibles. A chimney venting this fireplace must not vent any other appliance. For certain masonry applications, the current manual provides approved chimney and liner connection methods; the fireplace is not approved for a so-called positive flue connection to the clay tile of a masonry chimney. Alcove and mobile/manufactured-home installations are not approved.

A supply of outside combustion air is strongly recommended and is required by some jurisdictions and codes. The fresh-air connector components included with the fireplace are a 5" adapter, an air-inlet block-off plate, and four screws; the 5" insulated flexible duct, outside wall termination, and two adjustable clamps are not included. The intake connects at the right side or right-side/bottom location per the manual. Runs under 20 ft use 5" duct; runs over 20 ft, or with more than two deviations, use 6" duct, with a maximum duct length of 30 ft. The outside termination must not be located more than 50% of the total chimney height, more than 10 ft above the fireplace base, or more than 3 ft below it. Combustion air must come from outside the home — never from an attic, basement, or garage.

Included Equipment

• Convection blower, rated up to 176 CFM (included)
• Fresh-air connector components: 5" adapter, air-inlet block-off plate, and four screws (included with the fireplace)
• Refractory ceramic firebox interior (integral to the appliance)
• Double ceramic-glass doors with cast-iron frames (integral to the appliance design)

The 5" insulated flexible fresh-air duct, outside wall termination, and adjustable clamps are not included and are supplied by the installer when outside air is connected.

Compatible Accessories

Accessories are sold separately and installed per their instructions and the current Model 8420 manual.

Warranty

The WFP-100 is covered by the limited warranty published in the current Model 8420 owner's manual. In summary: combustion chamber welds, castings, the convector air-mate, and ceramic glass against thermal breakage carry lifetime parts coverage with four years of labor; plating carries lifetime parts coverage for manufacturing defects, subject to the written terms; stainless-steel firebox components, surrounds and heat shields, the C-Cast baffle, and secondary air tubes carry five years parts and three years labor; carbon-steel firebox components, glass retainers, and the handle assembly carry three years parts and two years labor; blowers, heat sensors, switches, rheostats, wiring, and controls carry two years parts and one year labor; and paint peeling, gaskets, insulation, and firebrick carry one year parts coverage. Lifetime coverage is subject to a one-time replacement limit. Coverage applies to the original consumer purchaser of a brand-new product in normal residential use, is not transferable, and requires authorized, qualified installation. 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 WFP-100 pairs HearthStone's textured European cast iron with the company's largest zero-clearance wood fireplace, 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 WFP-100, current pricing, and installation planning.