Osburn 3500-I Wood-Burning Fireplace Insert – OB03510
Powerful, High-Efficiency Wood Heating for Large Living Spaces 🔥
Upgrade your home heating with the Osburn 3500-I wood-burning fireplace insert, engineered for powerful performance, clean combustion, and long burn times.
Key Features
- Heats 1,000 – 2,700 sq ft effectively
- Powerful 110,000 BTU maximum heat output
- EPA 2020 certified high-efficiency wood insert
- Large viewing glass with an elegant cast iron door
- Includes a premium blower for improved heat circulation
- Long 10-hour burn time
- Heavy-duty steel firebox built for durability
- Customizable with optional door overlays and faceplates
⚠️ Important Installation Warning:
Wood-burning inserts must be installed only in an existing masonry fireplace and never in a wooden or combustible structure.
Product Features
High-Efficiency EPA Certified Heating
The Osburn 3500-I wood fireplace insert is EPA 2020 certified and engineered for clean combustion. Its advanced non-catalytic system delivers powerful heat while reducing emissions and maximizing fuel efficiency.
Large Heating Capacity for Bigger Homes
Designed for large living areas, this high-performance wood insert heats between 1,000 and 2,700 square feet, making it ideal for open floor plans, basements, and main living areas.
Powerful 110,000 BTU Heat Output
With a maximum output of 110,000 BTUs, the Osburn 3500-I provides reliable warmth during the coldest months while maintaining steady, comfortable indoor temperatures.
Long Burn Times
A large 3.5 cubic foot firebox allows for extended burn cycles of up to 10 hours, reducing the need for frequent reloading and providing overnight heating performance.
Advanced Secondary Combustion System
A stainless steel secondary-air system re-burns gases and smoke in the firebox, improving efficiency, producing a cleaner burn, and reducing creosote buildup.
Large Ceramic Glass Viewing Area
Enjoy a beautiful view of the flames through the large ceramic glass window, which features a built-in air-wash system to help keep the glass clean.
Premium Blower Included
The built-in 144 CFM blower improves heat distribution throughout the room, helping the fireplace insert warm your space faster and more evenly.
Durable Steel Construction
Constructed with heavy 3/16" steel and a reinforced top plate, this wood-burning insert is built for long-term reliability and demanding heating conditions.
Customizable Appearance
Personalize the look of your fireplace insert with optional:
- Door overlays
- Decorative trims
- Medium or large faceplate surrounds (Required)
This allows the insert to blend seamlessly into both modern and traditional interiors.
Product Specifications
Appliance Performance
| Specification |
Details |
| Fuel Type |
Dry cordwood (16" recommended) |
| Heating Area |
1,000 – 2,700 sq ft |
| Maximum Heat Output |
110,000 BTU/h |
| Burn Time |
Up to 10 hours |
| Firebox Volume |
3.5 cu ft |
| EPA Loading Volume |
2.88 cu ft |
| Overall Heat Output Range |
17,200 – 57,800 BTU/h |
| Average Efficiency (HHV) |
71% |
| Average Efficiency (LHV) |
76% |
| Optimum Efficiency |
77% |
| Optimum Heat Transfer Efficiency |
75% |
| Average Emissions |
1.6 g/h |
| Average CO |
73 g/h |
General Information
| Specification |
Details |
| Combustion Technology |
Non-Catalytic |
| EPA Certification |
EPA 2020 Approved |
| Maximum Log Length |
22" |
| Log Orientation |
Width or depth loading |
| Chimney Diameter |
6" |
| Flue Outlet |
6" |
| Minimum Chimney Height |
15 ft |
| Baffle Type |
C-Cast |
| Blower |
Included – 144 CFM |
| Door Type |
Single cast iron frame with ceramic glass |
| Glass Size |
18 7/8" W × 11 3/4" H |
| Firebox Lining |
Refractory brick |
| Secondary Air System |
Stainless steel |
| Shipping Weight |
540 lbs |
| Warranty |
Limited Lifetime |
Venting Requirements
| Requirement |
Specification |
| Vent Type |
Stainless Steel Chimney Liner |
| Liner Standards |
ULC-S635, CAN/ULC-S640, UL 1777 |
| Flue Diameter |
6 inches |
| Chimney Diameter |
6 inches |
| Minimum Chimney Height |
15 ft |
| Installation Type |
Existing Masonry Fireplace Only |
Appliance Dimensions
| Measurement |
Size |
| Overall Height |
24 7/8" |
| Overall Width |
30 3/8" |
| Overall Depth |
29" |
| Door Opening |
9 7/8" H × 19" W |
| Firebox Height |
12 7/8" |
| Firebox Width |
22 7/8" |
| Firebox Depth |
20 1/8" |
Required Surround/Faceplate Dimensions
| Option |
Width |
Height |
| Medium Faceplate |
44" |
32" |
| Large Faceplate |
50" |
32" |
Minimum Fireplace Opening
| Requirement |
Measurement |
| Height |
26 1/4" |
| Width |
31" |
| Depth |
18 3/8" |
Clearances to Combustibles
| Clearance |
Distance |
| Side Mantel |
9" |
| Top Mantel |
27" |
| Side Wall |
19" |
| Top of Unit |
84" |
| Shelf Clearance |
27" |
Certifications & Standards
| Standard |
Certification |
| Emissions |
EPA / CSA B415.1-10 |
| Safety (USA) |
UL 1482, UL 737 |
| Safety (Canada) |
ULC S628 |
| Tested By |
Accredited Laboratory (CAN / USA) |
The appliance is safety-tested and certified according to North American standards.
Safety Notice
⚠️ Installation Warning
Wood-burning fireplace inserts must be installed:
- Inside an existing masonry fireplace
- With an approved chimney liner
- According to local building codes and manufacturer instructions
Improper installation can pose fire hazards, cause property damage, and/or result in loss of life.
Warranty
Warranty Coverage – Osburn Wood Stoves & Inserts
Osburn wood-burning appliances are backed by a limited lifetime manufacturer’s warranty that covers specific components for varying durations. Coverage applies to the original purchaser and is subject to proper installation and use per the owner’s manual.
Warranty Coverage:
| Component / Description |
Parts Coverage |
Labor Coverage |
| Combustion chamber (welds only) and cast-iron door frame |
Lifetime* |
5 years |
| Ceramic glass**, plating (manufacturing defect**), convector air-mate |
Lifetime* |
N/A |
| Surrounds, heat shields, ash drawer, steel legs, pedestal, trims (aluminum extrusions), vermiculite, C-Cast or equivalent baffle**, secondary air tubes**, removable stainless steel combustion chamber, deflectors, and supports |
7 years* |
N/A |
| Handle assembly, glass retainers, and air control mechanism |
5 years |
3 years |
| Removable carbon steel combustion chamber components |
5 years |
N/A |
| Standard and optional blower, heat sensors, switches, rheostat, wiring, and electronics |
2 years |
1 year |
| Paint (peeling**), gaskets, insulation, ceramic fiber blankets, refractory bricks (fireplace only*) and other options |
1 year |
N/A |
| All replacement parts supplied under warranty |
90 days |
N/A |
Important Warranty Notes
- Lifetime coverage is limited to one replacement.
- Photo documentation may be required to validate claims.
- Warranty applies to manufacturing defects only.
- Damage caused by improper installation, misuse, abuse, over-firing, or failure to follow installation instructions is not covered.
- Labor coverage applies only where explicitly stated.
- Warranty terms are subject to the manufacturer’s full warranty policy.
What This Means for Homeowners
Osburn’s warranty reflects long-term confidence in the structural components that matter most—while clearly defining wear items and electronics that naturally experience use-related aging.
For full warranty eligibility:
- Installation must comply with the owner’s manual
- Appliance must be operated using approved fuels
- Routine maintenance must be performed as recommended
About the Manufacturer
Who Is Osburn?
Osburn is a Canadian manufacturer specializing in high-efficiency wood stoves and zero-clearance wood fireplaces designed for real-world home heating. The brand is widely recognized in North America for producing EPA-certified wood-burning appliances that combine strong heat output, clean combustion, and durable construction.
Founded in Québec, Canada, Osburn has built its reputation around performance-driven wood heating, offering products capable of heating entire homes while meeting modern emissions and safety standards.
What Is Osburn Known For?
Osburn is best known for:
- Wood stoves & inserts with high BTU output
- EPA 2020–certified wood-burning technology
- Non-catalytic combustion systems that simplify operation
- Large fireboxes and extended burn times
- Canadian manufacturing and engineering standards
Osburn stoves & inserts are designed to deliver both ambiance and functional heat, making them suitable for homeowners seeking a real wood fire that also contributes meaningful warmth.
Where Are Osburn Wood Stoves Made?
Osburn fireplaces and wood stoves are designed and manufactured in Canada. The brand operates under Stove Builder International (SBI), one of North America’s largest and most established hearth appliance manufacturers.
This manufacturing structure allows Osburn to maintain:
- Consistent quality control
- In-house testing and certification
- Long-term parts availability
- Proven reliability across product lines
Are Osburn Products EPA Certified?
Yes. Osburn fireplaces and stoves meet EPA 2020 emissions standards, making them compliant for installation in the United States. These certifications ensure:
- Lower particulate emissions
- Improved fuel efficiency
- Cleaner-burning fires compared to older wood fireplaces
Many Osburn models are also certified to UL and ULC safety standards for use in both the U.S. and Canada.
Can Osburn Fireplaces Be Used for Heating a Home?
Yes. Many Osburn wood stoves can heat 750 to over 2,000 square feet, depending on the model, home layout, and installation. While often installed for ambiance, Osburn stoves are frequently used as:
- Primary heat sources in open-concept homes
- Supplemental heating systems to reduce reliance on fossil fuels
- Emergency heat during power outages
Osburn’s Design Philosophy: Beyond Fire
Osburn describes its approach as “Beyond Fire”—a focus on preserving the authenticity of a real wood fire while reimagining it for modern homes. This philosophy emphasizes:
- Efficient combustion
- Clean-burning technology
- Durable materials
- Contemporary styling that fits today’s interiors
The result is a fireplace that delivers more than just appearance—it delivers dependable heat.
Why Homeowners Choose Osburn
Homeowners choose Osburn fireplaces because they offer:
- Canadian-made quality
- High heat output with clean emissions
- EPA 2020 compliance
- Large glass viewing areas
- Long-term manufacturer support
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