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Osburn
Osburn 3500-I Wood Insert
A 3.5 cubic foot wood insert for large masonry fireplaces, built for serious heat output with a 144 CFM blower and configurable cast-iron face.
Kaminos is our fireplace retail store under the same ownership. View current pricing and available options there. For installation enquiries, contact Brown Chimney; availability depends on your location.
About this model
Overview
The 3500-I is the largest insert in this selection, with a 3.5 cubic foot non-catalytic firebox and a cast-iron arched door. It is aimed at an existing large masonry fireplace where wood is the main heat source rather than an occasional fire.
Published figures are 71% HHV efficiency, 1.6 g/hr particulate emissions under EPA 2020 cordwood certification, up to 2,700 sq ft of heating area and a 10-hour maximum burn time, with a 144 CFM heat-activated blower included. The face is configurable: two faceplate sizes with black or brushed nickel trim and a matching or contrasting door overlay.
Is this right for your home?
A large masonry fireplace in a house where wood provides a substantial part of the heat.
Check before ordering
- The masonry opening against the minimum of 26 1/4" H x 31" W x 18 3/8" D.
- The chimney and the continuous liner the insert needs for its full height.
- Storage for seasoned firewood up to 22 inches long.
Worth knowing
- This is a large appliance; in a small or well-insulated room it can be more heat than the space needs.
- Non-catalytic operation is simpler to run but gives shorter burns than a catalytic appliance of similar size.
Specifications
Figures published by the manufacturer. Where a value applies to a specific model or configuration, it is noted in the row.
Installation
A large opening is the first requirement: 26 1/4 by 31 by 18 3/8 inches as a minimum. The insert is installed in a code-compliant masonry fireplace with a continuous stainless steel liner running the full height of the chimney, and professional installation is expected for an appliance of this output.
Brown Chimney can measure the opening, inspect the chimney and confirm the liner work involved before anything is ordered.
Service availability depends on your location.
What to check before installation
What an assessment of this model would cover:
- Measured height, width and depth of the masonry opening against the published minimum.
- Chimney condition and the full-height liner the appliance requires.
- Hearth extension, surround finish and which faceplate size covers the face.
Product documentation
Product details and imagery on this page come from the Kaminos product page.
Frequently asked questions
How large a fireplace does it need?
At least 26 1/4 inches high, 31 wide and 18 3/8 deep in the masonry opening. It is the largest insert in this selection, so the opening rules it in or out.
How much heat does it give?
Up to 110,000 BTU/hr with a published heating area of up to 2,700 sq ft. Real results depend on insulation, layout, climate and firewood moisture.
Can the face be matched to the room?
Yes. Two faceplate sizes are offered with black or brushed nickel trim, and the cast-iron door overlay comes in either finish, so the face can be matched or contrasted.