• Osburn 3500 wood insert shown with a black door overlay, medium faceplate and black trims, all sold separately
  • Osburn 3500 wood insert installed in a fireplace, high resolution photo
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Osburn

Osburn 3500 Wood Insert

Osburn 3500 Wood Insert

$3,819.00
$3,819.00
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Shipping calculated at checkout.
Freight Shipping Notice This item may require freight delivery due to its size or weight. Please complete your order normally. Qualifying freight ships free to 44 states plus Washington, DC. Alaska, Hawaii, Idaho, Montana, North Dakota, and South Dakota require a freight quote, and oversized pallets may require a quote to any destination. If a quote is needed, we will contact you after your order is placed. Freight charges are not included unless specifically shown at checkout, and any additional freight charge must be quoted, approved and paid before the order ships.
Osburn 3500 Wood Insert
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The Osburn 3500 insert (OB03510) is a high-output non-catalytic wood insert for an existing masonry fireplace, rated for 1,000 to 2,700 sq ft with a maximum heat output of 110,000 BTU/h. Its 3.5 cu ft firebox takes logs up to 22" long, loads across the width or the depth and burns up to 10 hours, behind a 19" x 11 3/4" ceramic glass door. A 144 CFM blower is included.

110,000 BTU/hMaximum heat output, dry cordwood
1,000 to 2,700 sq ftRecommended heating area
EPA 2020 approved1.6 g/h particulate emissions
144 CFM blowerIncluded with the insert

Specifications

ModelOsburn 3500 wood insert, OB03510
Heat output110,000 BTU/h maximum (dry cordwood); overall 17,200 to 57,800 BTU/h
Heating area1,000 to 2,700 sq ft
Efficiency71% average overall (HHV), 76% (LHV); 77% optimum overall
Emissions1.6 g/h average particulate, non-catalytic
Test standardEPA 2020 approved; tested to ASTM E3053-17 under 40 CFR Part 60, Subpart AAA; efficiency by the CSA B415.1-10 stack loss method
Firebox3.5 cu ft overall (2.88 cu ft EPA loading volume); 12 7/8" H x 22 7/8" W x 20 1/8" D
Burn time and logsUp to 10 hours; logs up to 22" long, loaded across the width or the depth
Overall size24 7/8" H x 30 3/8" W x 29" D
Minimum fireplace opening26 1/4" H x 31" W x 18 3/8" D
Flue6" outlet; continuous 6" liner to the top of the chimney (UL 1777)
Clearances (US)Side mantle 9", top mantle 27", side wall 19", 84" to the top from the platform
Shipping weight540 lb
BrandOsburn (SBI)
Masonry fireplaces only.Osburn forbids installing the 3500 insert in a factory-built fireplace. It goes only inside a masonry fireplace with a lined masonry chimney, and it is not approved for mobile homes. A certified installer or your local building official should check the installation before the first fire.

Questions people ask us

What do I need to order with the 3500 insert?

Osburn lists three required accessories, sold separately: a door overlay (black or brushed nickel), a faceplate (Medium 32" x 44" or Large 32" x 50") and matching faceplate trims. See the trims and fronts collection.

How much wood does it hold?

Logs up to 22" long, loaded across the width or the depth, in a 3.5 cu ft firebox with burns of up to 10 hours.

Can the 3500 insert go in a factory-built fireplace?

No. Osburn states that its wood-burning inserts must only be installed inside an existing masonry fireplace with a lined masonry chimney, never in a factory-built (zero clearance) fireplace or any wooden or combustible structure.

What chimney liner does it need?

A continuous 6" liner from the insert to the top of the chimney, listed to UL 1777 in the US. Liner adapters are in the venting collection.

Will it fit my fireplace?

The minimum opening is 26 1/4" H x 31" W x 18 3/8" D. Send us your measurements and we will check it with you. Ask us here.

Goes with this

Faceplates and trimsRequired finish parts Doors and screensDoor overlays and firescreens VentingLiner adapters and fresh air Osburn wood insertsThe full insert range

Manuals and warranty

Osburn manuals and warranty

Warranty terms come from Osburn and depend on the product. Read the manual and the warranty for your model before you order.

Our warranty libraryยท Osburn 3500-I wood insert install and owner's manual (PDF)ยท Osburn 3500-I dimensions (PDF)
Not sure this is the right insert? Send us your fireplace opening, chimney height and the area you want to heat, and we will confirm the fit and the faceplate size. No obligation either way.
Ask us before you order