Osburn 3500 Wood Insert With Blower | OB03510

Osburn 3500 Wood Insert with Blower | Model OB03510

The Osburn 3500-I OB03510 is built for a large existing masonry fireplace when homeowners want powerful supplemental heating without replacing the room's existing hearth. Its large glass viewing area and restrained faceplate details create a substantial fire feature without an overly ornate appearance.

The 3.5-cubic-foot firebox offers capacity for long burn cycles, while a built-in blower helps bring warmth from the insert into the living area. Door overlays, faceplates and trim choices let the surround be matched to the fireplace opening. This model is suited to larger heating spaces where fireplace fit and adequate chimney lining are essential.

Who Benefits from the Osburn 3500-I Insert?

The 3500-I serves homeowners with a large, properly constructed masonry fireplace who want a room-heating upgrade capable of taking substantial cordwood loads. Its 3.5-cubic-foot firebox and up to 10-hour manufacturer-rated maximum burn time distinguish it from smaller Osburn insert models. For a spacious living area with winter heating demands, the combination of a large fire-viewing door and included blower can make an otherwise inefficient open masonry fireplace much more useful as a controlled heat source.

Large capacity also brings a larger insert body, so measure the masonry opening carefully before making this the default choice. Osburn publishes minimum width, height and depth figures, but those do not replace checking damper-area clearance, hearth protection and available chimney-liner routing. The 3500-I requires an approved existing masonry fireplace; it cannot be placed in an ordinary wood-framed cavity. Confirm the selected surround, overlay and trim configuration, and verify that the 6-inch lined chimney is appropriate for the installation.

Why Choose the Osburn 3500 Wood Insert with Blower?

• 3.5 cu. ft. firebox with long-burn capability
• Included blower to circulate heat into the room
• Broad glass door and understated contemporary faceplate
• Selectable faceplate, trims and door overlay options
• EPA-certified non-catalytic wood heating

Osburn 3500 Wood Insert with Blower Specifications

• Manufacturer model: OB03510
• Manufacturer-recommended heating area: 1,000-2,700 sq. ft.
• Fuel: Dry cordwood (manufacturer recommends 16" pieces)
• Maximum heat output using dry cordwood: 110,000 BTU/h
• Tested overall heat output range: 17,200-57,800 BTU/h
• Maximum published burn time: Up to 10 hours
• Overall firebox volume: 3.5 cu. ft.
• EPA test loading volume: 2.88 cu. ft.
• Maximum log length: 22"
• Average overall efficiency (HHV): 71%
• Average overall efficiency (LHV): 76%
• Optimum overall efficiency: 77%
• Average particulate emissions: 1.6 g/h
• Overall dimensions (W x H x D): 30 3/8" x 24 7/8" x 29"
• Minimum fireplace opening (W x H x D): 31" x 26 1/4" x 18 3/8"
• Firebox interior dimensions (W x H x D): 22 7/8" x 12 7/8" x 20 1/8"
• Viewing glass size (W x H): 19" x 11 3/4"
• Door construction: Single glass door, cast iron frame
• Shipping weight: 540 lb
• Flue outlet diameter: 6"
• Manufacturer minimum chimney height: 15 ft; verify complete installation requirements
• Blower: Included 144 CFM
• Mobile home approval: No
• Combustion technology: Non-catalytic
• EPA listing: EPA 2020 approved (per manufacturer Specs/Manual)
• Manufacturer warranty: Limited lifetime; see written warranty for terms

Manufacturer figures are reference values, not guaranteed heating results. Maximum BTU output, tested output rates and burn-time estimates use different conditions; real performance depends on fuel quality, chimney draft, climate, home heat loss and operating settings. Confirm all dimensions and listed installation clearances in the current manual before ordering.

Installation and Compatibility

Designed for approved masonry fireplaces only; do not treat this insert as a zero-clearance fireplace. Measure the existing opening and confirm the listed 6-inch liner, surround coverage and clearances before installation.

Important: Wood-burning inserts must be installed only in a compatible existing masonry fireplace, in accordance with the manufacturer's listing and installation instructions.

Frequently Asked Questions

Can the 3500-I replace a zero-clearance fireplace?

Do not assume it can. This model is specified for approved existing masonry fireplaces and is not a factory-built zero-clearance fireplace replacement.

How does it compare with the Osburn 2000-I?

The 3500-I's 3.5-cubic-foot firebox and 10-hour published maximum burn time are larger than the 2000-I's 2.4 cubic feet and 8 hours. The 3500-I also requires an appropriate larger masonry opening.

Does the 3500-I include a blower?

Yes. Osburn lists a 144 CFM blower. Check the selected faceplate and finishing accessories separately because their inclusion can vary with the configured package.

Osburn Manuals and PDF Resources

• Osburn 3500 Wood Insert Owner's Manual (PDF)

Questions about fireplace fit, venting or compatible accessories? Contact WoodStovePro at info@woodstovepro.com or 888-418-0005 before placing your order.

California residents: Review Proposition 65 information before purchasing.

Tags: Osburn 3500 Wood Insert | OB03510, OBO3510, OB 03510, Osburn OB03510, Osburn 3500-I