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- Description
- Which Wood Stove Do I Need?
- Specifications
- Manuals / Catalogs
- FAQ
- Shipping / Freight / Return Info
Osburn 3500 insert: the largest wood insert in Osburn’s lineup
The Osburn 3500 insert is a wood insert for an existing masonry fireplace. Osburn rates it for 1,000 to 2,700 square feet, so it can heat a large home. It has a large firebox and one of the largest glass doors of any insert. An insert slides into the fireplace you already have and turns it into a real wood heater. It only goes into a masonry fireplace, the brick or stone kind, never a factory built one. Your chimney will usually need a steel liner run down to the insert, and the liner hookup parts are on the page.
Load it up and turn the air down, and it burns up to 10 hours. At full burn it puts out up to 110,000 BTU. It burns dry, seasoned firewood. You pick the door overlay on the page, the trim around the glass door, in black or brushed nickel. A faceplate is the flat panel that closes the gap between the insert and the fireplace opening, and you pick the size on the page, medium or large. The faceplate trims, the finished edge of the faceplate, come in the same two finishes and are picked on the page. An outside air kit, which feeds the fire air from outdoors, is optional. You can add a firescreen for open door fires and a glass hearth pad. Need something smaller? See the Osburn 2000 wood insert. The Osburn 3500 insert ships free from My Cozy Outdoors with No Sales Tax (except WY) and the full manufacturer warranty.
Which Wood Stove Do I Need?
Fireplace Finder
Answer a few quick questions and we’ll show you the right kind of fireplace for your home or backyard, plus the models that fit.
Where will your fireplace go?
What kind of fire do you want outside?
How do you want it built?
Outdoor fireplaces come two ways: a finished piece you set in place, or a firebox that gets built into a wall.
How big a fireplace do you picture?
Measured by the width of the fire opening, or of the whole unit for ready-made pieces.
What kind of fire do you want?
Not sure yet? Pick “Help Me Choose” and we’ll ask two easy questions.
Do you have natural gas at home, or would you use a propane tank?
Which sounds most like you?
What type of unit do you picture?
Can a vent pipe go through an outside wall or the roof?
Gas fireplaces either vent outside (direct vent) or need no vent at all (vent-free).
What matters most to you?
How big is the space you want to heat?
Enter the square feet of the room, or of the open area the fire will warm.
sq ft
×
What are your winters like?
How tall are the ceilings?
How well insulated is the space?
Is it an open floor plan?
How will you use the heat?
Which look do you like best?
|
Specifications
SKU: OB03510
| Fuel type | Dry cordwood (16″ recommended) |
| Recommended heating area-ft² | 1,000 – 2,700 |
| Overall firebox volume-ft³ | 3.5 |
| EPA loading volume-ft³ | 2.88 |
| Maximum burn time | 10 h |
| Maximum heat output-dry cordwood | 110,000 BTU/h (32.2 kW) |
| Overall heat output rate < | 17,200 BTU/h (5.0 kW) to 57,800 BTU/h (16.9 kW) |
| Average overall efficiency (dry cordwood) | 71 % (HHV) |
| Optimum overall efficiency | 77 % |
| Optimum heat transfer efficiency | 75 % |
| Average particulate emissions rate | 1.6 g/h |
| Average CO | 73 g/h |
Manuals / Catalogs
FAQ
Can the Osburn 3500 insert be installed in any fireplace?
No. Osburn’s warning is explicit: wood-burning inserts must only be installed inside an existing masonry fireplace, never in a wooden or combustible structure. Fit is determined by the data and drawings in the owner’s manual, so measure your fireplace opening against the published dimensions before ordering.
Do I need a chimney liner with this insert?
Your owner’s manual and local code determine the venting requirements for your chimney. If your installation calls for a liner connection, a Liner Hook Up System and an Offset Liner Adapter are available as add-ons directly on this page under Liners & Adapters, so they can ship with the insert.
How much space can it heat?
The recommended heating area is 1,000 to 2,700 square feet with a maximum heat output of 110,000 BTU/h, which puts it at the powerful end of the Osburn fireplace insert range. It is aimed at homes where the fireplace is a genuine heat source, not just ambiance.
Will it burn overnight?
Yes. Maximum burn time is 10 hours from the 3.5 cubic foot firebox, one of the largest in the lineup, and the insert pairs that capacity with one of the largest glass surfaces in its category. Osburn recommends dry cordwood cut to 16 inches.
How do I choose the faceplate and trims?
Because each house is unique, Osburn lets you choose the door overlay, the faceplate and the trims. On this page the door overlay (black or brushed nickel), the faceplate (medium or large) and the faceplate trims are required selections, so the insert arrives matched to your masonry hearth.
How clean and efficient is it?
Average particulate emissions are 1.6 g/h, with 71% average overall efficiency (HHV) and 77% optimum overall efficiency on dry cordwood. The overall heat output rate spans 17,200 to 57,800 BTU/h, so it can idle gently or work hard depending on the air setting.
Can I add outside combustion air?
Yes. A 5-inch fresh air intake kit and a 4-foot insulated flex pipe are offered under Fresh Air Intake on this page. Whether outside combustion air is required depends on your home and local code, and the owner’s manual governs how it is connected.
Shipping / Freight / Return Info
Same-Day / 24 hour shipping
Same-Day/24 hour shipping - If we have the product in stock, we can ship
same day if ordered before 12pm Monday - Friday (CST).
Please follow these very important steps when it comes to Freight Items that are damaged or missing
Freight Claims Policy
Please follow these very important steps when Returning Items. Contact our team.
Return Merchandise Authorization Policy
Customer Reviews
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What Our Customers Say
D
A sauna turns your garden into a spa oasis. We debated it for a while, but after renovating our house, we pulled the trigger and bought a sauna from Norse Steam and Maya. She was always super responsive and helpful throughout the process. Don't kid yourself, getting a really nice sauna is not that easy. Sizing and heating need to be figured out, as does the building, but we have always had a helpful partner on our side. She never upsold us on anything we didn't need, and we got some nice freebies when the sauna was delivered. And now we can really enjoy every moment in our garden.
KF
I'm really happy with my sauna purchase. Maya gave above and beyond excellent customer service. She wasn't pushy and gave impressive followup after the delivery to make sure everything was just right.
DE
I enjoy my FD2 Sauna with Red Light, Infrared and radiant heat. Use it 5x a week and my post workout soreness is minimal and sleep great. Maya at Norse Steam was excellent to work with.
B
We purchased the 3-person sauna for our outdoor garden. We chose the cube sauna for the aesthetic and could not be happier.
I assembled by myself except for the 2 large panels (requires a few people). Instructions were good - took me two partial Saturdays to complete and a few hours to unpack and organize in advance of assembly. Had my elec. add a NEMA enclosure on the back for the controller and power for lights and a 2nd panel for the wireless control.
Customer service was excellent
MP
Awesome Sauna and Awesome Company and Experience purchasing it from Maya!
After much research I chose the Finnmark FD-2 and it has met and exceeded all my expectations! Easy to assemble and it functions great - just as advertised. I highly recommend it for home use!
EA
Recently purchased the Finnmark one person after much research. Extremely happy with it and the ordering process. Maya was very responsive and helpful during the process and keeping us updated while we waited for shipment. There were several places I could have ordered this, but i chose Norse Steam based on the communication and customer service which was fantastic. The shipment was also excellent. The setup was pretty seamless for two people - but the best part is the sauna experience 10/10
G
Maya is amazing - super helpful and responsive. Looked at many stores, these guys have the best prices and service. Highly recommend
GR
Norse Steam, and specifically Maya, were extremely helpful as I was making the decision for our Sauna. I was able to get all of the necessary details to make a decision as construction was happening in my backyard to make space for it.
We absolutely love the CL7G. It is extremely comfortable for 6 people (can fit more less comfortably). The Thermory Spruce and Aspen in the interior smells great. The lighting is lovely. We paired the CL7G with the Harvia Spirit 10.5kw.
RS
Had great experience shopping at Norse Steam for the new heater. They had very good deal, with rocks. Customer service was good, and responded very fast with my questions. Received the heater, and it looks good, and the quality seem to be great. Will install soon, and am very excited to start experiencing sauna the way it ment to be
O
positive purchase experience - Harvia Legend 150 SL woodstove
thanks Norse Steam for flawless transaction - I got instant replies on my questions, received competitive price on the wood stove and got it delivered within two weeks!
Can highly recommend Norse Steam for others.
JR
Smoking Hot Tub!
I got the Norse Steam SaunaLife wood-fired hot tub, the S4N model, and its been seriously great. It heats up quicker than I expected, usually around an hour and a half, and once its hot, it stays that way for a good long while. The wood-fired system is simple to use, and honestly kind of fun.
The tub itself feels solid and well put together. The thermo-spruce exterior looks beautiful in person, and the fiberglass interior is smooth, deep, and easy to clean. Its the kind of setup that just works without a bunch of fuss, which I really appreciate.
Also, the team at Norse Steam was genuinely great to work with. Super helpful, quick to respond, and made the process really easy from start to finish. It felt like they actually cared that I was happy with it. The tub has totally become a go-to way to unwind, and I wouldnt change a thing.
S
Maya was so knowledgeable and responsive
Maya was so knowledgeable and responsive. She helped me understand the product options and found a fantastic solution that fit our needs. Her follow through was very helpful and made us comfortable with our decision. We are extremely happy with the end result!
W
Great service
I recently purchased the Harvia Club sauna equipment, and I am thoroughly impressed with both the product and the customer service experience. The heaters robust performance and durable stainless steel construction make it ideal for larger sauna spaces, providing consistent heat and a relaxing environment. Its compatibility with advanced controls ensures a personalized sauna experience every time.
The customer service team was exceptional, prompt, knowledgeable, and helpful throughout the purchase process. They ensured smooth delivery and provided clear guidance on installation and operation. Overall, I highly recommend Harvia Club for anyone seeking premium-quality sauna equipment backed by excellent support!
BT
Great Sauna & Purchase Experience
Great experience purchasing Finnmark FD-2 from Norse Steam. Good communication and easy to assemble. Temperature increases quickly (30 minutes or less to 140) and maintains well. So far this has been a great purchase.
M
Great sauna and great customer service
We purchased the Finnmark SD-1 sauna. Maya was extremely helpful with the purchase. We had an issue with the sauna not reaching the maximum temperature, and Maya connected us with the appropriate technician that explained how to correct the issue. The sauna now heats to the maximum temperature (170 degrees) in less than an hour, and it is a great unit. We are very happy with it, and we would definitely purchase from NorseSteam if we needed any other items.
JK
Sauna Review
I recently purchased a sauna from Norse Steam, and I couldn't be more impressed with the entire experience. From start to finish, their customer service was exceptional, and Maya deserves special recognition for her outstanding support!
Maya was incredibly knowledgeable and patient, answering all my questions about the sauna features, installation process, and maintenance. She went above and beyond to ensure I selected the perfect model for my home. Even after the purchase, Maya followed up to make sure everything was running smoothly and that I was satisfied with my sauna.
The sauna itself is top-notch beautifully designed, durable, and easy to use. It's clear that Norse Steam takes pride in the quality of their products and their commitment to customer satisfaction.
If you're considering a sauna, I wholeheartedly recommend Norse Steam. With their excellent customer service and high-quality products, you're in great hands. Thank you, Maya, and the entire Norse Steam team for a fantastic experience!
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