Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: menchhofer on February 25, 2014, 05:11:15 PM
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What would be the advantage/disadvantage of the octagon firebox vs. a round one? More surface area? Would it really matter?
Advantage of water insulated/cooled door on firebox?
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I don't see any real advantage to a water cooled doors, especially the ones that are exposed to the atmosphere, they'd lose as much heat as they'd pick up it seems to me.
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Round fireboxes seem to last the longest.
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Octagon firebox might mean more chance of weld failure due to extra corners? I would think that round would be more resistant to bending than flat steel. I can see that a small welding shop might prefer to build an octagon one because they don't have machinery to make a round one whereas a break would make an octagon one easily.
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Neither impress me
When u see odd stuff like that it's often an attempt to correct an issue
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I don't think round or octagon matters much as long as it ain't square. Square as in 90 degree corners are more prone to crack it seems.
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I don't think round or octagon matters much as long as it ain't square. Square as in 90 degree corners are more prone to crack it seems.
Cracks are more likely to form at the bends tho, one of the most common places to see a crack inside a stove is just inside the firebox where the door flange extends out. Where that 90 degree corner is you'll often see a cracked extend out from it, most never reach the water jacket tho
Anytime there is an angle this is more likely to happen
But with that being said, I think the top companies could make anything work. It's just like the ripple roofs, can central and Empyre do it, yes of course, could everyone? Im not sure. But I'm not saying it's a huge deal but just saying different styles have been problematic for some and not for others
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I don't think round or octagon matters much as long as it ain't square. Square as in 90 degree corners are more prone to crack it seems.
Cracks are more likely to form at the bends tho, one of the most common places to see a crack inside a stove is just inside the firebox where the door flange extends out. Where that 90 degree corner is you'll often see a cracked extend out from it, most never reach the water jacket tho
Anytime there is an angle this is more likely to happen
But with that being said, I think the top companies could make anything work. It's just like the ripple roofs, can central and Empyre do it, yes of course, could everyone? Im not sure. But I'm not saying it's a huge deal but just saying different styles have been problematic for some and not for others
All the boilers I built were ripple roofs, not one has leaked yet.
It's not so much the design as whether the company is paying for somebody that can just run a bead or are willing to pay someone that can actually weld. Technique plays a big a part as design. I've seen some factory welds from respectable company's that I'd never let leave my shop.
Speed, penetration, heat, undercut, the mix of the gas for MIG and termination all play a part. I've used both hands to adjust wire speed on my big MIG machine as I just needed the littlest tweak, somebody standing a arms length away wouldn't be able to tell if I had moved it or not, but it does matter.
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Yea.. I know a good welder could make anything work
I know that we often see stoves have similar issues tho and since once company goes into left field to fix it they have to have an answer for the question when someone asks. Like water cooled doors for example, needed? No. Was it a likely attempt to correct door warping and add efficiency, yes. Has it proven to be better than a well built insulated door, no, but they gotta tell ya something haha
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I can answer a very specific question about doors since I am the designed of Wood Boiler LLC. When I built the first boiler I had a very specific safety requirement. I did not want my small girls to touch the door and get third degree burns when I was not home and they were playing in the backyard. All other benefits are just a bonus. Warpage is funny statement because warp age occurs because of welding a water cooled door the hotter and longer the weld it is natural byproduct. Or you can use really thin metal and jig it that is another solution used by some companies.
We may be small be we have an in-depth knowledge of our products and quite frankly we have some of the best on the market.
As far as bending metal I have never witnessed a single crack in plate from a bend you have to keep in mind all manufacturers either roll or bend to reduce the number of weld points just part of the process. This in my opinion is a lack of metallurgy knowledge to say it causes cracks, this simply not the case if you understand the process.
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I can answer a very specific question about doors since I am the designed of Wood Boiler LLC. When I built the first boiler I had a very specific safety requirement. I did not want my small girls to touch the door and get third degree burns when I was not home and they were playing in the backyard. All other benefits are just a bonus. Warp age is funny statement because warp age occurs because of welding a water cooled door the hotter and longer the weld it is natural by product. Or you can use really thin metal and jig it that is another solution but the other companies.
We may be small be we have an in-depth knowledge of our products and quite frankly we have some of the best on the market.
As far as bending metal I have never witness a single crack in plate from a bend you have to keep in mind all manufacturers either roll or bend to reduce the number of weld points just part of the process. This in my opinion is a lack of metallurgy knowledge to say it causes cracks, this simply not the case if you understand the process.
Still do not quite understand the water cooled door. Kids can be taught not to touch no big issue there. Why the octagon firebox?
I live about 20 miles from Lebannon and seriously considering your boiler. Just have not had time to visit your place of business.
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I can answer a very specific question about doors since I am the designed of Wood Boiler LLC. When I built the first boiler I had a very specific safety requirement. I did not want my small girls to touch the door and get third degree burns when I was not home and they were playing in the backyard. All other benefits are just a bonus. Warp age is funny statement because warp age occurs because of welding a water cooled door the hotter and longer the weld it is natural by product. Or you can use really thin metal and jig it that is another solution but the other companies.
We may be small be we have an in-depth knowledge of our products and quite frankly we have some of the best on the market.
As far as bending metal I have never witness a single crack in plate from a bend you have to keep in mind all manufacturers either roll or bend to reduce the number of weld points just part of the process. This in my opinion is a lack of metallurgy knowledge to say it causes cracks, this simply not the case if you understand the process.
Thanks for weighing in, yes fewer welds is a good thing. Sharp corners is why I'm referring to as far as points where cracks can form, not bent corners.
Does your door temp Match the water temp of stove? If so are u concerned with that heat being lost
In regards to warpage, many doors work because there not properly insulated, I wasn't referring to the warping that comes from the welding process. I have seen many doors warp very badly due to heat from issues and low quality insulation
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I would think any steel door would risk warping without water in it because of heat unless a couple of factors one doors with inducers tend to be cooler because the air is injected front to back but they still get pretty darn hot, I have run ours without water more as a curious factor. Never warped but certainly would not want to touch. The heat loss to be far outweighs the risk.
Safety, I felt I could not teach every kid that might visit my daughter or close by kids. Just always and still do feel that is the reason, I built the water cooled door. The return water is sent through the door so it tends to be cooler than the rest of the boiler in general.
Octagon this applies to conventional style boilers
1. Round boilers provide about the best overall ability to feed the wood to the central fire however the center point at the top is the largest area of heat transfer in this design all you have to do is look at the thermal images to see this looks like about a 3-4 inch strip.
2. Square top boilers provide the largest heat transfer actually these provide the greatest surface area to transfer heat however keeping them burning is harder they tend to burn the center out leaving the side wood unburnt. Again a pretty nice and even transfer across the surface.
3. Octagon provides a mix of the 2 giving us larger heat transfer surface area whilst giving it a self feeding effect. This is why.
And if you are curious yes built and tested about every design type you can think of the octagon worked about the best in my opinion from durability to usability.
The downdraft units are a complete different ballgame.
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Scott on the door warp, I am not sure what your mean by insulation, I think you are referring to the refractory material? Which is a non issue with our boilers.
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Scott on the door warp, I am not sure what your mean by insulation, I think you are referring to the refractory material? Which is a non issue with our boilers.
No, I'm talking about actual insulation inside a pyramid shaped door
It's what most companies use, they stuff the pyramid cavity with stuff like vermiculite and other high heat insulations. These keep the door barely warm to the touch, for example the door on my heatmaster in 20 degree weather is probably 55 or 60 degrees. There are a lot of companies tho that use the same style door.
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Interesting.
Scott I have never seen anything as such but I have never really paid much attention to others on the market.
It takes thousands of hours in development to continue to build new products which leaves little time for much else.
It is an interesting concept never considered that myself. Though I would think whatever metal that is exposed to the heat would be at warp risk unless it is covered with a refractory material regardless of the insulation in between the outside and inside. Such as our E4 model has access to the secondary we utilize refractory to intensify the burn line. I think the same concept would apply to a main door if it was exposed to high heat situations. The maximum heat from a straight wood fire is in the 1200 range though same claim up to 1400 personally never measured that hot usually in the 1100 range, either is certainly enough to soften steel with a possible warp effect on cool down. In the gasification models we have seen around 2000 degrees with this much heat i would think it would be at risk of burn through but i never saw that occur even with several hundred hours of testing see you have to leave certain areas exposed to insert probes to measure items such as temp this you do not do in production models but it is part of the development process.
I would have to look at the reflection material properties of the materials you mentioned compared with the inside exposure temp at peak minus the heat loss to determine outside exposed material temp or you can do it by trial and error which is the industry norm. I would guess the inside piece of steel would be exposed to temps that could lead to warp but the outside is not thus the outside frame acts a jig that prevents the warp. I tend to prefer in those situation not exposing the interior piece of steel to that exposure and cover it with refractory and eliminate the chance from the beginning.
Now you take the downdraft units this very much becomes a non issue because the main doors are not exposed to nearly as much heat because of the design of the boiler. Heat never really reaches the door certainly not in the same way as older style units. So I would think on these units nearly most insulation material would work just as well because the temp exposure would be much less.
Interesting topic
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It's why a lot use the pyramid shape on the part of the door that enters the firebox.
The flat plate that's on the top of the pyramid which makes up the part closest to the fire sometimes can become distorted or develop a wave in it due to heat, but the shape around it is strong and it seems to work great.
Empyre for example don't use the pyramid shape tho, they have some type of high temp bat insulation simply laying behind a piece of 304 stainless, it to seems to work well as I've not seen it be an issue
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I was considering cutting the inner part of the door on my ncb175 off and adding insulation and then reattaching the piece of steel. Are you saying it would be better to attach refractory to the fire side of the door as a better solution to loosing so much heat from the door?
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I was considering cutting the inner part of the door on my ncb175 off and adding insulation and then reattaching the piece of steel. Are you saying it would be better to attach refractory to the fire side of the door as a better solution to loosing so much heat from the door?
Your new 175 door is insulated, although I've seen them have a few issues
It doesn't appear to be insulated as well as some others
But refractory on the front of it would be a huge help