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Author Topic: Higher efficiency conventional build scotch type  (Read 3708 times)

ben

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Higher efficiency conventional build scotch type
« on: March 08, 2015, 02:49:52 PM »

I'm building a conventional with a couple of modifications. We currently heat our house with a napoleon model 1400 that has a Gasification tube and they claim in the 70% efficiency. http://napoleonfireplaces.com/products/1400-pedestal-wood-burning-stove/
We love the stove, so I'm going to incorporate some of its features into a conventional water furnace.  I am also adding a few features borrowed from the current boilers on the market and a few ideas of my own (I think).
The firebox is 40 inches deep. The firebox is 1/4 plate, the floor is 3/8 plate. It has air intake in the bottom (also ash falls through), The floor is a V shape to allow ash and moisture and creosote to flow/fall into ash pan. There is slates welded onto the floor to allow a 1/4 air gap between a second steel floor plate. This will hopefully allow moisture and creosote to flow regardless of ash in the firebox. It will also insulate the coals and allow air up around the fire. The gasification tube is bolted in with slots to allow for thermal expansion. There will be plate baffles to keep the heat in the firebox that will sit on the brackets in the picture and rest on the gasification tube, just like the napoleon stove. It will have a ash pan, the ash compartment doubles as the air intake. There is a divider plate to keep the mess in the front. It is at the start going to be naturally aspirated, with a spot to add a fan down the road. I'm not sure if I'm going to go r26 or r40 on the insulation.
I wish I would have started taking pics sooner. There is a fair number in the gallery already with more to follow.
I have a rough sketch with some dimensions I will post when I get to my work computer this week.



Here is the gallery:
http://s1300.photobucket.com/user/benamyeby/library/boiler?sort=3&page=1
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hondaracer2oo4

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Re: Higher efficiency conventional build scotch type
« Reply #1 on: March 08, 2015, 06:30:45 PM »

Couple things for you.

First, you were so close to making this be able to be a gasser, why didnt you?

Second thing is I am not expert but I think that you are absolutely going to need a forced fan for that thing to operate at all. I don't think that there is any chance at all for it being able to draft on its own with those passes through the water jacket. I may be wrong.
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woodman

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Re: Higher efficiency conventional build scotch type
« Reply #2 on: March 09, 2015, 05:43:29 AM »

I agree with Honda, and I also worry about plugging those tubes with creosote rather quickly since it is not a gasser. Other than that concern it looks great!
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mlappin

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Re: Higher efficiency conventional build scotch type
« Reply #3 on: March 09, 2015, 06:43:11 AM »

Might just have to run a wire brush thru them once a week driven by a cordless drill, well seasoned wood should cut down on the creosote issue some.
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ben

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Re: Higher efficiency conventional build scotch type
« Reply #4 on: March 09, 2015, 07:18:34 AM »

So I'm at work now and can only post the dimensions file in a pdf file or a cad file so photobucket doesn't like it. The firebox width is 32.5 inches and the height is 43 inches. The tubes in the top are 3" id 1/4 wall, the collector boxes are 20" wide and the height depends on what box it is. I figure it should hold 200-220 gal of water. I have a rancho aquastat.

I thought pretty long and hard about going full gasser, but decided on this because I kind of wanted it to burn a bit of everything. We have 12 acres of mixed hardwood and sometimes when the wind gets blowing and knocks some trees down we only season the wood a couple months. We generally split that stuff smaller to help but there will be some higher moisture wood and woodshop scraps and stuff like that going in. I do like the simplicity of a conventional and we have a source of plenty of wood.

I have also thought about the creosote issue, In the first cleanout box (the one above the firebox door) there is actually a drain so if liquid drains out the top stretch of pipes and into the box it can flow back into the firebox instead of flowing out that door. You can see that square block in a couple of the pictures before the water jacket goes on. I also looked at the P & M conventional quite closely and I don't think my flue temps will be much colder than it. I just felt that the round tubes will be much easier to keep clean than the square. Also It can be fully cleaned from the front (except the chimney).

As I said in my first post I do have a spot and plans for a fan but I'm going to fire it up naturally first with a good stretch of insulated chimney to see what she does and what the exhaust temps are.

keep the comments coming!

In liberty
Ben
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Dan76

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Re: Higher efficiency conventional build scotch type
« Reply #5 on: March 09, 2015, 11:32:34 AM »

Looks to me like you are really handy.  Looks good and those tubes seem easy to access. Lots of heat will transfer to your water with those tubes. Looking forward to hearing how efficient it is when you start it up. :thumbup:
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BoilerHouse

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Re: Higher efficiency conventional build scotch type
« Reply #6 on: March 14, 2015, 09:54:40 PM »

Your design is a lot like mine.  Firebox is brick lined, heat transfer takes place in 6 x 2 inch tubes, single pass.  It is forced draft, by timer, on start up only.  After that its all natural.  Creosote is not an issue, but I brush flaky stuff from the tubes and pull ashes every Saturday. Takes about 20 minutes.





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wissel12

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Re: Higher efficiency conventional build scotch type
« Reply #7 on: March 15, 2015, 08:21:30 AM »

Have you made the door yet? I would like to see pictures of your door design.
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ben

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Re: Higher efficiency conventional build scotch type
« Reply #8 on: March 16, 2015, 06:23:42 AM »

I have just started the door. I've added a couple more pictures to the gallery. The door is 1/2" thick, with 1" rope gasket. I have ceramic insulation I will be putting in a stainless box on the inside. Some of the pictures are a little blurry. Sorry. I will add some more when I make more progress. I checked it with air. I had a few leaks... Seems the start and stop of the mig welding is where I was likely to have a leak. I patched them up. Hopefully everything stays sealed when she gets up to temperature. I'm not sure how much water it hold either. I was in a hurry but it takes about 40 minutes to fill up with the garden hose. I will have to time a pail and compare.

In liberty
Ben
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mlappin

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Re: Higher efficiency conventional build scotch type
« Reply #9 on: March 16, 2015, 06:41:30 AM »

Overlap you're terminations a little more. As in when you start a new weld at the end of an existing weld back up 1/2-3/4 of an inch and start the new weld on top of the old.

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ben

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Re: Higher efficiency conventional build scotch type
« Reply #10 on: March 16, 2015, 06:54:05 AM »

Thanks for the tip, I thought I overlapped enough. Apparently not though. I bet it would have been better if I could have cranked the heat to it and got into spray transfer mode but the water jacket is only .187 thick. I suppose I overlapped enough now, I just had to go back over them and find the spots after haha. I've also heard you have better luck running co2 instead of an argon mix for stuff like this. Live and learn!

In Liberty
Ben
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mlappin

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Re: Higher efficiency conventional build scotch type
« Reply #11 on: March 16, 2015, 08:11:44 AM »

Usually a straight Co2 mix causes even more spatter.

Another thing I do is before welding anything that has to be air/water/oil tight is to hit it with the needle scaler first to make sure ALL the mill scale is gone.
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ben

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Re: Higher efficiency conventional build scotch type
« Reply #12 on: March 24, 2015, 11:52:54 AM »

Added a couple pictures to the gallery. I have some of the latch, the hinges, the door insulation and basket. I have 3" of ceramic insulation in the door and 1" in the first cleanout box. In the chimney cleanout there is an angled stainless heat shield to deflect the flue gasses up the chimney. It just leans in there so I can take it out if it doesn't do anything.

In Liberty
Ben
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slimjim

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Re: Higher efficiency conventional build scotch type
« Reply #13 on: March 24, 2015, 12:19:01 PM »

Ben, I have been watching your boiler build, nice job although I think you may have some future issues with creosote in the tubes but I just noticed your signature, THANK YOU my fellow Patriot!
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ben

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Re: Higher efficiency conventional build scotch type
« Reply #14 on: March 24, 2015, 01:06:43 PM »

slimjim, Thanks for the comment!
First, it's amazing how many people pay lip service to things like freedom and liberty but have no Idea what they are....

Second, I appreciate the concern about the creosote. I have thought about this a while and only time will tell what happens. I do have a backup plan for a bypass if this thing turns out to be a turd. I roughly measured out the total heating area of my tubes and its not much different than the P&M. The cross sectional area of the tubes is about 15% larger than the 6" flue. I didn't want things to keep getting bigger as when gasses expand they cool. I am putting a probe in the stack and am hoping for 280-300 deg temps. I have purposely made it easy to wirebrush the tubes from the front so I can keep an eye on them. I am also hoping the interior firebox design will permit higher burn temps which hopefully burns more of that nasty creosote. I'm planning on large curved baffles on either side of the gasification tube to hold the heat in there (not it contact with the water jacket). Also with no water in the floor and brick down there, I don't think those things will hurt my chances.
 
I would really like if I could use both passes of tubes, it seems like a waste having 4-600 deg stack temps.



In liberty
Ben
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