# Secondary air conversion of old stove



## begreen (May 11, 2016)

Stumbled onto this video on YouTube today. This is a very nice and thorough conversion of an old Grizzly stove to a modern clean burner. Glass doors, airwash and baffle bypass damper were also added.


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## defiant3 (May 12, 2016)

Wow!  Wish I had that kind of spare time!!


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## jb6l6gc (May 13, 2016)

Unbelievable. This guy should build stoves


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## moresnow (May 13, 2016)

Nicely done!


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## fbelec (May 14, 2016)

your hired and a raise. that's amazing at the end no flame or smoke coming off the wood but plenty of flame up at the secondary


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## dafattkidd (Jun 26, 2016)

Wow. Thanks for posting that. That is really amazing. That guy must be a homesteader or something. I can't imagine how many hours of work it took to do that work. Such an incredible product. What a talented guy.


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## Corey (Jul 9, 2016)

Certainly amazing from a craftsmanship point of view.  There are a few technical 'nuances' I mention not to degrade any of the amazing work in the video, but in case anyone is following a similar path and using this as reference:

1)  The secondary air bars work best in a left-to-right configuration with the holes facing forward.  Ideally, flame from the back bar directly hits the bar in front of it, heating the second bar, flame from the second bar hits the third bar, heating it, ...third bar hits the fourth (if you have that many) and so on.  This 'cascade effect' insures each bar is as hot as possible, delivering the hottest air, and optimum efficiency.  The box / H pattern shown clearly works but with some of the flame directed into open space, you may loose some heat.

2) Thermal mass.  There is really no need for a 3/4" thick damper plate and huge rod, etc.  All this is mass that must be heated before secondary combustion can begin.  Plus, it would take some fairly beefy support for all that weight, again adding more mass.  Ideally, the only thing across the top of the firebox would some relatively thin stainless burn tubes.  These would be light enough to be self-supporting and have a layer of light weight fiberboard insulation across the top.  Again, all light weight, low thermal and mechanical mass, minimal danger of sagging loads under intense heat, etc.

3)  Burn tubes - while the big box sections certainly work, round tubing is much easier to squeeze in to tight fireboxes.  Also, when you go with stainless steel, you can get by with fairly thin tubes.  I happened to find some 1" OD x .050 wall tubing at the scrap yard, it has been perfectly fine for multiple years of use at orange heat.

https://www.hearth.com/talk/threads/burnin-orange-tonight.106714/

4) Air supply - Optimally, bring the secondary supply into the firebox at a low point, give it a large chamber to slow velocity and allow maximum warm-up time, then deliver it to the burn bars.  Again, this set-up clearly works, but having the supply outside the firebox misses out on some of the intense heat. 

5) Miscellaneous - looked like possibly some Grade 8 (yellow) hardware in there?  It will likely all temper back to Grade 2 in the intense heat...especially inside the firebox, and there is no way there should be 'that' much load on the hardware anyway, so might as well save your money and go with garden variety stuff.  A few thermal cycles and the bolts are likely to stretch, too ...dumping your clamping load and again, meaning the garden variety stuff is more than adequate.


Again, not to degrade the original work, but simply to post some points about 'optimal' factors for anyone using this as a guide - though obviously you can still have a great working system even if an optimum design is not incorporated.


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## Tar12 (Jan 29, 2017)

Good job! A very talented individual!


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## dafattkidd (Feb 1, 2017)

I'm glad you resurrected this old thread. That video is a real gem.


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