Secondary Air Distribution System

 
franco b
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Post by franco b » Sun. Aug. 31, 2014 8:56 pm

I don't think it worth the trouble and doubt it would work well.

Getting back to the secondary air there is a great deal of difference between bypassing some air from below the coal bed and doing it above the bed.

Lightning explained it very well. Air intake below the grate is fixed so any bypass will exaggerate air starvation of the coal bed as it ashes up. Secondary air above the bed will not have this effect as draft volume above the bed is not fixed; it has the full capacity of the chimney. Any bypass effect will be compensated by the baro and draft will remain constant through the coal bed. It will still suffer from ashing up but nowhere near to the same degree as the baro will compensate. With air coming from below the grate the baro can't sense a difference.


 
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Post by Jared43758 » Sun. Aug. 31, 2014 9:05 pm

I don't really care for your option on it. Now back to hotblast hopper

 
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Post by confedsailor » Sun. Aug. 31, 2014 9:59 pm

Jared43758 wrote:I don't really care for your option on it. Now back to hotblast hopper
That was a bit brusque... The thread isn't about hoppers, it's about overfire secondary air. If you want a thread about hopper feeding your stove, create it. The wise men of coal will be more than happy to discuss it with you, but an attitude like that will get you ignored in a big damn hurry.

 
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Lightning
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Post by Lightning » Sun. Aug. 31, 2014 10:19 pm

Jared43758 wrote:I don't really care for your option on it. Now back to hotblast hopper
HI Jared, I believe franco b was referring to Hotblast1357's design of how he plans to deliver secondary air over the coal bed by re-routing primary air. Richard (franco b) is a very smart fella and his opinion is always worth careful consideration. Please consider starting a thread based on your wish to design a hopper for our style appliance. I have considered a hopper, but weighing time and effort against likelihood that it would make for any appreciable advantage isn't working out (in my mind anyways).. Modifications of that magnitude call for replacing the stove, I'm thinkin..
Last edited by Lightning on Mon. Sep. 01, 2014 8:45 am, edited 1 time in total.

 
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Post by hotblast1357 » Mon. Sep. 01, 2014 6:43 am

franco b wrote:I don't think it worth the trouble and doubt it would work well.

Getting back to the secondary air there is a great deal of difference between bypassing some air from below the coal bed and doing it above the bed.

Lightning explained it very well. Air intake below the grate is fixed so any bypass will exaggerate air starvation of the coal bed as it ashes up. Secondary air above the bed will not have this effect as draft volume above the bed is not fixed; it has the full capacity of the chimney. Any bypass effect will be compensated by the baro and draft will remain constant through the coal bed. It will still suffer from ashing up but nowhere near to the same degree as the baro will compensate. With air coming from below the grate the baro can't sense a difference.
I know we frown on wood, and I know there's not a stove that burns both good, I'm just worried about installing the secondary tubes permanent like that and it not being sufficient for wood either, because I do burn it in the off seasons and don't want to loose that option, and I understand a wood stove and a coal stove are two different things, but a draft is a draft like everyone agrees on, and a wood stoves secondary burn comes in at the same "level" the primary air comes in, (over fire air) and that works efficiently to burn off wood gasses, so I don't see why it would be any different if it was over fire or under fire? The only difference is that it doesn't come in the exact same hole, but its still the same pressure and what not. I get that it will weaken the draft so couldn't I just let my draft in? From what I understood with William S. Post about the old hotblast parlor stoves, that's how its set up with tubes casted in the fire pot

 
franco b
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Post by franco b » Mon. Sep. 01, 2014 11:08 am

With Williams no. 6 the secondary air intake is just below the fire door, not below the grate. Many antique hot blast stoves had a pipe extending down from the top of the stove and terminating just above the fire pot.

For wood burning I think what you have in mind will work fine provided you give it plenty of air and the outlet for that secondary air is well above the fire.

Lopi was the first with an improved wood stove and their design did bleed off primary air up through a hollow baffle to exit at the front lip of that baffle. Look at some of the new wood stove designs and try to emulate. The trouble with wood is that it does not take kindly to air starvation as does coal. On heating the wood wants to give up half its heat value in the form of gas very quickly. If it is not burned we get smoke and creosote. If it is burned then the heat overwhelms the heat exchange and stack temps. are very high. When it reaches the charcoal stage it behaves very much like coal.The ideal is to feed small amounts frequently which is what a pellet stove does.

You might try experimenting with an upside down fire. The large logs go in first, followed by smaller, with kindling on top. Supposed to give a better controlled cleaner fire.

 
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Post by hotblast1357 » Mon. Sep. 01, 2014 11:35 am

Well it won't be long before we can experiment with all this


 
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Post by Jared43758 » Wed. Sep. 17, 2014 4:17 pm

http://www.amazon.com/gp/aw/d/B001TOHT78/ref=pd_a ... 15&simLd=1.
Can u check out this manometer and tell me if it will work at all for me? I don't wanna spend a lot of money. Also when u tap into your pipe do u tap in after the baro or before?

 
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Post by Lightning » Wed. Sep. 17, 2014 4:42 pm

Jared43758 wrote:http://www.amazon.com/gp/aw/d/B001TOHT78/ref=pd_a ... 15&simLd=1.
Can u check out this manometer and tell me if it will work at all for me? I don't wanna spend a lot of money. Also when u tap into your pipe do u tap in after the baro or before?
This is the one most of us use..
Probe the pipe between the baro and the stove.. :)

http://www.amazon.com/Dwyer-Mark-Model-Inclined-M ... r+model+25

 
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Post by Jared43758 » Wed. Sep. 17, 2014 4:55 pm

I seen those and liked them. Do they come with everything I need? Line and probe or whatever? Do u leave the manometer hooked up all the time? My stove was burning great, but when I put the baro on the flapper stayed open a little bit unless I backed the counter weight all the way back. So I'm thinking its drafting good and I don't wanna loose all my heat up my chimney.

 
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Lightning
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Post by Lightning » Wed. Sep. 17, 2014 5:04 pm

All ya gotta do is drill a small hole in the pipe between the baro and stove. Use a 12 inch section of 3/8 inch metal brake line (or something similar) to transition from the rubber tubing (that comes with the unit).. I crimped a small piece of tin onto the brake line tubing to act as a "stop" so that it could penetrate into the pipe a couple inches. I'll be back with pictures..

 
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Post by Jared43758 » Wed. Sep. 17, 2014 5:12 pm

Thanks

 
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Lightning
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Post by Lightning » Wed. Sep. 17, 2014 7:27 pm

Here's some pics of the mano probe..

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franco b
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Post by franco b » Wed. Sep. 17, 2014 7:31 pm

Just admiring the insertion stop you made. Very clever yet simple.

 
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Post by steamshovel » Thu. Sep. 18, 2014 6:40 am

something came to mind while reading this, the most important air flow and pressure in a coal stove, is what's under the fire, as that's the primary combustion source to burn coal.
with that in mind, a manometer probe in the ashpan area, in the side or back of the stove wall, would give an accurate reading of what the pull is on under the fire to feed it. it would be interesting to see what the difference is for mano readings below fire, above fire, and in flue pipe outside the stove. is there a large difference ?


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