Secondary Air Distribution System

Modern and vintage hand fired coal stove are similar to a wood stove and in some cases can burn either. They need to be regulated and fed by hand usually every 12 to 24 hours depending on your usage. They require no power to operate making them ideal for rural settings with long power outages.
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Lightning
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Post Tue. Nov. 26, 2013 6:43 pm

michaelanthony wrote:Delivery man by day and doctor of physics by night :up: I enjoy your "hootspa", I sure I spelled it wrong. Before you take off to your isle of solitude, could you attach a metal electrical box to the end of the conduit and cover with a solid steel cover and make your own "check damper"? Simular to Mr. Precision's avatar. Keep on truckin' Clark Kent! 8-)
That's awesome :lol: thanks Bro!

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Lightning
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Post Tue. Nov. 26, 2013 6:52 pm

I wonder too, since the secondary air is actually pulled in as opposed to being forced in, if that makes a difference on distribution.

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michaelanthony
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Post Tue. Nov. 26, 2013 7:11 pm

Lightning wrote:I wonder too, since the secondary air is actually pulled in as opposed to being forced in, if that makes a difference on distribution.
.

Hey dude remember the "Batman" series, they always had colored smoke! :idea:
never yell through a screen...you'll strain your voice.

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wsherrick
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Post Tue. Nov. 26, 2013 7:28 pm

Now that you put this in, you have to watch it and see the results. I bet you will notice a drop in your coal consumption. I would like to hear what happens now.

Sunny Boy
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Post Tue. Nov. 26, 2013 7:30 pm

Lightning wrote:I wonder too, since the secondary air is actually pulled in as opposed to being forced in, if that makes a difference on distribution.
Ummm, . . not really, unless there is some kind of forced draft. That's like saying hot air rises, when every physics major will tell you it's pushed up by heavier cold air.

Does your stove have forced draft ?

If not, then stove air is actually forced in, not pulled. When any gas is heated, it gets lighter. It's the higher pressure of the cooler, heavier air outside the stove and chimney that forces air into the stove and hot flue gasses out the chimney. The greater the temperature difference between inside and outside the stove, the more pressure to force air in.

Paul
So many stoves - so few chimneys. I must be coal-stone crazy.

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Lightning
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Post Tue. Nov. 26, 2013 7:56 pm

Yes sir, I follow that but since the pressure is lower in the stove doesn't it stand to reason that combustion air is being pulled in? Or should I look at it as if the pressure outside is higher so it's being pushed in?

No forced draft, all natural.
Last edited by Lightning on Tue. Nov. 26, 2013 8:01 pm, edited 1 time in total.

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Lightning
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Post Tue. Nov. 26, 2013 8:00 pm

wsherrick wrote:Now that you put this in, you have to watch it and see the results. I bet you will notice a drop in your coal consumption. I would like to hear what happens now.
Yes sir, I will post more observations. I expect coal consumption should fall slightly with the incoming secondary air being more efficiently used but probably not a dramatic difference. It may be hard to say since other variables at play like outside temp for example. I'll do my best to validate any decrease in coal consumption :D

Sunny Boy
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Post Tue. Nov. 26, 2013 8:40 pm

Lightning wrote:Yes sir, I follow that but since the pressure is lower in the stove doesn't it stand to reason that combustion air is being pulled in? Or should I look at it as if the pressure outside is higher so it's being pushed in?

No forced draft, all natural.
Then yes, it's outside higher pressure that forces the air in. Thinking that lower pressure inside the stove - "suction" - makes a stove work means that suction has to be "something", when it's actually a lack of something - a lack of pressure.

And, I'm sure your glad to know that when your stove is working right, . . it doesn't suck ! :D

Paul
So many stoves - so few chimneys. I must be coal-stone crazy.

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wsherrick
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Post Tue. Nov. 26, 2013 8:59 pm

Sunny Boy wrote:
Lightning wrote:Yes sir, I follow that but since the pressure is lower in the stove doesn't it stand to reason that combustion air is being pulled in? Or should I look at it as if the pressure outside is higher so it's being pushed in?

No forced draft, all natural.
Then yes, it's outside higher pressure that forces the air in. Thinking that lower pressure inside the stove - "suction" - makes a stove work means that suction has to be "something", when it's actually a lack of something - a lack of pressure.

And, I'm sure your glad to know that when your stove is working right, . . it doesn't suck ! :D

Paul
Um, vacuum effect, hence why check dampers work the way they do.

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Lightning
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Post Tue. Nov. 26, 2013 9:04 pm

As anticipated I'm seeing a more even burn of the coal bed since the secondary air isn't spilling onto the back half of the coal bed like it used to.

I'm seeing more warm air in my duct work too while igniting a fresh load of coal. It used to be around 108 degrees now it approaches 120 degrees. That's probably due to not having the load door propped open during burn off of volatile gases. Instead the secondary air distribution makes better use of the oxygen with the load door closed.

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nortcan
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Post Tue. Nov. 26, 2013 9:26 pm

Bravo. One of the best thread if not the best one. Lot of informations here...
One thing that runs in my head since the beginning of the present thread is this.
The fire pot in the Sunny beeing not very deep, the anth load gets sometimes higher than the fire pot contour.
So my question on the air over the fire is: supposed I, hum, or someone else decide to place an air ring on the top of the fire pot, and the anthracite covers the ring, then is it a problem to get an efficient gasses burning?

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Post Tue. Nov. 26, 2013 9:37 pm

I think as long as the air can find its way around the coal blocking it it will still contribute to burning the gas. Ash would block the holes but not fresh coal.

Sunny Boy
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Post Tue. Nov. 26, 2013 9:41 pm

wsherrick wrote:
Sunny Boy wrote: Then yes, it's outside higher pressure that forces the air in. Thinking that lower pressure inside the stove - "suction" - makes a stove work means that suction has to be "something", when it's actually a lack of something - a lack of pressure.

And, I'm sure your glad to know that when your stove is working right, . . it doesn't suck ! :D

Paul
Um, vacuum effect, hence why check dampers work the way they do.

You have to think about energy and where it is. There's no energy in a vacuum, so it can't do work. The work can only be done by pressure.

Check dampers only work by making an opening in a heat system to allow cooler, heavier air that is outside into the heat system. The cooler air lowers the temp of the hot gases making them heavier, thus less pressure difference inside vs outside. With less pressure difference, there's less force to push air in and flue gases out, so the draft slows down. With the decrease in incoming air volume ahead of the firebox, the fire dies down producing less heat.

Remember, vacuum is not "something" either. It's just a word to describe a lack of air pressure. Auto mechanics often use the term vacuum as if it was something, but a carburation engineers calls it "pressure drop", which is a more accurate way of saying what the force is that is actually in play.

Paul
So many stoves - so few chimneys. I must be coal-stone crazy.

franco b
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Posts: 8450
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Post Tue. Nov. 26, 2013 9:43 pm

Just like sunrise and sunset ain't really happening.

Sunny Boy
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Posts: 12666
Joined: Mon. Nov. 11, 2013 1:40 pm
Hand Fed Coal Boiler: Anthracite Industrial, domestic hot water heater
Baseburners & Antiques: Glenwood range 208, # 6 base heater, 2 Modern Oak 118.
Coal Size/Type: Nuts !
Other Heating: Oil &electric plenum furnace
Location: Central NY

Post Tue. Nov. 26, 2013 9:53 pm

nortcan wrote:Bravo. One of the best thread if not the best one. Lot of informations here...
One thing that runs in my head since the beginning of the present thread is this.
The fire pot in the Sunny beeing not very deep, the anth load gets sometimes higher than the fire pot contour.
So my question on the air over the fire is: supposed I, hum, or someone else decide to place an air ring on the top of the fire pot, and the anthracite covers the ring, then is it a problem to get an efficient gasses burning?
I would think that it would only be a problem if the ring is so buried that it somehow blocks off, or greatly restricts, incoming secondary air.

Paul
So many stoves - so few chimneys. I must be coal-stone crazy.

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