Simple Question... well, maybe

[johnstra]

There's a ton of great information here about how to dial in an EPA stove by controlling the primary air control. Very generally, the preferred approach is to dial down the primary air control when the stove gets up to temp in order to allow secondary combustion to occur. This is the most efficient way to operate an EPA stove.

My question is, when we turn down the primary air control, is it cutting air into the firebox or is it diverting it to the tubes up top?

-john

 

[NH_Wood]

Great question and one I've been wondering about as well. Since you can achieve secondaries with the primary air completely open (at least my stove will have jets of flame exiting the secondary burn tubes with primary air open), I'm guessing that the secondary tubes get air all the time, but the secondaries only become noticeable as the stove gets very hot and heats the air exiting the tubes to a point when the gases can ignite. But, this is only my best guess - our panel of gurus will certainly straighten out my thinking! Cheers!

 

[pen]

Picture a paper towel tube.

Now, take the tube and stab it w/ a pencil leaving about 1 dozen 1/16 in holes along the top.

If you take and draw air (representing the draw of your chimney) through the tube w/ the end open the air will mostly take the path of least resistance and come through the large open end (your primary air control).

If you start closing down the air control and the same draft is sucking on the stove (paper towel tube), then more air will be pulled in through the secondaries (small holes in the tube).

pen

 

[NH_Wood]

Picture a paper towel tube.

Now, take the tube and stab it w/ a pencil leaving about 1 dozen 1/16 in holes along the top.

If you take and draw air (representing the draw of your chimney) through the tube w/ the end open the air will mostly take the path of least resistance and come through the large open end (your primary air control).

If you start closing down the air control and the same draft is sucking on the stove (paper towel tube), then more air will be pulled in through the secondaries (small holes in the tube).

pen

Pen - aren't there 2 separate intakes? Does this change the situation at all? Cheers!

 

[begreen]

It depends on the stove. Some stoves have separate secondary intakes, some don't.

 

[NH_Wood]

It depends on the stove. Some stoves have separate secondary intakes, some don't.

Okay - so how would the situation work in both scenarios? Cheers!

 

[johnstra]

he he... we think alike, NH_Wood. C'mon, gurus, curious minds want to know.

 

[pen]

Never mind then, I've already said too much...... Just go on and consider that it must be magic, just like the magic heat reclaimer.

The secrets of the stove must not be made public.

We are sworn to hold our physics defying knowledge to absolute secrecy.

:blank:

pen

 

[NH_Wood]

Never mind then, I've already said too much...... Just go on and consider that it must be magic, just like the magic heat reclaimer.

The secrets of the stove must not be made public.

We are sworn to hold our physics defying knowledge to absolute secrecy.

:blank:

pen

Pen! I like your answer, just wondering how the situation would work if there are 2 intakes - would your same answer apply. Your paper towel tube metaphor was just fine! Cheers!

 

[pen]

unless you can directly contol (w/ a lever) the amount of secondary air, it shouldn't change the fuctionality. the admission of 2ndary air is all based upon the pull of the stove sucking it in through those tubes. This is aided by the fact that the air is warmed in the stove.

That is to the best of my understanding. If a stove designer came on maybe they could explain it more clearly.

pen

 

[vvvv]

any air entering the stove will go to the hottest spot. when the 2ndaries aint firing the air still goes to the hottest spot. the trick is to get the hottest spot on top moreso & when 2ndaries are firing the top gets hotter & results in the load burning from the top down as the wood heats up & gassifies. If the load burns from the bottom up, the gassification accelerates as each lower piece heats the ones above............get it?

 

[firefighterjake]

Great explanation Pen.