I'm Completely Confused About Airflow And Its Effect In Stove!

[BrotherBart]

Frankly, I don't know how you would overfire a 1.4 cf firebox stove. It is a more frequent concern with larger fireboxes with a full fuel charge in them.

With negligence it can be done with the Castine. I came close when learning about the compressed wood products and have seen some poor stoves that this has happened to. If you want to push the stove to 900+ it is possible, especially if you stoke it like a fireman and leave the air control half open.

Agreed. I started to come back and do an edit saying a normal burn cycle was being assumed and got distracted sticking wood in a stove. :red:

 

[turbocruiser]

Frankly, I don't know how you would overfire a 1.4 cf firebox stove. It is a more frequent concern with larger fireboxes with a full fuel charge in them.

BK, that is an interesting comment. It really has me thinking. It would seem to me that the size of the fire box would be irrelevant, because the amount of wood would be relative to the size of the fire box.......smaller fire box, less wood needed, less btus needed to overfire. Bigger fire box, more wood needed, more btus needed to overfire. Am I missing something?

Yes that has me thinking too BrotherBart and it isn't really what we're seeing so far not to argue at all; I mean if I didn't close the air to 1/2 I think the stove would race right up to 1000 if I let it loose with a "large" wood load. I still honestly don't know what temperature would be considered as an overfire but I do know I'm not going to let the stove go above 750 at least for a few months more experience without damping it down to maintain that 750 at the most. So strictly from my own limited observations so far I think I'm seeing what tfdchief is saying in that the size of the firebox is irrelevant and it might not be a big stove burning at 750+ but it still is a stove burning at 750+. Again not as an argument, just as an amateur's initial observations.

A few things this thread has helped me understand so far I think is that "flushing" the firebox with regular room air by opening the door while at the same time also "closing" the secondary tubes by closing air controls can indeed cool both the firebox and the chimney. Secondly, this is the proper procedure in the event that closing air controls alone won't work to prevent or to stop the overfire. These are all awesome things to know. Now what I'm wondering still is if the whole thing with the overfire getting worse even with the air completely closed on some stoves is really the result of still having too much air allowed through those openings? So the thought there is while some stoves (large or small) can effectively prevent or stop overfires from the air controls alone, others cannot and sometimes have to have the "flush" to cool things down? Maybe that's what BrotherBart was trying to say?

I guess I'd also ask as an aside how large the opening that is intended to always allow air in actually is on other stoves and again whether something as small as 1/4" hole can possibly provide enough air to sustain the overfire. Based on the answers there, I think I will know in what order to respond to an overfire; either try to prevent/stop with closing air controls first as my manual states, or, go straight to opening the door along with also closing air controls. Thanks So Much!

 

[BrotherBart]

In the first place I would be very surprised, shocked and awed in fact, if that stove of yours shuts down secondary air when you close the primary air control. If it did it would be screwed trying to pass the EPA cert. test.

If closing down the primary air backs the stove down that is great. An actual overfirie takes on a life of its own. Burns faster and faster and the "EPA hole" or holes can't be closed. and on no stove that I know of can the secondary air intake be closed without grabbing something and plugging it. So the hotter it burns the harder the chimney draws pulling air into those un-regulated intakes and the hotter it burns.

All I can tell ya is that I think seven hundred degrees is more than plenty of temp in a steel stove and I try to stay below that. Secondly, at 1,000 degrees stove top temp last year I blew off any thought of shutting anything else off on that 30-NC that has had the EPA holes blocked since 2007 and swung the door wide open and brought that bad boy down fast.

Others may have other results. YMMV in other words. I would not suggest running a test to find out. :lol:

 

[turbocruiser]

In the first place I would be very surprised, shocked and awed in fact, if that stove of yours shuts down secondary air when you close the primary air control. If it did it would be screwed trying to pass the EPA cert. test.

If closing down the primary air backs the stove down that is great. An actual overfirie takes on a life of its own. Burns faster and faster and the "EPA hole" or holes can't be closed. and on no stove that I know of can the secondary air intake be closed without grabbing something and plugging it. So the hotter it burns the harder the chimney draws pulling air into those un-regulated intakes and the hotter it burns.

All I can tell ya is that I think seven hundred degrees is more than plenty of temp in a steel stove and I try to stay below that. Secondly, at 1,000 degrees stove top temp last year I blew off any thought of shutting anything else off on that 30-NC that has had the EPA holes blocked since 2007 and swung the door wide open and brought that bad boy down fast.

Others may have other results. YMMV in other words. I would not suggest running a test to find out. :lol:

Just to clarify my comments above, I'm not saying that my stove totally shuts down secondary air ... I'm saying it shuts all but that last little 1/4" inch hole off at least as far as I can tell. It sort of looks like a triangular thing with another hole adjacent to the triangle such that no matter how much you close the control that hole there is always an open airway allowing in at least a little air. I should try to post pics of that becuase that would make more sense than me trying to describe it. If this works the first pic is with the air at 1/2 and the second pic is with the air at 0/2.



Again with the temperatures that I'm getting I'm measuring this at the hottest point which is the chimney connector right at the area where that meets the actual top to the firebox. The thermometer on the stove top which is actually floating above the top to the firebox will be reading a lot lower than that. That's another area of confusion for me ... really where I'm supposed to shoot the temperatures from. Anyway, if you are suggesting I stay at 700 as opposed to 750 I will definitely do that I just want to make sure my temperature measurements are measured at right area. Thanks Again.

 

[BrotherBart]

I have to go to bed. But as I said before, your primary air control does not control the secondary air to the tube up at the baffle. It is unregulated.

From the stove manual:

"Both the primary and air wash drafts are controlled
by the control rod located on the left side of the unit
(when facing the unit). To increase your draft - pull
open, and to decrease - push closed. All units have
a secondary draft system that continually allows
combustion air to the induction ports at the top of
the firebox, just below the flue baffle."

There is another hole somewhere.

 

[turbocruiser]

I have to go to bed. But as I said before, your primary air control does not control the secondary air to the tube up at the baffle. It is unregulated.

From the stove manual:

"Both the primary and air wash drafts are controlled
by the control rod located on the left side of the unit
(when facing the unit). To increase your draft - pull
open, and to decrease - push closed. All units have
a secondary draft system that continually allows
combustion air to the induction ports at the top of
the firebox, just below the flue baffle."

There is another hole somewhere.

Okay, now THAT makes much more sense to me. I didn't realize that the primary draft and the secondary draft were separate and that the secondary draft is designed to be totally unregulated and always on open. Thanks that really lights the lightbulb for me finally! Now I gotta go find the other hole offering air to the secondary draft system.

 

[Battenkiller]

Auh, come on BK, that's no fun......I like it better when you stick your neck out...... ;-P Your admirer, Chief

Yeah, what the heck. I've been playing chicken with that guillotine blade my whole life. Why quit now, eh?

 

[turbocruiser]

Okay I thought I had the light all lit up but then something else started confusing me ... if the secondary draft supply is indeed unregulated and always on open ( and I'm not arguing that it isn't) why then would opening the doors take the secondary tubes "offline" as several posts here have stated?

Hang in here with me please I'm just trying to learn the concepts the right way. Thanks.

 

[begreen]

It doesn't shut them down 100%, maybe 95%? This is simply a matter of suction. It takes increased suction to pull the air through the secondary passages, manifold and out the small holes. Air will take the path of least resistance. When you open up the stove door, the suction (draft) drops and the air goes directly from the room and up the flue. The effect of the secondaries at that point is negligible.

Imagine if you will, that you are in a submarine. There is a minor but persistent leak in the forward compartment (secondaries). Then someone accidentally opens the top hatch flooding the submarine (front door). Think you are notice that minor leak?

 

[turbocruiser]

Awesome! That I think completely clears it up for me. Thanks so super much for helping me through my confusions!