information about the secondary air inlet tubes measure

[FROMITALY]

Sorry for my english, I write from Italy and I am following the forum for a while on the modification of the secondary burn
I would like to ask whether entry of secondary air may be sufficient as measures 2 pipes from 1/2 inch
"Room size wood stove 40 cm x 40 cm x 35 cm"

Thanks
Mirko

 

[begreen]

Welcome. Are you trying to modify a stove to add secondary air? Is there a baffle already in the wood stove firebox? Can you put up a picture of the stove?

 

[FROMITALY]

Welcome. Are you trying to modify a stove to add secondary air? Is there a baffle already in the wood stove firebox? Can you put up a picture of the stove?

yes


my project for now but with galvanized steel pipes will be replaced with stainless stee

 

[webby3650]

Interesting project! I have wanted to do this for a while, just haven't made the time for it. I think the only way to find out correct sizing would be to mimic a stove that is currently being produced. You could also put a damper of some sort on the incoming secondary air, so if it's too much you can reduce it.

 

[FROMITALY]

yes
is inside the stove pipes are 3/4 inch but I want to make two holes external connection 1/2 INCH (This is for the sake of simplicity), but I am afraid that the holes are not sufficient -

I do not know how much air is used for the secondary.

 

[webby3650]

Most stoves here in us use channel iron to make the air manifold. It's about 1.5"x2.5". Rough numbers of course.
This manifold runs around the perimeter of the firebox at the top, so the air can be preheated. The inlet at the bottom of the stove is usually 2"x2" or so.

 

[webby3650]

Although, the size I mentioned is for primary as well as secondary. So what you have planned might be about right.

 

[FROMITALY]

my preheated is the line red



I hope it's enough, ......................................... the green lines are the air outlet holes 4 mm

 

[begreen]

4mm is a large air hole size as compared to most stoves. I would make them 2mm to start with. They can always be drilled out larger.

 

[FROMITALY]

2 mm is very small ...... of course I can always enlarge ..........................
or make more holes 2mm
reading many posts here in our forum I think the pre-heating is the most important thing

 

[FROMITALY]

else

I would not drill holes in the bottom for air intake into the combustion chamber as the chamber and 'small and I would go further reduce the space

I would like to drill 4 cm above the outlet holes, of course, would go on the outside to pick up air from below ................. I do not know if I have explained


I enclose drawing


it's a problem ??????? for you

 

[begreen]

2 mm is very small ...... of course I can always enlarge ..........................
or make more holes 2mm
reading many posts here in our forum I think the pre-heating is the most important thing

I would think that the total area of the holes would equal a little more than the intake area which is .375 squared x pi or ~.44 sq inches. If you have 10 holes total (5 on each side) then each hole would be .04 in. which would be tiny (about 1mm). I would change the design so that instead of one common 3/4" intake there are two, 1/2" inch intakes, one on each side with only two 90 degree angles.

Right now there are 5 turns for each manifold. Each elbow or right turn is going to add resistance to the air flow. Can you go directly into the back down low instead of using so many 90 deg. angles and use two separate pipes? That would mean only two 90 deg. turns for each manifold.

Also, is there insulation behind the side and back panels in the stove? That will help the fire to be hotter.

 

[FROMITALY]

I did not understand what you mean

 

[begreen]

 

[FROMITALY]

ok I understand you feel the warm air and 'adequate?

I also thought a single entry by 3/4? well what do you think??

 

[begreen]

Better, there are three 90 degree turns in the air flow.

Is there insulation behind the side and back panels the stove firebox? That will help the fire to be hotter.

 

[FROMITALY]

ok here are the two final projects to test

the tubes are made of stainless steel 316, thickness 1.5 mm

nr 1



nr 2




one with three corners 90 and only entry by 3/4 from the bottom

the other with angles of 90 and 5 and only entered 3/4 from bottom

I await your comments

 

[FROMITALY]

I would like to form your own opinion on what you think is better
The drawing shows the combustion chamber from above
The two black lines are the two releases fumes and the white center is the deflector
What solution do you think of the tubes is best




Thanks

 

[FROMITALY]

anyone who answers??

ok proceed with the project nr 2

 

[webby3650]

No one knows for sure, we are all speculating. Its a neat project, but will most likely end up being a trial and error project. Good luck!

 

[begreen]

I have already voted for having the least amount of 90 degree turns in the airflow.

 

[FROMITALY]

ok thanks

Work in progress

 

[FROMITALY]

made the first test fire the result is not 'very positive

I will have to make changes

 

[DanCorcoran]

made the first test fire the result is not 'very positive

I will have to make changes

Do you understand that it takes very dry wood and (for me) 30-60 minutes or more, before the fire begins in the secondary tubes?

 

[begreen]

Also, how are you regulating the primary air? After the stove has completely warmed up, try reducing the primary air in steps so that the flames on the wood are getting lazy. Wait then 5-10 minutes for the fire to regain strength and close the air down again until the flames get lazy. Watch for flames to start coming from the secondary manifold. Reducing the primary air will encourage air to be pulled from the secondary manifold.

Do you have pictures of the current installation and the fire? How many holes are in each pipe? What diameter are the holes?