Stove modifications

[slowzuki]

I'm not talking paint, I'm talking torches and welders here, anyone done it?

I'm thinking of adding a stainless secondary air manifold to my little pre-epa'er. A loop of pre-heat then drilled orifices.

I know there are people out there who have tried! Speak up!

 

[slowzuki]

May even cheat and use a stainless bbq burner, who knows!

 

[begreen]

Sounds like a fun project. What's the stove?

 

[slowzuki]

Its a Connestoga model built by Findley or something, they only make old timey cookstoves now. It was free and is getting moved to secondary duty soon, I don't mind sparking up the plasma cutter to show it some new tricks.

I plan to get a new epa stove soon anyways so I thought I might do some learning, the main problem is no glass doors so it will hard to view the airflow changes etc.

 

[begreen]

Cool. Take lots of pictures. What are you using for a baffle? What is your design guide?Paging Corie to the front desk.

As to the door, it should be easy to create a view. Maybe weld in a pyrex pie plate port while you're at it?

 

[Roospike]

I have rebuilt steel stoves and did a little upgrades to them , the secondary burn chamber is doable , stainless steel is the way to go .

If i remember correct member "cozy heat for my feet" did something like this too. (or is going to)

If you look at the secondary burn chambers of the Pacific Energy stove , this would / should be a good custom set up to add in to a pre EPA stove.

I'm guessing you have the tools and the know-how to fabricate something like this.

 

[slowzuki]

The biggest issue will be the size of the fire box, it is a very small stove and the existing baffle I'm sure is causing a lot of problems. It is 1/4" plate so when flames are impinging on it they are getting quenched leading to unburned particles going up the stack. I'm guessing it may be 45% efficient now, my goal would be to reduce wood consumption by 20% maybe? Not likely to happen but fun anyways.

Yes I've got the tools to make it happen, not the time but thats besides the point!

 

[laynes69]

I'm going to do the same thing this summer to my wood furnace. I will use rectangle tubing for the sides to carry the air and stainless tubes running under the baffle. I already have the hole in the back for my secondary air. I see flames shooting from the piece of channel out the sides, So I want to build in secondary tubes. I have plenty of room in my woodfurnace to do this. I do wonder If its done, if my burn times would increase. I know for sure the heat output would increase. When I rebuilt my furnace I beefed up the baffle and welded support to keep it from warping, and the side channels were replaced with heavier ones. If I do it and it works well, I won't replace my furnace. If you have the tools and the ability go for it and give it a try, I will.

 

[slowzuki]

Somebody had to be first, so it is a lot easier for us now.

 

[Corey]

I added secondary air to my pre-epa'er a couple of years ago. (Would have sworn I just replied to a similar post) Works much better and much cleaner. I'm thinking of giving it 'round two' this summer. It's not terribly hard to go out and look at some of the new epa stoves to get a feel for what you need. The basic key's are the burn tubes, warming the air before it is blown out into the smoke, and insulation on top of the baffle to keep the heat in the burn.

Corey

 

[laynes69]

Does anyone know around what percentage of air is used for primary and secondary?

 

[BrotherBart]

Does anyone know around what percentage of air is used for primary and secondary?

I am highly suspecting that on the Englander it varies. That is that as the primary air is adjusted, more is let into the secondary manifold. Can't prove it since the stuff is welded into the bottom of the stove but in operation it sure looks that way.

 

[webbie]

Some secondary air inlets are metered, other are fixed. Also, it is doubtful anything of this sort will work without also lining the firebox and making other mods in order to try to keep temps very hot in there - and then, if this is done, too much heat may end up at places - like the output stack, meaning all the work did not get the result - and possibly made the install more dangerous.

Corie built his own stove, using lots of torches and welders, so perhaps he can give some hints.

 

[Corie]

I'd say the most important parts of adding a secondary system to a stove would be:

Insulating the firebox to keep the heat in, that means firebricks inside, a ceramic fiber blanket over the baffle or a thermoceramic hardboard baffle

Getting the right amount of secondary air in. Since many secondary air inlets are unregulated and velocity and mass flow rate of the air is important, drastically oversizing the channels and then attempting to control the flow with a damper at the inlet won't always work. Too small channels and the air will be at too high a velocity and too low a mass flow rate to work.

The area the smoke flows through after the secondary system is also important. A large area allows the gases to expand, slow down, and spend extra time in the stove conducting more heat to the room. Too small an area may keep the gases moving so quickly they don't have time to fully transfer their heat to the stove body. On the real extreme small end of things, you can end up with a stove that is draft sensitive because of the high frictional losses to the flow associated with "necking down".

Preheating the secondary air is important. It doesn't mean you have to include a channel inside the firebox, although that makes things easy. Just make sure the air for the secondary spends some time in contact with the hot stove body before being injected.

All that said, it isn't really that complicated. There is a range where it will work, even if you don't have each component sized dead on. Just start experimenting. You'll see that the size of the holes in the tubes, the shape of the tubes, the way the holes face, the restriction of the secondary before entering the flue, etc, etc, etc will all have an effect on the performance of the stove.

If you can, make some parts easily changeable, and make a few sets to experiment.