A Tinker's got to tinker...

[Soloridr]

I have had the stove of death for 3 years now. I've got it running smoothly and non-smoky with a few minor mods and burn habits. But, alas, it won't run more than 3 hours then fuel must be added to the glowing coal bed.

Here's what I'm tinkering on, making it into a long burn cat(in flue) stove. To do this, my idea is to build a spring loaded adjuster over top of the 2 open holes in the door. It has no primary air adjustment so controlling the air through those holes seems to slow down the burn but makes it a dirty burn as the secondaries tend to stop burning when that happens. So I will add the flue catalytic combustor, with a temp guage to monitor exit temps on the cat. I have 8 feet of single wall inside the room that I hope will harvest a lot of the heat off the cat. And hopefully the cat will clean up a slow burn and keep the pipes clean.

Now please analyze what I'm doing and offer productive ideas, not "buy a good stove" or "that stove is junk". I find it a challenge to make something that's less than ideal, useable and reliable.

What say you!?

 

[SpaceBus]

I'm not sure why your secondary burn dies when obscuring the primary air. Are you covering it all at one time or gradually reducing air with somehow? Do you have an angle grinder? Perhaps you could make a slider for the door air and have some control. A catalyst will be tough without having a way to bypass it on cold starts.

With dry wood that little stove should be relatively smokeless even with the primary air closed most of the way. What does the inside look like? We considered this stove before we knew anything.

 

[stoveliker]

If you can't route the flue gases away from (bypassing) the cat, then it'll clog up quickly as the first minutes of a cold start produce the most creosote and those minutes are precisely when the cat is not yet active.

That's why cat stove have a (cat-) bypassing path that can be closed off until the cat is warm enough.

 

[Soloridr]

The flue cat pivots like the flue damper. So it is pivoted to be vertical at start up, then when temperature gets to firing temp, its pivoted horizonal forcing hot gasses through catalyst holes, lighting it off.

 

[stoveliker]

Ok. Please check the temps a cat may reach and the limits of your single wall stove pipe... I guess that these two values won't be compatible.

 

[ABMax24]

A flue cat won't give you longer burn times necessarily, it might if you choke the stove off, but then the heat is just escaping up the flue. As @stoveliker mentioned this flue gas will also likely be hotter than the single wall pipe is rated for. Another issue is you still need air for the cat to work, a catalyst only speeds the reaction, if there isn't enough air to completely burn the wood gases they will still pass through the cat and exit the chimney as smoke. It seems you are designing a "for emission compliance" hybrid stove, these hybrid stoves use the cat for emissions reduction, not higher efficiency or extended burn time.

I think you are really after a true catalytic stove and as such need to look at a catalyst in the firebox, at least that's what I'd consider. I think that's the best way to slow the burn and increase efficiency, allowing the stove top to transfer the heat from the cat to the room.

One thing to consider is modifications to a UL/EPA listed stove invalidate these certifications, and could impose legal and liability ramifications in the event of a stove caused fire, or for violating the clean air act.

 

[Soloridr]

The 22 guage pipe it is mounted in is the same as my internal single wall pipe so I think it's fine temperature wise. I will have a cat temp sensor on it to monitor temps and would pivot the cat horizontal to bypass feeding gas through the cat holes and cool the cat.

 

[stoveliker]

I feel compelled to write a not of caution; flue pipes are not meant to see cat temperatures (1600 F...)

 

[Soloridr]

How could this product be legally sold if it's going to melt the pipe it's mounted in?

 

[sesmith]

Back a few years ago, I made a "cat box" add on for my old stove. Mounted between the stove and stove pipe and had a bypass damper in the box with the cat. It worked great. Combined it with secondary burn tubes I added. Details in this old post of mine:

Cleaning up an old smoke dragon and making it more efficient

I already put a link to the page below in a reply I had in another thread, but thought I'd give it a thread of it's own (so sorry for the repeat for anyone who's already seen this), I bought our current stove back in 1981 from a local dealer. The brand (Wood Saver) I've never seen before or...

www.hearth.com

 

[ABMax24]

How could this product be legally sold if it's going to melt the pipe it's mounted in?

There's a difference between "not rated" and "melting". Think of a car tire, lots are only rated to 100mph, will they go faster, likely, but is the manufacturer going to say they are built to, and be liable if you try and fail, absolutely not.

You also have to remember there are lots of things sold that shouldn't be, there is no governing body to approve everything that gets sold, only sometimes do extremely dangerous items get pulled from shelves. Cigarettes, alcohol, etc kill people everyday, yet they are sold almost everywhere.

 

[Soloridr]

How did the regular stove pipe above the cat handle the high cat temps?

Back a few years ago, I made a "cat box" add on for my old stove. Mounted between the stove and stove pipe and had a bypass damper in the box with the cat. It worked great. Combined it with secondary burn tubes I added. Details in this old post of mine:

Cleaning up an old smoke dragon and making it more efficient

I already put a link to the page below in a reply I had in another thread, but thought I'd give it a thread of it's own (so sorry for the repeat for anyone who's already seen this), I bought our current stove back in 1981 from a local dealer. The brand (Wood Saver) I've never seen before or...

www.hearth.com

 

[Soloridr]

Brainstorming. Ideas about this setup.

 

[WoodScrounger]

A cat installed in the pipe is only possibly going to help with smoke pollution. It won’t help with extended burn times, it could it fact hinder because for a cat to work certain temps have to be maintained . Keep working on it though , I can appreciate the “Tinker“ spirit .

 

[Soloridr]

Thinking theoretically:
1. This stove burns wide open, hot and fast with no ability to adjust primary air or secondary.

2. If I can tinker a primary air adjustment and do what good stoves do when they starts burning hot, turn way down the primary air enough to keep temps at the cat good with the secondary heated air, I believe I could burn at a consistent lower level(longer) than full burn. Keep the cat burning and try to harvest cat heat, maybe.....still thinking about a design to do this.

3. Cat inside stove is not feasible, no room.

A cat installed in the pipe is only possibly going to help with smoke pollution. It won’t help with extended burn times, it could it fact hinder because for a cat to work certain temps have to be maintained . Keep working on it though , I can appreciate the “Tinker“ spirit .

 

[SpaceBus]

I would copy a Jotul or Morso long box stove. Drill some holes in the door to mount a slider mechanism. Pursuing a cat setup on such a small stove will have you chasing your tail.

 

[sesmith]

How did the regular stove pipe above the cat handle the high cat temps?

No problem. Cat temp ran 1000-1200 and the cat box ran 400-600 degrees. No issues with the singlewall pipe.

Edit... but cat was not in the pipe. It was in its own special steel box with a bypass damper in it.

 

[bholler]

Thinking theoretically:
1. This stove burns wide open, hot and fast with no ability to adjust primary air or secondary.

2. If I can tinker a primary air adjustment and do what good stoves do when they starts burning hot, turn way down the primary air enough to keep temps at the cat good with the secondary heated air, I believe I could burn at a consistent lower level(longer) than full burn. Keep the cat burning and try to harvest cat heat, maybe.....still thinking about a design to do this.

3. Cat inside stove is not feasible, no room.

You do realize about the time you get this figured out the castings will probably start to crack.

 

[mellow]

Most of have found that the cat is up to high to get a good light off and maintain the temperatures needed to maintain the cat being lit. That contraption has been around for a long time, just like the magic heat.

 

[Soloridr]

I will live and learn.

 

[David.Ervin]

Interesting thought experiment here anyway. I'm thinking the two 90º turns in your sketch to get in / out of the cat may really mess up draft, which will have the effect of artificially slowing the burn anyway. If the secondaries die when the primary air is closed, you might want to invest some time figuring out how to get more air into the secondary tubes. Could be that they're getting cut off when the primary is closed too, which would be less than ideal.

Another thought is to just let the stove run hot, but add a ton of thermal mass (soapstone? weld on a bunch of cast iron?) so it absorbs and releases more slowly into your living space. Same total amount of heat, just slower release time.

 

[SpaceBus]

what's the heaviest load of wood you have ever put in the stove? There are only 7,000 btu/lb of wood, so even the cat might not solve the problem you are having with short burn times. You may just need a bigger stove. The thermal mass idea is a start, but you would need at least 1,000 lbs to make it meaningful.

 

[john26]

I had a cat installed in a woodchuck furnace in the secondary chamber inlet, essentially it was just an internal flue pipe it did nothing except make the fire hard to start. I seen no change in burn times or temps in the heat exchanger behind the cat. I had a thermocouple install with an analog temp gauge. I didn't even really notice any difference in smoke output it looked like a smoke dragon either way. The cat cat was old stock never used not sure if shelf life matters.

 

[Indianawood]

I had a cat installed in a woodchuck furnace in the secondary chamber inlet, essentially it was just an internal flue pipe it did nothing except make the fire hard to start. I seen no change in burn times or temps in the heat exchanger behind the cat. I had a thermocouple install with an analog temp gauge. I didn't even really notice any difference in smoke output it looked like a smoke dragon either way. The cat cat was old stock never used not sure if shelf life matters.

So glad I found this. I also had a wood chuck 2600?
I thought about adding the cat before i luckily decided to junk the stove and bought a Blaze King Ultra. So glad I did. The wood chuck nearly turned me off of burning wood completely. Man that thing ate wood. To say im happy with this blaze king would be an understatement.
I love to tinker also but this project id have to pass on. Used cat stoves are cheap on fb classifieds.

 

[john26]

I ended up converting mine to a secondary burn using water pipe it helped some. I usually ran it with the primary at least 90% closed. I removed it when I sold my house and noticed the secondary heat exchanger was cracked where welded into the main firebox. It is disconnected in the basement of my new house but getting replaced with an Ashley AF700 this weekend.
Back on Solordir's subject what stove is this? Is there baffle boards above the secondary's? I would attempt getting a better secondary burn before investing in a costly cat.
There were some products years back with a cat that went inline with the flue one even worked like a key damper maybe research that if you are dead set on using one.

Wood Stove Catalytic Converter Retrofit – Mother Earth News

If you'd rather burn the smoke from your stove than clean it from your chimney, consider adding a retrofit wood stove catalytic converter.

www.motherearthnews.com