Secondary tube engineering question?

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BobUrban

BobUrban

Minister of Fire
Jul 24, 2010
1,933
Central Michigan
To begin I am burning a pre-EPA stove but will be upgrading for next season for sure. My question is regarding the secondary tubes in all the stoves I have looked at.

Without disrespecting anyone or any manufacturer I have noticed that they all seem like simple and light gage steel? In the videos they seem to be glowing red when working properly, is this correct or am I seeing things? Is this an engineering thing and necesary or is this a money saving thing? Do they ever burn up or need to be replaced? How often? Or how long can you expect them to last under normal use and care?

If they do wear out or Burn up over time would it be foolish or prudent to replace them with something hardier? If you had to replace the tubes and had access to all things steel regarding a professional maching shop, welders and all the fabrication tools to duplicate them with a heavier gage steel would this change the way they work? I fully realize that all these stoves have been extensively engineered to do what they are suppose to do with the OEM equipment but they also are all built for economy and price point. I am asking if this is an area that could be improved if cost were not an issue.

I am not trying to out think the stove manufacturers, just looking for opinions regarding the tubes and longevity from those with experience either burning or building stoves.

Thanks for any input
 
Virtually all of the tubes are 304 stainless steel. They will melt somewhere around 2,500 degrees. Right around the time the rest of the stove starts becoming a puddle in the floor. They are in more danger of getting smashed with a wood split or poker.

The only burned out tubes I have seen anything about here in six years were some mild steel tubes one manufacturer used but has since changed to stainless. They get hot and they glow at around 1,400 degrees. But they also have relatively cooler air flowing through them.
 
Thanks BB - I knew someone would set me straight here.
 
Puddle....LMFAO. If you have a puddle of stove steel on your floor, you have much, much bigger problems!
All I got is a saggy baffle box. Starting to look like 2 u know whats. LOL
Tubes are used because it is what works for those particular stoves and the way they are set up. Just like baffle boxes do, and cats also. Each has their own system and design. All work, and are proven.
 
I can't speak for all stoves, but the tubes in mine come out easily. I remove them in order to take the baffle boards out every time I sweep my chimney. If they ever need to be replaced, it won't be a hard job.

-SF
 
There are stoves that do not have tubes or baffle boards for the secondaries. My Drolet has a solid stainless top plate with the secondary air holes in the plate. I believe PE and maybe some others use this or a similar design also. So there are options if it is a concern for you. I believe the main advantage for the baffle board/ secondary air tubes is the insulation factor and thinner tubes heat up quicker resulting in better emissions testing results. This was a concern I had about the solid stainless plate design but in real life I have found it to work great as I can run my stove as low as 400-450* stove top with sustained secondaries and no smoke. It takes the right touch but it can do it. I am happy with mine and especially on nights like tonight when I was shoving and cramming that last 8" split in there.
 
BrotherBart said:
Virtually all of the tubes are 304 stainless steel. They will melt somewhere around 2,500 degrees. Right around the time the rest of the stove starts becoming a puddle in the floor. They are in more danger of getting smashed with a wood split or poker.

The only burned out tubes I have seen anything about here in six years were some mild steel tubes one manufacturer used but has since changed to stainless. They get hot and they glow at around 1,400 degrees. But they also have relatively cooler air flowing through them.
Click to expand...

+1 Even though the tubes may glow red on the outside, a steady stream of air is coming through them which has the effect of cooling them from the inside.
 
blwncrewchief said:
There are stoves that do not have tubes or baffle boards for the secondaries. My Drolet has a solid stainless top plate with the secondary air holes in the plate. I believe PE and maybe some others use this or a similar design also. So there are options if it is a concern for you. I believe the main advantage for the baffle board/ secondary air tubes is the insulation factor and thinner tubes heat up quicker resulting in better emissions testing results. This was a concern I had about the solid stainless plate design but in real life I have found it to work great as I can run my stove as low as 400-450* stove top with sustained secondaries and no smoke. It takes the right touch but it can do it. I am happy with mine and especially on nights like tonight when I was shoving and cramming that last 8" split in there.
Click to expand...

+1 - If thin gauge tube bother you, then some manufacturers use a thicker baffle plate with holes drilled in it. My Jotul Rangeley is this way with 1 tube mounted up front in the firebox to accomodate the pivoting top-load baffle. Most Pacific Energy units are baffle plate designs too IIRC.
 
blwncrewchief said:
There are stoves that do not have tubes or baffle boards for the secondaries. My Drolet has a solid stainless top plate with the secondary air holes in the plate. I believe PE and maybe some others use this or a similar design also.
Click to expand...

Yes, a perforated stainless plate, often stepped, were the first secondary air systems I believe. Still widely used (Morso 2110 and 2B, Jotul F602, others), many are part of fixed baffle systems. The stainless tubes have the advantage of being easily removed for servicing and seem to induce more turbulence in the firebox, mixing the gasses with the secondary air better.

Some recent designs coming out of Europe have neither; just a single "rail" with holes that is built into the back, up near the baffle. This approach appears to require a non-rectangular firebox to make work.
 
I was told that the reason that the tubes are thin is so they can be mass punched in a press. Stainless is hard to drill. Why I went with P.E. Tim
 
Not that I like, or do not like them. I am certain I will be burning a stove with tubes next season and look forward to it. I was just curious if they wear out? Answer recieved is no - at least not on a regular basis.

and are they a place where engineering meets with price point? Stainless, so very solid, but possibly light gage for ease of manufacture to save cost.

I guess I should have ask - if you HAD to replace your secondary tubes for any reason. Do you feel there would be any advantage/disadvantage to replacing them with heavier gage steel if you could have either for free. Is the light gage engineered as part of the burn or savings? If the tube steel was twice as heavy and all other things were equal(holes, angle, etc...) Will they burn the same but just last longer?

I am just curious.
 
I know where your going with your thoughts.
Maybe thinner is better in secondary tubes?
Maybe they heat up quicker and hotter being thinner?
If you would I'm curious why not a cat?
 
BobUrban said:
Not that I like, or do not like them. I am certain I will be burning a stove with tubes next season and look forward to it. I was just curious if they wear out? Answer recieved is no - at least not on a regular basis.

and are they a place where engineering meets with price point? Stainless, so very solid, but possibly light gage for ease of manufacture to save cost.

I guess I should have ask - if you HAD to replace your secondary tubes for any reason. Do you feel there would be any advantage/disadvantage to replacing them with heavier gage steel if you could have either for free. Is the light gage engineered as part of the burn or savings? If the tube steel was twice as heavy and all other things were equal(holes, angle, etc...) Will they burn the same but just last longer?

I am just curious.
Click to expand...

The Pacific Energy stoves use a heavy S/S baffle instead of tubes which is guaranteed for life.. It works very well and the stove interior is flat on all sides.. The new Woodstock Progress stove uses a S/S plate with holes too and I believe there are others too.. Not saying tubes are bad just that I prefer that the stove inside is made this way..

Ray
 
[quote author="Hogwildz" date="1326517608"]Puddle....LMFAO. If you have a puddle of stove steel on your floor, you have much, much bigger problems!
All I got is a saggy baffle box. Starting to look like 2 u know whats. LOL
Tubes are used because it is what works for those particular stoves and the way they are set up. Just like baffle boxes do, and cats also. Each has their own system and design. All work, and are proven.[/quot

@ Hogwildz...how much does your you know whats sag? haha Is this a typical problem with baffle boxes?
 
HC - 100% cost!! I looked at the BK's and they offer some things that the others do not for sure. I just do not want to shuck out that level of cash and if I had that much room in my budget I would probably go with a big Hearthstone. I could get long burns and sustained heat with the HS as well as the looks. Hard to argue that HS stove are not some of the pretiest out there.

My home and budget are closer to steel box than stone and with all the positive feedback for the Englader-30 I cannot really justify spending more.

Beyond cost - the cat has my attention.

And yes, you did get my question. All these stoves, no matter how nice, are mass produced and there are always places that corners are shaved to allow them to be resonably priced. That goes with anything mass produced. I was just looking at one simple area that, when replaced(if ever needed) could possibly be upgraded. I could fab up stronger tubes for any stove with the tools and shop I have. I just wondered if heavier would not work due to engineering. Probably a moot point if they last 5-10 years with normal use and care.

I look at these steel boxes and know I could build one if I had one in the shop to tear apart. It would cost me about 10X the price point of the stove to do so in material and time but I could fab up exact replicas for sure. Not even thinking of trying it because it would be foolish but if there are wear and tear part I would consider making my own if I could improve quality.
 
and are they a place where engineering meets with price point?
Click to expand...
Yes, they are currently the most cost-effective solution. And they work very well. The worst I've ever seen is a bit of sagging in the middle, nothing to worry about. Unlikely you'll have to replace them for a long time. I wouldn't go heavier, the OD has to remain the same so you'd be sacrificing internal area for thicker walls.
 
BobUrban,

Would be cool to build your own stove!
Inspection and homeowners might be a problem though...such as the world today.

Some on here think I hate tube stoves..that's not the case.
I hate the idea that there is no adjustment or a fast shutdown of the secondary air..that's all.
My best guess is the epa is afraid consumers would run them wrong and burn dirty...and they have a valid point if that is the case.

But just a red button marked emergency shutdown would be in order if I was God.
You can find plenty of post on here of pucker moments.

My sister has a tube burner and she freaks over it way to much.
I do explain to her the stove won't melt and as long as the flue is clean don't worry so much about super high temps.
Thing is I didn't help things any when I showed her that my stove can go from a inferno to no flame in under 60 seconds flat.
 
HotCoals said:
I hate the idea that there is no adjustment or a fast shutdown of the secondary air..that's all.
Click to expand...

Agreed. Fortunately it's pretty easy on most stoves to add a secondary air shutoff. It also nets you increased burn times and less heat carried up the chimney after flames die out.
 
No way I would ever get insurance on my home if I built my stove - even if it was an over built exact replica of any stove out there. Making it would be no problem as the air flow and perfect design is already done. I would just be copying someone elses RnD. When I finish my pole barn I will build a small stove for the sauna I put in there and will use some of the modern design principles but it will be a little more old technology, smke dragonesque due to limited burning and desire to just have a really hot - rather quick burn fire every so often.

I had to fight with my insurance company to keep my policy after installing the Defiant - cannot imagine what my agent would say if I told him, "oh, it's a stove I built in the shop".

Thanks everyone - I appreciate the feedback
 
precaud said:
and are they a place where engineering meets with price point?
Click to expand...
Yes, they are currently the most cost-effective solution. And they work very well. The worst I've ever seen is a bit of sagging in the middle, nothing to worry about. Unlikely you'll have to replace them for a long time. I wouldn't go heavier, the OD has to remain the same so you'd be sacrificing internal area for thicker walls.
Click to expand...


Much agreed, the airflow is rather specific through those tubes. Some manufactures have different sized holes for the different tubes, others just more holes in one etc. Thicker probably wont really get you anything.

The jotul i have noticed the tubes are bigger diameter than some other brands.
 
I wonder if you did replace the tubes with ones that had a slide plate in them to fine tune the air if that would be a advantage?
Of course once the fire was going I don't think you could adjust them...probably best done at the intake.
 
HotCoals said:
I wonder if you did replace the tubes with ones that had a slide plate in them to fine tune the air if that would be a advantage?
Of course once the fire was going I don't think you could adjust them...probably best done at the intake.
Click to expand...

Best done at the 2ndary air intake. I have such on the Quad and X33. Without a way to continually automatically adjust it to fire conditions, it ends up being a bit tweaky unless you are sitting in front of your stove all day and have nothing better to do. :)

I just open mine when I (re)load and close it when the flames die. That gives you 90+% of the potential benefit.
 
precaud said:
HotCoals said:
I wonder if you did replace the tubes with ones that had a slide plate in them to fine tune the air if that would be a advantage?
Of course once the fire was going I don't think you could adjust them...probably best done at the intake.
Click to expand...

Best done at the 2ndary air intake. I have such on the Quad and X33. Without a way to continually automatically adjust it to fire conditions, it ends up being a bit tweaky unless you are sitting in front of your stove all day and have nothing better to do. :)

I just open mine when I (re)load and close it when the flames die. That gives you 90+% of the potential benefit.
Click to expand...

Sounds good!
 
In regard to the Lopi stoves like I have. My local dealer, and it's a big one, has replaced one set of burn tubes in a stove like mine. That was before they were upgraded to stainless. I considered having another set on hand in case of a problem, but I realized a was probably over thinking it. In the year or so I have been following this forum, I have noted very few people with tube problems. One person I recall bought a used stove with a missing tube and maybe one or two damaged by logs.
 
HC, I love all of that thermal mass in your hearth, I bet it works great. Is there a larger pic of it I can see? Is it on an outside or inside wall? Is it thermally isolated from the wall?
 
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