Harman TL300 - Love/Hate - I want to design a robust afterburner

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DaveA-inCO

Member
Feb 24, 2019
3
Fort Collins, CO
I've had a Harman TL300 for about 10 years now. In general the stove is great. However a couple aspects of it drive me nuts.

1) The afterburner gets clogged up, falls apart, needs replacing every 3yrs or so, and is expensive ($450)

2) The fancy bricks surrounding the afterburner throat crack and are also expensive.

After recently having to pull _all_ the bricks out in order vacuum out the afterburner, and noticing it is about needing replaced, and most of the bricks are broken... I started shopping around for something to replace it with.

However I haven't found anything I like better. The huge/sealed ash bit with grate that the ashes just fall into is my main "must have". That I cannot find that feature on any other stove. If anyone knows of one, I'd like to know.

I'm an engineer, and as such I feel the desire to "design something better"... Does anyone have thoughts on building a steel afterburner to replace the fragile fiber-board POS? I realize it needs to maintain the heat to do do it's job - (I assume that is the reason for the fiber-board.) So a steel AB would need to be well insulated (on the outside).

I would like to design it such that any internal baffles could be easily removed from the front for ease of cleaning. And while I'm at it, replace the fancy custom bricks with some standard bricks... I wonder if the air chambers in those bricks really do much anyway?

Love to hear anyone's thoughts - would this be a waste of time, or worth a try?
 

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DaveA-inCO said:
I've had a Harman TL300 for about 10 years now. In general the stove is great. However a couple aspects of it drive me nuts.

1) The afterburner gets clogged up, falls apart, needs replacing every 3yrs or so, and is expensive ($450)

2) The fancy bricks surrounding the afterburner throat crack and are also expensive.

After recently having to pull _all_ the bricks out in order vacuum out the afterburner, and noticing it is about needing replaced, and most of the bricks are broken... I started shopping around for something to replace it with.

However I haven't found anything I like better. The huge/sealed ash bit with grate that the ashes just fall into is my main "must have". That I cannot find that feature on any other stove. If anyone knows of one, I'd like to know.

I'm an engineer, and as such I feel the desire to "design something better"... Does anyone have thoughts on building a steel afterburner to replace the fragile fiber-board POS? I realize it needs to maintain the heat to do do it's job - (I assume that is the reason for the fiber-board.) So a steel AB would need to be well insulated (on the outside).

I would like to design it such that any internal baffles could be easily removed from the front for ease of cleaning. And while I'm at it, replace the fancy custom bricks with some standard bricks... I wonder if the air chambers in those bricks really do much anyway?

Love to hear anyone's thoughts - would this be a waste of time, or worth a try?
Click to expand...
I agree with you completely about the engineering of these stoves they can work very well but they are hard and expensive to maintain. I don't think steel would hold up to the temps in that chamber.
 
If you are able to make templates off of the old one, maybe you could fab up new ones out of a sheet of baffle board. Even if they're not as durable, they're likely to be a lot cheaper than $450!

Looking at photos of the thing online, it seems like it wouldn't be hard to make one out of baffle board and furnace cement, but you'd probably end up needing a regular program of rebuilding it as the furnace cement failed. I don't have any sense as to whether that would mean twice a month or once a year.

I wonder if a porcelain and refractory cement version would last at all.... thermal shock would probably trash it pretty fast.
 
The after burner in my first 300 was very fragile. My second one has a better one-3-40-06999. My problem is the front of the damper assy warping.
 
I replicated the combustion box in a VC encore out of Skamol. It was a fun project and looked awesome, it just didn’t hold up well. It wasn’t able to expand and contract enough and cracked pretty bad after a short time. Perhaps if I made it a little smaller? Instead I just trashed the stove.
 
You guys are troopers. I couldn't keep repairing a stove knowing it is doomed to fail.
DaveA-inCO said:
However I haven't found anything I like better. The huge/sealed ash bit with grate that the ashes just fall into is my main "must have". That I cannot find that feature on any other stove. If anyone knows of one, I'd like to know.
Click to expand...

You might have a look at the Woodstock brand stoves. I believe the Ideal Steel model has a grated floor with ashpan (option). I am not certain how many of there models have that option. Worth a peek.
 
Power went out, heavy winds. Cooking our supper on top of the 300. Love it, got us thru sandy. My only to date repairs after five years are zero but have a big one coming up. After reading all the cat posts I will surely repair
 
paulnlee said:
Power went out, heavy winds. Cooking our supper on top of the 300. Love it, got us thru sandy. My only to date repairs after five years are zero but have a big one coming up. After reading all the cat posts I will surely repair
Click to expand...
Why do you say that? 5 years is about average for what we see from Harman combustion chambers. But the damper warping is pretty uncommon. There are other much more durable stoves available.
 
My first Harmon went thru three in 7 years. This one none but when I replace the damper assy I will put in a new one. Maybe it's me but my first Harmon also needed the damper replaced. This thing runs non stop Oct-May- only heat source.
 
paulnlee said:
My first Harmon went thru three in 7 years. This one none but when I replace the damper assy I will put in a new one. Maybe it's me but my first Harmon also needed the damper replaced. This thing runs non stop Oct-May- only heat source.
Click to expand...
Do you check and keep the damper adjusted properly? Most I work on are full time heaters also with no damper issues.
 
Only adjustment I'm aware of is bolt/nut in damper itself and it closes and seals fine. Well it used to. Now the bolt head is what I'm using to open & close damper
 
Fixing someone else’s flawed design can be fun or frustrating. Rarely do I find fun. Finding high temp materials should be strait forward. Once you know the cost to make say 5 (as I doubt you can get around the fact that these will be a consumable and the first couple might be scrap) you could say that it might be worth my time or “I think I’ll get a new stove and spend my time figuring out the cheapest way to make a temperature dependent fan speed controller”. Thats just what would go through my head.

Really technology and materials can make considerable progress in a decade but 10 years ago a professional thought that’s was the best most cost effective design. The odds of coming out with a better solution aren’t great unless you have experience working with high temp materials. My two cents.
 
paulnlee said:
My first Harmon went thru three in 7 years. This one none but when I replace the damper assy I will put in a new one. Maybe it's me but my first Harmon also needed the damper replaced. This thing runs non stop Oct-May- only heat source.
Click to expand...
And you bought another one? That’s an absurd amount ofparts in only 7 seasons. I just can’t imagine signing up for that again, there’s so many other well designed, durable stoves out there.
 
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Thanks for the thoughts on the topic. All good points. And after getting it cleaned out this last time it is burning great again, so my joy has returned with this stove. It will at least last me through the winter. 10 years with replacing the AB & bricks once (and coming up on a 2nd) maybe isn't so bad. I agree, it could be very frustrating to try to improve on the design, and as spouse and friends point out - I may end up burning the house down in the process :( Always good to get a reality check.

Regarding the bypass damper, I haven't had any warping issues - but it does get pretty sticky - I have to work the handle back and forth a few time to get it to open - and that varies depending on the temperature or phase of the moon, or something...
 
DaveA-inCO Wow that a nasty afterburner picture. Im thinking these afterburners must be sensitive to the wood type or something, mine still looks like new. I dont use my TL-300 full time but over the last 10 years i probably put 2 or 3 full seasons on it. I vacuum out the air holes in the ceramic bricks every few burns and the damper door does need adj every now and then. I try not to overheat it too much by not allowing the stove to run in bypass for too long. One of the best things about this stove is the TOP loading. That really allows you to pack it full of wood for a long overnight burn. The stove i want to redesign(Just the door area) is my Englander Summers heat 2400 . When the warranty runs out ill be doing just that.
 
webby3650 said:
And you bought another one? That’s an absurd amount ofparts in only 7 seasons. I just can’t imagine signing up for that again, there’s so many other well designed, durable stoves out there.
Click to expand...

They redesigned the AB that's why I went with another + the price. AB's covered under warranty.
 
DaveA-inCO said:
Thanks for the thoughts on the topic. All good points. And after getting it cleaned out this last time it is burning great again, so my joy has returned with this stove. It will at least last me through the winter. 10 years with replacing the AB & bricks once (and coming up on a 2nd) maybe isn't so bad. I agree, it could be very frustrating to try to improve on the design, and as spouse and friends point out - I may end up burning the house down in the process :( Always good to get a reality check.

Regarding the bypass damper, I haven't had any warping issues - but it does get pretty sticky - I have to work the handle back and forth a few time to get it to open - and that varies depending on the temperature or phase of the moon, or something...
Click to expand...

It's not the damper itself but the lower front of the frame. It comes forward allowing the rod behind the damper to drop too low. First sign is what you described-sticky.
 
paulnlee said:
They redesigned the AB that's why I went with another + the price. AB's covered under warranty.
Click to expand...
Redesigned, improved, lifetime warranty, got all the bugs worked out...
We’ve heard this from all the manufacturers that utilize rear secondary combustion systems that were prone to failure. Nothing has really changed, warranties that aren’t honored, or won’t cover any labor on an extensive repair.
I hope you have better success with this one, 5 years is pretty poor in my opinion, especially the damper frame.
 
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paulnlee said:
Yeah, that part of the frame is about 3/4" wide and right at the hot spot. Piss poor design
Click to expand...
It is not a common failure point at all. I am wondering it you are overfiring the stove or running with the damper open to much.
 
paulnlee said:
Could be on the over firing although when damper was operating as it should I ran stove more closed then open and down on notch 2.
Click to expand...
The bypass should be closed all the time after the stove gets up to temp.
 
In spite of the flaws you mentioned, and the longer learning curve involved, and the baby-sitting required, my Harman Oakwood is still my favorite stove purely in terms of its intense heat output and its good looks. I like top-loading, and I like cast iron. But I couldn't justify the expense involved in the way the various components failed.

The Woodstock Absolute Steel is a close second, which I prefer over the Ideal Steel (due to a preference for side-loading and the seeming better control of coals/ashes/smoke that I got with the AS). These hybrid stoves seem much better engineered that the downdraft Harman, but do not have the raw power and beauty of the Harman.
 
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