Harman TL 300 test

Seasoned Oak said:

the only way the AB gets damaged is by direct contact. Heat will not damage it, and you cant physically puncture it unless the ceramic bricks are not in the right place or cracked

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Trouble is, while heat won't directly damage it, it will degrade the AB so that if it ever needs to be cleaned it becomes very difficult to do without damaging it.

And unfortunately, the cast ceramic bricks ARE prone to heat damage AND physical damage, as I discovered a few years ago, and especially this past season. Since the AB likes to burn hot, it's a fine line between running a stove hard and overfiring it. The stove itself is built like a tank, but some of us have had the brick degrade sooner than anticipated.

The Harman owners manual does warn users not to consistently run the stove on high. That may be the difference between accelerated AB degredation and normal wear and tear. I consistently run my stove with the air setting almost all the way down except for startup.
Its seems to me ,i don really get any more heat at a higher setting anyway ,it just burns up the wood faster. With dry wood this stove pumps out tremendous heat on the lowest setting,no need to overfire it. It heats my drafty 3000SF, 100 year old poorly insulated house on the lowest air setting.

I have the insert version of this stove and getting ready for my 6th year of burning.Except for replacing the door gasket all is well.I wont take apart the afterburner section for a visual or cleaning unless it starts to fail.I just try to keep the holes and the open bottom area by the chamber vacuumed occasionally.I love the long burns! The only thing i dont like i need to clean the glass more often if i damper the stove way down.

Seasoned Oak said:

I consistently run my stove with the air setting almost all the way down except for startup.
Its seems to me ,i don really get any more heat at a higher setting anyway ,it just burns up the wood faster.

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Same here. But others have had downdraft stoves run away on them even with primary air low, due to high draft.

Yes, the downdraft stove pumps out tremendous heat on the lowest setting, but that could mean one might accidentally overfire it. My experience is, surface temps on the rear of the stove where the AB is can push over well over 800f even as the stove top is in an accepatable cruising range of 600-700f.

Seems people have fewer problems w/ the 300 than with the Oakwood, maybe due to the larger firebox or other variations? Also, for that matter, seems people have fewer problems w/ the Oakwood than with other downdrafts like the Leyden and older VCs.

I have a very tall chimney about 35 Ft that produces a strong draft. overdrafting was never a problem , in fact i usually have to use one notch above the lowest setting to keep the stove from stalling. Of course if your bypass door was not sealing tight for some reason im sure you could overfire the stove inadvertantly. The surface temp at the rear of the stove should get very hot as its just above the AB outlet path. If the AB is operating at something like 1500 deg id expect the area just above it to be at least 800. Iv used this stove in 3 different locations so far with excellent results in each one. Burning pine during the day and oak at night in each place.

Seasoned Oak said:

If the AB is operating at something like 1500 deg id expect the area just above it to be at least 800.

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Yes, and over 800f is what many commonly consider the beginning of overfire range. It's a little short of a glowing stove, but getting close.