Harman Tl 300 Question

[John59DT]

Last night i woke up to a cold house, i went down stairs to take a look inside the stove i found that a log fell against the opening of the fire dome and was blocking the vent into the fire dome. that night prior to going to bed i loaded the stove right up to the top loading door and left about an inch gap between the fire dome and the wood. Should i pile the wood in right up aginst the fire dome to avoid a log rolling down and blocking the fire dome? yes the afterburner was engaged. tips on loading this stove is grately appreciated

 

[branchburner]

I wish I had a perfect answer, but even after a few years I find that opening gets blocked occasionally, causing the AB to stall. (Can also happen to me if the coals are TOO deep when running the stove hard during 3-4 straight days of real cold weather.). Before loading up, with a deep pile of coals back there, I make a little valley in the middle with two off-center coal mounds, leaving the throat more exposed.

The problem of blocking happens more often with big rounds/spilts than with smaller branch-wood or splits, so I try to put bigger towards the front of the box, smaller to the rear (being smaller, they not only cover less surface against the back wall but also coal faster). I sometimes try to angle the splits just a bit, so they are not perfectly parallel with the back wall, or each other, but that means you can't always fill the box quite as full.

I do often give more thought to whether the AB will keep cruising. rather than to how full I can fill every cubic inch of the box. One trick I use whenever I can is to put pieces that are a bit crooked or uneven, with bends or knots or branch stubs, in the back -- since they won't fall evenly across the whole back, they are less likely to block air flow.

 

[John59DT]

thanks for this great information i tried this last night and it worked great. it seems to burn better and i can watch the fire going into the afterburner. which is great

 

[MishMouse]

A trick I do is place a smaller piece of wood ~2" wide standing up at the back R or L corner of the stove.
That way the wood is always away from the chamber.

 

[branchburner]

A trick I do is place a smaller piece of wood ~2" wide standing up at the back R or L corner of the stove.
That way the wood is always away from the chamber.

Funny you mention that today, because just last night I had a small split fall in and stand up vertically, by accident, up against the back and just off-center from the throat. Instead of trying to "fix" it, I left it there because I knew it would serve the purpose of keeping the throat clear.

It's happened before, also by accident... for some reason I never thought of trying it on purpose!

 

[Seasoned Oak]

I always stack the wood so as to have a sort of tunnel down the middle at the bottom ,so i can view the AB in action. Makes easy to tell when its firing. At times on minimum air setting when the firebox is completely dark except for the AB chamber which is glowing bright orange/red. I suppose that why iv never blocked off the throat opening.

 

[CRE10]

I always stack the wood so as to have a sort of tunnel down the middle at the bottom ,so i can view the AB in action. Makes easy to tell when its firing. At times on minimum air setting when the firebox is completely dark except for the AB chamber which is glowing bright orange/red. I suppose that why iv never blocked off the throat opening.

Could you take a picture of the glowing AB? I thought I had my stove figured out, but it's giving me trouble again and I'm getting a lot more visible smoke and creosote build up. I'm thinking my AB is clogged.

 

[Seasoned Oak]

Not currently using the harman, but do what i told you, stack the wood so you can see the AB opening. Looks like a blast furnace bright orange color. Also if you can keep your hand on the upper portion of the heat shield in back just below the flue collar your AB is NOT active and you need to open the bypass a while longer to get the stove hot enough. When the AB if firing you CANNOT keep your hand there.It gets so much hotter. A stove top temp gauge is not always a good way to tell as the AB may operate within a range of stovetop temps from 400 to 650.

 

[branchburner]

I'm thinking my AB is clogged.

The only way I'm positively sure my AB is cranking is to check the temps of the rear burn chamber itself, which is easy to do on the Oakwood, but maybe not on other models. Say my top is running 450-550f.. if I am getting good secondary burning, the AB will run 500-800f, but if not, it's only 250-350f.

Are you burning good dry wood, and is the flue clean and drafting well? Both are essential for good AB action. Have you removed the shoe brick, and vacuumed out any ash when the stove is dead cold? That is good to do at the end of every season, but maybe mid-season, too, if needed.

 

[CRE10]

I got an in pipe thermometer, stove top magnetic, and a magnetic stuck on the back right behind the flue. Definitely significantly lower temps in back. I thought I had it under control, but now it's like the AB really takes some major heat to kick it in. I think it's plugged as I'm burning bone dry wood and flue temps hit 500 with bypass closed is top. 550 is top end according to the book. Usually cruises at 400. Just seeing visible smoke no matter how hot I'm burning. The creosote on my cap is what worries me.

I cleaned stove and chimney a month ago so it's clean. I'm thinking the AB is plugged so I will vacuum it today.

One thing I'm worried about is the first time I cleaned the pipe I was dumb and had my bypass closed so who knows how much crap got down into the AB chamber. That was last fall, but it has worked since.

I'm curious if the AB can be removed and reinstalled. I've read all the old threads where this is some debate on that. I emailed Harman, but based on what I've read on their customer service I doubt I will hear from them.

 

[branchburner]

I'm curious if the AB can be removed and reinstalled.

Yes, by removing the rear panel of the stove the AB can be pulled straight out the back, but sometimes is difficult to re-seat it properly when reinstalled. It is also prone to damage if care is not taken, though the newer versions are sturdier.

Removing it allows for a complete (gentle) cleaning of the AB and surrounding area, and also allows you to check the gasket of that rear panel and allows for easy access to check and adjust/tighten the damper ramp, damper frame bolts, etc. But you probably want to do that after the burning season, unless you get a nice mid-winter thaw.

My stove rear vents into a tee, so cleaning is easy, but if you top vent straight up then you probably did get some crud falling back there when you cleaned. I don't know if that would clog the AB, though. Hopefully a vacuum through the shoe brick area can pull some of it out. Be careful you are not too aggressive with the vacuum, as it can pull off hunks of the AB itself.

I have problems getting the AB to kick in if there are not enough coals, or there is a split blocking the shoe brick, or my splits are too large... so there are other factors that might be involved besides ash buildup.

 

[CRE10]

I'm a straight run so it definitely fell in. I open it now and put a piece of plastic to channel the crud into the firebox now.

I'm excited to take it apart just to see how it works. I think I will vacuum it and see what happens. I may try to limp it through until it warms up then take it apart. When I take it apart I want to have a Firedome on hand so I'm not real excited to buy one.

Upon looking through the service parts it looks like you can purchase a Firedome with gaskets or gaskets only. That sounds good. There's a combustion package cover which is the metal plate over it on the back, but then there's a part called a package cover so I'm not sure what that is.

 

[Seasoned Oak]

I got an in pipe thermometer, stove top magnetic, and a magnetic stuck on the back right behind the flue. Definitely significantly lower temps in back. I thought I had it under control, but now it's like the AB really takes some major heat to kick it in. I think it's plugged as I'm burning bone dry wood and flue temps hit 500 with bypass closed is top. 550 is top end according to the book. Usually cruises at 400. Just seeing visible smoke no matter how hot I'm burning. The creosote on my cap is what worries me.
.

Those temps sound low to me. When i start from a cold stove the AB usually dont kick in until the stovetop temps are almost 600 or higher. On a hot reload, it will still light off between 450 and 550. Once My stove top is down to 400 or lower all thats left are coals and i need to let the bypass open for a bit to gets the temps back up. THats the only flaw in this stove IMO is you need to run it hot if you want a smoke free operation so not so great for shoulder seasons. Can easily overheat the space if you dont need much heat. PS i never clean my flue pipe or chimney without first disconnecting the stove. After several years of burning its amazingly clean around that AB in back.
You can easily see all around it with the flue pipe off.

 

[branchburner]

Not sure what that package cover might be either. I bought a new CP a few years ago, it was $275. Might pull it this spring to see how it looks.

It is pretty neat to pull the stove apart to understand it better. Until I did, what happened behind the firebox was a complete mystery to me.

 

[Seasoned Oak]

My stove is 6 years old and the firedome is like new yet.I never had it apart. Probably have 2-3 year steady burning on it. When vacuuming the ash from the front just vacuum around the perts that you can see ,those are all ceramic.

 

[CRE10]

My stove top temp is usually cruises at 460 and flue temp is 500 then cruises at 400.

I have never had the stove top up to 600. If I got it up to 600 then my flue temp would be greater than 550. The books says you will damage the Firedome if flue temp is above 550. It says 300-400 flue temp is ideal.

 

[begreen]

Sounds like they are measuring this on single wall with a surface thermometer. 550F flue temp for a double-wall connector with a probe thermometer is not high.

 

[branchburner]

For myself and the Oakwood, I find flue temps a much better indicator than stove top to tell me if the AB will kick in well. I take an external reading about a foot above the stove. With the air open to 3/4 the flue temps usually need to spike pretty high (600-700 external), especially from a cold start, for me to shut the bypass without the AB stalling. Then I step the air back to 1/2 and 1/4 and they drop back to cruise at 200-300 external, depending on air setting and outdoor temps... they run higher if its really cold out, or if the AB is NOT working.

 

[branchburner]

books says you will damage the Firedome if flue temp is above 550. It says 300-400 flue temp is ideal.

Is that for cruising? Your 550 internal would be maybe 300 external... I could NEVER get my AB to fire well at that temp. Yes, it will cruise below 500 internal, but to get the heat to launch the AB into sustained burning, I need that internal temp to push 1000f or more for a minute or two.

I think by following the Harman rules, you are preventing yourself from using the Harman burn technology! I don't like pushing my flue that high, it's one of the things I dislike about this stove (along with excessive heat in shoulder season mentioned above), but without a brief spike in flue temps the AB won't run.

Is that the owner's manual you are referring to? Do you have a page #, or a link?

 

[branchburner]

I found the manual online... they are referring to a 550 external as overfiring, so that may be around 1000f internal? They also say nat to "operate" at that temp, so it is unclear if they mean that as a sustained temp (a definite no-no) or as a temp not to reach for even a moment (which, if true, means I couldn't run their stove if I followed their directions for running their stove).

If you are not letting your flue above 550f INTERNAL (maybe 300f external?), then you are not getting hot enough for good AB performance.

 

[Seasoned Oak]

My stove top temp is usually cruises at 460 and flue temp is 500 then cruises at 400.

I have never had the stove top up to 600. If I got it up to 600 then my flue temp would be greater than 550. The books says you will damage the Firedome if flue temp is above 550. It says 300-400 flue temp is ideal.

550 would never damage the fire dome. That thing runs at somewhere north of 1100 Deg. which is the minimum temp it lights off on. Probably 15-1600 .What you may damage is the bypass door if it remains open too long under high draft .Mine gets loose and doesnt close tightly when it gets too hot.

 

[Seasoned Oak]

After awhile you will know when the stove is hot enough for AB function. The dead givaway is the ting,ting,ting sound right after you close the bypass which is the AB chamber quickly heating up from the intense heat produced by the reburn. IF the AB does not start right away i always reopen the bypass as its not good to burn in bypass mode with no AB function,will get creosote in stove and pipe. I learned this the hard way. Burned a whole load of wood with a cold AB ,the whole stove area including the flue pipe was tarred up. This stove burns very very clean when operated properly with good AB function.

 

[Seasoned Oak]

One warning in the manual i think is valid is not to continuously run the stove with the air setting wide open. For one you will go thru wood fast unnecessarily, the stove may overheat. This stove produces tremendous heat with the air setting in the lowest third of the range. I dont think i ever ran it over half other than during warm up .Mostly about a quarter open. It also seems to produce twice as much heat while the AB is functioning.

 

[CRE10]

550 would never damage the fire dome. That thing runs at somewhere north of 1100 Deg. which is the minimum temp it lights off on. Probably 15-1600 .What you may damage is the bypass door if it remains open too long under high draft .Mine gets loose and doesnt close tightly when it gets too hot.

If I get my flue temp pushing 550-600 my bypass handle gets loose and creeps forward, but the bypass remains closed.


I guess I figured 400-550 internal would be around 3-400 external on single wall.

This is my first year with the thermometers. In the previous two years I didn't have near the creosote build up inside and on the rain cap. The rain cap has major tar like creosote on it.

My chimney pipe extends up through the house and comes out about 3' off my peak, 3' high, but only about 1.5' above peak that is within 10'. This year I added a one foot section because I wanted to see if it would draft better and be the 2' above. I never had the build up that I've had until this year. Today I cleaned everything and took the 1' section off to see what will happen the next few weeks. I cleaned the chimney and stove pipe and vacuumed the Firedome.

Right now I just ran the flue temp up to 900 degrees with 16% mc wood stacked so I can see the Firedome. I'm not seeing the darn Firedome glow like you said. I hear the woosh though. It's dark so I will have to play with it more in daylight.

I'm curious to see what taking the 1' section off does. I'm also wondering what effect my tightly insulated spray foam house has on the stove.

 

[Seasoned Oak]

Something is wrong. I can get my stove into AB within an hour of a cold start. IF you can see the opening to the AB chamber and its dark something is definitely wrong.
On Mine you can see the flame coming from the air holes in the ceramic brick right away and after awhile the whole area starts to glows bright orange. I dont have even a hint of creosote in my flue pipe or chimney. This stove does not make creosote when its operating properly. Sounds like your air holes in the ceramic bricks may be blocked. Check the air intake at the back of the stove near the bottom ,.make sure it s not obstructed.