Tarm Flue Temperature - Revisited

[jebatty]

The easiest way to solve a problem yourself is to ask someone else the question. Well, my flue temp problem is solved, and the solution came to me in my sleep last night.

The Tarm draft fan has a damper with an adjustable stop. I had adjusted the stop all the way down so that the damper would open the least, and still I had high flue temp. Based on my sleep solution, I took another look at the draft fan damper this morning and found that I could adjust the damper stop lever so that the adjustable stop would close the damper even further. With this done and a little time to adjust the stop with the boiler operating, flue temp only rose to 700 on a fresh charge of pine and then settled down to 600-650 for a long burn. 600 is what Tarm recommends. Gassification was just purring - a real beauty. I may tinker a little more to drop the temp into the 500-600 range and check results.

For any others, be aware that the Tarm may be delivered with a mis-adjusted draft fan damper lever. I assumed that the damper lever was where it was supposed to be, and obviously with my very good chimney draft, this was not the case. In all events, an easy user solution.

With 3-1/2 months of operation and burning only pine, my chimney still is practically new-shiny clean, and there is a small accumulation of ash dust at the bottom of the elbow where the flue exits the boiler. I do not anticipate any creosote problem this burning season. BTW, -16F last night.

 

[kuribo]

Because I was curious, I called Tarm and asked them about their flue gas temps. They told me that they should be closer to 400F, rather than 600F, for those without storage. With storage, they recommend installing the turbulators, which they said should lower the exhaust temp roughly another 100F or so.

A review of several other manufacturers shows exit temps from around 300F are not uncommon. I have talked with a manufacturer in Mauston, WI who just came out with an outdoor gasifier and they told me that during testing they were seeing outlet temps under 300F. Too low though and you run into condensation issues...

If you look at test data for masonry heaters, which have a long history as highly efficient burners, you find that exhaust temps in the literature of 250-300F are not uncommon.

Clearly, one is not getting all the heat energy available with high flue temps....

 

[jebatty]

Because I was curious, I called Tarm and asked them about their flue gas temps. They told me that they should be closer to 400F, rather than 600F, for those without storage. With storage, they recommend installing the turbulators, which they said should lower the exhaust temp roughly another 100F or so.

A review of several other manufacturers shows exit temps from around 300F are not uncommon. I have talked with a manufacturer in Mauston, WI who just came out with an outdoor gasifier and they told me that during testing they were seeing outlet temps under 300F. Too low though and you run into condensation issues...

If you look at test data for masonry heaters, which have a long history as highly efficient burners, you find that exhaust temps in the literature of 250-300F are not uncommon.

Clearly, one is not getting all the heat energy available with high flue temps....

Interesting, especially because Tarm's manual says 600F or more.

 

[Eric Johnson]

Most wood-fired boiler manuals that I have seen are a wealth of misinformation. I'd expect Tarm to be better, but things can get lost in translation, and sometimes the technology changes faster than the manual updates.

That's one of the many benefits of forums like this. How else could you communicate with dozens of other people using the same equipment?

 

[kuribo]

[/quote]

"Interesting, especially because Tarm's manual says 600F or more."[/quote]

I specifically mentioned that and they said that they didn't believe there was anything in the manual about flue gas temps. I told him that this is what people on line are referring to...He said that they recommend 400F....

Maybe call them and see if they tell you something different....

 

[jebatty]

Thanks for the comment. To beat a dead horse to death:

My Tarm came with an insert for the 339N Probe Thermometer with Tarm's logo on the insert, stating: "If you are burning dry wood that is well split you should achieve temperatures of 600 or more on the probe thermometer. If you are not achieving temperatures this high, check the following things . . . ." The insert then goes on to say that if this temperature is being achieved and then one notices that temperatures are going higher, then "it is time to brush the dust from the heat exchanger tubes."

To me all of this means that one should seek to obtain 600 on the probe thermometer. Regardless, I now will move towards 400 and see what happens. I also will consider turbulators, which Tarm advised should lower stack temps by 100 or more.

 

[Reggie Dunlap]

Kuribo,

Do you have a Tarm?

Reggie

 

[kuribo]

No....

 

[Jim Post]

I have a tarm w/o storage and I make it a habit to watch my chimney cap whenever I am out around the house....I have noticed wisps of smoke or steam many times when the tarm is idling. Is this a common occurrence with gasifiers that idle?

Last weekend, I brushed my chimney and cleaned my heat exchangers...my stack temp is right at 400 when well into gasification. Should I be trying to get closer to 300 by adjusting the draft fan damper....I just left it at the factory setting as well.

Last night low temp was 0 with a low of -4 forcast for tonight...I stoked full at 10 pm added a 3 more splits at 3am when the #%&(#&$ dog wanted out and restoked full at 6am today. I'll be interested to see what time my wife will restoke with highs in the teens today.

stay warm,

 

[Eric Johnson]

Mine smokes sometimes during idle--usually closer to the beginning of the cycle. Once you get down to coals, there's no more smoke to spill.

 

[kuribo]

visible smoke would mean incomplete (non-gasification) combustion. That is usually normal at start-up until gasification temps are reached. It would also be normal during an idle phase when dampers are closed to limit the air supply, resulting in incomplete combustion.

If you are at 400F flue gas temps, which is what Tarm told me was their recommendation, you would seem to be operating in accordance with Tarm's recommendation. You might try to reduce the draft slightly to slow the exhaust gas velocity which may enable the exhaust to linger a bit longer and give up more heat. I would think that increasing the water circulation rate might also lower exhaust temps by removing more heat from the flue gases....

 

[EricV]

Interesting. I'm going to try to adjust mine to get closer to the 400.

My manual has all the 600 degree data that everyone else is talking about. I bet Eric is right and updates or translations are off a bit.

Eric

 

[brad068]

Because I was curious, I called Tarm and asked them about their flue gas temps. They told me that they should be closer to 400F, rather than 600F, for those without storage. With storage, they recommend installing the turbulators, which they said should lower the exhaust temp roughly another 100F or so.

A review of several other manufacturers shows exit temps from around 300F are not uncommon. I have talked with a manufacturer in Mauston, WI who just came out with an outdoor gasifier and they told me that during testing they were seeing outlet temps under 300F. Too low though and you run into condensation issues...

If you look at test data for masonry heaters, which have a long history as highly efficient burners, you find that exhaust temps in the literature of 250-300F are not uncommon.

Clearly, one is not getting all the heat energy available with high flue temps....

I have also talked with mauston manufacturer. If the manufacturer you talked with is Sequyoah, then we have spoken to the same gentlemen, Rick. High E and I spoke with him and I think we got him on to the gasification track 2 years ago. I hope his owb gasification boiler does well for him.

If I may ask, what town do you live in in sw Wisconsin? We may be fairly close.

 

[kuribo]

Yeah, I spoke with Rick. Their boiler looks very well built.

I am near Prairie du Chien....

 

[EricV]

I made that adjustment last night and dropped my flue temp to about 375 during gasification. I'll try that for a week or so and see how it goes.

Eric