Finally figured it out!

[LarryD]

After 3 mos of burning (burning almost 3 cords of wood), I have finally figured out how to get higher stack temps. I have been plagued with 400* max stack temps and slow heating of the storage tank. I have really struggled with the fact that it is my wood. I know for a fact it would be beyond perfect for a wood stove. But that was exactly the issue. The wood is split for burning in our Isle Royale! After reading post after post on stack temps, starting procedures, etc, etc, it dawned on me. Why not try and just burn a load of very finely split kindling and starter wood. Poof! 400* almost instantly I am now re splitting all of my wood before I put into the boiler to no larger than 3x5. The lengths vary form 10"-20" (That is what I get for letting my guys cut my firewood!)

Is this exteme? Seems like the wood has to be pretty fine for a boiler this size. All of my wood is Red Oak

It is a time like this that you appreciate these forums and the help they have been. If it weren't for this site, I wouldn't be this far along with the learning curve.

Thanks to all that post frequently, us lurkers really benefit!

LarryD

 

[RJP Electric]

For best results in my Biomass, and my rule of thumb, if the wood on the edge is larger than a playing card it is too big!

Check out this thread

https://www.hearth.com/talk/threads/30239/

 

[LarryD]

I never thought of a playing card as a gauge!! That is true!

LD

 

[Medman]

Large wood size was my issue as well. All my wood was split to burn in the PE stove - the bigger the better for long even burns. Now I am resplitting all wood smaller to give me higher temps and reduce bridging. It seems to be working well. I am getting 24 face cord of oak and maple delivered next week and will split that smaller for the boiler. Since installing the EKO, I have only used the PE two or three times - not enough to justify keeping any big pieces around anymore.
Im not looking forward to all the extra splitting, though...

 

[Tarmsolo60]

I too was amazed when I tried a load of my wood split smaller than I had been using.

 

[heaterman]

Curious as to why higher stack temps are desired? Usually the lower the stack temp the more efficient you are running.

 

[Nofossil]

Curious as to why higher stack temps are desired? Usually the lower the stack temp the more efficient you are running.

My guess: if you don't have a combustion temp probe, then flue temp is a good proxy for combustion temp. Too low means you're not getting good secondary combustion.

I'll agree with your point, though. You want the biggest difference between combustion and flue temp that you can get.

 

[Eric Johnson]

At first I thought he had a conventional wood-fired boiler, which needs high stack temps to avoid creosote buildup. Then I saw the Tarm in his sig.

Funny contrast.

 

[sdrobertson]

Curious as to why higher stack temps are desired? Usually the lower the stack temp the more efficient you are running.

My guess: if you don't have a combustion temp probe, then flue temp is a good proxy for combustion temp. Too low means you're not getting good secondary combustion.

I'll agree with your point, though. You want the biggest difference between combustion and flue temp that you can get.

This is how I'm trying to tune the boiler - I look for lower air flow with higher stack temps which tells me that I'm going in the right direction. I just clean the boiler more often to keep the efficiency the same.

 

[Nofossil]

My brother's condensing gasifier now has a cold air preheat exchanger in the flue, so his flue temp out the top of the chimney is around 100 degrees....

 

[stee6043]

I can't wait to burn tonight when I get home from work. I'm going to split my wood into toothpicks (maybe not quite that small) and load the beast up. Can't wait to see how it affects my temps all around. You guys make my afternoons at work very long. Just waiting to get home and try something new with the EKO....

 

[Nofossil]

I can't wait to burn tonight when I get home from work. I'm going to split my wood into toothpicks (maybe not quite that small) and load the beast up. Can't wait to see how it affects my temps all around. You guys make my afternoons at work very long. Just waiting to get home and try something new with the EKO....

It's probably time for a dose of harsh reality here....

Just as bigger is not always better, the same can be said for smaller. Too much surface area means too much wood gas generation, which can lead to puffbacks and smoking. There's a pretty broad range in the middle, but expect to find problems if you go too small. This is more of a problem with really dry wood.

 

[sdrobertson]

I can't wait to burn tonight when I get home from work. I'm going to split my wood into toothpicks (maybe not quite that small) and load the beast up. Can't wait to see how it affects my temps all around. You guys make my afternoons at work very long. Just waiting to get home and try something new with the EKO....

It's probably time for a dose of harsh reality here....

Just as bigger is not always better, the same can be said for smaller. Too much surface area means too much wood gas generation, which can lead to puffbacks and smoking. There's a pretty broad range in the middle, but expect to find problems if you go too small. This is more of a problem with really dry wood.

My wood is far from perfect so I'm trying to split it pretty small. I ordered a electric splitter that should be delivered on Monday so in the mean time its split by hand down to 4"s which is working well for me. All of my wood is still split up for owb size and being a little wet yet - I'm thinking this is the majority of my final tuning problems. I'm close to full tilt on this beast but I can't wait for next year with properly dried wood

 

[Rick Stanley]

Larry,

It sounds like you're not happy with storage heat-up times and wood usage. Is that right?

Now that you have higher stack temps, I'd be interested in knowing how that effects those two things.

Is it better? Or too early to tell?

Rick

 

[LarryD]

Given some of the replys here, it is making me wonder if I am going in the wrong direction. Prior to reducing the size splits I was using, I struggled to get 400* max stack temps. I never had much if any smoke, but it never seemed to "gasify" the wood. Now the flame comes out of the "refractory" and wraps around towards the rear of the boiler. This is what is shown on my book I got from Tarm. The flame is white/blue instead of orange/yellow.

I do want to clarify. I dont want 800* stack temps. I do want higher efficiency (Nofossilesque if possible) I was dissapointed in the amount of wood I was using to get the results I was getting. It seems like I am using much less wood and getting more heat stored into the tank. The boiler is ideling more now, I will admit that.

LD

 

[LarryD]

Rick Stanley-I am not happy yet with the amount of time/wood it takes to get the tank to 150*. I have never had the tank much higher than that. I will say this that over the past 2 days that amount of time has dropped significantly. I run the tank down to about 120* and up to about 150*. This is enough at the moment to heat our 4,000 sqft House and garage over night. Very comfortably I might add!!

My next goal is to somehow measure what my return temps are in the boiler. They seem a bit high from the "hand" test. Not very accurate :-0

One last note, I only have 1/2 my turbulators in. I do plan to put the rest in this weekend. It will be interesting to see how that will impact things. Right now I have 1/2 in and I staggered them.

Overall I am thrilled with the unit. I just know it can be far more efficient.

LD

 

[Rick Stanley]

Larry,

I'm not a Tarm guy or an expert on any of this, but I think you're on the right track. Once you're sure that good gasification is happening, whether by splitting wood finer

or using drier wood or whatever, the only other thing left is heat exchange, I think. I'm pretty sure that the purpose of the turbulators is to slow and mix flue gasses for

more efficient heat exchange. Maybe half the turbs means half the efficiency?? Anyway, beyond the actual heat exchange is the flow to storage to consider. Are you

sure the pipes and pump are sized ok to get the heated water to storage and back at the right flow rate? Sorry, more questions than answers. The reason I ask that is

because it seems odd to me that you have over 2000 gallons of water sitting there struggling to reach 150 and your boiler is idling. Here's a question: Can you raise the

storage temp higher with no call for heat anywhere?

 

[LarryD]

sure the pipes and pump are sized ok to get the heated water to storage and back at the right flow rate? I assume they are based on my answer to the next question


Sorry, more questions than answers. The reason I ask that is

because it seems odd to me that you have over 2000 gallons of water sitting there struggling to reach 150 and your boiler is idling. Here’s a question: Can you raise the

storage temp higher with no call for heat anywhere? To clarify, I have 922 gallons of storage. From 120* to 135* the temp in the storage tank will rise 3*-5*/hour. Depending if one of the 4 zones is calling. It does seem like above 150*, the heat transfer certainly slows down. Perhaps it is because I generally fire at night when I get home from work? The day is cooling off and there is a higher heat demand? Example though, I started the boiler at about 5:00 pm tonight it is now 8:45 PM and the tank has gone from a low of 111* to 135* in that period of time. Does that seem slow?

Thanks for your response.

LD

 

[Bad Wolf]

Larry
We've probably discussed this before. I have a Tarm 2000 with all six turbulators in and 1200 gallons storage. I have no problem getting the tank up to 170*. Stack temps are around 400* sometimes 500* with good dry wood. I usally spilt it around the playing card size mentioned earlier. What are you using for HX? I have two 150' coils with grunfos pumps set on high. I 'm sure my wood is not the best but I'd say with no load I can raise the storage by 10*/hr. The way mine is set up if a zone is calling for heat then almost nothing is going to storage. It only gets heat when nobody else wants it. I build a good fire when I get home around 5:30 and then stoke it again at 10:00 when I go to bed and the termostats drop down for the night. I usually gage how much wood I add by the storage temp. A full firebox will buy me about 30* in storage if no zones are calling. I almost never let it get down to below 130*.

Greg H

 

[heaterman]

My brother's condensing gasifier now has a cold air preheat exchanger in the flue, so his flue temp out the top of the chimney is around 100 degrees....

Condensing gasifier? You have my attention NoFo. What kind of a rig is that?

 

[Duetech]

My brother's condensing gasifier now has a cold air preheat exchanger in the flue, so his flue temp out the top of the chimney is around 100 degrees....

I thought about doing something like that to pre condition the intake air. I did not know one was available in a retail scenario. do you have a link for the pre heat exchanger? Thanks...

 

[LarryD]

Greg H-

probably discussed this before. I have a Tarm 2000 with all six turbulators in and 1200 gallons storage. I have no problem getting the tank up to 170*. Stack temps are around 400* sometimes 500* with good dry wood. I usally spilt it around the playing card size mentioned earlier. What are you using for HX? I have two 150’ coils with grunfos pumps set on high. I TO HAVE (2) 150' COPPER COILS AND A TACO 0010 PUMP

I ‘m sure my wood is not the best but I’d say with no load I can raise the storage by 10*/hr. The way mine is set up if a zone is calling for heat then almost nothing is going to storage. It only gets heat when nobody else wants it. I build a good fire when I get home around 5:30 and then stoke it again at 10:00 when I go to bed and the termostats drop down for the night. I usually gage how much wood I add by the storage temp. A full firebox will buy me about 30* in storage if no zones are calling. I almost never let it get down to below 130*. WHAT IS THE LOWEST WE SHOULD RUN THE TANK DOWN TO? I DIDN'T SEE A RECOMENDATION.

Sorry for the caps. I could figure out another way to do that.

 

[Nofossil]

My brother's condensing gasifier now has a cold air preheat exchanger in the flue, so his flue temp out the top of the chimney is around 100 degrees....

Condensing gasifier? You have my attention NoFo. What kind of a rig is that?

He (being a madman) built his own from scratch. Critical dimensions and flow rates are based on the EKO 25, but with more than 3x the heat exchanger surface area. All HX is stainless. First stage heats water (to 100 degrees max) for radiant floor. Second stage heats DHW. Third stage heats air for top floor, and fourth stage preheats incoming cold air. The fan is a heater fan from a Dodge pickup, and the heater fan speed switch has been replaced by relays. Control and datalogging is via a variant of the world-famous 'NoFossil Control System'.

It's a pretty spectacular system. He burned 2.5 cords of wood last year, and there's no other heat source.

 

[Bad Wolf]

Larry I don't remember seeing a recommendation for low temps but I just know that the smaller the delta T the less efficient the heat transfer is. Its a lot easier to heat a room to 68* with 180* water than 130* water. You can do it, it just takes a lot longer.

Where/how are you measuring your tank temps? When I say I'm at 170* that's at the top of the tank maybe 6" below the surface. The bottom of the tank may be as much as 15* cooler.

 

[Eric Johnson]

My brother's condensing gasifier now has a cold air preheat exchanger in the flue, so his flue temp out the top of the chimney is around 100 degrees....

Condensing gasifier? You have my attention NoFo. What kind of a rig is that?

He (being a madman) built his own from scratch. Critical dimensions and flow rates are based on the EKO 25, but with more than 3x the heat exchanger surface area. All HX is stainless. First stage heats water (to 100 degrees max) for radiant floor. Second stage heats DHW. Third stage heats air for top floor, and fourth stage preheats incoming cold air. The fan is a heater fan from a Dodge pickup, and the heater fan speed switch has been replaced by relays. Control and datalogging is via a variant of the world-famous 'NoFossil Control System'.

It's a pretty spectacular system. He burned 2.5 cords of wood last year, and there's no other heat source.

It's a beauty (house and boiler). I've seen it.