Fast creosote build up and condensation

[cornerstone4.2]

I just swept my chimney/smoke pipe a few days ago and I already have a thin layer of creosote and have moisture condensation collecting on the chimney cap and forming icicles. I did this install a couple months ago.

I burn 2 year seasoned wood. I try to stay within the “safe temperature zone” on my thermometer. I also do a hot burn once a day. But often damper the stove at night.

Are there any modifications I can make that will prevent the creosote/condensation??
I was thinking of getting a stove that vents out the top thus removing the 90 degree elbow off the back?

 

[begreen]

The wood is most frequently the cause of this. If it's poorly or partially seasoned it's going to cool down flue gases and gunk up the chimney. Two year wood should be dry, but sometimes it is not. I had some 2 yr old maple that was still wet. The tarp I had on the stacks was leaky and actually trapped moisture under it.

Try not turning it down quite as much overnight and see if that helps.

 

[jetsam]

Everyone and their dog is gonna say "wet wood", so go ahead and explain how it's seasoned and stored.

That IS an awful lot of elbows, and I should imagine you may have draft issues... but that's not really a primary cause of creosote buildup. Low temperature is your culprit.

Add the icicles, and... wet wood.

 

[coaly]

Agreed low temperature in chimney is the problem. It must remain 250* f. to the top. (when smoke is present during burn)
Where are you setting the flue damper for overnight?

Try not closing your flue damper too far. (or not at all) Control it more with the intake. The flue damper is a variable resistance.
The most resistance is the air intake opening. That stove should have a baffle plate inside which is resistance within the firebox, then you have resistance from the elbows and pipe, you don't need to add much more resistance with the damper. The damper adds resistance to slow velocity of rising gasses in chimney (it is a chimney control that affects the stove) which I doubt you need to slow down until extremely cold outside when draft is much stronger.

 

[Doc C]

That's crazy! Usually there is a pretty obvious reason. Doesn't seem like the angled are enough to cause an issue. Doesn't seem like the wood is an issue unless you have some really hard wood. Would be a good idea to verify it with a moisture meter to be safe.

I would probably make sure your pipe is insulated which it looks like it probably is and I would make sure your temp guage is around 18" which it looks close.

Other then that.....going to have to burn hotter fires.

 

[cornerstone4.2]

Agreed low temperature in chimney is the problem. It must remain 250* f. to the top. (when smoke is present during burn)
Where are you setting the flue damper for overnight?

Try not closing your flue damper too far. (or not at all) Control it more with the intake. The flue damper is a variable resistance.
The most resistance is the air intake opening. That stove should have a baffle plate inside which is resistance within the firebox, then you have resistance from the elbows and pipe, you don't need to add much more resistance with the damper. The damper adds resistance to slow velocity of rising gasses in chimney (it is a chimney control that affects the stove) which I doubt you need to slow down until extremely cold outside when draft is much stronger.

Ya, there’s a baffle plate inside.

I think u guys are right, it all boils down to keeping the damper closed for too long. I was hoping someone was seeing something more than just that. Because I wish I could keep this thing on low heat most of the time to save wood. Also, this stove is like a runaway freight train if left wide open. Which probably means I have proper draft.

The only other things I may consider is removing the chimney cap or finding a different one and/or putting in a draft fan. But if the flue gases aren’t hot enough to begin with, I guess it won’t matter how fast they escape.

Thanks, happy burning [emoji91][emoji16][emoji111]️

 

[begreen]

Draft should be fine. This is a pre-EPA stove which will work on a shorter chimney without issue. With just a pair of 45s the offset in the connector is not the issue.That is not a lot of elbows. Don't remove the chimney cap. That won't solve anything, but it will allow rain to come in the chimney and down to the stove pipe.

Try to char the nighttime load of wood a bit longer before closing the air control more. Turning it down right after a reload is going to cause the fire to smolder with a cool chimney. That's an invitation for creosote.

 

[Tar12]

What kind of stove is that?

 

[coaly]

I didn't guess, I'm going by pictures of system and using the System Resistance Coefficient charts from the ASHRAE Handbook.

IF that is two -3 foot sections of 6 inch ID chimney equaling 6 feet, the relative capacity is 60. (Chart uses arbitrary number of 100 for 20 foot 6 inch chimney) Then you subtract system resistance from resistance chart;
In this case,
5 foot connector pipe = 3.0 (.6 per foot)
2- 45 els = .5 each or 1.0 total
1 90* el = 1.0
Cap without screen = .5
Inlet = 10 to 40 (using for small stove - large stove with 2 inlets = 5 -20)
Plus internal baffle not figured into calculation.
That is a Total System Resistance of 45 with air inlet set to minimum opening. OR 15 at maximum setting.

Using the Coefficient chart subtracting 45 from 60 is 15. The curve on chart gives pounds per hour of mass flow up chimney of air representing flue gas flow. (Resistance UP the chart, flue gas minus outdoor temperature ACROSS the chart) 300* f. average flue gas temp with outdoor 40* temp is 260* differential. (I don't know where OP is, so outdoor temp could average much colder) On chart the curve at 15 and 260* is 180 pounds per hour.
That size "small closed stove" is rated at 100 -200 pounds per hour OR 22-44 Cubic Feet per Minute. That is within range.

Now add the variable resistance of flue damper when used from resistance chart = 5 to 20.
This brings the coefficient used in chart down to10 slightly closed to 0 closed.
By the chart curve; 10 requiring 400* in the same system, 3 requiring 600* and the chart goes down to 1 requiring 800*.
Notice these numbers are always average flue gas temp. NOT a temperature taken at any given distance from stove outlet.
Therefore any more than slightly closing damper is too much resistance for entire system.

These tables and charts are in The Wood Burners Encyclopedia with a good explanation of how to use them ,taken from ASHRE Chapter 26 1975 Equipment Volume.

 

[jetsam]

It looks like relocating the stove a few inches to get rid of all 3 elbows would be pretty easy.

Given that, why not get a modern stove? The old stove sounds like it's giving you the choice between 'Creosote Factory' and 'Inferno' with not much in between; almost any EPA stove will be an upgrade from there.

Sounds like being able to burn more controllably might fix the original creosote problem, too.

If you're thinking, "I can just sweep more. This stove works and there's not a great reason to replace it."- you will cut down your wood usage (possibly by a lot), and have a more flexible heater (possibly a lot more flexible; some setups can burn right through 50 degree days without creosote issues or open windows).

 

[cornerstone4.2]

What kind of stove is that?

It’s an old knock off Jotul 118 “cigar burner”. Not a bad stove but my father in law used to have one and he had similar issues with creosote.


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[cornerstone4.2]

I didn't guess, I'm going by pictures of system and using the System Resistance Coefficient charts from the ASHRAE Handbook.

IF that is two -3 foot sections of 6 inch ID chimney equaling 6 feet, the relative capacity is 60. (Chart uses arbitrary number of 100 for 20 foot 6 inch chimney) Then you subtract system resistance from resistance chart;
In this case,
5 foot connector pipe = 3.0 (.6 per foot)
2- 45 els = .5 each or 1.0 total
1 90* el = 1.0
Cap without screen = .5
Inlet = 10 to 40 (using for small stove - large stove with 2 inlets = 5 -20)
Plus internal baffle not figured into calculation.
That is a Total System Resistance of 45 with air inlet set to minimum opening. OR 15 at maximum setting.

Using the Coefficient chart subtracting 45 from 60 is 15. The curve on chart gives pounds per hour of mass flow up chimney of air representing flue gas flow. (Resistance UP the chart, flue gas minus outdoor temperature ACROSS the chart) 300* f. average flue gas temp with outdoor 40* temp is 260* differential. (I don't know where OP is, so outdoor temp could average much colder) On chart the curve at 15 and 260* is 180 pounds per hour.
That size "small closed stove" is rated at 100 -200 pounds per hour OR 22-44 Cubic Feet per Minute. That is within range.

Now add the variable resistance of flue damper when used from resistance chart = 5 to 20.
This brings the coefficient used in chart down to10 slightly closed to 0 closed.
By the chart curve; 10 requiring 400* in the same system, 3 requiring 600* and the chart goes down to 1 requiring 800*.
Notice these numbers are always average flue gas temp. NOT a temperature taken at any given distance from stove outlet.
Therefore any more than slightly closing damper is too much resistance for entire system.

These tables and charts are in The Wood Burners Encyclopedia with a good explanation of how to use them ,taken from ASHRE Chapter 26 1975 Equipment Volume.

Whooh, all those number make my head spin! I will look into that, thanks for the reply and info!


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[cornerstone4.2]

It looks like relocating the stove a few inches to get rid of all 3 elbows would be pretty easy.

Given that, why not get a modern stove? The old stove sounds like it's giving you the choice between 'Creosote Factory' and 'Inferno' with not much in between; almost any EPA stove will be an upgrade from there.

Sounds like being able to burn more controllably might fix the original creosote problem, too.

If you're thinking, "I can just sweep more. This stove works and there's not a great reason to replace it."- you will cut down your wood usage (possibly by a lot), and have a more flexible heater (possibly a lot more flexible; some setups can burn right through 50 degree days without creosote issues or open windows).

If I run the pipe straight down I will lose the needed clearance. [emoji53] But I’m gonna try adjusting the elbows, adding pipe and therefore decreasing the angle.
I’m gonna start looking into a new stove.....


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[begreen]

If I run the pipe straight down I will lose the needed clearance. [emoji53] But I’m gonna try adjusting the elbows, adding pipe and therefore decreasing the angle.
I’m gonna start looking into a new stove.....


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We've run an F602 with less chimney and little creosote. I don't think the chimney is the issue for this stove. It is getting turned down too much at night. Try opening it up a little more for a week or two and see if that solves the problem.

 

[Tar12]

It’s an old knock off Jotul 118 “cigar burner”. Not a bad stove but my father in law used to have one and he had similar issues with creosote.

There is your answer...
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