Masonry thermal-mass stoves, and perhaps "rocket" mass stove question...

[Tedinski]

I've been reading up on masonry stoves & rocket mass stoves. They are quite intriguing!

Recently I switched from heating with a wood stove (Lopi) 24/7 through the cold months to a pellet stove, and my Lopi with 2 cords of wood as backup for when (not if!) the electricity goes out.

Pound for pound, I'm burning a GREAT deal less fuel. The stove always had to be banked down very low in order to keep from roasting out of the house! That's an inefficient way to burn wood.

When banked down, I've noticed I sometimes even get icicles hanging from my chimney cap. The flue temperature isn't high enough to keep the cap from collecting all the H2O that's produced from the burn.

Is this a major problem for thermal-mass stoves & rocket mass stoves? The flue temperatures are supposed to be almost ridiculously low. 120F to 140F, and (of course) full of water vapor.

I'm thinking of switching the Lopi out for a masonry stove, but I'm worried I'll end up with a huge block of ice on top of the flue.

Any ideas or experiences anyone can share will be greatly appreciated!

 

[EatenByLimestone]

The only place I've seen icicles hanging off a chimney that was being used it was a smoker at a butcher shop and I'm not sure the icicles weren't creosote. Not surprisingly, the place burnt down a couple years ago.

120-140F is still well above the temperature that water freezes at.

How long did your wood sit cut, split and stacked before you burnt it? It seems like might be a crazy level of water still in it. How clean was your chimney when it was cleaned?

Matt

 

[Tedinski]

The only place I've seen icicles hanging off a chimney that was being used it was a smoker at a butcher shop and I'm not sure the icicles weren't creosote. Not surprisingly, the place burnt down a couple years ago.

120-140F is still well above the temperature that water freezes at.

How long did your wood sit cut, split and stacked before you burnt it? It seems like might be a crazy level of water still in it. How clean was your chimney when it was cleaned?

Matt

Heya Matt! Thanks for the reply.

I've had to keep the wood stove damped down VERY low to keep from getting heat stroke! Creosote build up has been rapid. Last year I had 2 chimney fires, when starting a fresh/hot fire after loooong periods of slow fires!
When it's damped down (to keep me from opening all the windows!) icicles form on the cap of my chimney. There have been times I've had to go out & use a long pole to knock them down. They start to restrict the air flow out of the flue!

I'm sure this is an abnormal (RARE!) thing to have happen for most people. I have a VERY small house, and perhaps a too-large woodstove.

But.. It did get me thinking about similar circumstances, i.e. a masonry stove with low exhaust temperatures. Do masonry stoves experience this? is it common?

As far as the moisture content of my wood, I do not have a moisture meter. The wood I burn has typically been cut, split, and stacked for at least 6 months.

Does this help you follow my train of thought?

Thanks

 

[EatenByLimestone]

I think you'll need to let your wood dry out longer in order to avoid the creosote issue with a masonry stove. Due to the flue designs on them, they would probably be harder to clean too.

You are probably burning similar woods to what I have up here. Some species are ready to burn after 6 months in the wind, but most aren't. The oaks and hard maples take much longer... like 2+ years to get enough moisture out of them. You may want to change stoves though. One of the soapstone stoves will absorb the heat into thermal mass like a masonry stove and slowly radiate it back out to the room. This would allow you to use your existing chimney after it was swept.

Matt

 

[Tedinski]

I think you'll need to let your wood dry out longer in order to avoid the creosote issue with a masonry stove. Due to the flue designs on them, they would probably be harder to clean too.

You are probably burning similar woods to what I have up here. Some species are ready to burn after 6 months in the wind, but most aren't. The oaks and hard maples take much longer... like 2+ years to get enough moisture out of them. You may want to change stoves though. One of the soapstone stoves will absorb the heat into thermal mass like a masonry stove and slowly radiate it back out to the room. This would allow you to use your existing chimney after it was swept.

Matt

Sounds like a plan!
Don't masonry stoves get fired on "full draft", and therefore very high temperatures? The end-flue temperature is low due to the thermal mass though... I shouldn't think creosote would be a problem, but moisture content in the wood might make quite the difference... something to think about. I could certainly be wrong! I'm new to these forums!
Thank you for your input.

 

[EatenByLimestone]

A lot of the heat from the fire is being used to turn that moisture to steam, which collects on your flue. If the moisture wasn't in the wood when you tried to burn it, it wouldn't condense on the flue or help to form creosote.

 

[Tedinski]

I thought H2O was a large product of combustion... even if there's no water in the wood?
I'm far more familiar with natural gas & propane combustion though.... when burning gas, you CREATE H2O that wasn't there to begin with.
Complex carbohydrates (wood) I'm sure burn in a far more complex way. I don't know the chemistry.

 

[EatenByLimestone]

When any hydrocarbon is burnt, water is a byproduct. The trend is less and less carbon in fuels... eventually we will probably be burning straight hydrogen and will still get water, but no carbon dioxide. The question becomes how much water you want to add to the process. Adding water doesn't help the wood burn.

 

[Tedinski]

When any hydrocarbon is burnt, water is a byproduct. The trend is less and less carbon in fuels... eventually we will probably be burning straight hydrogen and will still get water, but no carbon dioxide. The question becomes how much water you want to add to the process. Adding water doesn't help the wood burn.

I worked on a "clean coal" project that sequestered all the CO2 that came from the combustion chamber. Very clean, but HORRIBLY inefficient. All the energy to separate the CO2, then lots of power to compress it to a liquid, then to ship it by truck to boats that go far out in the ocean & pump it down to the DEEP ocean floor.

So much wasted power!

I'm sure they'll come up with some other process. Till then, wouldn't it be nice to have Thorium reactors making clean energy?