Incomplete Burn?

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snowaggie

New Member
Mar 26, 2025
5
North America
Hello Friends: I have been learning the nuances of my new stove for nearly a full season and am happy with it in all respects. I can burn it hot or warm, catalytic or not, and it all works great. One thing I have noticed though: When it has gone completely cold and I'm shoveling out cold remains, there are a not insignificant amount of chunky black coals....light, mini-briquettes if you will. There will be grey ash too, maybe a 50-50 ratio. Everything is stone cold so the burning process is over. How do I get to 100% ash?
 
Often this is a consequence of wood that's a bit too wet still.
Also some species do this a bit more than others (oak more fir not - though I can get a 2.9 cu ft firebox down to ashes and two 1" pieces of coal).


I think it can also be dependent on the flue system. If it's A little short, or the weather is warmer, draft at the very end of a burn may not be enough to allow enough air into the stove to combust the last pieces?

Do open the air during the last half to whole hour of a burn if you're letting it go cold

But what stove is this?
 
Open the primary air supply towards the tail end of the load.
Burn it all down.
You can also put in a single dry split at the tail end of your load and run it wide open to burn down the coals.
 
Often this is a consequence of wood that's a bit too wet still.
Also some species do this a bit more than others (oak more fir not - though I can get a 2.9 cu ft firebox down to ashes and two 1" pieces of coal).


I think it can also be dependent on the flue system. If it's A little short, or the weather is warmer, draft at the very end of a burn may not be enough to allow enough air into the stove to combust the last pieces?

Do open the air during the last half to whole hour of a burn if you're letting it go cold

But what stove is this?
It's a Hearthstone brand. I do run it wide open when it has broken down into red coals. Maybe just not enough air draw at that point to get it all to ash? I wonder if leaving the door cracked at that point would do it?
 
Never burn with the door wide open. It'll needlessly pump out a lot of warm air from your room into the chimney.

How long has your wood (and what species) been split and stacked off the ground?

And how tall is your chimney?

(And whereabouts are you located?)

On the other hand, using a cat poo scooper you can filter the coals out, scoop the ashes out with a shovel, and just leave the coals in the stove for the next burn.
 
Never burn with the door wide open. It'll needlessly pump out a lot of warm air from your room into the chimney.

How long has your wood (and what species) been split and stacked off the ground?

And how tall is your chimney?

(And whereabouts are you located?)

On the other hand, using a cat poo scooper you can filter the coals out, scoop the ashes out with a shovel, and just leave the coals in the stove for the next burn.
Top of pipe is 5 foot above roof peak. I burn from scrounging in Michigan, so mainly maple, ash, birch and beech. The stack I'm working on now has been split and stacked for 2 years, though it's in the weather. I would be curious as to moisture content and welcome any product suggestions down that road.
 
But the total flue height from stove top to cap ?

2 years may be okay. Likely barely below 20% but not crazy bad. If top covered it'll be better.

Moisture content: I have a mmd4e moisture meter.
$26 or so.
Get a big split,.bring it inside, let it get up to temperature throughout in 24 hrs, then split it in half, and measure with the pins as deep as they go, parallel to the grain, on the freshly exposed surface. That'll give you the inside moisture content which is what you want to know.
 
Well...flue goes through a 9 foot ceiling and a 7 foot attic. It's all straight as far as I can remember. Just ordered the meter you suggested and will follow your procedure. Look for results...FYI: That meter is now $30...guess that's the world we're living in!😁
 
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Okay. The flue is of good height at 21 ft.

Note that if it's 45+ outside draft will also suffer.