Temp down, draft up... right?

[burnt03]

Been right around freezing for the past week or so. Start the night fire at about 8PM, set the air at about 1/8 open, have lots of coals to start the fire the next morning at 5:30 before work.

Got a bit colder last night (23 F) and fire was out this morning. Is it just cause the draft is stronger when it's colder?

If I want coals the next morning, I guess I'll need to add bigger splits and maybe turn the air down all the way?

 

[Slow1]

I've often wondered how much (objectively) the draft increases with changes in outdoor temperatures. I know there is a big difference in the way that my stoves have operated when the outside temp is 50* vs 30*, but then I don't know if there is as much of a difference in the next 20* down to 10*.

But to your experience, I would not be surprised if a change in temperature can cause the stove to pull more air and burn the load faster, that does happen to me as well - but with only a 10* difference I'm surprised that it was a dramatic change. You may have had other factors too - such as the particular splits you chose being a bit more/less dense or dry etc.

 

[binko]

The greater the temp difference the greater the difference in air density. With greater density difference, the less dense air will want to rise further and faster-just like lighting the flames on a hot air balloon. Physics 101.

 

[Hogwildz]

Yes, it will draft harder with colder outside temps. Large splits, and try to get the air turned down as far as you can without smoldering.
My liner is 27' double wall rigid insulated, and drafts too well I think sometimes. I cut my air all the way back.
You will neeed to experiment and see what works best for you. Large hardwood splits should get you through the night depending on what size firebox you have.

 

[Slow1]

The greater the temp difference the greater the difference in air density. With greater density difference, the less dense air will want to rise further and faster-just like lighting the flames on a hot air balloon. Physics 101.

Can't argue with that - but the thing that gets me is the question of what temperatures are most material in the calculations. If one didn't have a fire in the box then it would simply be the indoor and outdoor temperatures perhaps. However, the temperature of the stove/chimney system clearly makes a difference too. Now if it was just the indoor/outdoor delta that matters then that 10* drop outside from 30-20* is pretty significant if inside temp is say 65* then you are going from a 35* - 45* delta. However if you are looking at the flue temp to outside then if one has a 400* flue at stove exit (if that is where it mattered) then the delta would be a difference of 370* vs 380* which I can't imagine is nearly as significant. Then the net draft is affected by the house stack effect which is going to be a function of indoor/outdoor temp and will likely reduce the draft on the chimney in most cases (with increasing amount of affect as the outside temp falls/inside temp rises)... The solution is clearly more complex than two points of measurement so I think it would likely take something beyond a 101 level course to create and solve this model, likely a 401 or grad level

Then again - all this is minutia really, the bottom line is as the OP stated in the subject; "temp down - draft up" and that should pretty much answer it for all practical wood burning use.

 

[Backwoods Savage]

Whatever you do, please also remember that it makes a tremendous difference in the type of wood you burn. So a natural question to ask yourself is, "Did I burn the same type of wood both nights?" Size of splits also makes a difference as does a round vs a split.

Definitely save the hardest and best for mid January and later because that is when you need the most heat.