Insert burns longer in colder weather?

[firebroad]

This is kind of trivial, but I have noticed that my Alderlea T5 insert burns longer when the temps are below 20F. It seems kind of counter productive, as I actually will keep the air a little more open to get the fire going, and yet every time I get a real overnight burn, it has been really cold, like lately. Even during the day, I don't seem to have to keep feeding it as much.
Of course, it doesn't really put out tons of heat, which is to be expected. But I was wondering if maybe you engineer types can explain it, maybe the cold air is "pressing" down the chimney draught, or some such thing?
Not complaining, just curious.
Oh yeah, outside stone chimney, single story home. North side.

 

[BobUrban]

Is it Burning longer -or Heating longer? If there is visible fire for a longer period my best guess is due to increased draft from the colder temps. This would provide more primary air over the fuel and give the illusion of longer burns from the longer lasting flame period before coaling. With higher temps there is less draft and sooner coaling all other things being equal.

 

[firebroad]

I would say that the coaling stage starts normally, but the primaries will last a little longer. You are right, I am not getting the heat so much as the glowing coals; this makes is easy to restart, but doesn't really give off any extra heat. But since it is already single digits outside, I would think this is normal.
So are you saying that the colder temps are "sucking" more air from the house?

 

[velvetfoot]

My insert fan actually turned off before I got up this morning, which it never does, with the usual coals.

 

[mellow]

I have to load more in colder weather due to increasing the primary air to get more BTU's. Colder weather increases the draft which should increase your firebox temps.

 

[firebroad]

My insert fan actually turned off before I got up this morning, which it never does, with the usual coals.

...And mine usually turns off, except during this cold weather! Go figure.
Of course, I am strictly a night a weekend burner, since I am away from home so much. That will change when I retire.

 

[firebroad]

I have to load more in colder weather due to increasing the primary air to get more BTU's. Colder weather increases the draft which should increase your firebox temps.

I usually do that as well. However, I find that the house doesn't heat any better when it is 30 degrees than when it is 3 degrees. But I have glowing coals in the morning, having loaded the same amount of wood. We've had three or four of these extra cold snaps over the past two years, and I have observed the same behavior in the stove. 'Course, we get a little nippier up here in near Hampstead than you guys get down in Salisbury...

 

[mellow]

Are you sure you are not just smoldering the wood longer?

 

[firebroad]

Are you sure you are not just smoldering the wood longer?

Jeez, I hope not! I do get up to...you know...in the middle of the night, and nudge the lever open a wee bit more to burn the coals to ash. I haven't seen anything on the glass, how else could I tell? It's not like I can check the liner easily.

 

[mellow]

The main point of concern will be in the beginning stages of the reload, that is when your off gassing will occur and hence secondary flame action happening at your baffle, once the wood stops off gassing and gets to the coaling stage only heat will be released and smoldering is of less concern. One way to tell if your smoldering would be to check to see if you have dark smoke exiting the chimney during the peak burn and not a white smoke that dissipates quickly.

 

[firebroad]

The main point of concern will be in the beginning stages of the reload, that is when your off gassing will occur and hence secondary flame action happening at your baffle, once the wood stops off gassing and gets to the coaling stage only heat will be released and smoldering is of less concern. One way to tell if your smoldering would be to check to see if you have dark smoke exiting the chimney during the peak burn and not a white smoke that dissipates quickly.

Thanks! No smoldering. Even when the weather is humid and foggy and the smoke tends to pour out in the beginning of a burn, it is white. I have two year old wood, and it ignites well; I just hope with all this cold weather I won't have to dip into 2011's stacks.