Primary air intake question

[mervmaster]

From jotul website:
AIR!
The wood is utilised in the best way when the draught control is fully open and the flames are intense. That will also reduce pollution, because gas particles are combusted and produce heat instead. Once your home is warm, the temperature is regulated by the amount of wood, not the air control.

OVERNIGHT HEATING
Very few wood stoves can burn longer than two to three hours on one wood load. The old way of closing the air supply so that the coals will smoulder overnight is a source of pollution and creates the risk of a chimney fire. In addition, the heat benefit is poor as the gases are not combusted and the energy is not utilised. The last wood load in the evening should be some bigger hardwood logs that burn as normal with the air vents open. Even if the fire dies out, the insulation in the house will keep the heat in. The stove and chimney will still be warm in the morning and it is no problem to get the fire going again.

My question is this- if I’m supposed to leave the air supply wide open all the time, why have it at all? It seems to me that I’ll be more wood efficient if I turn it down even a small bit overnight.

Any thoughts?

 

[kennyp2339]

My question is this- if I’m supposed to leave the air supply wide open all the time, why have it at all? It seems to me that I’ll be more wood efficient if I turn it down even a small bit overnight.

There are some new <1.5cu ft stoves that have no air control on them, but from what I understand air is only half the equation, draft is the other half, actually the chimney is the engine that drives the stove, so I you hook a stove up to a chimney that has a high draft .12" water column that the user may experience over-fire conditions running the stove at full bore, but the same stove connected to a chimney that measure .005" water column will be more sluggish and have a slower burn due to the exhaust not allowing the stove to pull in more air.
So the statement above from jotul seems pretty vague, every setup is different, variables include - wood types, moisture contents, chimney drafts; the best bet is to get a stove thermometer and find the happy place(cruise mode) of your stove (500-600 deg f) this may take some time with different air adjustments

 

[begreen]

Link? Was this from the US or European Jotul website? It sounds more like the European way of burning, with just a few logs at a time. Stoves in Europe usually are just room heaters and not run 24/7. They also still sell simpler versions of stoves are just baffled and don't have a full secondary burn.
Running a modern secondary combustion stove with a full load of wood with the air wide open would likely overfire the stove and exceed the tested rating for the stove pipe.

 

[yooper08]

Agreed, it's generally not advisable to run a stove wide open 100% of the time. Air supply to the fire is a function of draft as kenny mentioned, so that has to be taken into consideration. Gas and smoke particles in EPA-certified stoves burn in the secondary combustion when the air supply is turned down.

What is true though is that temperature is controlled by how much wood is in the stove.

 

[mervmaster]

Thanks guys, I just wanted to make sure I’m not crazy, I don’t think there was any way I would have left that thing wide open, but I wanted to check with some experienced people.

 

[begreen]

What is true though is that temperature is controlled by how much wood is in the stove.

True that. Though what I have found over the past few years that with our stove the timing of air shut down also directly affects the stove top temp. Shut it down as early as possible, guided by flue temps (not stove top), and the stove will cruise at about 100º less than if the stove is shut down a little later with higher flue temps. The latter is more typical of deciding when to turn down the stove air based on stove top temps. In addition to draft and air control setting another factor that will affect the stove top temp is the size of the splits. Lots of small dry wood will combust more quickly and hotter than a load of large, thick splits.

 

[yooper08]

True that. Though what I have found over the past few years that with our stove the timing of air shut down also directly affects the stove top temp.

Also very true.

Essentially merv, there is no one way to operate a stove. It's a dynamic system with several variables that need to be considered. Bottom line, you can turn down the air without concern to manage the fire.