Which is more efficient?

[USSTONE]

We have a fireplace insert that works fine and we burn wood (almond wood and construction lumber cutoffs mainly) ..My wife and I are having a debate.. she thinks it is better to leave the glass doors open when the fire is burning and I am not so sure if we are better off with the doors closed. The unit has a little fan that moves the air around quite well, but I am wondering what is the most efficient way to operate the unit..? thanks.
rz

 

[BrotherBart]

Door closed is the most efficient, hands down. That is how it was designed to burn. The door open is just sending your heat up the flue just like an open fireplace.

 

[begreen]

Definitely more efficient with the doors closed and much cleaner burning. If you don't want your neighbors complaining about smoke, keep the door closed. Word is that's a very touchy subject in CA.

 

[Jerry_NJ]

Most inserts and stoves will run too hot if the door is open, even a "crack". This results in the wood being burned too fast, lots heat going up the chimney, and a chance you'll over-fire/heat the insert/stove.

All new/EPA stoves/inserts are designed to be run with the doors closed and most of the time with the primary air throttled down to control the burn rate/temperature.

 

[Pagey]

I would caution you to read this article before burning too many mill ends.

(broken link removed to http://www.chimneysweeponline.com/homillends.htm)

If you know your mill ends do not contain this junk, you will probably be okay, but I think the article merits a read.

 

[LLigetfa]

When I was building my house in the fall and winter, I installed and started to use the stove before I even had all the insulation up. All I had to burn then was the construction scraps and the wood I cleared off the property in the spring. Mixing the scraps with the unseasoned wood was the only way it would burn.

 

[Kilted]

Definitely more efficient with the doors closed and much cleaner burning. If you don't want your neighbors complaining about smoke, keep the door closed. Word is that's a very touchy subject in CA.

DOOR CLOSED only! I live in CA, go and read the stuff on http://www.baaqmd.gov/, http://www.sparetheair.org/, http://www.sparetheair.com/. In Santa Clara county you can now get a fine for burning at the wrong time.

Dig around those sites and you will find that there is a strong current against any kind of residental wood burning, except commercial power generation. Santa Clara County recomends no wood burning fireplaces in new construction. Some towns outlaw fireplaces completely.

Even if you have a pellet stove or EPA cord wood stove on Spare the Air nights/days you can now get a fine if you "light up".

So close THE DOOR and burn cleanly. You will be helping to keep my stove running - Avalon PerfectFit.

-- Brandy

 

[velvetfoot]

Why would there be more smoke if the door is open?

 

[Martin Strand III]

Guyz:

You're mostly on the right track but haven't made it clear or mentioned 'why' too much air is not efficient or will not produce the hottest fire.

Here's the scoop:

An "efficient" fire burns hot (so the smoke containing considerable BTU's is burned, less creosote, etc - you know this, or should). When the fire just starts, more air (by cracking the door a little for just a few minutes) is good to help the fire spread to the fuel which needs to get up to its ignition temperature before pyrolysis can occur.

The ideal amount of air ("theoretical combustion air") required to burn wood fuel can be calculated from the chemical composition of the wood (essentially C, H, O2, H20 and ash) in an exothermic chemical equation to yield H20, CO2 and, naturally, energy (heat). I won't bore you with the math but the result approximates 4 - 5 cubic meters of air per Kg of wood.

If you add excess air through the firebox, air that does not take part in the chemical equation, by leaving the stove door open too long or too wide, the extra air "lowers stack temperature" and adds to heat loss.

How do you know how much air you are moving through your stove? You don't. It's engineered in the design of your stove with the caveat that a metal stove cannot be fired anywhere near the "efficient" temperature that wood burns without over firing the stove.

So, as in life, you are face with compromise. In short, follow the Mfg directions for burning your stove, don't think about the process too much and enjoy.

Aye,
Marty
Grandma used to say, "Beware of too much of a good thing."
Ref: www.mha-net.org

 

[Bill]

I thought about adding a screen for my stove, for the shoulder season's, and there is a company that makes one. But I checked with the manufacturer and my stove is not tested nor rated to be run with the doors open.

 

[ksting]

That looks kind of like a Lopi Freedom Bay which is designed to run with the doors closed. Running it with the door open or with a bad seal on the door gasket will most likely cause an overfire condition. If it doesn't overfire, you'll still burn through your wood too fast.