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Old 11-24-07, 10:45 PM   #1
Portis
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Why is my fireplace hotter?

For years now i have always wondered why my fireplace never puts out as much heat as my father in law's and also my uncles'. My fireplace always seemed to burn wood faster than theirs and never put as much heat into the room.

I just always attributed it to the fact that their's was designed better than mine. But after observing my father in laws one more time over thanksgiving it sort of dawned on me. He always burns his with out a screen or doors, just a fire open to the room.

I have always burned mine with my cast iron screened fireplace doors closed. I figured it wouldn't matter because like i said, they are screened. So anyway, last night i decided to try with the doors open compeletly and just fire exposed directly to the room.

Wow! What a transformation. The effect was nearly immediate. The room quickly grew to an almost intolerable temp. Anyway i repeated the procedure today and the findings are conclusive. It was 80F in there today and i had to put shorts on.

So now i ask why? I know that obviously there is more heat going into the room. Also the wood is burning MUCH slower than before. But why would a set of iron doors with mesh screen make such a huge difference? What is the scientific basis for what is going on here?

Last edited by Portis; 11-24-07 at 10:53 PM.
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Old 11-24-07, 10:59 PM   #2
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How open is the mesh? My first thought would be that with the doors open, the fire is getting that much more oxygen, and is thus able to burn more efficiently and hotter. I wouldn't think the wood would last longer if that were the case, though.
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Old 11-24-07, 11:46 PM   #3
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Could also be a factor of the cast iron grate absorbing a lot of heat causing some of these effects. Holding the heat in the fireplace instead of letting it out? I don't have a degree in thermodynamics though.
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Old 11-24-07, 11:48 PM   #4
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convection.
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Old 11-24-07, 11:54 PM   #5
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The screen holds more heat inside the fireplace, which increases the draft.

Therefore you have a lot more air (AND HEAT) going out the chimney.

The increased airflow across the fire increases the rate at which it burns, makes it even hotter, which increases the airflow....
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Old 11-25-07, 12:18 AM   #6
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The screen holds more heat inside the fireplace, which increases the draft.

Therefore you have a lot more air (AND HEAT) going out the chimney.

The increased airflow across the fire increases the rate at which it burns, makes it even hotter, which increases the airflow....
Correct. Great Reply.
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Old 11-25-07, 12:41 AM   #7
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Quote:
Originally Posted by Portis View Post
For years now i have always wondered why my fireplace never puts out as much heat as my father in law's and also my uncles'. My fireplace always seemed to burn wood faster than theirs and never put as much heat into the room.

I just always attributed it to the fact that their's was designed better than mine. But after observing my father in laws one more time over thanksgiving it sort of dawned on me. He always burns his with out a screen or doors, just a fire open to the room.

I have always burned mine with my cast iron screened fireplace doors closed. I figured it wouldn't matter because like i said, they are screened. So anyway, last night i decided to try with the doors open compeletly and just fire exposed directly to the room.

Wow! What a transformation. The effect was nearly immediate. The room quickly grew to an almost intolerable temp. Anyway i repeated the procedure today and the findings are conclusive. It was 80F in there today and i had to put shorts on.

So now i ask why? I know that obviously there is more heat going into the room. Also the wood is burning MUCH slower than before. But why would a set of iron doors with mesh screen make such a huge difference? What is the scientific basis for what is going on here?
If your really serious about heating with wood you need an EPA insert or Woodstove. An open fireplace draws cold combustion air through all the cracks and crevices to bring cold air into your house. The area within 10 feet of the fireplace will be warm but the bedrooms will be frigid. An air tight stove uses less combustion air and has more heat transfer to the house and at the same time it will require a zillion less wheel barrows of wood. I heat my 3 story house on 1 heaping wheelbarow load of wood @ 32F per day. Thats real heating where all the rooms are warm. Best investment ever was the woodstove and its a super place to lounge after a winter bike ride. Plus the warm house makes the wife happy.
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Old 11-25-07, 12:58 AM   #8
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I wish I had a woodstove here. Damn gas heat.
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Old 11-25-07, 01:25 AM   #9
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I can remember the last time I started a nice roaring fire in the living room one frigid winter night...

You never heard so much carrying on about not having a fireplace in your life.
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Old 11-25-07, 09:11 AM   #10
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Good replies. Sounds logical. I don't want an insert. I've always mainly considered the fireplace to be an aesthetic fixture, as i love having the open flame and crackling fire. I was just more inquisitive from a curiosity standpoint as to why my fire always burned differently. Now i know..
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Old 11-25-07, 09:15 AM   #11
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It may heat better, but if you are going to use a fireplace with no screen at all make sure that nothing combustible is anywhere near the fire. One good pop from the fire can send an ember a surprisingly long distance.
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Old 11-25-07, 09:18 AM   #12
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It's not your fireplace... It's the inside of your walls. They are smoldering, generating the heat. They will continue to do so till it burns thru, when it does the fire will flaks burning the structure to a crisp immediately, just like in an old Woody Woodpecker cartoon.

Enjoy the warmth.
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Old 11-25-07, 09:19 AM   #13
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It may heat better, but if you are going to use a fireplace with no screen at all make sure that noting combustible is anywhere near the fire. One good pop from the fire can send an ember a surprisingly long distance.
^^^ My thoughts exactly.

We had wood "pop" and out came a firey hot little bastid. Sucker flew at least five feet across and onto the carpet. Good thing I was right there when it happened.
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Old 11-25-07, 09:22 AM   #14
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Airflow and BCM nailed it.
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Old 11-25-07, 09:59 AM   #15
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It obviously requires more caution to operate the fireplace with the doors open, but I burn ash which doesn't spark.

I have thought about replacing the doors but they were made by a German prisoner of war sho ended up living in this community and it has more "character" than a lot of them you see in the store. Even if it ain't the purdiest.

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Old 11-25-07, 10:08 AM   #16
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Whoa. Nice little pile up of ash there. Better get a shovel.

And don't forget to clean out the chimney every other year. My neighbor had a chimney fire and that was scary.

That grate is the kind that directs heat into the house, I need to get one of those.
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