Indoor Fire Pit


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Old 02-05-13, 09:44 PM
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Indoor Fire Pit

I have an idea that involves putting this:



inside of this:



My searches for examples have not been very successful. I did find this image:



My question is: if I put a fire pit of that size inside a cathedral ceiling'd structure, what size would the vent need to be, and how high could I raise it above the pit safely? I would prefer not to have a forced air system if possible.

I realize I may not get an answer, but a little direction would be helpful. Who can I contact for more information, or what is a good resource for venting design?

Thanks for your help.

-Derpinger
 
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Old 02-06-13, 03:13 AM
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Welcome to the forums! Oh, you'll get an answer, although it may not be what you want to hear. First and foremost, contact your insurance company and building authority, as I don't know if either will approve such unless architectural drawings are submitted, along with approved exhaust system designs.
 
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Old 02-06-13, 04:56 AM
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Welcome to the forum.
Larry nailed what I was going to say on the head.

It may be different in other areas, but locally here, I see a few things my insurance company would toss this idea out for.
The chimney running through the interior of the house (new construction and refurbished construction) is really tough to get the insurance company to accept.
The open burning (not in an enclosure like a fireplace or wood stove) would be a huge insurance risk. Not only is there the spark and flying embers issue, there is no safe guard from someone sticking oversize wood (too long) which would also set the building on fire. Ignoring the fire risk, the open burning means smoke and uncontrolled CO2. Your chimney would probably need to be fan forced, and even with that, there is no guarentees that it will be turned on when in use or that a cross wind (other fan, etc) would move some smoke and CO2 out of the chimney hood area.

Assuming the building in picture #2 is what you are looking to put this in, what would the primary purpose of this be? Looks or Heating?
 
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Old 02-06-13, 05:45 AM
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Thanks yall for the replies.

I would ignore the insurance concern for now. Think of it as a thought experiment.

The pit would be both for looks and heating.

You mentioned smoke and uncontrolled CO -- I thought a properly designed chimney would create a draft to remove those things. From reading things like this: http://www.woodstove.com/pages/guide...od_Chimney.pdf I get the idea that a sufficiently tall and wide flue, and perhaps a little insulation, would suck anything away from the pit.

Obviously a chimney company would be a logical contact, but I was hoping to do some research on my own and gain an understanding before contacting one.
 
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Old 02-06-13, 05:47 AM
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A sealed combustion solution would be much better. Search "see through fireplace".
Here is one with nice pictures: See Through Fireplace Design, Pictures, Remodel, Decor and Ideas

Bud
 
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Old 02-06-13, 06:33 AM
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Have you considered vent free gas logs? Fireplaces are notorious for wasting energy by letting most of the heat go up the flue. I imagine a free standing fire pit would be even worse.
 
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Old 02-06-13, 06:51 AM
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When a fireplace is in full swing, yes, most smoke and CO can go up the chimney as desired. However, downdrafts and end of fire operations can result in larger amounts of CO and insufficient draft to exhaust same. Fall asleep in front of a nice fire and never wake up.

As for heat, all studies have shown a net loss of energy due to more heat going up the chimney than they generate. A sealed combustion unit uses all outside air and can produce more heat than it wastes. And they are safer.

One other consideration is the lack of any screening on that unit pictured. I have experienced hot coals being ejected more than 20 feet across a room when something decides to snap inside the fire. Fortunately I saw it and no problem. We also had a couch when growing up the ended up with a mysterious burn spot where an ember was ejected and no one saw it. Scary.

Bud
 
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Old 02-06-13, 07:19 AM
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For looks? Sure, that does look cool.

For heat? Pretty sure this would be a heat loss rather than a gain with all of the house air you would have to eject up the chimney to be safe.
 
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Old 02-06-13, 07:20 AM
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When a fireplace is in full swing, yes, most smoke and CO can go up the chimney as desired. However, downdrafts and end of fire operations can result in larger amounts of CO and insufficient draft to exhaust same. Fall asleep in front of a nice fire and never wake up.

As for heat, all studies have shown a net loss of energy due to more heat going up the chimney than they generate. A sealed combustion unit uses all outside air and can produce more heat than it wastes. And they are safer.

One other consideration is the lack of any screening on that unit pictured. I have experienced hot coals being ejected more than 20 feet across a room when something decides to snap inside the fire. Fortunately I saw it and no problem. We also had a couch when growing up the ended up with a mysterious burn spot where an ember was ejected and no one saw it. Scary.

Bud
The risks Bud mentions may appear to be one off chances to us, but the insurance company....

A few restraints and lodges I've seen with a central fireplace had a screen coverage and very low chimney hood over the fire. From a fire marshal's perspective (and probably and insurance compny's perspective, it's an enclosed fireplace. Most cases, it was more for show, and less for heating.
This may work for you.
 
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Old 02-06-13, 07:35 AM
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Dane has already voiced my suggestion, gas logs. Still there would be more of a personal safety concern both trip and fall (adults and children) and young children attracted by the fire that would be greater than with a conventional fireplace.
 
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Old 02-06-13, 09:54 AM
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Northern Mike: I think that would work. I like the idea of the chain mesh screen hanging around the inverted vent cone.

I get the heat loss argument, but there must be ways to increase the pit's heat capacity through material choice and design.
 
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Old 02-06-13, 10:08 AM
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The problem from a heating standpoint is you have to make sure the exhaust gases go up the chimney and not into your house. From a practical standpoint with an open design, you can only do that by having a lot of air go up the chimney, which takes a lot of heat with it and causes your house to have a lot of cold air infiltrating from the outside to make up the difference. Now, if the combustion chamber is sealed, you can bring in all the air you need directly from the outside into the combustion chamber and then only that air goes back up the chimney, allowing you to recover often a considerable amount of heat.
 
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Old 02-06-13, 10:16 AM
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@ Derpinger "I get the heat loss argument, but there must be ways to increase the pit's heat capacity through material choice and design."
There are three modes of heat transfer, convection, conduction, and radiation. Conduction is eliminated with the open space around it. Convection is, by necessity, sending that heat up the chimney. That leaves only radiation, which feels nice but accounts for less than (rough number) 1/3 of the thermal energy. But there are materials and designs to increase the pit's heat capacity, called a sealed combustion fireplace.

I love a fireplace but switched to a sealed glass front unit many years ago and have since been enjoying both the aesthetics and the efficiency. With a center of the room design, a physical barrier is needed to prevent someone from falling into the pit. Search that and there are stories.

Bud
 
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Old 02-06-13, 10:23 AM
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Keep in mind that fireplace design and efficiency is nothing new and is something people have been working hard on for hundreds of years. You are not (I say with 99.99999999% certainty) going to be able to come up with some magical way to make an open fire more efficient than has already been done.
 
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Old 02-06-13, 05:44 PM
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I get where you're coming from. However the idea was to put a fire pit, much like at a campsite, inside an empty barn with a dirt floor, benches, and tables. My concerns were mainly CO.

Shouldn't a fire pit built from materials with a high heat capacity be warmer than a camp fire sitting outside on the ground? I'm not concerned about efficiency. This will be an infrequently used feature that will burn lumber from trees on the the property.

Sorry if I haven't been clear about the goal.
 
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Old 02-06-13, 08:44 PM
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OK, yeah, that might be warmer but we're not talking about the fireplace being in a heated structure anymore and, at least IMO, that makes a big difference.

You still want to make sure you have adequate make up air for the combustion and loss up the chimney but an old barn ought to be pretty darn leaky to air whereas a house is supposed to not be, hence you're essentially degrading the efficiency of the house for safety from combustion gases.
 
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Old 02-07-13, 05:22 AM
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If you are not having a fire in a heated space than there is not much to loose with a large open flue. How long will the fire be burned when it's used?

If just an hour or so I think you would be best off with the fire sitting on the ground and largely uncontained. The infra red from the fire could radiate out with being impeded by a surround. If you build a heavy surround it will eventually heat up but will take some time. Before it heats up anyone around the fire will have cold feet & legs. And the heat absorbed by the surround will be released after the fire dies and you've left. The longer you plan on burning the fire I think it lends itself more to having a massive surround to moderate it's heat output somewhat.
 
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Old 02-07-13, 07:50 AM
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@ Derpinger:
I get what you're trying to accomplish and I'm sure I've seen similar in old movies with ski lodges in the Alps or whatever.
I'm sure you'd get very different responses in a Swedish DIY forum

I hope you can find a way to safely accomplish your "sheltered campfire" goal...sounds cool. Just make sure you do consider all the safety issues. Don't want to read about you suffocating a Boy Scout troop...
 
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Old 02-09-13, 05:48 AM
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A packaged fireplace system open on two sides would keep you within UL safety standards, and give you the open fire look you're looking for...if it's ok with local code officials and Ins co
 
 

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