# Smoking fireplace



## artisanstone (Nov 27, 2007)

Maybe you guys can give me some perspective on this. I built an outdoor fireplace a few weeks ago. The homeowners call me today to say that it does not draft. Of course I say "no problem, I stand behind my work, I'll be there tomorrow, etc". I'm rehearsing possible scenarios in my head about why this would happen. I'm hoping that the poor people just don't know how to build a fire, but:shutup:

The facts:
-Firebox is 36x24 or so.
-Flue liner is 16x16 (Big because outdoor fireplaces are not tall....maybe this is the problem).
-Chimney height is about 6' above firebox floor, plus a 2' chimney pot.
-Fireplace is built to a plan by the BIA. They call it a Rumford, but it really isn't. Only modifications are, no damper, shorter, and arched opening.

Suspected problems:
-Fireplace is at the bottom of a very steep partially wooded lot. 3+ story house absolutely looms above. House is probably 150' away and 60' higher at the top.
-Chimney pot is considerably smaller than the flue. Homeowners already had it (antique). It measures about 13x13.
-I've never built a fireplace to this plan before. It was chosen to reduce cost.

I'll post more if I think of more. I realize that most of you won't be around on Friday evening, but TIA.


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## Tinstaafl (Jan 6, 2008)

artisanstone said:


> -Fireplace is built to a plan by the BIA. They call it a Rumford, but it really isn't. Only modifications are, no damper, shorter, and arched opening.


What's shorter; the firebox or the flue? A smaller firebox shouldn't hurt, though the arched opening could affect the _pattern_ of airflow--i.e., air that would normally enter lower and closer to the fuel would come in a bit higher and not fan the fire quite as much.

I could be wrong, but I doubt the location/surroundings as described play much of a role. I've built many _open_ fires in just about every type of locale, and none have affected their efficiency much at all.



> -Chimney pot is considerably smaller than the flue. Homeowners already had it (antique). It measures about 13x13.


That's a definite eyebrow-raiser. Obviously, that's going to choke the draft down a bit. I wouldn't expect it to be an extravagant amount, though.

Other thoughts...

How many fires have they tried? Some days, the combination of barometric pressure, temperature, humidity and bad karma make a wood fire burn frustratingly poorly even in a well-designed and normally well-functioning setup. Maybe try again after a significant change in the weather.

What fuel are they using? Take some good dry oak with you and try that out. 

Are they burning on the floor of the firebox, or an elevated grate? Big difference there.

But I agree, there's probably a good chance they just don't know how to build a fire--or maybe what "good draft" is. :laughing:

And for typing all this after a long day of shingling, I demand a pic! :w00t:


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## Tscarborough (Feb 25, 2006)

The pot shouldn't be a problem, as that is the size needed for a 36". The height of the chimney could be an issue but probably isn't. The placement sounds good. What is the depth and did you use a Rumford style throat and smoke chamber? Is there a smoke ledge?


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## dbrons (Apr 12, 2010)

yes, I agree. Often, the problem lies in what's between the firebox, and the first flue. 

I almost always use a damper on an outdoor fireplace, but with or without, you need a throat above the lintel, and a chamber shaped kinda like a funnel to direct the smoke into the flue.

Dave


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## artisanstone (Nov 27, 2007)

The throat and smoke chamber are built to this plan. http://docs.google.com/viewer?a=v&q...o1GLa_&sig=AHIEtbRwhCHqC_PRcCrxMA1oe14kfvadGA

Smoke chamber is made with two cut-down liners. There is two feet of chimney above the smoke chamber, and then the pot on top.

They've only tried burning it twice. They seem to be a little smoke sensitive, as this was built to replace a previous fire-pit because it was too smoky.


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## jomama (Oct 25, 2008)

Two things I notice from the link:

- The smoke chamber is only 12" high, so your only at about 4-5 feet above the firebox. Could be a tad short for this site. I normally would cut the SC a full 2' high if I was making it myself.

- You missed the detail in the drawing for the gas log set. Once you install that, all smoking problems will vanish.

Seriously now, I have this problem at home occaisionally, as the opening of mine is facing West, to prevailing wind. Good, dry wood is critical, as well as burning upright or "tee-pee" style. When burning that way, you'll be suprised how fast the smoke rises.

Good luck.


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## dbrons (Apr 12, 2010)

Thanks for showing the design. It looks real official, but frankly, I wouldn't trust that design. 

The throat looks fine, though with an arch you would have to have it extend from the arches highest point, not from the low points. 

The design has no smoke chamber - the flue sits right down on the damper. That's not good, and *without the damper* to at least funnel the smoke, you probably have too abrupt a transition into the flue. That, and I wouldn't really trust how shallow it is either, but that may just be me. I know a lot of people use the Rumfod design, but I always modify them and make them deeper.

I'm not sure how to suggest a fix. You could try removing the pot and replacing it with one or two flue pipes stacked up there dry, to see if that helps. You could raise the floor of the firebox with another layer of firebricks, or lower the arch.

Dave

PS Joe makes a good point - this is suggested for a gas log, not wood.

PPS OK, I do see now that this is a kit with a smoke chamber, I had just looked at the side view and didn't notice. 

Still, as Joe suggested, when you build one with brick, it's usually at least 2' tall.


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## Tscarborough (Feb 25, 2006)

That is not a Rumford other than the depth. My understanding of the design, based on the Count's own words are that the throat cross section is critical when building that shallow. An arched opening will make it even more critical.

I would just show them how to light a slow starting fire to warm the flues and expect some smoking since it is outside.


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## bytor (Jan 23, 2010)

dbrons suggestion is a good one...to remove the chimney pot and dry stack a couple (or three) of flue liners up to see if there would be any benefit to additional chimney height. We've run into this problem on occasion, and it's surprising what a little extra chimney height can do....


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## jvcstone (Apr 4, 2005)

One other thing to consider--a good draw depends on a temperature differential between the air feeding the fire, and the air surrounding the flue top. That's not often the situation with outdoor fireplaces--especially if it is being used on a relatively warm night. I've built several outdoor fireplaces, but always let the client know that there might be draw problems some of the time. and explained why. Thus, never a call back.

JVC


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## dakzaag (Jan 6, 2009)

This thread is worthless without pics. :w00t:

With pics, it could be one of the most informative masonry pics this site has ever seen.:thumbup:

Lets see some pics


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## artisanstone (Nov 27, 2007)

OK, I went to look at it today. (Sorry, no pics as of yet.) I burned a fire in it, and it draws surprisingly well! The problem is that when the wind blows, it will blow some smoke out of the firebox. Meanwhile, it is still streaming out of the flue. I put my hand above the chimney pot (climbed up it ) and there is good velocity of exhaust up there. The other thing I noticed is that the smoke, after leaving the flue, was going back down to the ground and flowing along it. This makes me suspect air pressure problems as discussed before. 

I saw a couple of things I could have done better, and these will be fixed. The breast could be more streamlined in shape, and I may add a half-brick course around the immediate firebox opening to try to reduce some wind effects. 

I think that the owners may be hypersensitive to smoke, and I will suggest a glass door as the only complete solution. Thanks for the advice, I'll let you know how it works out, and I'll get some pictures.:thumbsup:


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## MALCO.New.York (Feb 27, 2008)

As with many open flow systems, one may need to preheat the Stack Vent. Light a wad of Kindling Paper, hold into Flue, allow there to begin an up-draft! Should rectify the situation.


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## cdkyle (Jul 12, 2009)

Lintel or arch opening is probably too high off floor of firebox. Lower the lintel or install glass doors. On that size box, the height of lintel should not exceed 24". Seen many set at 27" and above, and they have the same problem.


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