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-   -   outside fireplace not drawing (http://www.diychatroom.com/f105/outside-fireplace-not-drawing-166878/)

perkinstl 12-19-2012 10:11 AM

outside fireplace not drawing
 
Smoke pours out of the front of my new outside masonry fireplace. While the smoke does rise through the chimney, a large amout of smoke also comes out the front continuously. The firebox is approximately 72" wide at the opening, 34" high, and 38" deep. The rounded masonry ceiling rises approximately 18" to the 8-foot chimney which is comprised of 17" x 17" masonry flues that are each 2' long (a total of 4 flue pipes= 8'). The chimney is in the center of the firebox.

The fireplace is located approximately 35' from the closest point in my residence to the north. The masonry residence has 10' ceilings with a 10pitch hip-style roof. The 2 adjacent residences are approximately 50' away to the south and west.

The mason temporarily added an additional 2'-17" flue to the chimney (10' total) with no reduction from the smoke pouring out the front.

Any suggestions?

joecaption 12-19-2012 10:16 AM

http://www.askthebuilder.com/firepla...gn-dimensions/

tony.g 12-19-2012 10:27 AM

Is it possible that the flue itself is in a cold position? If so, it can take a lot longer for the flue to warm up. If the flue is relatively cool, the cool air in it tends to press down on the warmer air from the fire (because the cooler air is heavier) and prevents all the smoke going up, thus forcing it back out of the fireplace opening.
Where I am most domestic construction is masonry, and it is well-known that fireplaces/flues on external walls often don't draw well because they remain damp and cool.

perkinstl 12-19-2012 10:35 AM

Quote:

Originally Posted by tony.g (Post 1076009)
Is it possible that the flue itself is in a cold position? If so, it can take a lot longer for the flue to warm up. If the flue is relatively cool, the cool air in it tends to press down on the warmer air from the fire (because the cooler air is heavier) and prevents all the smoke going up, thus forcing it back out of the fireplace opening.
Where I am most domestic construction is masonry, and it is well-known that fireplaces/flues on external walls often don't draw well because they remain damp and cool.

Thanks for your response. The new fireplace has not been used for any extended period.. so perhaps the flue did not had sufficient time to 'warm-up.

Tscarborough 12-20-2012 07:30 PM

A 17x17 flue is not large enough. In general, the flue needs to be at least 10% of the opening, and that is with a "normal" stack of 15+ feet and not exposed to wind.

72"x34"=2448 SqIn, a 17x17 square flue has an interior working surface area of approximately 177 SqIn (for square flues, you consider it round and use that dimension, which for a square flue is the outside dimension, the thickness of a 17" flue is around an inch, so 3.14159(7.5 squared)=177).

Not much you can do at this point, other than increase the height of the stack and build a small warming fire to heat the flue before you build a normal fire. Personally, I would put gas logs in it and call it good, because without a bigger flue it will always smoke.

perkinstl 12-21-2012 07:37 AM

Thank you .

tony.g 12-21-2012 11:50 AM

Quote:

Originally Posted by perkinstl (Post 1076011)
Thanks for your response. The new fireplace has not been used for any extended period.. so perhaps the flue did not had sufficient time to 'warm-up.

Also remember that if it is new, the masonry will still contain a lot of water. This will take time to dry out and, in the meantime, will tend to keep the chimney cool.

itsreallyconc 12-22-2012 06:26 AM

howzabout mounting an exhaust fan on top to suck out the smoke ? :whistling2:

jomama45 12-22-2012 10:14 AM

How about a picture or two, the FP opening seems like an odd profile size......You could probably try choking the opening off (width-wise) first to see if that helps, because as Tscar noted, the flues are too small for that big of an opening..........


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