fireplace smokes, firebox not made right


  #1  
Old 10-02-12, 02:24 AM
M
Member
Thread Starter
Join Date: Oct 2012
Location: USA
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
fireplace smokes, firebox not made right

We have an outdoor fireplace built by a contractor who built our flagstone retaining walls. It smokes out the front of the firebox when we try to use it.

The flue size to opening is correct. However, the roof of the firebox itself is flat. We have been told that it needed to be sloped to trap gasses and direct them up the flue. Is the correct?

If it is, what can we do? We can't afford one of those fans. Will a smoke guard help? Are there convection grates that might help? Fans that work off of heat, .... Some combination of stuff?

We would love to use this fireplace. Can anyone out there help?

Thanks
 
  #2  
Old 10-02-12, 03:03 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 36,607
Upvotes: 0
Received 9 Upvotes on 8 Posts
Welcome to the forums! I would invite the contractor back to fix it properly. If he wasn't a certified fireplace contractor, he probably didn't build it properly. As you stated the inside of the firebox must be angled in the back in order to create a vortex and take the smoke up the chimney. The only thing I can offer, aside from having it done correctly, is to put a fireplace insert in the opening. It would, at least, have the correct inner workings.
 
  #3  
Old 10-02-12, 03:20 AM
M
Member
Thread Starter
Join Date: Oct 2012
Location: USA
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
I think we're past fixing it. Tearing it out and replacing it would cause more issues. Is it possible to get an insert that provides the required slope (vortex), maybe just reshape the back of the box and provide a slope up into the flue or do you think a whole new firebox insert is needed.
 
  #4  
Old 10-02-12, 04:08 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 36,607
Upvotes: 0
Received 9 Upvotes on 8 Posts
I don't think you can retrofit an already built unit to where it will work correctly. Complete tear down and rebuild would be necessary. Placing an insert in the unit would have the correct slopes necessary for proper draw. You may want to post pictures of your fireplace (not close ups) so we can see what you see. A close up of the inside of the firebox may help. http://www.doityourself.com/forum/el...your-post.html
 
  #5  
Old 10-02-12, 04:47 AM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 9,500
Received 68 Upvotes on 62 Posts
Yes, pics would help.

It might be possible that increasing the chimney height would crate additional draw and you may be able to do this with a metal adapter.
What is size of the firebox and what size and height is the chimney?
 
  #6  
Old 10-02-12, 06:05 AM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 9,460
Received 47 Upvotes on 43 Posts
Yes, pictures would help, Chandler's link will help.
Height of chimney?
Is the chimney masonry or metal? I assume masonry, thus slow to warm up.
The height of the chimney and the difference in temperature between inside and out determines the draft pressure. If you are a geek like I am:
p = .0067 x h x t
"p" will be in pascals
"h" height of chimney in feet
"t" in degrees F
The actual number you need for pressure is difficult to determine, as a breeze flowing over some trees or a house next door will push down on that flat roof. But the equation tells us, the more heat in the chimney the better and the more height the better.

My first thoughts are a taller chimney as GregH suggested and maybe, in combination with, a metal chimney insert that will heat up faster. But pictures if you can.

Bud
 
  #7  
Old 10-02-12, 11:40 AM
M
Member
Thread Starter
Join Date: Oct 2012
Location: USA
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
pictures and measurements

first, wow, thanks for all the help.
two pics attached.
one from the front.
the other so you can see the problem with the firebox.
as you can see we tried extending the chimney a little
and yes, its all masonry

the opening is 39X21, the box is 31" deep.
the flue pipe is 12" in the first section and 15" in the extension.
from the top of the firebox to the top of chimney (where the opening is, not all the way to the top) is roughly 5 feet.

[ATTACH=CONFIG]3924[/ATTACH][ATTACH=CONFIG]3925[/ATTACH]
 
Attached Images   
  #8  
Old 10-02-12, 01:07 PM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 9,460
Received 47 Upvotes on 43 Posts
Wow is right, I can see what happened. The unfortunate traditional view of hot air is that it rises by itself and "pulls" a draft behind it, thus he thought the smoke going up the chimney would continue to pull more smoke behind it. What really happens is, the warm air gets pushed up the chimney (because it is lighter) by the surrounding cold air and without some sloped surfaces, all of that smoke is having a hard time finding that chimney opening. Some of the smoke will go up the chimney, but some will bounce off that flat area around it and, well you know where it goes.

It is a shame, as there are so many resources available that any amateur can copy a design without knowing how a fireplace works.

Faced with major modifications or patch work that I'm not sure would fix it, let me try another approach. I've seen small metal fireplace units with a chimney coming straight out the top. If you could fit one in, it would at least give you something to enjoy while you wait for a better time (and more planning) to tackle a long term fix.

The patch I was thinking of, and no assurances it will help the problem, would be a metal front similar to the nose on a range hood. It would extend out a bit and provide a slope up and towards the chimney opening.

Let's see if others have any ideas.

Bud
 
  #9  
Old 10-02-12, 02:37 PM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 9,500
Received 68 Upvotes on 62 Posts
Bud's idea is pretty good and a simple way to experiment is to install a metal flashing along the top edge to allow the flue gas to heat up the top portion of the firebox to create some draft.
You might try reducing the height by about 6 inches or so and see what happens.

You could attach it by using a lead anchor and metal screws to hold the strip in place.
Paint it flat black and it would look like it belonged.

Another course of action is to call the folks that built it and have them make it right because I assume you paid them to build it.
 
  #10  
Old 10-02-12, 04:01 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 36,607
Upvotes: 0
Received 9 Upvotes on 8 Posts
Good suggestions. One concern I have is I see no lintel to hold those horizontal stones in place. What is to keep them from bellying down and falling??
 
  #11  
Old 10-03-12, 07:57 AM
M
Member
Thread Starter
Join Date: Oct 2012
Location: USA
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
This sounds like a smoke guard. Like you would buy if the opening to flue size was wrong. I have found them in custom lengths and spring loaded so you fit them in without having to anchor them. Do you think that and then maybe a metal pipe inside the flue to create more heat might work?

I don't really understand the insert idea.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: