three story chimney too tall?

Reply

  #1  
Old 03-05-18, 08:53 PM
Member
Thread Starter
Join Date: Apr 2012
Location: USA
Posts: 163
three story chimney too tall?

Hi

Have house with two fireplaces. One has two story chimney and draws fine. Other has three story chimney and does not draw well, room gets smokey.

Is three stories just too much? Or should I search further for a reason?

Thank you
 
Sponsored Links
  #2  
Old 03-06-18, 04:03 AM
Member
Join Date: Jan 2017
Location: USA
Posts: 368
How much of the chimney is exposed to the outside environment? Is more of it exposed to the outside elements, (greater distance above the roof), than the chimney that draws? Are there any obstructions that are closer to the poor drawing chimney than the good drawing chimney? Is the top of the chimney beneath any other obstruction such as a higher roof or hillside. Is the chimney constructed exactly the same as the good chimney? Is it the same relative dimension inside as the good chimney? Is the inside surface clean of debris and a build-up of soot or creosote . Things such as air currents, higher obstructions , outside exposure to the elements (cools the chimney) will affect it's draw. Usually the higher the chimney the greater the draw. I worked in the commercial and industrial boiler business and was amazed as to things that affected chimney draw (draft).
 
  #3  
Old 03-06-18, 04:07 AM
Forum Topic Moderator
Join Date: Mar 2005
Location: USA
Posts: 44,363
Is the inside surface clean of debris and a build-up of soot or creosote .
That was my first thought. When was the last time the flue was cleaned? are you able to inspect it?
 
  #4  
Old 03-06-18, 05:59 AM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 18,337
There are many books and articles that tell you all about fireplaces and how to build them so it works. This is old tech that was worked out hundreds of years ago. Many things affect whether or not a fireplace will draw and the chimney is just one. The shape and size of the firebox, throat and smoke shelf can also affect how well it draws.
 
  #5  
Old 03-06-18, 08:02 AM
Member
Join Date: Oct 2008
Location: New England
Posts: 10,136
Sorry PD, had to chuckle a little as you are echoing old school and ironically they never new and still don't understand how a chimney drafts. Too long to explain here but I'll let you know when the book comes out.
Basically chimneys don't draw, the warm air goes up because it is being pushed by heavier cooler air from below.

My question for engrav is, is the problem fireplace located one story down resulting in the taller chimney. A fireplace in a basement is subject to natural house pressures which combined with a cold chimney can make it a problem getting the smoke pushed up and out.

I'll wait for the op.

Bud
 
  #6  
Old 03-06-18, 09:25 AM
Member
Thread Starter
Join Date: Apr 2012
Location: USA
Posts: 163
Hi and thanks

How much of the chimney is exposed to the outside environment?
3 or 4’ pic below

Is more of it exposed to the outside elements, (greater distance above the roof), than the chimney that draws?
Both are the same.

Are there any obstructions that are closer to the poor drawing chimney than the good drawing chimney?
Don’t see any.

Is the top of the chimney beneath any other obstruction such as a higher roof or hillside.
Don’t see any.

Is the chimney constructed exactly the same as the good chimney?
I think so.

Is it the same relative dimension inside as the good chimney?
I think so.

Is the inside surface clean of debris and a build-up of soot or creosote .
Just had both cleaned.

Are you able to inspect it?
I can look up inside.

My question for engrav is, is the problem fireplace located one story down resulting in the taller chimney.
Problem fireplace is one story down, on the ground floor, and so taller chimney.

Thanks again.
 
Attached Images  
  #7  
Old 03-06-18, 10:51 AM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 18,337
Has the problem fireplace ever drawn well or has it always had a problem? If it worked previously but doesn't now then I'd give the chimney a thorough inspection for obstructions. Birds may have built a nest inside or maybe the damper isn't opening properly.

If that fireplace has always had trouble drawing I think you are best reading up on fireplace design. What works and what doesn't was worked out hundreds of years ago and is very well documented in numerous books and on the Internet. We can't see your fireplace or measure it's dimensions so that part you'll have to do on your own. But, if you find that there is a design or construction problem with the fireplace then you can address it. Many texts describe methods to help make problem fireplaces draw better.
 
  #8  
Old 03-06-18, 10:56 AM
Member
Join Date: Oct 2008
Location: New England
Posts: 10,136
Both look to be inside chimneys so mostly warm, exception being the exposed section above the roof and whatever is exposed inside the attic, assuming it is a cold attic. Test both on a cool or cold day when not in use using a small piece of paper, light it and blow it out and holding it inside the fire box see which way the smoke goes. If the smoke goes up in either then that one is in good shape. If both backdraft then cold air is flowing down against the air pressure inside the house.

The working one is either exhausting inside air all the time or with less cold air above the fire box it is able to start and maintain the proper flow.

The non-working chimney is apparently not able to develop a sufficient large or warm volume of air directly below the chimney to offset the weight of the cold air above.

Note, all of this assumes the the fire box does not have a leak.

Be careful with the age old advice of opening a window. For one, it would be best if the window were lower than the fire box as doing so shifts the house pressure towards the new opening.

Window above firebox makes air pressure in front of fire more negative.
Window below firebox makes air pressure in front of fire more positive. And more positive is what you want.

There are other devices like exhaust fans that can result in backdrafting and there is a caution. Once a problem fireplace is forced into working there is a risk when the fire dies out. Buried coals produce large quantities of CO and lower amounts of heat. If the heat isn't sufficient to maintain the upward draft, worse if someone closed that window, then backdrafting may resume but with CO and no smoke.

They make draft inducing fans fro stubborn fireplaces.

Bud
 
  #9  
Old 03-06-18, 05:37 PM
Member
Thread Starter
Join Date: Apr 2012
Location: USA
Posts: 163
Has the problem fireplace ever drawn well or has it always had a problem?

Donít really know this as we have not lived here long and this fireplace is rarely used.

Both look to be inside chimneys so mostly warm, exception being the exposed section above the roof and whatever is exposed inside the attic, assuming it is a cold attic.

There is no attic. Chimney goes thru bedroom and out the roof.

Test both on a cool or cold day when not in use using a small piece of paper, light it and blow it out and holding it inside the fire box see which way the smoke goes. If the smoke goes up in either then that one is in good shape. If both backdraft then cold air is flowing down against the air pressure inside the house.

Will do the test.

The non-working chimney is apparently not able to develop a sufficient large or warm volume of air directly below the chimney to offset the weight of the cold air above.

Well the one the basement certainly has a taller chimney to deal with, maybe 15í.


Window above firebox makes air pressure in front of fire more negative.
Window below firebox makes air pressure in front of fire more positive. And more positive is what you want.

Windows are above the firebox.

There are other devices like exhaust fans that can result in backdrafting and there is a caution. Once a problem fireplace is forced into working there is a risk when the fire dies out. Buried coals produce large quantities of CO and lower amounts of heat. If the heat isn't sufficient to maintain the upward draft, worse if someone closed that window, then backdrafting may resume but with CO and no smoke.

Got it. Thanks.
 
  #10  
Old 03-07-18, 04:04 AM
Member
Join Date: Jan 2017
Location: USA
Posts: 368
The draft (negative pressure) in the chimney is dependent upon the temperature of the flue gasses. Hot gasses are lighter than the surrounding air are flow upwards, if those gases cool, they become heavier and tend to stratify or fall. That is one reason for a cold chimney not to draw and in many cases will reverse flow or have a down draft. The problem with the longer chimney may be that the flue gasses are cooling due to their longer distance of travel. A fireplace chimney that is used with a small pellet stove for instance, may never heat the air in the chimney enough to have an upwards flow and sometimes need a draft inducer of some type. Larger boilers that I serviced and started had this problem especially at the lower or minimum firing rates. Sometimes the chimneys would reverse flow when the boiler.s input was reduced for a long period of time and would have to be outfitted with a draft fan.
 
  #11  
Old 03-07-18, 06:37 AM
Member
Join Date: Nov 2012
Location: USA
Posts: 908
Wild guess, try leaving the basement door open, see if the fireplace draws.better.

Another wild guess- What sort of heat to you have? A furnace and forced air heat?

The combination of a basement furnace and forced air heat will usually create negative pressure in the basement, (draw from furnace, air handler fans are usually not sealed very tightly) which keeps the basement chimney from drawing.

First floor draws ok because (usually) the rooms are larger and more open to allow air to move around.
 

Last edited by Hal_S; 03-07-18 at 07:00 AM.
  #12  
Old 03-07-18, 09:41 AM
Member
Thread Starter
Join Date: Apr 2012
Location: USA
Posts: 163
Wild guess, try leaving the basement door open, see if the fireplace draws.better.

Will try this. I tried the burn paper test in the upper fireplace and smoke went up nicely. Cannot try the basement now as we are painting the room.

Another wild guess- What sort of heat to you have? A furnace and forced air heat?
Heat is baseboard in both areas.

The combination of a basement furnace and forced air heat will usually create negative pressure in the basement, (draw from furnace, air handler fans are usually not sealed very tightly) which keeps the basement chimney from drawing.

First floor draws ok because (usually) the rooms are larger and more open to allow air to move around.
True, upstairs is larger.
 
  #13  
Old 03-07-18, 12:30 PM
Member
Join Date: Oct 2008
Location: New England
Posts: 10,136
As others are suggesting, if the basement room is sealed from the outside (where replacement air ultimately must come from) then it could well have draft problems. If the smoke test fails repeat with more doors open.

Where that chimney passes through the upstairs room it is an inside chimney, but is it adjacent to an exterior wall?

Bud
 
  #14  
Old 03-07-18, 01:14 PM
Member
Thread Starter
Join Date: Apr 2012
Location: USA
Posts: 163
As others are suggesting, if the basement room is sealed from the outside (where replacement air ultimately must come from) then it could well have draft problems. If the smoke test fails repeat with more doors open.

Basement is sealed. How do I know? Fragrances linger a long time. Will do smoke test when painting done.

Where that chimney passes through the upstairs room it is an inside chimney, but is it adjacent to an exterior wall?

is inside chimney, not adjacent to outside walls.

Thanks.
 
  #15  
Old 03-07-18, 02:03 PM
Member
Join Date: Oct 2008
Location: New England
Posts: 10,136
With walls and ceiling drywalled the fireplace could be having difficulty breathing. Not really a good term but what goes up the chimney has to be easily replaced without a lot of negative pressure. A louvered door to other basement areas that are not well sealed would help. If you installed an air vent to that room for just the fireplace there are guidelines somewhere but a 6" diameter opening would not surprise me.

The smoke test may help, but remember, it would still not be worst case. If it fails the test is valuable. If it passes it doesn't say it will always pass, other exhaust fans and outside temperatures/winds are not at their worst.

Bud
 
  #16  
Old 04-12-18, 10:03 AM
Member
Thread Starter
Join Date: Apr 2012
Location: USA
Posts: 163
Hi
So I did the smoke test
Burned some newspaper
Smoke went up nicely but...
When paper fire went out I could see smoke debris coming back down and floating into the room and the odor was apparent
 
  #17  
Old 04-12-18, 01:45 PM
Member
Thread Starter
Join Date: Apr 2012
Location: USA
Posts: 163
Am now wondering about dimensions.
is 32 wide and 30 high and 24 deep. Does not seem to match standards found on the web.
Thanks.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes