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LazyKB

New Member
Mar 20, 2020
11
VA
I just joined the forum. I have a situation where I need some advice. This is likely to be a long introduction so please stay with me. A year and a half ago we purchased a house. We had a home inspection performed. One of the items was cracks in the masonry crown of the chimney. The recommendation was to have these repaired to prevent water entering the masonry and causing problems. There was also some roofing concerns. I had a reputable roofing company come out give me an estimate for the roof. While they were here I asked if they did crown repair. They said no but they could fabricate a chimney cap that would prevent rain from entering the masonry. I agreed. They came out and did a great job on the roof. They then came out with a man lift and installed a stainless steel cap. This is when I began having problems.

We had gone one winter prior to having the cap installed. We live in a two story house with two fireplaces on the main floor and a thimble for a wood stove in the basement. The fireplace in the family room is equipped with an insert, buck I think, with glass doors. We use this to supplement the propane furnace. The second fireplace is in the bedroom and while it is functional we have never used it. The thimble is sealed . There are three separate flue tiles protruding from the chimney. The one to the family room is in the middle. Last year we had no issues with burning wood in the family room. This year with the chimney cap installed we are getting a smoke smell in the house. Not every time we have a fire but often enough to be a concern. I contacted the roofing company. They wanted to bring in a chimney company to evaluate my chimney as it may need cleaning or repair. I told them the previous owner had it cleaned prior to the sale a year and and a half ago. He had never had a problem with smoke and neither did we until the cap was installed, why would it be my chimney and not the cap.?

The roofing company came out today and reduced the height of the flue tiles thereby increasing the distance between the cap and the crown. I started a fire in the insert. It appeared to draw pretty well. I closed the door and the firebox filled with smoke. I opened it and it went up the chimney. I closed it and it filled again. The settings have not been changed. I went into the bedroom and there was visible smoke. We live in a valley and there is wind or a breeze daily. Today was windy and temperature 73 degrees. Can any one tell me the cause and what to do to fix it?
 

begreen

Mooderator
Staff member
Nov 18, 2005
89,638
South Puget Sound, WA
Can you post a picture of the chimney top and identify which flue goes where? With 73º outside temp it is likely the draft is weak, especially if windows are open on a floor above.
 

LazyKB

New Member
Mar 20, 2020
11
VA
Sorry not able to provide a picture, too old to get on the roof. The flues are lined up side by side. The family room is in the middle. It and the one going to the bedroom are larger than the one going to the basement thimble.
 

snaple4

Feeling the Heat
Dec 18, 2017
284
AR
If they, originally, didn’t change the flue system then I don’t see how the roofing company is at fault. Possible they dented or broke a cap but unlikely. Sounds more like a draft problem due to warm temps as begreen mentioned, your chimney is getting dirty, or you have wet wood.

my guess based on what you said is all three. Just pay a company to come out and clean/inspect. Should be done yearly with good dry wood or monthly with crappy wet wood like what I have.
 

LazyKB

New Member
Mar 20, 2020
11
VA
Thank all of you for your input so far. Does the height of the cap in relation to the tile make a difference? It seems to me that the smoke would come up the chimney hit the underside of the cap, swirl around and maybe go back down one or more of the flues?
 

begreen

Mooderator
Staff member
Nov 18, 2005
89,638
South Puget Sound, WA
I still don't understand why the wood stove was fired up with 73º temp outside. We have an ideal flue setup and I don't know if it would perform well when the outdoor temp = the indoor temp.
 
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LazyKB

New Member
Mar 20, 2020
11
VA
Begreen, I am not as informed as folks on this site. I thought I would test the flue after the roofers trimmed the flue tiles. I see your point thanks. I am here to learn.
 

Sodbuster

Minister of Fire
Sep 22, 2012
1,506
Michigan
Not meaning to be impolite, but why are you trying to burn a fire with an outdoor temp of 73? That and the wind will cause very poor draft conditions. I would try it again if it gets colder, or wait until fall to give it an honest test.
 
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LazyKB

New Member
Mar 20, 2020
11
VA
Sodbuster I am not as informed as folks on this site. I thought I would test the flue after the roofers trimmed the flue tiles. I see your point thanks. I am here to learn.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,277
NE PA
Is this a large cap over all three flues to protect the entire chimney crown? Are all the flues now the same height? Were they originally different heights ? Is there now also a screen around the opening?
The height of the cap must allow the same square inch open area as the size of the flue. (example 8 X 8 square flue requires minimum 64 sq. inch opening) Your chimney wasn't drafting enough to get oxygen into the stove or evacuate the smoke.

The reason it needs to be cold is the hot exhaust gasses rise up the chimney and create a low pressure area in the chimney and stove. The pressure drop is measured as draft. Draft is caused by the temperature differential between the inside and outside of flue. The colder outside, the faster the lighter gasses inside rise. The low pressure area in stove created by chimney allows the higher atmsopheric pressure to PUSH air with oxygen into the stove. Opening door gives the higher air pressure more square inch area to push into the stove, rising up the chimney easier. The intake air control is the most resistance to flow in the system. You can see why opening the doors allows the rush of air in and the fire kicks up. The chimney wasn't hot enough creating low enough pressure to allow enough air through the smaller intake openings.
Keep this basic principal in mind when operating the stove and you can troubleshoot most problems.

The cap and spark screen will add resistance to flow in the vent system. If you used a flue damper inside, this may need to be opened a bit more than you ran it to make up for the added resistance. The flue damper is a chimney control that is a variable resistance. It should be wide open when trying this when this warm since you need much hotter faster rising flue gas to make up for the lack of temperature differential.
 

Highbeam

Minister of Fire
Dec 28, 2006
19,165
Mt. Rainier Foothills, WA
I still don't understand why the wood stove was fired up with 73º temp outside. We have an ideal flue setup and I don't know if it would perform well when the outdoor temp = the indoor temp.

I burn a lot when outdoor temp = indoor temp. Works great. The temperature differential that creates draft comes from the fire, not the ambient air.
 
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LazyKB

New Member
Mar 20, 2020
11
VA
Coaly, There is one cap over the three flues. Originally the middle flue, the family room with insert, was a bit higher. I am not sure what height they are now. The workers came while I was not home. There is a screen involved.


Now having said all of that: today's temperature is 44 degrees. I have built another fire and am experiencing NO problems. I may be able to chalk this up to operator error. However we did have a couple of issues this past winter when it was cooler. Maybe trimming the flue did the trick and it was just too warm to test.
 

Woody Stover

Minister of Fire
Dec 25, 2010
12,266
Southern IN
don't understand why the wood stove was fired up with 73º temp outside
Heheh. My wife can feel a bit chilly if it drops to 70 in the house. ==c She's thinner than she used to be, though..
As unlikely as it may be, LazyKB might be older than even you, begreen! _g ;lol
The temperature differential that creates draft comes from the fire, not the ambient air.
I dunno..draft seems to get noticeably stronger when the temp drops near single digits, and the difference between 30 outside, and 10, doesn't seem that great in relation to flue gas temps. Single digits is probably something you haven't seen often, to know what I'm talking about.
There is one cap over the three flues. Originally the middle flue, the family room with insert, was a bit higher.
Could you tell where the smoke was coming from? Was it being pulled down the basement flue?
One of the solutions mentioned in other posts, to smoke being drawn down an adjacent flue, is to extend one flue so that the smoke comes out at a different level than the other flue. That, and the cap, may be the reasons it's now easier to draw smoke down the other flue. Can you estimate how much higher the center flue was than the others, before they cut the flue tiles down?
Use the magnifying glass (search) at the top of the page to read other threads on this topic.
 

Stinkpickle

Minister of Fire
Jan 13, 2015
575
Iowa
Wait...was the last time the chimney was swept back when previous owner had it, and you’ve burned for a winter since then?
 

LazyKB

New Member
Mar 20, 2020
11
VA
Friday the smoke was being pulled down the bedroom flue.

The last cleaning was right before we purchased the house in August of 2018. The previous owner said he had it cleaned every three years.
 

Woody Stover

Minister of Fire
Dec 25, 2010
12,266
Southern IN
Bedroom upstairs? I'm assuming no; Air would be exiting up there.
 

begreen

Mooderator
Staff member
Nov 18, 2005
89,638
South Puget Sound, WA
Begreen, I am not as informed as folks on this site. I thought I would test the flue after the roofers trimmed the flue tiles. I see your point thanks. I am here to learn.
No problem. This article maybe helpful.
 

Hogwildz

Minister of Fire
With warm temps outside, you are getting poor draft, and probably reverse draft in the other 2 flues. Meaning the exhaust from the flue being used is exiting and drafting down the other two flues. If the other 2 are not used, they should be capped off.
 

LazyKB

New Member
Mar 20, 2020
11
VA
No problem. This article maybe helpful.

Yes, thanks a lot.
 

LazyKB

New Member
Mar 20, 2020
11
VA
With warm temps outside, you are getting poor draft, and probably reverse draft in the other 2 flues. Meaning the exhaust from the flue being used is exiting and drafting down the other two flues. If the other 2 are not used, they should be capped off.

Good idea, thanks.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,277
NE PA
Friday the smoke was being pulled down the bedroom flue.

The last cleaning was right before we purchased the house in August of 2018. The previous owner said he had it cleaned every three years.
Back to the basics; The smoke isn't being pulled down the other bedroom flue.

The atmospheric pressure outside was greater than the pressure in bedroom flue allowing the higher pressure outside to PUSH into the bedroom. It probably always has, now with the cap and flues the same height the air entering is carrying exhaust particles from nearby with it.
 

Stinkpickle

Minister of Fire
Jan 13, 2015
575
Iowa
It sounds like it could be a combination of issues causing the draft problems. Some other things to check...if draft is fine with stove door open but chokes out when you close it, could the air inlets be blocked? Is the insert old enough that it’s a “slammer” install? Those can be dangerous, if they’re not cleaned often enough. I’m leaning towards the roofing company’s advice of having a certified chimney sweep inspect your setup. I think that would be money well spent.