Relationship between chimney draft and height

[Oregon aloha]

I thought all EPA stoves have a 15' min. height because that is the EPA testing height. Is this not true?

 

[brenndatomu]

See post 32, line 5...EDIT, I'll pull it back up, see next post.

 

[brenndatomu]

Sorry, maybe this was already covered elsewhere, but I'm assuming you have a masonry chimney with SS liner? Is it insulated? That would add some draft if it was.
As to one of your original questions, how to extend your chimney height, again, assuming masonry chimney with a SS liner. They make a top plate that adapts from flex liner to class A pipe. I know I have seen a link to one here somewhere before, maybe someone else can put their finger on it more quickly than I.
I have no experience with those draft inducer fans, but to me, that looks like a real PITA on a wood burner chimney...

Lemme see if I can find a link for ya...EDIT, here's one example
(broken link removed)

 

[dafattkidd]

Lemme see if I can find a link for ya...EDIT, here's one example
(broken link removed)

Perfect. Thanks. Unfortunately (or fortunately) it has been too warm for burning. I will pick up a piece of four foot galvanized and have it ready for the test burns. If this doesn't work are the draft inducing fans a viable safe option?

 

[STIHLY DAN]

Your chimney may be the problem, Have you looked into the house being in a negative pressure? Exhaust fans, combustion air, dryer. Try opening a window when you open the door to the stove. Also why would you have smoke at all when reloading a burnt down fire? Is your wood actually dry?

 

[Woody Stover]

I thought all EPA stoves have a 15' min. height because that is the EPA testing height. Is this not true?

The Keystone manual says 14' but that's with a 7" flue. I'm running 6" at 17'....drafts great.
The Hearthstone Manchester says 10'....from the floor!

 

[Sprinter]

The Keystone manual says 14' but that's with a 7" flue. I'm running 6" at 17'....drafts great.
The Hearthstone Manchester says 10'....from the floor!

Yeah, I think that's just a suggested minimum, and probably a good rule of thumb, but mine is only 13' and drafts okay (not great, but okay). Some stoves seem to "breathe" better than others.

 

[begreen]

Some stoves definitely breath easier than others. Cat stoves that don't rely on secondary air can often get along with a bit less chimney than secondary burners. The design of the secondary intake manifold plays a major part. If it is narrow and/or has a long path with 90 degree turns then it is going to require stronger draft to work well. That is my theory as to why the PE stoves breath easier. They have a large rectangular secondary tube in the back that goes straight up into the large baffle plenum. That is much less restrictive than a stove which has a longer secondary manifold with a couple right angle turns and say a 1" tube intake.

That should not fault a good secondary burner. With a decent height chimney they can perform very well. Case in point would be the Englander 30NC which is an exceptionally clean burning stove.

 

[dafattkidd]

Your chimney may be the problem, Have you looked into the house being in a negative pressure? Exhaust fans, combustion air, dryer. Try opening a window when you open the door to the stove. Also why would you have smoke at all when reloading a burnt down fire? Is your wood actually dry?

My wood is ok. That's not the issue. My house is pretty drafty so I doubt that it's negative pressure. In fact I've tried loading with a window open and no help. I'm pretty positive it's the chimney height or the offset box, or both.

 

[Dustin]

What type of stove? I get smoke spillage each and every time I open the door to my quad. No matter what I do.

25 feet of flex on an interior chimney. Some stoves like putting a little smoke in the room I think

 

[dafattkidd]

What type of stove? I get smoke spillage each and every time I open the door to my quad. No matter what I do.

25 feet of flex on an interior chimney. Some stoves like putting a little smoke in the room I think

I have an Osburn 2400 insert. It's a basic unit. No bells and whistles just a beast. There are other members on the forum with the same unit who do not share this experience. It's not the stove. It's the chimney system.

 

[Sprinter]

Here's my version of the math: 12 ft chimney + 3 ft (25%) increases draft by 25%. Is this correct?

I believe the math is right. I've read other sources that confirm that kind of relationship. So if you go ahead and add 3 ft, you probably will get about 25% more draft which more than likely will solve your problem. Every additional increase in height, though, will have a lesser affect.

Do what others have suggested and temporarily add some cheap stovepipe. That will tell the tale.

 

[BCC_Burner]

I think adding height is the best option here. Also, don't overlook the basics to help improve things a bit before you add height. Open the primary air all the way for 30-60 seconds before opening the door, and open the door slowly. I usually leave mine cracked open just slightly for a couple seconds before slowly opening it the rest of the way. Being vigilant about those two steps really reduced smoke spillage in my experience.

 

[begreen]

What type of stove? I get smoke spillage each and every time I open the door to my quad. No matter what I do.

25 feet of flex on an interior chimney. Some stoves like putting a little smoke in the room I think

Something doesn't sound right there. Did the liner get flattened a lot to pass thru the damper? Is the baffle all the way to the rear of the stove? Has the baffle been checked to see if there is a mound of soot sitting directly under the flue collar? Is the cap screen clean?

 

[oldspark]

Yea 25 feet of chimney should not spill smoke back into the room, I only have 18 feet and it never spills back into the room and it did not with the old chimney and old stove.

 

[Charles1981]

I have a 27 foot 6 inch chimney. My masonry chimney is completely interior in the middle of the home in the basement. I have 6 inch SS pipe all the way up (my installer said because I have a interior, clay lined masonry chimney I had no need for insulated double walled pipe.

I have it hooked up to a encore 2 in 1.

From some other posts drafts have been a significant issue for people with this stove. I am wondering if because of the height, location, and diameter of chimney/liner this is one reason the stove has been performing as it supposed to? Seems like i have an ideal situation for any stove...unless there was a problem with too much draft...but I'm not sure how to tell if I have too much draft?

 

[dafattkidd]

So for the past two weeks I have been running the unit with a four foot piece of single wall stove pipe attached to the top of my liner. The additional four feet has slightly improved my smoke in your face problem, but not really fixed it. It has to be the offset box. I have a mason coming to my house today to tell me if I can make some adjustments to the masonry to eliminate the offset box.

I do however like the way my stove runs with the longer chimney. It seems to take off faster, I can pack the splits tighter and have a more complete burn. It looks RIDICULOUS though. Holy cow it looks terrible. I'll post a picture just for kicks.

I'll update the thread after speaking to the mason today. For the record: The mason who is meeting me at my house today has done a ton of work for my company (we build very high end homes in the Hamptons). So his opinion holds a lot of weight in my book.

 

[dafattkidd]

Ok. Bad news. There are some options, but they are pretty invasive and expensive. My last hope is this: The fireplace has a steel box with vents that was most likely installed in the 70s or early 80s. Based on the measurements it looks like behind this steel box is a full masonry fireplace. The only way to tell is to cut out the steel. If I do this, I can slip my insert further back into the fireplace eliminating the need for an off set box. I think the steel is most likely too think to cut with a sawzall. We think we probably need to hit it with a plasma cutter.

Can anyone confirm that the steel boxes installed in the 70s and early 80s were too thick to be cut with a sawzall?

 

[Jags]

I have cut 1/4" plate with a sawsall. Goes faster than you think.

 

[MDFisherman]

Or a angle grinder with a cutting wheel will make short work of that for sure.

 

[dafattkidd]

Good to hear.

The plan would be: Disconnect the liner from the insert. Slide insert out of fireplace. Cut the steel box out. Pray that it is fully masonry behind that. Slide my insert deeper into pocket of the fireplace so the exhaust passes the lintel. Directly connect the liner to the insert. Light a massive fire with no smoke spillage, and drink a beer.

Most likely the actual outcome: Attempt to disconnect liner from insert, but the tight squeeze between the top of the insert and the lintel lead me to have to sawzall the God forsaken off set box. Pullout insert and damage my hearth. Begin to attempt to sawzall steel box. Break/destroy several sawzall blades. Run out buy ore sawzall blades. Burn out sawzall. Engage in raging break down. Run to nearest fireplace supplier purchase offset box. Connect offset box to liner. Slide insert back into place, connecting offset box as the I shimmy the insert back into place. Light fire. Get face full of smoke. Drink beer. Nod head repeatedly in disappointment. Post results on Hearth.com

 

[Jags]

You are quite the optimist. I would expect the outcome to be much worse.

 

[brenndatomu]

keepin it real this morning...

 

[mellow]

Mine had another steel back behind the steel back that you are cutting out to allow the heat to move behind it for the heatilator vents.

 

[oconnor]

Instead of cutting the entire fireplace out, can you just cut the fireplace throat so you can get a better angle to the liner?