The Forestry Forum

General Forestry => Firewood and Wood Heating => Topic started by: dustintheblood on July 28, 2015, 09:55:35 PM

Title: 28' chimney on a woodstove - any experience out there?
Post by: dustintheblood on July 28, 2015, 09:55:35 PM
Hi all,

First and most important, the chimney we put in isn't in a residential dwelling.  It's in a barn as a secondary heat source for a workshop.

Question is whether anyone has any experience on what kind of draw I can expect?  The woodstove is inside, then it goes out to insulated pipe for 28'. 

I expect that getting it heated to draw initially may be a bit of a pain, but it's the only way I could get it up.

Thanks!

G
Title: Re: 28' chimney on a woodstove - any experience out there?
Post by: SLawyer Dave on July 29, 2015, 12:26:46 AM
I don't have any experience with exterior type chimneys as you have described, but so long as the chimney ends up above the roof you "should" be alright.  The hot gases entering the chimney are still going to want to rise.  It is unlikely in my opinion that the exterior temps are going to be able to cool these gases enough to stop the upward draft.  That uprising draft is going to create a vacuum at the bottom of the chimney, thereby increasing the draw.  To the extent that you can use 45 degree elbows rather than 90s, that will also help keep the chimney draw strong.

Good luck and let us know how it works.
Dave
Title: Re: 28' chimney on a woodstove - any experience out there?
Post by: uplander on July 29, 2015, 10:00:11 AM
 I would expect that flue to draw well. I am running a 24 foot flue and have to open my barometric draft regulator all the way so I do not lose all my heat up the flue.

 Good luck with it.
Title: Re: 28' chimney on a woodstove - any experience out there?
Post by: dustintheblood on July 29, 2015, 11:46:19 AM
Thanks everyone for weighing in.  I suspect the same as everyone.  If in the dead of winter I have to pre-heat the pipes with the salamander for a couple of minutes, no big deal.

Will let you know how it worked out.  For now it's kissing 36C here, so I don't need to worry about it for a while
Title: Re: 28' chimney on a woodstove - any experience out there?
Post by: beenthere on July 29, 2015, 02:01:36 PM
Should draw well, but not until after you get some heat generated and moving up that long cold pipe upon start-up.

That may prove to be the frustrating part, but if you keep a fire going then all should be fine.

No guarantees  ;D
Title: Re: 28' chimney on a woodstove - any experience out there?
Post by: Geeg on August 02, 2015, 01:21:39 AM
We have an indoor wood stove running about 30-32' and it seems to draw ok in fact I have really never had an issue with it not drawing air initially. Since out home is airtight, we run a separate air intake from outside that goes through the bottom of the stove and runs along the floor joists to the outside.

 (http://www.forestryforum.com/gallery/albums/userpics/21627/image_28929.jpg)
Title: Re: 28' chimney on a woodstove - any experience out there?
Post by: beenthere on August 02, 2015, 01:48:13 AM
But the OP said 28' of outside pipe.. insulated but still a cold pipe on start-up.

Nice setup on the inside pipe and stove.. beautiful room too. smiley_thumbsup
Title: Re: 28' chimney on a woodstove - any experience out there?
Post by: Geeg on August 02, 2015, 02:02:50 AM
Oopps, didn't see that, guess I should be using my glasses. Please disregard my last post, carry on.
Title: Re: 28' chimney on a woodstove - any experience out there?
Post by: pabst79 on August 02, 2015, 01:41:31 PM
I have a 8" class A chimney that runs about 18' all on the exterior of my shop, I've had no issues other than I need to clean out the creosote 3-4 times a season. Leave a cleanout cap at the bottom of a tee where you exit the building and it will make soot removal easy. Getting to the top of the stack may be a different story  :), I use a 22'  ext ladder that I leave strapped near the chimney all winter.
Title: Re: 28' chimney on a woodstove - any experience out there?
Post by: Holmes on August 02, 2015, 09:08:38 PM
If My 18' outside chimney looses draft I put a wad of newspaper inside the 6" smoke pipe and light it .Just stuff it into the pipe any way you can. This gets the draft restarted. Exterior chimneys are great at making creosote.If you try to run a low smoldering fire you will get a huge amount of creosote. Best to run the fire as hot as you can with plenty of combustion air getting into it.
Title: Re: 28' chimney on a woodstove - any experience out there?
Post by: joecoin on August 03, 2015, 07:08:52 AM
The air pressure inside needs to be higher than outside. If not, air will attempt to equalize by coming down the chimney. Sometimes, opening a window about a half inch across the room from the stove will give you a decent draw.