Right Angle Stovepipe Elbow Connections and Draft

Okay, now explain a down draft for us.

oliver power wrote:Air traveling across the top of the chimney causes draw.

oliver power wrote:A chimney with good draw, has good draft. A chimney with poor draw, has poor draft.

So, If the wind isn't blowing the chimney doesn't have good draft?
I don't understand.. I think yer messin with my head

Rob R. wrote:
YES.

Right.. I agree. Less bends, less resistance. Could the difference between one bend and three bends be measured on a manometer during mid burn? Hmmm... Anybody gonna try it? Oh, make sure all the variables are consistent.. Would using three bends be a deal breaker on a set up? Probably not..

A short chimney from having a stove upstairs? I think this could be the bigger problem OR maybe stack effect in the house will compensate? Interesting dilemma..
:nice:

you probably aren't gonna get much worse then this

yea thats the backup stove
the chimney probably isn't more then 20 foot total length from stove to top plenty of draft somedays a little bit to much for that stove
as people have said so long as you got good air moving and a fairly strong fire don't worrie about it to much you will know strait away if you are gonna need to move stuff around

Wow that's quite the pipe layout ↑

I have an interesting observation that could help the original poster. When it's cold out, I can open a window upstairs and feel air from the house rushing out. It makes sense that stack effect in the house is at play. SO, having a stove upstairs would have the same pressure pushing against it, since the chimney simulates the open window and air would be trying to find its way out thru the combustion air intakes.

My guess is that draft pressure would be dramatically dictated by temperature outside given the short chimney and stack effect of the house.

Lightning wrote:

oliver power wrote:Air traveling across the top of the chimney causes draw.

oliver power wrote:A chimney with good draw, has good draft. A chimney with poor draw, has poor draft.

So, If the wind isn't blowing the chimney doesn't have good draft?
I don't understand.. I think yer messin with my head

I didn't say anything about the wind blowing. I said "Air Movement". Down Draft = Low atmospheric pressure, and /or turbulence. Can be caused by many factors, including an overly strong draft coming to an end. EXAMPLE: Your traveling down the road, and you have to stop. You step on the brakes. You get slower, and slower, as you are forcing the vehicle to stop. Once you come to a dead stop, it's that little "jerk back" we all feel. This sudden "jerk back" of roaring gasses explodes once it is ignited by open flame. You just tended your stove. Ash pan door is open. Fire gets to roaring. You close ash pan door. Seconds later, BOOM!!! BOOM!!! can also happen when introducing fresh oxygen to a fire box full of gasses. Oliver

Ut oh.... Stack effect in the house opens a new can of worms for the manometer too. To get a true reading that would include stack effect in the house, You would need to run the open side of the mano downstairs with tubing. Otherwise, You would be comparing the chimney draft pressure against the stack pressure of the house. For example, if you read -.02 at the stove location but stack effect of the house contributed an additional -.02 than you would actually have a total of -.04 in the stove.

By running the open side of the mano downstairs with tubing it would then show the true reading of -.04

Does that make sense to anyone else? Or am I missing something.

Edit- I knew it would come to me hahaha. I got it backwards. Running the open port downstairs would discount the stack effect. Having the open port on the same floor as the stove would add stack effect of the house to the mano reading. Not enough coffee this morning lol.

@Oliver - I thought the sudden jerk back when I stop was due to the suspension system rebalancing since the forward momentum of the car isn't there anymore.

the 'true reading' for the manometer and stove is relative to its location in the house. if the stove is on the first floor then that is where you want the manometer and its 'open' port. if the stove is in the basement that is where you want the open port. the manometer reading is then meaningful to the stove location.

if I understand your statement correctly about 'true reading' I would agree it would give a wrong reading to have the stove in the basement with the tubing from the flue running to the manometer upstairs and the other manometer port open to the air upstairs.

i just thought of a solution for the guys with industrial draft sucking the heat out of their stove....
how about a flue pipe installation that looks like the plumbing pipes from that 3 stooges episode many moons ago?!?!
that should knock down the draft a bit!

Wow...great thread...lot's of information here. If I have a shorter chimney, will I need to run a Baro as well as a MPD. I've always been told by Emery to not run MPD's with old antique stoves. They are great for the modern stoves but don't work well with the old ones. I've run my Herald No. 18 with 2 MPD's and it runs like a champ. From what I'm reading, would the addition of a baro help with draft. I would consider the air being added, over the fire air so in theory wouldn't it slow down the burn and lower the temp? There is a lot of information on this thread and I'm trying to wrap my head around it. Thanks again, everyone, for your help on this.

Lightning wrote:@Oliver - I thought the sudden jerk back when I stop was due to the suspension system rebalancing since the forward momentum of the car isn't there anymore.

It's also true of your body.

Titliest, yer right. I edited my post

B Patrick, a barometric damper won't improve a draft that is weak. It will only "limit" a draft that is too strong. By limiting draft the result is a steady heat output thru the burn cycle.

Thanks Lightning, Thats what I wanted to know. It's an old farmhouse built in 1850's and it isn't airtight. I was hoping that this would help and the ceiling are 13'. I'd go to the center of the attic and put the stove in there and go up 3' past the roofline at the peak. I'd think I'd gain some height and get a little draft.

Stack effect in the house should help too, especially if the house isn't real tight.