Fun with downdrafts

[Skier76]

We had a wonderful fire on Saturday night up in VT...I had our downstairs area up to 84 degrees...I was in shorts and a t-shirt...stove was chugged along at 550 or so. Finally, my wife said: "We need to open a window...it's a little hot in here!" Main level of the house was abou 75F. Life is good.

Next morning, house is down to about 61. brr! 36 or so outside... Well, we did leave a few windows cracked. I go downstairs to start the stove and take the chill off. I open the door. "Whoa! Breeze" Quite a bit of cold air was running down the ol chimney and into the stove. So I rolled/tied of two bits of newspaper, threw them into the stove and lit. I then enjoyed the smell and taste of burnt newspaper as all the smoke exited the firebox via the air intake on the back of the stove. My wife awoke to me running her hair dryer as I attemped to heat up the stove pipe.

Lesson learned: A) Get a cheap hair dryer so I can heat up the stove before I light ANYTHING in the fire box. B) Get a small propane torch in order to reverse the draft in situations where the power is out.

 

[DAKSY]

Put the paper on TOP of the baffle & light it, leaving the loading
door cracked a little to get air into the system.
You'll establish a draft quickly - you'll hear it - with this method...

 

[ControlFreak]

Surprising to see that your flue cooled off that fast. Do you have an external stove pipe running up the exterior of your house?

 

[Skier76]

Surprising to see that your flue cooled off that fast. Do you have an external stove pipe running up the exterior of your house?

Yep! External Metalbestos with no chase. I was burning pine too...

DAKSY,
I'll have to give that a shot. There's not much room to squeeze the paper in, so I'll have to get creative.

 

[velvetfoot]

Did you crack open a window near the stove? That always works for me.

 

[Skier76]

Yeah, I did that too.

The stove is on the lower level of the house...and has an external chimney. I'm thinking as things cool off, I'll have warm things up before starting the fire. One it gets going though....it's awesome. That stove can put out some heat. I'm still amazed at these new EPA stoves. It's really neat to look at the chimney and see nothing but heat waves coming out of the top.

 

[oconnor]

We had a wonderful fire on Saturday night up in VT...I had our downstairs area up to 84 degrees...I was in shorts and a t-shirt...stove was chugged along at 550 or so. Finally, my wife said: "We need to open a window...it's a little hot in here!" Main level of the house was abou 75F. Life is good. ....

So your stove is in the basement - next time, open a window during start up and see if that improves things.

Your basement is a relative negative pressure area compared to the outside, and when you opened the stove door, you opened the "fresh air refill valve" so to speak.

The Guide to Residential wood heating in my signature block covers the subject in more detail. Give it a read.

 

[learnin to burn]

You said you left a few windows cracked - If they were upstairs and still open that may have contributed to your problem.

 

[Skier76]

You said you left a few windows cracked - If they were upstairs and still open that may have contributed to your problem.

I think you nailed it!

Had 3 windows cracked: Two on the main level (bathroom, living area) and one in the loft (bedroom).

Looks like I need to work on my window management before I light the next fire. :red:

 

[Skier76]

I managed to do this again last night. :red: I let the fire die out during the day because it was pretty warm yesterday. I heated up the area above the baffle plate with my burnz-o-matic...but still felt a bit of air rushing down. I smoked things out a bit, but luckily, the draft was established shortly after. The window to the bathroom was open upstairs. D'oh!

Million dollar question: How long after closing the house up should I wait to establish a draft? I find that this usually happens on days the fire dies out or we have some windows or doors open. When we get to the place for the weekend and everything is cold, (after the house was buttoned up all week) I never have a problem establishing a draft.

 

[Wet1]

Cracking widow(s) on the same level and close to the stove should reduce the problem. Opening windows upstairs could make it worse. After opening/closing the windows, you should notice a change in the draft pretty quickly.

 

[Skier76]

Cracking widow(s) on the same level and close to the stove should reduce the problem. Opening windows upstairs could make it worse. After opening/closing the windows, you should notice a change in the draft pretty quickly.

I will give that a shot next time. Both times, I've been bitten by the "oops, a window upstairs was open." Plus, with shoulder season winding down, chances are we won't be opening windows much longer.

 

[grommal]

I managed to do this again last night. :red: I let the fire die out during the day because it was pretty warm yesterday. I heated up the area above the baffle plate with my burnz-o-matic...but still felt a bit of air rushing down. I smoked things out a bit, but luckily, the draft was established shortly after. The window to the bathroom was open upstairs. D'oh!

Million dollar question: How long after closing the house up should I wait to establish a draft? I find that this usually happens on days the fire dies out or we have some windows or doors open. When we get to the place for the weekend and everything is cold, (after the house was buttoned up all week) I never have a problem establishing a draft.

Should take almost no time at all for whatever pressure change to happen. If you open a window on the lower level, be sure that it's not on the downwind side of the house. You want air flowing IN the window, not out.

The flue heating solutions are also good ideas. I've wrestled with some funky downdraft problems for almost 25 years. I will not try the newspaper approach as long as the chimney is downdrafting. I've had enough occasions where that just doesn't turn it around, and 100% of the paper smoke ends up in the house. With my old VC, I could stuff the paper up into the flue exit, and that still did not always turn it around quickly. I'm resigned to occasionally use the propane torch for up to 20 minutes to get it to updraft.

Fortunately, this does not happen too often. If it did, I would have tried extending the chimney and/or going for an insulated reline (our is an external clay-lined masonry).

Good luck!

 

[PunKid8888]

Should take almost no time at all for whatever pressure change to happen. If you open a window on the lower level, be sure that it's not on the downwind side of the house. You want air flowing IN the window, not out.

This is definitely a must if its windy out. I finally determined that the window I was using was the downwind (low pressure) side of the house because all the leaves roll off the roof and build up against the house. Now I open the window in the bathroom on the other side of the house and it makes a huge improvement.

 

[Wet1]

I'd stick a small/cheap ceramic heater inside the stove before I tried burning paper or sat there for 20 minutes with a torch.

 

[drewboy]

I have a basement stove as well and occasionally run into the same situation. Last winter on some real cold days I had the house filled with smoke and the alarms going off. I found that starting the fire the "conventional" way when you have a wicked downdraft doesn't cut it, and I also tried my makita heat gun one time with no real success. I do crack a window also but the best way to get the draft going for me is to use a small butane torch (or propane torch) and light as much of that paper and kindling as fast as possible, stack the paper high up in the back of the firebox against the flue.

 

[Skier76]

Thanks everyone. Thankfully, this doesn't happen that often. I'm hoping it'll be less of an issue when it's colder and the windows are all shut snug. But it still could be an issue with a metal exterior chimney.

That's a good tip on building the fire. On Sunday, once that fire started going a bit...it reversed the draft pretty quickly and sucked all the smoke out of the fire box.

 

[Greg123]

I have had down draft problems as well with my external chimney. My external chimney is 25 feet high. Since this is a new stove and setup for me I’m learning that when I open the door to the stove and a feel the cold air, I’m going to have an issue. What I have done to reverse the down draft is start the fire with really small kindling and fire starters and some paper on top the Idea is to try and get as much heat as fast as possible to reverse the draft., I also have a sliding glass door about 4 feet from the stove that I open about a foot which really helps reverse the flow. I still get some smoke but not to bad.

I’m thinking this will not be much of an issue, when I start burning 24 / 7 as the stove will never really cool down that much.

 

[Skier76]

Burning 24/7 will certainly help. This stove is at our weekend place, so there's always going to be a "cold start".

 

[grommal]

I'd stick a small/cheap ceramic heater inside the stove before I tried burning paper or sat there for 20 minutes with a torch.

In my old VC I had made a cradle that held the torch blowing directly into the flue, so I didn't have to hold it all that time! With the baffle in the Oslo in the way, this is more difficult. I might try the ceramic heater idea. I was also considering buying a heat gun, as that would produce a higher volume of hot air than the torch, and a higher air temperature than a hair dryer. Maybe that will work more quickly.

 

[Greg123]

I’ve been reading that some people have down draft problems during the night waking up to fire alarms going off with a smoke filled house, after they cut back the air flow down for the night. I understand that some how the chimney cooled enough to reverse the flow.

What I don’t understand is how does this happen if you load up the stove get it nice and hot than cut the air back, although I never cut back the air on my stove all the way. I have had several over night burns, and have not had any issues with the chimney reversing during the night. The nights when I did have over night burns the outside air was cold getting down to 23F one night with snow in the morning.

Would the reversal during the night happen more if it was warmer or colder outside?.

 

[grommal]

I’ve been reading that some people have down draft problems during the night waking up to fire alarms going off with a smoke filled house, after they cut back the air flow down for the night. I understand that some how the chimney cooled enough to reverse the flow.

What I don’t understand is how does this happen if you load up the stove get it nice and hot than cut the air back, although I never cut back the air on my stove all the way. I have had several over night burns, and have not had any issues with the chimney reversing during the night. The nights when I did have over night burns the outside air was cold getting down to 23F one night with snow in the morning.

Would the reversal during the night happen more if it was warmer or colder outside?.

Even with all the startup downdraft issued I've had over the years, I've never seen it reverse overnight. These must be cases where the fire has burned out or smouldered to a halt quite early, and the chimney has had a chance to cool almost down to ambient.

 

[Greg123]

I’ve been reading that some people have down draft problems during the night waking up to fire alarms going off with a smoke filled house, after they cut back the air flow down for the night. I understand that some how the chimney cooled enough to reverse the flow.

What I don’t understand is how does this happen if you load up the stove get it nice and hot than cut the air back, although I never cut back the air on my stove all the way. I have had several over night burns, and have not had any issues with the chimney reversing during the night. The nights when I did have over night burns the outside air was cold getting down to 23F one night with snow in the morning.

Would the reversal during the night happen more if it was warmer or colder outside?.

Even with all the startup downdraft issued I've had over the years, I've never seen it reverse overnight. These must be cases where the fire has burned out or smouldered to a halt quite early, and the chimney has had a chance to cool almost down to ambient.

That's what I thought also, they never had a hot enough fire to begin with, which caused the the temp to drop in the chimney causing it to reverse in the middle of the night. The nights that I had overnight burns the next morning my double wall stove pipe was still slightly warm to the touch and the stove top was also warm to the touch, and it had some hot coals left in the fire box.

 

[oconnor]

I’ve been reading that some people have down draft problems during the night waking up to fire alarms going off with a smoke filled house, after they cut back the air flow down for the night. I understand that some how the chimney cooled enough to reverse the flow.

What I don’t understand is how does this happen if you load up the stove get it nice and hot than cut the air back, although I never cut back the air on my stove all the way. I have had several over night burns, and have not had any issues with the chimney reversing during the night. The nights when I did have over night burns the outside air was cold getting down to 23F one night with snow in the morning.

Would the reversal during the night happen more if it was warmer or colder outside?.

Even with all the startup downdraft issued I've had over the years, I've never seen it reverse overnight. These must be cases where the fire has burned out or smouldered to a halt quite early, and the chimney has had a chance to cool almost down to ambient.

That's what I thought also, they never had a hot enough fire to begin with, which caused the the temp to drop in the chimney causing it to reverse in the middle of the night. The nights that I had overnight burns the next morning my double wall stove pipe was still slightly warm to the touch and the stove top was also warm to the touch, and it had some hot coals left in the fire box.

While it may not be likely to occur, it isn't unconcievable - all you need is for the stack effect in the house to overcome draft. Likely that won't happen with dry wood - flow might reverse come morning, but the wood would be used up by then. With wet wood, I could see the smoke alarm issue.

The key is to be aware of how stack effect within the home envelope can alter flue performance when the states of operation of the stove changes.

The topic is covered in the Guide to residential Wood Heating in my sig below.

 

[Skier76]

Just a quick update.... I let the fire die down Saturday night. I know...seems strange...but when you go to bed and it's 78/80 in the house... :lol:

The next morning, I made sure all the windows were closed. I went down stairs, built the fire, gave a quick blast from the propane torch to the area above the baffle and then light the fire. Success. Thanks again for the help. It's amazing what one small window, just cracked open (upstairs) will do to the draft.