A little advice? Unstoppable backdraft during the storm..

[Matt Ruggeri]

Hey all, just looking for advice to see what the hell i did wrong! Friday night during the storm, had my CDW2461 going strong, nice secondaries going (even with my toasted cat), house was at a toasty 77, and then one gust of wind (measured at 66MPH on my WeatherStation) changed all that. Stove started backpuffing, then the puffing turned into a non-stop backdraft. I tried everything my few brain cells could think of to reverse it - Opened windows on one side of the house, then both sides, then the doors. I then tried a fan in the window blowing in (for positive pressure) Everything i tried made it progressively worse, then the power started flickering. Got terrified as the fire got bigger, and the flames started heading for the air inlets. Opening the bypass created a downward fireball.

SOOOOOO, I RAN for the fire extinguishers, opened the firebox door, sprayed it, and NOTHING! 2 Boxes of Baking Soda, Dirt from house plants, and another fire extinguisher barely stopped the flames. Grabbed a 10 gallon metal tub of "standby" water, pulled out the logs, and gave them a bath! Luckily, my father-in law stopped by as this was going on, and helped me out. We both agreed we'd never seen anything like that before.. We were trying to figure out what would cause the "Endless Loop". I didn't have a thermometer handy, but i'm sure the pipe was plenty hot enough, and i'm burning well seasoned Beech, Black Cherry, and White Oak. I tried 5 more times Saturday after the wind died to get it going again, and same thing. On Sunday, I was able to use a portable heater, stuck it right inside the firebox and let the pipe warm up, and all is back to normal, for now. This happened once before in a storm, but I was quickly able to reverse it. I've been a wood burner in one form or another for the last 13 years (except for 2 seasons) and I'm terrified it will happen again, and am thinking about investing in a generator instead of a new stove.

A little info about the install - Ground floor of a "cottage" in our living rm, this part of the house was an addition with a shorter roof. Rest of the living space is 2nd floor. It's a VC/CDW 2461, top exit 2ft of vertical pipe up to a 90deg, then 30" of horizontal pipe to the outside, to another 90, then about 22ft of Duravent (Double Wall, obviously) outside vertical pipe, to the cap. There is a roof vent for a kitchen exhaust fan in the main roof. It's about 6ft higher than the chimney. Could this be creating the negative pressure, and pulling from the stove? The entire house was caked in snow/ice, and any usual air infiltration spots were blocked? A combination of the 2?? I was thinking about an updraft vent cap, or am i way off? I could post pics if that would help. Sorry for the long-winded post, but any pointers may ease my mind!

 

[KodiakII]

Not much help here, but I have never heard of anything like that before...minor down drafts yes, but again nothing like that.
How close is your chimney to the other roof, and how much higher is the other roof? If the wind was blowing down the other roof it could have been setting up some sort of vortex over the other roof and your chimney. Maybe a little higher chimney or one of those anti down draft caps might be in order.

 

[Redlegs]

A picture of the roof and chimney area would help.

 

[Jon1270]

Stove started backpuffing, then the puffing turned into a non-stop backdraft.

Could you clarify what you mean by 'backpuffing' and 'backdraft?' I'm no expert, but I was under the impression that backpuffing refers to a small explosion that happens when a fire is starved for oxygen and a bunch of unburnt smoke builds up and suddenly ignites. That doesn't seem to be what you had going on, so I can't picture what you were dealing with (except that it was scary -- that part I certainly get).

 

[Slow1]

I'll bet that an inspection of the roof/chimney will show that you have a setup such that when the wind blows in the 'right' direction & force that it is pushing the air down your chimney. Keep in mind if you have trees nearby they could contribute too...

Pictures of the outside of your house and knowing what direction the wind was blowing in the pictures would help a lot here...

 

[Ashful]

Could you clarify what you mean by 'backpuffing' and 'backdraft?' I'm no expert, but I was under the impression that backpuffing refers to a small explosion that happens when a fire is starved for oxygen and a bunch of unburnt smoke builds up and suddenly ignites.

Not exactly starved of "oxygen", but just too little airflow to move the volatile gasses coming off the wood out of the firebox and into the secondary system at sufficient rate. The distinction here is that you will never add enough oxygen to completely burn these gasses in the firebox, without going into overfire conditions on a large load of wood. We just settle for providing enough airflow to move these volatiles out of the firebox and into the secondary system, at a rate sufficient to prevent backpuffing.

All that has nothing to do with the OP, though. I wish I knew enough to offer some advice here, but I'm sure someone else will! Perhaps the moderators can make this one a sticky? The title of this thread is a work in the art of understatement / does not do your problem justice!

edit: Perhaps follow the thread title with:

 

[Corey]

So you say 'backdraft' - was smoke pouring back into the room continuously? That would imply a true 'backdraft'. I'm wondering if the combination of wind/humidity meant the stove couldn't fully draft as it should and maybe couldn't get hot enough for secondary combustion? I've seen wind make some lively flames in the firebox and just recently a 45mph gust made them appear to go 'down' for just a split second, but then they recovered. The only time I'd consider using a fire extinguisher like you mention is if smoke was pouring back into the house. Otherwise, you're probably just best to 'let it ride' and rely on properly installed flue and stove.

 

[Matt Ruggeri]

So you say 'backdraft' - was smoke pouring back into the room continuously? That would imply a true 'backdraft'..

Exactly, but the smoke turned to flames, then they were coming down to the inlets on the front of the stove. As for the other comments, it was inspected and passed no problems. I'm starting a war at home with this, but i'm suspicious of the kitchen exhaust being about 6-8ft higher than the pipe, as i think this is part of the problem... I just got home from a super long day at work. I'll post some pics of the setup tomorrow. For the first night all winter, i'll shamefully admit that i'm too tired to burn anything tonight! 38 outside and 65 inside. i'll be ok!

 

[blwncrewchief]

That is very strange. A short back draft from high pressure is very possible, however as soon as the high pressure subsides the chimney should reverse back the correct direction. The only way a chimney should be able to continue a reverse draft would be high pressure outside forcing it, the house in a negative pressure, or the chimney is cooled below the ambient temp. In a chimney not in use that is not uncommon however with the stove running at temp that is very strange. Pics may help so let us take a look at them when you get a chance.

 

[KodiakII]

How old is the house, is it insulated and well sealed? I just can't picture your exhaust fan causing that much negative pressure, if that is what you are referring. You might have passed inspection ok, but you might have a situation where you have to go code plus to solve you problem...if it ever happens again.

 

[HotCoals]

You might have had a chimney fire with blockage at the cap.
Do you have a screened cap?

 

[danham]

At a previous home I had a gas hot water heater that would have its pilot blow out during certain wind conditions -- Murphy's Law dictating that these conditons came on the coldest, nastiest nights of the year.

The problem, despite a very tall chimney for the appliance, was that the gable end on the house was creating a vortex that sent wind down the stack and blew out the flame. Relocating the chimney was the only solution that anyone could come up with, but that was never done prior to the whole house being rebuilt anyway (long story involving two hurricanes and much money).

-dan

 

[pen]

What is the overall height of the chimney? What diameter is the chimney? SS liner, class A, masonry? Does the chimney follow the 10-3-2 rule above the roof line?

pen

 

[KaptJaq]

At what point in the storm did this occur? Did snow build-up on the roof change the characteristics of your roof line enough that it cause the wind to blow down the flue? (see attached image) Did a mound of snow and heavy snow on a nearby tree cause something like the flue on the right of the image?

The other possibility, a flue fire with a partially blocked cap, is also a good guess. Did an inspection afterwards show any signs of a flue fire?

You mentioned your cat is shot, any other maintenance issues with the stove?

Pictures of the roof line, the flue, and the cap will help sort things out.


(Click image for larger view)

KaptJaq

 

[Matt Ruggeri]

I'll try to answer all the questions in one shot! The house is an old summer beach cottage, built in the 30's. it's obviously been through a ton of changes, It was dragged to it's present location and jacked up for a garage some time in the 50's. In the mid 70's they added the back half of the house (wood stove is on the ground floor of this part), Central Heat, and insulation added (R-13/ 2x4 walls). In the 90's they added Vinyl Windows, re-sided and wrapped the house, then added R-48 to the attic. We took it over 2 years ago, and did tons of sealing (took every window out and insulated around them), caulking and replaced every door (except 1 storm door). So yes, it's a pretty tight house!
Hah, issues with this stove? Worst one i've ever had. It works the way it's supposed to, but there's way too many parts to go bad, and it's way too complicated to work on.. As stated above it's 6" Duravent Class A Stainless, about 18' vertical exterior. Inside, from the flue collar is 3' to a 90deg, then 2ft of horizontal through the wall "thimble", then outside to the "T", cleanout on the bottom. No evidence of blockage or a chimney fire, and it's actually a lot cleaner than i thought it would be since i checked it a month ago. Less than a 1/4" of fly ash built up.
Hopefully you guys can see from the pics what my concern is. This exits on an exterior wall, is 3ft over the roof height of this section of the house, and the total height difference between the chimney and the exhaust fans, and furnace is almost 8ft. I've watched the way the chimney works against the wind, and it always seems that it comes over the higher roof, and works its way down.

 

[Matt Ruggeri]

At what point in the storm did this occur? Did snow build-up on the roof change the characteristics of your roof line enough that it cause the wind to blow down the flue? (see attached image) Did a mound of snow and heavy snow on a nearby tree cause something like the flue on the right of the image?

The other possibility, a flue fire with a partially blocked cap, is also a good guess. Did an inspection afterwards show any signs of a flue fire?

You mentioned your cat is shot, any other maintenance issues with the stove?

Pictures of the roof line, the flue, and the cap will help sort things out.

View attachment 93571
(Click image for larger view)

KaptJaq

KaptJaq, I just saw this, YES, this is EXACTLY what I was trying to get at. And YES, the side if the house with the Chimney is always on the leward side. We live on the water, and the wind is almost always out of the south, Chimney is on the North Side of the house.

 

[begreen]

Looks like you are working two stoves in this house. Were both burning? If yes, how did the other one do?

 

[Matt Ruggeri]

I wish I had 2 stoves! The other pipe is the furnace, and the 3rd at the peak of the roof is the exhaust for the kitchen hood.

 

[begreen]

Is there any possibility of moving the flue & stove over to the windward side? If not, maybe a different cap would help.

 

[Matt Ruggeri]

It's good thought. I think a different cap would help. Moving the stove would probably be impossible, as we don't own this property yet (hoping to buy in a fwew years), we rent/manage it for my wife's father. 6 different installers passed on this install, all because of 3 reasons - It was a corner install, the owners didn't want the roof cut, and they would've had to custom build those extra heat shields for the back/side walls around the hearth, as requested by the local inspector (and in the install guide). All of them said it was too much work. Most guys around here want to do the least amount of work for the most they can charge!

 

[KaptJaq]

Another possibility would be to add a section of pipe to the top to raise it above the turbulent airflow. If you do this make sure you add pipe braces as necessary. I would also consider adding a MPD (manual pipe damper). The extended pipe will increase the draft on normal days and the MPD will enable you to control it better.

KaptJaq