Liner fire

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vovo222

New Member
Dec 15, 2007
11
Lexington, MA
About 3 weeks ago I built a new hot roaring fire with some yard scrap....in less than 15 minutes the stove starts whining with airflow like a turbine engine, with rapid whuffling ignition and flame sounds coming from the flue pipe above the stove...within 3 minutes more, the flue pipe started to glow: deep red and getting noticeably orange. I cutback the secondary thermostat control to minimum air intake, to no effect. The griddletop seal sounded like the nozzle of a vaccum cleaner: brief opening allowed a full rush of air into the stove that you could tell the fire really wanted. Looking from outside, the chimney was belching thick clouds of brownish smoke with an acrid "way too hot!" smell. At its peak, a single glowing dustball ember drifted down from the liner's exterior onto the top of the stove, as if to demonstrate there was a real fire danger. Although, my stovetop temps never rose above 400 F during this event, I believe either the creosote burned completely (at least at the base of the flue) and/or the primary thermostat finally warmed up and reduced the airflow enough to extinguish the fire.

Notes: I have a 20' all-vertical run through an internal fireplace chimney with 10x10 clay liner (5' of 6" oval Homesaver ovalflex to 15' of Ventinox 6" round), with a 5' SecureTemp HT insulated chimney topper pipe. The chimney extends 5' from roof. There are no wall braces on the liner -- it just has 2 points of support and rests on clay in areas. House is c.1963. I am considering adding external air intake vent kit run down through chimney (for preheating) to increase overall heating efficiency, so do not want to use poured insulation.

So, with that as an opener, come my questions:
Should this be considered a normal burn-off of creosote?
Wife asks, "If home alone, how do I stop the fire?"
Although internal chimney does not require it, would adding 1/2" insulation blanket around liner act to keep this from happening again?
 
Uhm, that's the kind of chimney fire they test these liners for to avoid burning down your house, but after doing one I think it needs to be inspected by a chimney sweep to see if it's still usable or if you need to replace it.
Yeah, not good...
 
INSPECT THAT INSTALL. If you do not feel qualified, then get a sweep that is.

You have just had a chimney fire.

Its a normal burn off - FOR A CHIMNEY FIRE.

When was the last time your chimney has been swept? What kind of stove do you burn, and what is the fuel source like? Seasoned?

This is SCARY stuff man. Don't take it lightly. Something needs to change for the future.

(strike the stove question - it's in your sig line).
 
Definitely have a certified sweep inspect your liner. Though they are designed for brief sustained temps of 2,100F (if they are UL 103 HT rated), a chimney fire CAN compromise a liner. Though chimney fires do happen, I would personally never consider one normal in any way. They can easily lead to a structure fire if the liner fails.
 
woodweasel said:
So, with that as an opener, come my questions:
Should this be considered a normal burn-off of creosote?
Wife asks, "If home alone, how do I stop the fire?"
Although internal chimney does not require it, would adding 1/2" insulation blanket around liner act to keep this from happening again?
Click to expand...

That sounds like a classic chimney fire. I would not assume anything about the system's integrity until it has been completely inspected. Fires like this place a lot of stress on the metal in the flue.

It is definitely not a normal way to burn off creosote. The real issue though, is why was there a bad accumulation of creosote in the first place? When was the chimney last cleaned?

I am going to guess that either the stove is burning wet wood or it is being run too cool, or both. Your wife should never be put in a situation having to deal with this problem. Tell her to call 911 and get out of the house if it happens again.
 
woodweasel said:
About 3 weeks ago I built a new hot roaring fire with some yard scrap....
Click to expand...

1. What does it say in your owners manual about burning 'yard scrap'?

2. What else do you burn in your stove?

3. When was your chimney cleaned last?

4. Get a pro in there to check out your chimney for integrity - sounds like you may have damaged it.

Shari
 
Dang woodweasel, you got us all worked up with that description of a chimney fire. That'd scare the bejeeezus outta me.

You still burnin' in that thing?

I'd love to see some pics of this setup you got there.

Do come back and tell us what you're up to with that woodstove!
 
I picked up some Chimfex off of a eBay but I hear a wet toilet or paper towel role works well if you have a chimney fire.

http://www.chimfex.com/chimfex_for_home_owners.php


instructions.jpg
 
I have a few of the Chimfex I bought for Forum members left. The Chimfex plus Parcel Post mailing runs around seventeen to nineteen dollars depending on how far away the member lives from my Post Office in Virginia.

Or they are available on eBay and Amazon. Though I suspect that those eBay sellers don't realize that it is against the law to send them any other way than Parcel Post.
 
BrotherBart said:
I have a few of the Chimfex I bought for Forum members left. The Chimfex plus Parcel Post mailing runs around seventeen to nineteen dollars depending on how far away the member lives from my Post Office in Virginia.

Or they are available on eBay and Amazon. Though I suspect that those eBay sellers don't realize that it is against the law to send them any other way than Parcel Post.
Click to expand...

I had to check on mine... I got two for $19 via some liquidation sale on eBay and they were shipped USPS.
 
Treacherous said:
BrotherBart said:
I have a few of the Chimfex I bought for Forum members left. The Chimfex plus Parcel Post mailing runs around seventeen to nineteen dollars depending on how far away the member lives from my Post Office in Virginia.

Or they are available on eBay and Amazon. Though I suspect that those eBay sellers don't realize that it is against the law to send them any other way than Parcel Post.
Click to expand...

I had to check on mine... I got two for $19 via some liquidation sale on eBay and they were shipped USPS.
Click to expand...

Great deal. Yeah UPS ships lots of hazardous stuff, most they even know about, but the rates are nuts unless you ship a lot of stuff with daily pickups. Used to do that before I retired.
 
OK, I'm hearing that a liner fire is NOT normal, but then how do you distinguish a fire like this from "burnoff of creosote" (a phrase that seems common in this forum)? It WAS scary for all 5 minutes of it, and yes, it is same process as a chimney fire... but then isn't this one of the main reasons we use a full liner... to prevent a fire in the masonry chimney?

Here are photos of the stove setup:
http://lifestream.aol.com/photos/stream/heerdaborgen?pid=AgAAAAAIOohaCSRVGA

Note: the heat-blistered paint over this huge 4ft wide fireplace is from pre-stove days when oversize open fires were common -- use of the stove here is way safer than an open fire! The masonry chimney was swept by a pro prior to stove/liner installation.

The grade of flex pipe used is TI-impregnated 306 alloy (thickness of the type I could stand and jump on, 250+ lbs. force, without bending any metal). The pipe connectors are all SS and are directionally correct (dripless). Liner pipe sections were purchased used, and were undamaged. The 1990 VC Encore #2140 cat stove had been overfired by previous owner and was completely rebuilt with new full fireback and refractory kit one month before installation. The top & andirons came from a parts stove, and the inner glass is new.

The fire happened on about the 10th burn of the season. The 'yard waste' that started it was a pile of deadfall sticks and twigs (oak and pine). Recent burns had been fueled with a high percentage of dried rotten wood and several bagfuls of bark planks, chips & green sawdust from a recent splitting session, however the door glass never really smoked up enough to need cleaning.

We've been burning splits now for 3 weeks with no problems whatsoever... no CO alarm soundings, and an absolutely smokeless exhaust when in cat burn mode. I suspect the low grade fuel and a lack of a yearly sweep were to blame for the liner fire. I'll have a pro take a look to make sure everything's OK, but I expect the short duration of the fire and the heavyweight liner material will have saved me from doing any rework this time. Please comment on this installation -- would adding insulation to liner here be wise, or just be an overkill?
 
The confusion may be coming from reading about folks starting off the day with a hot fire to "burn off the creosote". That's more of an expression, but is also a much safer practice because the daily hot fire can help stop creosote from accumulating. But it is not a substitute for burning dry wood or flue cleaning.

Was the flue not cleaned since installation? It seems like the stove was possibly burning not so good wood since it was installed last January. The hot fire of yard scraps touched the creosote off. You really don't want to do this too often. It is stressful on the best system. Also, without insulation on the pipe, the liner may be in direct contact with the clay liner, which means the 2000°F+ heat of the chimney fire could be conducted to the chimney at these contact points. If there is wood in contact with this chimney, it may reach ignition point (pyrolysis) after repeated heatings.

The safest way to prevent these fires is to burn dry wood and keep the flue gases above condensation temperature. What temperature does the stove normally run at?

The liner may be fine if this is the first chimney fire it's seen. We can't tell that over the internet. Considering it was used before installing, it's worth having it checked out. In order to assess the setup, tell us a bit more about the liner and chimney. What is the diameter of the liner? It looks quite oval before the stove, how is it adapted to the flue connector? Is this an interior or exterior chimney? How tall is it?
 
I think the term "burn off the creosote" is a holdover from much older days when people would burn a hot fire first thing in the day to "burn off" anything that may have accumulated from the previous night's choked down, smoldering fire. I have NEVER "burned off" anything in my chimney intentionally. I burn dry, seasoned wood for a purpose: so there's nothing there to "burn off," accidentally OR intentionally.

Burning off creosote is NOT a substitute for a good, manual cleaning. A chimney fire, "minor" or "major," should never be a substitute for manually sweeping and inspecting the flue.

Again, please have your liner inspected before you burn again, as it is not worth the risk to your family and home.
 
BeGreen, please see my initial post to topic for the other liner/stove specs. you ask about. The chimfex is interesting, but will using it foul a catalyst? Wet paper towels seems the way to go here. Regarding cautionary input, I think I will move my combo CO / smoke alarm down near the fireplace while continuing to burn: if there's a cracked flue, I will be duly notified... at ultra-high volume :)

No one has touched the main question yet: is installing a blanket going to change things?
 
It depends on why the chimney fire happened in the first place. We don't hear many reports of chimney fires with your type of setup - a modern cat stove with and interior flue. Do you know why the creosote accumulated in the first place? Was there a lot of unseasoned or semi seasoned wood burned since the liner was put in?
 
BeGreen speaks with much wisdom. Listen to him closely and for sure, forget about that crap of burning off the creosote. You should not have any creosote in a cat stove.....or any stove. The key is good fuel. Do with the stove as you do with the car. Burn good fuel. Put poor fuel in your car and what performance can you expect? Same with a stove.


btw, welcome to the forum woodweasel and we hope you'll stick around.
 
Welcome to the site.

I did not have a chimney fire but i found out how bad it can build up in under 2 weeks. My problem was not wet wood but i was running my stove way to cool if had not took my pipes off and found out about the buildup. The ending would have been very bad.

Keep an eye on the pipes.
 
No need to "burn off the creosote" with a hot fire . . . if you don't have any creosote to burn off.

1. Burn seasoned wood . . . and be sure it truly is seasoned and not just called "seasoned."
2. Burn at the Goldilocks temp . . . not too hot and not too cold . . . having stove top and flue thermometers often help.
3. Check and clean your chimney on a regular basis.


Do Steps 1-3 . . . and you'll never see me . . . or my fellow brother and sister firefighters.

Oh yeah . . . also it would be a good idea to have a sweep check out your liner at this point. Better safe than sorry.
 
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