Wood stove pipe just blew out of the flue! - Holy Cow!

[HolyCow]

Greetings from NH. Would appreciate any advice. I Have a newer Jotul wood stove that has been working great for the past three years. I dont use it a lot. I like to use thewood stove when it snows or gets really cold to take the load off my oil furnace(seperate flue). I just put in new stove pipe a few weeks ago and it has been working fine. (There is just one 90 degree bend up where it goes into wall. I had been using it all day and had just filled it with wood for overnight and used the ashpan door just to get the fire going and then shut it. I walked away and boom! the stove pipe blew out of the wall and the clean out door down in the basement even blew open with so much force that it bent the metal. I didn't see any chimney fire outside. What could have caused it? What do I do now?

 

[adrpga498]

Sounds like there weren't 3 screws attaching the stove pipe to the thimble. Put the fire out if you haven't done so already.

 

[BrotherBart]

All about it right here:

https://www.hearth.com/talk/threads/what-just-happened-and-how-dangerous-was-it.102088/#post-1313586

 

[adrpga498]

Ash pan door being open to prime your load created too much pressure me thinks what "caused it" .

 

[HolyCow]

Sounds like there weren't 3 screws attaching the stove pipe to the thimble. Put the fire out if you haven't done so already.

I put on my gloves and put the pipe back into the wall and pulled out all the wood and threw it outside. There are only 2 screws I have is where the pipe inserts into the stove collar. The other two peices were just fitted together with furnace cement. What could have caused that much pressure? Do you think I could have damaged my chimney liner? I didn't see any chimney fire? Thanks for the response.

 

[HolyCow]

All about it right here:

https://www.hearth.com/talk/threads/what-just-happened-and-how-dangerous-was-it.102088/#post-1313586

I just read the thread you gave. I don't feel that bad now about crapping my pants now. At least I have company. Thanks BrotherBart.

 

[binko]

I think it may have been a major back puff where the unburned combustibles in the fire box ignite all at once. The air expands faster than the chimney draws it with its draft and therefore you have a brief positive pressure in the flue. It's like lighting a firecracker under a can-upon ignition, it lifts the can off the ground.
Some people have a different version of this where the back puff briefly lifts the top of their stove cover to relieve the pressure.

 

[HolyCow]

Ash pan door being open to prime your load created too much pressure me thinks what "caused it" .

Sounds like that may be it the case. My main concern is if this type of pressure could have cracked my chimney liner which I think is made out of that clay colored firebrick material. Thanks for the response MoF.

 

[HolyCow]

I think it may have been a major back puff where the unburned combustibles in the fire box ignite all at once. The air expands faster than the chimney draws it with its draft and therefore you have a brief positive pressure in the flue. It's like lighting a firecracker under a can-upon ignition, it lifts the can off the ground.
Some people have a different version of this where the back puff briefly lifts the top of their stove cover to relieve the pressure.

But the stove was running all day. Could draft have been a problem with a warm chimney? Thank you for the response binko.

 

[remkel]

I agree you had a sudden combustion of built up gases in the firebox. When you shut the ash pan door, did the flames die down? Was there more smoldering going on? If so, there would have been a gradual increase in oxygen and all of a sudden WHAM (or WHOOF) the gases will ignite.

I don't know which model stove you have, but using the ash pan door for draft could do quite a bit of harm to your stove. If your model has a side door, I would recommend keeping this door cracked open to help get the fire started.

 

[BrotherBart]

Draft wasn't the problem, you not giving it any air and getting the burn stabilized was the problem, thereby building up un-burned smoke in the stove and the flue. Then when a little air and a lick of flame hit it the stuff exploded. And quit using that ash pan door to crank up a fire. The Jotul manual specifically tells you NOT to do that. You will wreck the grate in the bottom of the stove and be back here looking for where to get the stove rebuilt. Use the primary air control on the stove for that and close it down in stages maintaining a stable burn. Never use an ash pan door for an air supply.

As to the flue tiles they may be fine. They can take more pressure than the pipe stuffed into the thimble without a positive connection. But get three screws in every joint of that pipe including at the thimble before you strike a match in that stove again. You got lucky this time.

 

[begreen]

When I first had the Castine I made the same mistake. Don't use the ashpan door for starting!

What happened is the wood started burning with the forge like air supply coming from below the fire. When you closed the ash pan door, the strong underneath air supply was cut off and the fire started to smolder. The wood was hot enough to emit wood gases, but there was no flame. Finally a flame appeared, in a firebox filled with explosive wood gas, and it ignited. If the chimney is cold and draft is sluggish, then you first need to warm up that chimney with a more robust burn.

I would examine your reload technique and change it. Get yourself a batch of carpentry cutoffs from a jobsite. Take a hatchet and cut them down into 1-2" thick pieces. On reload, place 2 of these kindling pieces about 6" apart, parallel to the stove sides, in the middle of the stove. Then place your normal reload of wood on top of these kindling "sleepers". The dry kindling will ignite faster and will allow air to get underneath the bed of logs for a faster and better restart. Then, leave the door open a small bit (1/4" is fine) until the fire has ignited and is burning well.

 

[HolyCow]

Draft wasn't the problem, you not giving it any air and getting the burn stabilized was the problem, thereby building up un-burned smoke in the stove and the flue. Then when a little air and a lick of flame hit it the stuff exploded. And quit using that ash pan door to crank up a fire. The Jotul manual specifically tells you NOT to do that. You will wreck the grate in the bottom of the stove and be back here looking for where to get the stove rebuilt. Use the primary air control on the stove for that and close it down in stages maintaining a stable burn. Never use an ash pan door for an air supply.

As to the flue tiles they may be fine. They can take more pressure than the pipe stuffed into the thimble without a positive connection. But get three screws in every joint of that pipe including at the thimble before you strike a match in that stove again. You got lucky this time.

Lesson learned. It just seemed the fastest way to get the fire going. Will be using the fire control from now on. Have screws where it is connected to stove but will put screws in where the sections connect. But what about where the pipe plugs into wall (thimble) I cant use screws there(see my avatar). Should I just use furnace cement there? Thanks again BrotherBart.

 

[HolyCow]

When I first had the Castine I made the same mistake. Don't use the ashpan door for starting!

What happened is the wood started burning with the forge like air supply coming from below the fire. When you closed the ash pan door, the strong underneath air supply was cut off and the fire started to smolder. The wood was hot enough to emit wood gases, but there was no flame. Finally a flame appeared, in a firebox filled with explosive wood gas, and it ignited. If the chimney is cold and draft is sluggish, then you first need to warm up that chimney with a more robust burn.

I would examine your reload technique and change it. Get yourself a batch of carpentry cutoffs from a jobsite. Take a hatchet and cut them down into 1-2" thick pieces. On reload, place 2 of these kindling pieces about 6" apart, parallel to the stove sides, in the middle of the stove. Then place your normal reload of wood on top of these kindling "sleepers". The dry kindling will ignite faster and will allow air to get underneath the bed of logs for a faster and better restart. Then, leave the door open a small bit (1/4" is fine) until the fire has ignited and is burning well.

Thanks begreen. Won't be using the ashpan door again. This scared the bejeezus out of me. The pressure was so great that it even bent the latch on the cleanout door in my basement which is made of sheet metal when it got blown open.

 

[begreen]

Seal that cleanout door tightly, use silicone or tape if it's ungasketed. It sounds like the stove venting into a clay tile flue, is this correct? If so, what's the flue tile interior dimension? How tall is the chimney?

 

[HolyCow]

I agree you had a sudden combustion of built up gases in the firebox. When you shut the ash pan door, did the flames die down? Was there more smoldering going on? If so, there would have been a gradual increase in oxygen and all of a sudden WHAM (or WHOOF) the gases will ignite.

I don't know which model stove you have, but using the ash pan door for draft could do quite a bit of harm to your stove. If your model has a side door, I would recommend keeping this door cracked open to help get the fire started.

Thanks remkel. Lesson learned. Its a Jotul F 500. I had a bed of hot coals which I had spread out and then packed the stove for the night. I had only used the ash door for a couple of minutes just to get the new wood burning then I shut it. About 30 seconds later the whole top section of pipe blew out of the wall and landed on the floor. Smoke filling the house, smoke alarms going off, wife screaming at me while I was tryng to fit the pipe back in. I think I need therapy now..and I'm former EOD. Holy cow!

 

[HolyCow]

Seal that cleanout door tightly, use silicone or tape if it's ungasketed. It sounds like the stove venting into a clay tile flue, is this correct? If so, what's the flue tile interior dimension? How tall is the chimney?

The pipe is 6 inch that goes to eight inch into the wall. yes its a clay tile flue. I'm not sure about the dimension of the chimney, but its real tall. Its a three flue cinderblock chimney thats covered by the faux stone. one flue is my oil furnace, one flue wood stove, and one that is for if I want to put a wood stove in the basment. I will try and post pics.

 

[remkel]

No problem, Holy Bovine

I have the F600 and only once did I see the effect of pulling air in through the ash pan door. I was emptying the ash pan and forgot to open the side door when I did it. Luckily I clean out the pan in the morning after an overnight burn, so there weren't too many coals.

Look atbitbas a lesson learned. Make certain you seal that clean out door, if you don't a lot of cooler air will be sicken into your flue and you will start seeing creosote buildup in your flue. That is spoken by someone who went through that experience.

 

[begreen]

The pipe is 6 inch that goes to eight inch into the wall. yes its a clay tile flue. I'm not sure about the dimension of the chimney, but its real tall. Its a three flue cinderblock chimney thats covered by the faux stone. one flue is my oil furnace, one flue wood stove, and one that is for if I want to put a wood stove in the basment. I will try and post pics.

The interior flue tile size is very important. If the inner area of the cold stone flue is large, the stove is going to draft poorly which will make the stove hard to start and will greatly exacerbate the puffback issue. Check this out or ask your chimney sweep for the dimensions.

Is the chimney on an exterior wall?

 

[HolyCow]

The interior flue tile size is very important. If the inner area of the cold stone flue is large, the stove is going to draft poorly which will make the stove hard to start and will greatly exacerbate the puffback issue. Check this out or ask your chimney sweep for the dimensions.

Is the chimney on an exterior wall?

Thats a negative. The chimney is within house. I put a picture below.

 

[CT-Mike]

A strong lesson learned, and thankfully no one was hurt, or any major damage to your home. I hate reading stories about people who lost everything they had because of operator error, bad install, etc. Get out your owner's manual and read it cover to cover and ensure that you are thoroughly familiar with the operation of your stove.

 

[remkel]

Don't know where you are in NH, but looks like we both have just about the same amount of snow.

 

[begreen]

Thats a negative. The chimney is within house. I put a picture below.

Well, actually that's a positive. It will help keep the flue warmer.

That's quite a bit of snow you have there.

 

[HolyCow]

Well, actually that's a positive. It will help keep the flue warmer.

That's quite a bit of snow you have there.

Yup. I love New Hampshire and wouldnt live anywhere else, but I could pass on the snow if I had my way. I see your from WA. Was there in the 80's at Ft.Lewis and loved it.

 

[HolyCow]

Don't know where you are in NH, but looks like we both have just about the same amount of snow.

If your SW NH I'm between you and Concord. This is my first house with a wood stove stove though. Other than what happened last night I love my Jotul. It heats up the house great.