Vermont Castings Dauntless Flashback Problem

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Ant428

New Member
Jan 13, 2023
34
New York
Hello Everyone. Im fairly new to burning, coming from an old 1978 Frontier Wood stove that was pretty easy to run. I just purchased a new VC Dauntless wood stove. I do not have the CAT installed because they are on back order right now. Last night I had the stove going and decided to load it up with about 5 pieces of wood, which almost filled it. After it heated up, I close the bypass ( which makes the fire sound like a blow torch for some reason). No smoke is coming out of the chimney. The stove top remains about 450 but the flue is heating fast, approaching 450 as well pretty quickly. I decide to damper it down a bit with the heat control, but the heat is still climbing. I waited a bit and gave it another turn lower on the heat control. It was still running hot and the stove top was still climbing. I turned down the heat a bit more slowly, until the flames began to calm down (im afraid of the stove overheating over 650). I noticed I could not see the flames much anymore and the glass on the door turned really smokey. I turned the heat one click hotter to give it some air, and BOOM. There was an explosion and the top loader door swung open and shut. Scared the crap out of me! I'm really nervous to run it again. Any thoughts on what happened?
 

Eman85

Minister of Fire
Oct 10, 2022
696
E TN
You had the wood in the box ignite and flash over. The combustion created pressure in the firebox that pushed smoke out of the top. Seems many of us have VC puffers that do this. seems the box starving for air will pull it down the flue and cause the flashover. Mine did it this morning. My stove is 35 years old and it's done it since new, but mine has a cat and it only does it with the cat engaged.
 
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EatenByLimestone

Moderator
Staff member
You had unburnt volitiles waiting for air to ignite it. It got some air and ignited.

I have some friends with an old Frontier. It’s a beast of a stove!
 
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Ant428

New Member
Jan 13, 2023
34
New York
Is there a way to prevent that from happening ever again? Seem dangerous. Why would there be so much smoke build up and ignite like that?
 

Eman85

Minister of Fire
Oct 10, 2022
696
E TN
Is there a way to prevent that from happening ever again? Seem dangerous. Why would there be so much smoke build up and ignite like that?
It's a fine line between enough air to prevent that and not enough air that causes that. Others have had problems controlling temps with the bypass closed.
 

begreen

Mooderator
Staff member
Nov 18, 2005
99,717
South Puget Sound, WA
Is there a way to prevent that from happening ever again? Seem dangerous. Why would there be so much smoke build up and ignite like that?
It could be dangerous in the extreme case. If nothing else, it is upsetting. Wet wood and/or weak draft can exacerbate this situation, especially when the air is suddenly opened to revive the fire while the firebox is full of smoke. I had this exact situation happen to me a long time ago with our Castine. I was trying to get a balky fire to start with some maple that had gotten wet in places. The fire started to smolder and I mistakenly opened up the ash pan door (don't do this!) to rush some air under the fire. That cause a flame to appear which ignited the firebox full of smoke. The resulting back puff was strong, sending smoke out of every orifice and pipe seam. Lesson learned and not repeated.

If the air is turned down too low so that the flame goes out and the wood begins to smolder and the cat activity is marginal or dead, then the wood gases will build up in the firebox. At that point, a new little flame or spark can ignite the wood gases and create a small to fairly large explosion called a back puff. A back puff can push smoke out of the intake, stovepipe seams, etc. The best thing to do is to keep a small flame by not turning down the air to the point where there is no flame. And only burn dry wood.

VC stoves can be temperamental in non-cat mode. There is a long history here. In the early days the NC stoves from VC earned the nickname of NeverBurn. There is a skill needed to make them burn will without the cat. This depends on dry wood and a decent draft. The jet noise you heard is the afterburner combusting the wood gases in the secondary burn chamber at the back of the stove. Note that 650º on the stovetop is ok, 800º would be a prudent limit.
 
Last edited:

Ant428

New Member
Jan 13, 2023
34
New York
It could be dangerous in the extreme case. If nothing else, it is upsetting. Wet wood and/or weak draft can exacerbate this situation, especially when the air is suddenly opened to revive the fire while the firebox is full of smoke. I had this exact situation happen to me a long time ago with our Castine. I was trying to get a balky fire to start with some maple that had gotten wet in places. The fire started to smolder and I mistakenly opened up the ash pan door (don't do this!) to rush some air under the fire. That cause a flame to appear which ignited the firebox full of smoke. The resulting back puff was strong, sending smoke out of every orifice and pipe seam. Lesson learned and not repeated.

If the air is turned down too low so that the flame goes out and the wood begins to smolder and the cat activity is marginal or dead, then the wood gases will build up in the firebox. At that point, a new little flame or spark can ignite the wood gases and create a small to fairly large explosion called a back puff. A back puff can push smoke out of the intake, stovepipe seams, etc. The best thing to do is to keep a small flame by not turning down the air to the point where there is no flame. And only burn dry wood.

VC stoves can be temperamental in non-cat mode. There is a long history here. In the early days the NC stoves from VC earned the nickname of NeverBurn. There is a skill needed to make them burn will without the cat. This depends on dry wood and a decent draft. The jet noise you heard is the afterburner combusting the wood gases in the secondary burn chamber at the back of the stove. Note that 650º on the stovetop is ok, 800º would be a prudent limit.
Thank you for the reply. Do you think if I get the CAT, I will have an easier time with this stove? I honestly want to return it at this point. I feel like it's unsafe.
 

EatenByLimestone

Moderator
Staff member
I don’t think it will be any easier running the cat.

Newer stoves run differently than the Frontier did. I don’t see a way around the learning curve, though VC stoves seem more temperamental than many/most.

The Frontier does fairly well with pretty wet wood. You’re not going to find that with any of the newer stoves. My friend has been burning wood this winter happily that easily needs 1+ more years drying.

Try picking up some compressed sawdust logs from tractor supply or some grocery store kiln dried wood. See if it’ll burn better. Pallets are another source of dry wood.
 

Eman85

Minister of Fire
Oct 10, 2022
696
E TN
Thank you for the reply. Do you think if I get the CAT, I will have an easier time with this stove? I honestly want to return it at this point. I feel like it's unsafe.
I've no experience with your stove but I'd say it's not going to be "easier" with the cat. Controlling cat temps becomes another task in itself, or at least it is with my stove with a temp probe on it.
 
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Ant428

New Member
Jan 13, 2023
34
New York
Thanks for the insight everyone.
I've learned this stove is a difficult to use because it's a downdraft style stove. When I went to the dealer looking for a stove, I asked for something easy to use that I could slow burn all night. Not sure why he sold me this stove. Downdraft style stoves are known to be finiky and need attention. You need a 3" coal bed in the back of the stove for it to work. If you loose that, it won't work properly. I wish I could return this for another brand. They are coming out to look at it next week.
 

Kevin Weis

Minister of Fire
Mar 3, 2018
1,163
Union Bridge, Md
Thanks for the insight everyone.
I've learned this stove is a difficult to use because it's a downdraft style stove. When I went to the dealer looking for a stove, I asked for something easy to use that I could slow burn all night. Not sure why he sold me this stove. Downdraft style stoves are known to be finiky and need attention. You need a 3" coal bed in the back of the stove for it to work. If you loose that, it won't work properly. I wish I could return this for another brand. They are coming out to look at it next week.
Yep, they are draft needy stoves for sure. Harder for a draft to pull heated air down versus letting the heated air/gasses rise through the stove somewhat naturally. Exacerbated by try to slow the burn rate to extend the burn through 10 hours or so. Letting it cruise at a high temp may help it perform better. A viable burn time of 10 hours really doesn't happen much with the smaller VC's.
 

Ant428

New Member
Jan 13, 2023
34
New York
Well I think I found a problem with the stove. It has 9 heat settings on the side. You can move the heat from high to low with 9 clicks on the dial. When doing so with the stove cold, I looked into the intake in the back to watch the air flap move. On setting 6, it is completely shut.
Now, when the stove is hot, there is a thermostatically controlled part that will shut the flapper more when getting too hot. Tis could be shutting the flap completely on setting 4 or 5?
 

Kevin Weis

Minister of Fire
Mar 3, 2018
1,163
Union Bridge, Md
Well I think I found a problem with the stove. It has 9 heat settings on the side. You can move the heat from high to low with 9 clicks on the dial. When doing so with the stove cold, I looked into the intake in the back to watch the air flap move. On setting 6, it is completely shut.
Now, when the stove is hot, there is a thermostatically controlled part that will shut the flapper more when getting too hot. Tis could be shutting the flap completely on setting 4 or 5?
Yep, that was how my Intrepid flexburn was set up that I bought about 3 years ago. I adjusted the chain so at cold on the lowest setting it is just closed. I did this adjustment in increments to see how the stove performed at each increment. It definitely ran better with this adjustment. But this an Intrepid not the Dauntless and the control settings may be a little different. The Intrepid doesn't have the "click" settings on the primary control lever. I think the airflow set up is pretty much the same though.
 

dvukin

New Member
May 18, 2021
15
Ohio
I have experienced all the same problems with my VC Dauntless (2nd burn season.) I've been burning wood for 45 yrs and have never had a more finicky stove than this. Steep learning curve. Still trying to reliably manage smouldering or overheat, black glass, flashback. I have yet to find a way to do a long burn without overheat or smoulder or flashback with thick carbon deposits on the glass. Small hot fires are fine, but require reload with two or three splits every hour or so. Have had no problem in the past with Jotul, older VC's, and my favorite, an Efel Montana that I replaced with the Dauntless for longer burns, more efficiency, and clean glass. Should have kept the Efel! (Chimney height/draft/dry wood, etc not an issue.) It's a nice looking stove, but if I had it to do over....
 
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a59cheffy

New Member
Jan 18, 2023
22
Coos Bay, OR
The VC Dauntless is a head scratcher for sure! Being my first wood stove, ignorance is bliss so that great philosopher Will Rogers once said! I thought is was normal to clean the glass with ez off every day, not fill the fire box more than half way, make sure there really is a 3-4 inch coal bed and keeping the wood and coals away from the front glass and back downdraft vents at the same time! Keeping the temperature in range to not have a jet engine roaring in the back of my stove!
 

Ant428

New Member
Jan 13, 2023
34
New York
I have experienced all the same problems with my VC Dauntless (2nd burn season.) I've been burning wood for 45 yrs and have never had a more finicky stove than this. Steep learning curve. Still trying to reliably manage smouldering or overheat, black glass, flashback. I have yet to find a way to do a long burn without overheat or smoulder or flashback with thick carbon deposits on the glass. Small hot fires are fine, but require reload with two or three splits every hour or so. Have had no problem in the past with Jotul, older VC's, and my favorite, an Efel Montana that I replaced with the Dauntless for longer burns, more efficiency, and clean glass. Should have kept the Efel! (Chimney height/draft/dry wood, etc not an issue.) It's a nice looking stove, but if I had it to do over....
I get black glass in the same spot every burn. It's a semi circle across the top. Pictures attached. Does yours do that too?

PXL_20230131_222911161.jpg
 

vernorz

New Member
Aug 26, 2021
32
Massachusetts
My glass get dirty in the same spots, also a little in the lower corners on the hinge side of both doors. The left door seems to get dirtier than the right for some reason, but never anything I can't wipe off with a wet paper towel and some ash.
 

GrumpyDad

Minister of Fire
Feb 23, 2022
1,094
Champion, PA
I get black glass in the same spot every burn. It's a semi circle across the top. Pictures attached. Does yours do that too?

View attachment 309027
Id recommend you point a flashlight in your flue and take a picture of it with your phone to check for creosote. These can be creosote monsters if you dont burn hot.
By running below 450 without the cat, Here's what I was able to produce with two 24 hour burns with a cold start in between (so about 8 hours of idle in between)...using the exact stove you have.
That's alarming, but this was done to test how truly bad the downdraft combustion is and how wasteful this stove can be, and because I had a creosote burn off (aka chimney fire) from many 10 days of usage. So now I try to keep my temps to a level that I feel confident and inspect as often as I can.

image000000.jpg
 

Catesy

New Member
Dec 23, 2022
23
Maine
I've given up on cleaning the glass. The Dauntless bakes it on thick. A decent hot fire cleans it good enough.
 

Mirco22

Feeling the Heat
Jan 7, 2022
299
italy
explosion is not a stove problem, it is normal if you shut off too much air, suffocating the fire, (but gases continue to come out of the wood) and you open the air again, they explode. Naturally this does not happen when the wood is carbonised, the gases are almost finished, only in the first hour with new wood can you run into that problem, if you smother the fire. However these things allow to understand many things about the stove and wood
 

Eman85

Minister of Fire
Oct 10, 2022
696
E TN
explosion is not a stove problem, it is normal if you shut off too much air, suffocating the fire, (but gases continue to come out of the wood) and you open the air again, they explode. Naturally this does not happen when the wood is carbonised, the gases are almost finished, only in the first hour with new wood can you run into that problem, if you smother the fire. However these things allow to understand many things about the stove and wood
Well it is sort of a stove problem, especially with a cat. I think it's on the Applied Ceramics or the Midwest Hearth site that addresses it. The off gassing of the wood is what does it when the cat is very hot it flashes over the gasses. I can have mine do it 3 hours or more into a burn sometimes depending on how much wood is in the box and how hot the cat is. I've had it do it with the air control in different positions.
 

GrumpyDad

Minister of Fire
Feb 23, 2022
1,094
Champion, PA
explosion is not a stove problem, it is normal if you shut off too much air, suffocating the fire, (but gases continue to come out of the wood) and you open the air again, they explode. Naturally this does not happen when the wood is carbonised, the gases are almost finished, only in the first hour with new wood can you run into that problem, if you smother the fire. However these things allow to understand many things about the stove and wood
Hmmm.
Explosion and normal in a home appliance should probably not be minced together.
 

Mirco22

Feeling the Heat
Jan 7, 2022
299
italy
Well it is sort of a stove problem, especially with a cat. I think it's on the Applied Ceramics or the Midwest Hearth site that addresses it. The off gassing of the wood is what does it when the cat is very hot it flashes over the gasses. I can have mine do it 3 hours or more into a burn sometimes depending on how much wood is in the box and how hot the cat is. I've had it do it with the air control in different positions.
drowning fire, also blocks flue draft, but the gases keep coming out of the wood, piling up in the combustion chamber, and boom. Writing that the stove is the problem, then manufacturers will add holes, which will give little control on the fire intensity and the experts they will close with magnets! stove is not an appliance, starting from the fact that high surface temperatures can harm people, and then for situations like these! I wouldn't want a stove full of electronic controls to avoid this problem or that air can not be reduced enough, a little awareness and education is needed to use these splendid objects
 

Mirco22

Feeling the Heat
Jan 7, 2022
299
italy
Hmmm.
Explosion and normal in a home appliance should probably not be minced together.
wood stoves, they are definitely not appliances, we just want to think about possible absences of air intakes in a house hermetically closed and monoxide risk, we are not joking, using a wood stove requires learning, and when learning is good, yes the stove will become like a home appliance