Hearthstone Mansfield backfiring mystery

[Njwoodburner]

Hi all,
First time poster trying to figure out a backfire issue with my woodstove. I have searched the web, and found many scenarios, but mine seems to defy everything I've read. I have a hearthstone Mansfield that is 4 years old. I have about 6ft of single wall pipe exiting straight out the top of the stove connecting to 16ft of double wall stainless chimney pipe. Everything was installed by my local dealer while the house was under construction. I only burn seasoned wood, and every two years I get my chimney swept which only produces a very small amount of creosote crumbs. Every season I change the seals on the door and ash pan door.myproblem started right after I changed the seals this year. I noticed the fire was burning a little faster than normal so I decided I better change the seals before it got too cold. Ever since I changed the seals, I can't seem to control the fire. It seems to rage out of control if I load more than a few pieces of wood. Anything more than 25 percent capacity and the fire takes off uncontrollable and starts to backfire. Tonight I'm pretty sure I saw a flame come out of the joint in the flue. My throttle was half open when this happened, so I opened it all the way which is what everything I read says to do. This did not solve the problem, so I closed the air control all the way, the fire slowed down, and the backfiring stopped. I suspect I have an air leak at the ash pan door, but shouldn't the stove be over firing instead of backfiring? Everything im experiencing goes against everything ive read on this subject. I've changed the seals 3 times in the past month trying to correct this, and I'm starting to think I may have another problem all together. I had this thing dialed in for the past four years and now I'm afraid to use it. If anyone has any ideas, I'm all ears.

 

[BrowningBAR]

Every season I change the seals on the door and ash pan door.

That really shouldn't be needed. You should easily get several years of use out of your gaskets on the door and ash pan door.

myproblem started right after I changed the seals this year. I noticed the fire was burning a little faster than normal so I decided I better change the seals before it got too cold. Ever since I changed the seals, I can't seem to control the fire. It seems to rage out of control if I load more than a few pieces of wood. Anything more than 25 percent capacity and the fire takes off uncontrollable and starts to backfire.

Well, it is possible that with all the gasket changing you have cement build up which is causing the doors not to seal properly.

Tonight I'm pretty sure I saw a flame come out of the joint in the flue. My throttle was half open when this happened, so I opened it all the way which is what everything I read says to do. This did not solve the problem, so I closed the air control all the way, the fire slowed down, and the backfiring stopped. I suspect I have an air leak at the ash pan door, but shouldn't the stove be over firing instead of backfiring? Everything im experiencing goes against everything ive read on this subject. I've changed the seals 3 times in the past month trying to correct this, and I'm starting to think I may have another problem all together. I had this thing dialed in for the past four years and now I'm afraid to use it. If anyone has any ideas, I'm all ears.

Now, if you closed down the air and the backfiring stopped and the fire slowed down, I have my doubts that there is an air leak, because an air leak would continue to feed the fire. Is there a chance you finally have good dry wood and you are not used to the stove taking off so quickly?

 

[Highbeam]

I had a hearthstone heritage, the next size smaller, for about 5 years and way more than 25 cords. I never changed a gasket on that stove and it always performed well. Quit doing that.

What is a backfire? Does the flame go out, make lots of smoke, and then suddenly burst into flames in a violent pop? When things get hot, turn the air down. All the way down won't hurt anything.

 

[Dairyman]

What is a backfire?

Exactly what I'm wondering, we need more details on this. What are your stove temps when this happens?

 

[BrowningBAR]

How I took it was that the stove is taking off more quickly than the owner is used to. At no point does the owner describe a backpuffing or woofing or off-gassing or whatever. But, the owner is still able to cut the air and kill the flame. I may be assuming way too much at this point, but it seems like the owner might be experiencing a case of "dry wood."

 

[Njwoodburner]

Thanks for the responses. I will stop changing the gaskets every year. They seemed worn out, that is why I thought I should change them. To answer your questions, I cut and split my own wood every year for the following year. There is no difference In the wood. What I am referring to as backfirining are explosions in the flue, at least I think. I keep hearing a thump like my stack of wood fell over in the stove, except there's only 3 pieces in there. Also my kettle rattles on top of the stove and a large bubble comes up every time it happens. This happens when the fire is raging and my flue temp was at 325. Once I cut the air back, and the thumping stopped I noticed the flue temp was 275. I'm not sure what the correct term is for what is happening here, backfire seemed like the only thing that applied. The fire is taking off quicker than I'm used to at all stages. From lighting my kindling to loading wood, it takes off no matter what position the air control is in. The only positive is it has never been so easy to get a fire started.

 

[Dairyman]

I would start with a chimney inspection/ cleaning. Maybe the explosions is creosote lighting off?
What type of wood are you burning?
Have you tested the gaskets since replacing them?
Does the fire seem to be blowing from somewhere abnormal? Possible cracked stone or failure in between stones.