Getting blow back after three years

Hello. So I have been using my RMH for three winters now. This winter I have noticed some blow back here and there. The first time was because too much cold air was sitting in the exhaust. So I opened the clean outs and turned on a fan to push the cold air out and the RMH was fine afterwards but now I have noticed that from time to time fire will be kind of chaotic with its direction. The fire in the bottom of the feed moves horizontally but sometimes the fire will travel up a piece of wood and flames or smoke will come out the feed. Then will go back to normal. This will only last as long as let it by moving around the wood frantically or place two fire bricks over the feeds. I don’t know why it’s starting to do this. My design is from the Wisner’s book, to the T. The J tube with a 35 ft run, chimney is out the roof and above the peak 2 feet. Any insight why my fire acts up from time to time?

I wonder if conditions outside have changed?
Trees taller changing wind eddies around the flue?

Hi Diane, When was the last time you cleaned your stove? In other words, lifted the barrel, cleaned out the ash in the horizontal ducting, roof cap inspection etc...
There may be enough room for the exhaust to travel around ash build up most of the time but perhaps when coupled with a warmer day (less delta T) and/ or wind, you may see problems like this.

Hi Diane;
I agree with Gerry.
Something has changed inside your RMH.
Ash buildup is the most likely suspect.
A leaf blower is messy but efficient way to clear your mass pipes of ash.
However, it could be your riser has an issue.  What style of riser did you build?
Hopefully, your barrel has an opening lid for easy inspection.
You could have an ash buildup where the pipe leaves the mass and goes vertical.
A bird/squirrel could have gotten past your chimney cap and then expired inside the pipe.
Possibly your J-Tube burn tunnel bricks are having issues.
Bright lights and mirrors can help you see into dark ashy places.

Gerry Parent wrote:Hi Diane, When was the last time you cleaned your stove? In other words, lifted the barrel, cleaned out the ash in the horizontal ducting, roof cap inspection etc...
There may be enough room for the exhaust to travel around ash build up most of the time but perhaps when coupled with a warmer day (less delta T) and/ or wind, you may see problems like this.

I clean it out every year. I take the top off clean out the barrel as well as the heat riser. I also take the clean out lids and use a shop vac to clean out the exhaust. Maybe I didn’t clean it as well as I thought I did or maybe I missed a spot. Or when I dig the ash out I don’t go back far enough. I’ll have to investigate.

Have you swept out the vertical chimney?