Try a couple of things. With the draft meter hooked up, have someone open a door or window to the outdoors and see if the draft gets stronger or weaker. This is to see if the house is just too tight and you need to provide an outside air source.
Do the same test with the draft meter reading in the ash pan area.
When you had only a small area of still hot coals to rebuild a fire from, was the dark, not burning area burnt out coal [ashes], or unburnt coal? I'm trying to figure out if there is ash blocking the grate in this outer ring, or the draft is so weak that there is only enough air to support the small fire in the center. What revitalizes the fire?? fresh coal, added air? Shaking the grate?? opening an outside door?
Mark [Cap]: I'm not sure I'm on the cutting edge with ideas or not. Sometimes my 'edge' seems pretty darned DULL !! I've found that when I post an idea I get about two or three new ideas or viewpoints back, which is very helpful. So I post a lot in my drive to learn [and to help others].
I may be getting a bit carried-away with posting though , my post count is starting to be embarassing. I have a few minutes of spare time on my hands virtually every day, and I really am focused on coal burning right now. So I visit the site often when I have internet access. When I'm sitting in a hotel with insomnia, I have lots of time.
Take care Greg L