First .. Happy Thanksgiving!
A short follow-up on my outside air source box and fan: The set-up seems to have been an improvement. The biggest changes without the fan, seem to be that the coal burns more completely ... meaning, that it seems to go more to powder, than burned pieces of coal. The fire picks up more quickly, thus making heat sooner. Also, the bed of hot coals, seems to be deeper ... raking it down, until the hot coals are at the grate, doesn't leave me as much room to add new coal. The other thing, which I notice, is that the air flow from the outside air tubes is directly proportionate to fire intensity. ... with the damper open and all red hot coals, the air flow was fairly strong. Once I added fresh coal, the air flow from the tubes slowed. With everything burning at full tilt, the slide damper controls the max burn rate (MPD closed).
With the fan running, burn "pick-up" rate is quicker and max burn rate is higher than I would like, with the same damper opening settings. The fan could be an asset on certain days. The fan kind of "forces" the fire.
I give thanks!