Auto start when 42 items are ready to burn.
It would have been preferable to place the threshold at 48 (8 items per coal x 6 furnaces). But on some server, the eighth item randomly consumes one more coal. So I developed this automatic furnace on a trigger of 7 item per furnace. Which ensures efficiency of coal 87%.
The architecture is inspired by the chemical factories (pipe transporting the material in system, and smoked glass to protect access to the mechanics)
This furnace is part of a larger automatic item sorting project (under construction).