My very first furnace was a Brunco 190. It sure was a heavy beast and well constructed. I found it to be an excellent wood burner but, it struggled to burn coal with. I attempted two years to get that Brunco 190 to burn well with anything but wood. I did not do any modifications to the furnace. What I should have done is take the ash door to a metal shop and have a draft spinner installed. The only air opening to the fire is the draft blower up front that blows the air into the fire. If air was allowed to enter through the ash door under the fire I believe the furnace would have performed much better burning coal.
The metal secondary baffle plate above the fire collected a lot of fly ash. Therefore insulating the secondary chamber and reducing the air flow passage to the flue. Trying to keep that area clean was a challenge because of the metal draft flap hanging half way down in front of the feed door. It would not open all the way up to allow for easy cleaning of the secondary draft passage. The draft blower would forge the front of the fire, clinckering the coal and would not supply an even flow of air for the fire to burn coal nice, even and long.
So I sold the Brunco 190 and purchased a Clayton 1600. In my opinion, the Clayton is a far better design and efficient furnace. But after finding this forum, in retrospect, I would have tried to modify the ash door with a draft spinner, even though Brunco says it will void their warranty. I also would have installed foil backed insulation to the inside of the red sheet metal panels to give a better heat exchange to the duct work. The outside of that furnace got really hot and more heat radiated into the basement that was blown in the duct work.
Another reason I got rid of the Brunco 190 was the fact that it was very difficult to try to install a domestic hot water coil into the firebox. The rear of the furnace has two 1/4" steel plates space out an inch or so and the location the coil would need to be was very hard to drill through and too close to the flue.
Overall the Brunco is a very well heavily constructed furnace, but truly designed for the wood burner in mind. But now with the knowledge obtained from this forum, I know that it could be modified to burn coal much better and longer.
Hope this helps. DOUG