plumber wrote:snip... However, I'm puzzled on required maintenance of the stoker itself, what routine should I follow there?
The grate needs to be removed once a year and the fines vacuumed out, be sure and place the gasket back in place if it falls off when you remove the grate. A little RTV can hold it in place, just be sure the gasket doesn't interfere with the feeder carpet by sticking up too much. The combustion fan has oil holes for a couple drops of 30W (one is under the electrical junction box). Also remove the feeder carpet and clean under it, while the feeder is removed you can inspect it to make sure everything looks good. All of this is in the manual but we need to have some videos to help make it easier, that is in work.
Thanks again for your feedback
In answer to the question on coal usage it becomes a simple math problem, coal is ~ 13,000 but per #, if it is 8% ash it will take less to produce the same heat as coal having 18% ash, the fact that you turned your feed rate down indicates that the coal burned slower and there fore needed a slower feed rate as not to send it off the grate while still burning.