WAY too much temp. swing for it, it will feed, and feed and feed to make up the difference and normally overshoot.
COAL is NOT like a gas furnace, it takes TIME to respond, it not like it can be shutoff immediately at the temp. setpoint, it will take and hour or more for the temp to come back down and stabilize.
If you read some of the posts about using the Coaltrol, most of us do NOT use the setback, if you do, only use it a few degrees and give it at least and hour before you want the temperature setpoint.
Most of us just leave it a set temperature.