The combustion fan needs to stop during the off time to prevent overtemp, in Jpen's case he has his unit tied through another boiler to dump the heat. The best set up for idle fire on a WL110 involves as much coal as possible burning (width from front to back) with a minimum flame as accomplished by turning the combustion fan rheostat down so the flames are 1-2" at idle with the fan running. This provides a quicker recovery when the fan comes on full speed for a call for heat. If there is an issue with un-burned coal, the coal bed can be made a little narrower and the flames made a bit bigger, the issue with this setup is that after a prolonged call for heat the coal bed will be of sufficient size to overheat the boiler during idle with the larger flames. 12 gallons of water is a fickle companion when matched up to a solid fuel fire.