Natural Stack Draft
Natural draft has a decided effect on the operating economy of the stoker installation. Check the draft and baffle damper, which should be adjusted to give the lowest possible draft without causing smoking from the fire door.
The check damper in the smoke outlet to the furnace can also be used advantageously when extreme natural draft conditions exist. The ideal arrangement is obtained by limiting draft just to the point at which smoke or fumes are not emitted from the fire door when the stoker is in operation.
Manual Air Adjustment
As the fuel bed builds up to the desired condition, the air adjustment should be made in the following manner: Open or close the manual air damper to give a yellow and practically smokeless flame (not white-hot) and a fire fed with no intense blasts from air ports in the burner. Sufficient air must be delivered to maintain an even- burning fuel bed with a fairly consistent depth.
Automatic Air Control
Each stoker will usually have some means of automatically con- trolling the pressure and volume of air delivered by the fan so that the correct amount is supplied to the fire as burning conditions vary. Usually no adjustment is necessary, as the setting made at the factory will enable this control to function properly on most installations.
Changing Coal Feeds
On some stokers, the coal feed change is easily made by altering the position of the drive belt from the smaller to the larger or from the larger to the smaller pulleys of the motor and transmission.
Follow these instructions:
1. Cut off the stoker line switch.
2. Move the belt-change lever down to reduce the tension on the belt.
3. Move the belt to the pulley desired.
a. Belt on the large pulley of the motor gives maximum feed.
b. Belt on the center pulley of the motor gives intermediate feed.
c. Belt on the small pulley of the motor gives minimum feed.
4. Move the belt-tightening lever up to the original position.
5. Throw in the line switch.
Motor Overload Protection
The stoker motor will have a built-in device for protection against excessive motor temperatures. Should the motor become over- heated, the protection device on the motor will prevent damage by breaking the electrical circuit. Motor overloads are usually caused by lack of bearing lubrication, low voltage, or excessive belt tension. To reset, push the reset button on motor after the motor has cooled sufficiently.