Normal operation of the burner should be with the switch in the automatic position and under the direction of the modulating control. The manual position is provided for initial adjustment of the burner over the entire firing range. When a shutdown occurs while operating in the manual position at other than low fire, the damper will not be in a closed position, thus allowing more air than desired to flow through the boiler. The hot flame to cool air cycling subjects the pressure vessel metal and refractory to undesirable conditions.
With the switch set at “Auto,” the burner will operate on a modulating basis according to the load demand.
The burner will continue to operate with modulated firing until the operating limit pressure or temperature is reached, unless:
- The burner is manually turned “off.”
- A low-water condition is detected by low-water level control.
- The electrical or fuel supply is interrupted.
- The combustion air pressure or atomizing air pressure drops below minimum level.
There can beother reasons for shutdown such as motor overload, flame outages, tripped circuit breakers, blown fuses, or through other interlock devices in the circuitry.
When the burner is shut down normally, by either the ‘’'Operating Limit Control ‘’'or by manually switching the burner off, the load demand light no longer glows.
Shutdown through conditions causing safety or interlock controls to open will actuate the ‘’‘Flame Failure Light ‘’’(and alarm if so equipped) and the ‘’'Load Demand Light ‘’'will remain lit. The cause of this type of shutdown will have to be located, investigated, and corrected before operation can be resumed.