Chapter 5 — Starting and Operating Instructions
Part No. 750-184 5-15
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
cycling of hot flame to cool air 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:
1. The burner is manually turned “off.”
2. A low-water condition is detected by low-water level control.
3. The electrical or fuel supply is interrupted.
4. The combustion air pressure or atomizing air pressure drops
below minimum level.
Note: There can be other 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. Refer to the “trouble-shooting”
section in Chapter 7.
Shutdown - When the Operating Limit Control setting is reached to
open the circuit or if the burner switch is turned “off,” the following
sequence occurs.
The fuel valve is deenergized and the flame is extinguished. The
timer begins operation and the blower motor continues running to
force air through the furnace in the post-purge period.
At the end of the programmed post-purge period, the blower motor
is turned off. The air pump motor of an oil-fired burner is also turned
off. The timer has returned to its original starting position and stops.
The unit is ready to re-start.
It is advisable to check for tight shut-off of fuel valves. Despite
precautions and strainers, foreign material in either new or
renovated fuel lines may lodge under a valve seat and prevent tight
closure. The situation is especially true in new installations.
Promptly correct any conditions causing leakage. Failure to follow
these instructions could result in serious personal injury or death.
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