Chapter 5 STARTING AND OPERATING INSTRUCTIONS
5-20 750-177
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 undesirables
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 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 troubleshooting 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 timer has returned to its original
starting position and stops. The unit is ready to re-start.
!
DANGER
WARNING
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
G. CONTROL OPERATIONAL TEST
AND CHECKS
Proper operation of the various controls should be verified
and tested when the boiler is initially placed into service, or
whenever a control is replaced. Periodic checks should be
made thereafter in accordance with a planned maintenance
program.
The operating limit control may be checked by allowing
steam pressure or water temperature to increase until the
burner shuts down. Depending upon the load, it may be
necessary to manually increase the firing rate to raise steam
pressure to the burner shut off point. If the load is heavy, the
header valve can be closed or throttled until the pressure
increases. Observe the steam gauge to check the cut off
pressure as the operating limit control shuts the burner down.
Slowly open the header valve to release steam pressure and
check the cut-in setting as the burner restarts. Check the
modulating control for the desired operating pressure range.
See Chapter 6 for instructions on the adjustment of controls.
The water temperature on a hot water boiler that may be
operating at less than full load may be raised by manually
increasing the firing rate until the burner shuts down through
the action of the operating limit control. Observe the
thermometer to verify the desired settings at the point of cut-
out and again when the burner restarts. Return the manual
automatic switch to “automatic” and check the modulating
control for the desired temperature range. See Chapter 6 for
instructions on the adjustment of the controls.
Check the proper operation and setting of the low-water
cutoff and the auxiliary low water cutoff (and pump operating
control, if used).
Proper operation of the flame failure device should be
checked at startup and at least once a week thereafter. Refer
to Chapter 8 for information on flame safety checks. Check
the program relay’s annunciation for any system failure.
Observe the promptness of ignition of the pilot flame and the
main flame.
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