CHAPTER4
sr
ARTING
AND
OPERATING
INSTRUCfiONS
NOTE:
There can be other reasons for
shutdown such as, motor over-
load, flame outages, tripped cir
..
cuit
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
liL
The cause
of
this type
of
shutdown will have
to
be located,
investigated, and corrected before operation can
be
resumed. Refer to Chapter 6.
Shutdown.-
When the operating limit control
setting is reached to open the circuit
or
if
the
burner switch
is turned "of:f," the following
se-
quence occurs.
The fuel valve is
de--energized and the flame
extinguished. The timer begins operation as 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 de--energized. The air pump
motor
of
an oil-fired burner is also de--energized.
The timer has returned to its original starting
position and stops. The unit
is
ready to re-start.
75Q..150
CAUTION!
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
preventing
tight
closure.
This
Is
especially
true
In
new
Installations.
Promptly
correct
any
condi-
tions
causing
leakage In
order
to
avoid
damage
to
the
equip-
ment.
I. 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 there-
after 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 the 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 cutoff 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 desired operating
pres-
sure range. See Chapter 5 for instructions on the
adjustment
of
controls.
CHAPTER
4-11
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