CHAPTERS
High Turndown
Burner
Low
Fire Adjustment (Light Oil)
Fuel input at low fire should
be
approximately
125%
of
that
at
high fire. The low fire cam screw
should
be
adjusted to obtain this flow rate with
resulting flue gas content
of
8.5-9.5%
ccn
and
9.3-7.8% 02. The second cam adjusting screw
may
need to
be
adjusted
in
order to maintain a
smooth cam profile.
At the
low·
frre
screw,
the
oil flow should
be
adjusted to obtain
the
necessary input for the
fuel
turndown required. The second adjusting screw
may
need to
be
adjusted
in
order to maintain a
smooth cam profile.
V.
BURNER
DRAWER
ADJUSTMENT
There are relatively few adjustments that can
be
.
made to the burner. However, a check should
be
made to see that
all
components are properly
located
and
that
all
holding screws
are
properly
tightened. Figures S-10
and
S-11
show various
views or portions
of
the burner.
The diffuser location on gas fired boilers
is
quite
important. There should
be
1/4"
between
the
edges
of
the diffuser
fins
and
the
gas
outlet tubes
(spuds). (See Figure
5-11) The setting
of
an
oil
fired burner
is
less exacting
and
the
diffuser
should
be
located with
the
skirt approximately
1-1/8" from the end
of
the burner tube.
When
the
proper diffuser location
is
ascertained,
the
setting
of
the nozzle
in
relation to the diffuser
should
be
checked. This generally
is
set
at
the
time
of
manufacture
and
seldom needs altering.
It
is
most important that
oil
spray does not im-
pinge upon the diffuser. The distance that the
nozzle
is behind
the
diffuser
has
some latitude
and
individual installations may require a slight
deviation. The spacing indicated
is
2".
Check
the
setting
of
the
ignition electrode(s) for
proper gap
and
position. See Figure 5-10 for
the
gas
pilot electrode
and
Figure
5-9
for
the
light oil
750-150
ADJUSTMENT PROCEDURES
pilot. Make sure that
the
porcelain insulator
is
not
cracked and that
the
ignition cable connections
are tight.
The oil
nozzle tip
sho1:1ld
be
seated tightly
in
the
body
with
the
swirler
and
the
seating spring
in
place.
See
Section G
in
Chapter 7 for additional
nozzle tip information.
Cleek to see that
the
flame detector sight tube
and
the gas pilot tube extend through their
respective openings
in
the
diffuser face. .
W.
OIL
DRAWER
SWITCH
The integral contacts
of
this
control
are
closed by
proper positioning
and
latching of
the
oil
drawer
in
its
forward position. Adjustment
of
the
switch
must
be
such that
its
contacts open if
the
oil
drawer
is·
not properly positioned
for
oil
firing.
The switch
is
electrically removed
from
the
cir-
cuit
when a combination
fuel
burner
is
fired
on
gas.
X.
LOW OIL
TEMPERATURE
SWITCH
This control prevents
the
burner
from
starting, or
stops
its
operation, if
the
temperature of
the
oil
is
below the normal operating temperature.
To adjust
this
control, insert a screwdriver
into
the
center slot
in
the
control cover
and
tum
the
dial until the fixed (center) pointer
is
ap-
proximately
30•F lower than the oil heater
thermostat setting. Tum
the
differential adjusting
screw (located above
the
dial) until
the
movable
indicator
is
approximately
s·
F above
the
setting
on
the
main scale.
On
a hot water boiler,
the
low
oil temperature
switch
is
an
integral part
of
the
electric
oil
heater.
The switch
is
nonadjustable
and
is
factory set
at
approximately
40•
F below
the
maximum operat-
ing
temperature
of
the
heater.
CHAPTER 5·23
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