CHAPTER!
GENERAL DESCRIPTION AND PRINCIPLES OF OPERATION
that
is
provided to supply heated oil on cold
starts. The steam heater thermostat controls the
operation
of
the steam solenoid valve to permit a
flow
of
steam to the heater when steam
is
avail-
able.
A hot water boiler
is
equipped to heat the oil with
hot water from the boiler unless other pre-heating
equipment
is
utilized. The electric heater, which
is
housed separate! y, is sized to provide heated
oil on a cold start. The hot water thermostat
controls the operation
of
a pump that supplies hot
water
to the oil heater when hot water
is
avail-
able.
The heated oil flows through a fuel oil strainer to
prevent any foreign matter from entering the
control valves and nozzle.
The fuel oil controller contains in a single unit
the necessary valves, regulators and gauges to
regulate the pressure and flow
of
oil to the burner.
The program relay energizes
or
de-energizes the
solenoid oil valve to permit
or
cut
off
oil fJow to
the burner. The oil solenoid
is
closed when de-
energized. It cannot
be
opened (energized) unless
the combustion air proving switch, the atomizing
air proving switch and the low oil temperature
and any pressure switches are closed. These are
satisfied, respectively, by sufficient combustion
air pressure from the forced draft fan, pressurized
air from the air pump and sufficient oil tempera-
ture and pressure.
Oil flow to the burner
is
controlled by the move-
ment
of
the metering stem
of
the oil metering
valve,
which
varies the flow to
meet
load
demands. The metering valve and the air dam per
are controlled simultaneously at all times by the
modulating motor to proportion combustion air
and fuel for changes
in
load demand.
Oil
is
purged from the burner gun upon each
burner shut down. The air purge solenoid valve
opens
as
the fuel valve closes and diverts atomiz-
ing air through the oil line. This assures a clean
nozzle and line for the subsequent restart.
750-150
P.
GAS
FUEL
FLOW
The gas flow system
is
shown in Fig. 1-4. Gas
flow
is
indicated by arrows and the pertinent
controls are shown. Combustion air travel
is
also
shown and indicated by a different type
of
arrow.
Metered gas from the utility flows through the
pressure regulator at a reduced pressure suitable
to the burner's requirements, through the main
gas
shut-off
cock,
main
gas
valve(s)
and
modulating butterfly gas valve
to the non-premix
orifice type burner.
The main gas valve
is
of
the normally closed type
and
is
opened (energized) in proper sequence
by
the programming relay.
The butterfly gas valve modulates the flow
of
gas
from low through high
flre settings. The position
ofthe
butterfly valve disc
is
governed by the gas
modulating cam. The butterfly gas valve, and the
air control damper are controlled simultaneously
by the modulating inotor to proportion combus-
tion air and fuel for changes
to
load demand.
The gas flow rate required for rated burner input
depends upon the heating value (BTU/cubic
foot)
of
the gas supplied. The gas pressure
regulator adjusts the gas pressure (flow rate)
to
the entrance
of
the gas train. The regulator
is
not
always supplied with the burner, but may
be
provided by others.
The
main
gas
valves
cannot
be
energized
(opened) unless the combustion air proving
switch
is
closed
to
indicate a sufficient supply
of
combustion air. The low gas pressure and high
gas
pressure switches must
be
closed
to
prove
sufficient, but not excessive, gas fuel pressure.
CHAPTER
1·21
To Next Page
Loading...
