Installation
2-14
IC-SA-1511 (02/2014)
V/LNV Series Manual
LOW-HIGH-OFF OPERATION - LOW or 60% DAMPER PURGE
Combustion Air
Gas
Oil
COMPONENTS
DESCRIPTION:
A two blade damper is controlled
by a two position, spring return
actuator with mechanical
linkage. For 60% damper purge
a mechanical stop is provided on
the damper to ensure sufficient
air flow is provided during pre-
purge. Damper position is
controlled by a two position,
spring return actuator with
mechanical linkage. The actuator
also contains a limit switch which
is used to actuate the second
stage of the oil supply system.
(see oil at right)
Two safety shut off valves are
provided to initiate the flow of gas.
The primary is a diaphragm or
motorized type. On diaphragm gas
valves the time to open can be
adjusted by a bleed valve. On
models with motorized valves the
time to open is fixed at 13
seconds. A butterfly type gas
metering valve is linkaged directly
to the damper actuator and
provides gas flow metering during
the drive to the high position. A
manually adjusted gas regulator
limits maximum firing rate.
Pressure Atomization:
Two solenoid type safety
shut off oil valves initiate the flow of oil from the
high pressure pump to the nozzle. The oil pump
has a built in solenoid controlled two level
pressure regulating system. Low and high flow
rates are set on the pump based on pressure and
the nozzle's flow rating.
Operating Sequence
PRE-PURGE:
Damper is in its closed or low fire
position. For 60% damper purge
this would be against the
mechanical stop.
Valves are closed.
The pump is operational but the valves are closed.
Oil is flowing through an internal relief valve and
returning to the supply system.
STARTUP,
IGNITION:
Damper remains in its low fire
starting position.
Valves open. To prevent a surge
the primary gas valve opens at a
slowed rate. Gas flow to the
manifold is metered based on the
butterfly valves low fire setting.
Safety shut off valves open allowing oil to flow
from pump to nozzle. Oil pressure at the nozzle is
based on the pump's low pressure setting.
Excess oil is flowing through an internal relief
valve and returning to the supply system.
RUN,
MODULATE:
Damper is driven open in 30
seconds by the two position
actuator. Low-High-Off burners
have no provision to modulate
the burner once high fire rate has
been achieved.
The gas valves remain in their
open position. The actuator begins
it's travel to the high fire position
opening the gas metering valve.
The burner will remain at high fire
until demand is satisfied.
The safety shut-off oil valves remain open. The
pump's solenoid is energized by the auxiliary
switch within the damper actuator as it opens the
air damper. Oil pressure is then increased based
the pumps high pressure setting. The burner will
remain at high fire until demand is satisfied.
SHUT DOWN,
POST-PURGE:
Damper returns to its start
position based on the 25 second
closure speed of the mechanical
actuator.
On shut down all gas valves close
within 1 second. The butterfly
valve closes in 25 seconds with
the two position actuator.
All valves immediately return to their startup or de-
energized position. The oil pump is operating with
post-purge, but oil is flowing through an internal
relief valve and returning to the supply system.
VARIATIONS:
None
None
For pumps without the internal dual pressure
solenoid an external pressure relief valve and
normally open solenoid valve are used.
LIGHT
OIL
PUMP
S
S
NOZZLE
SAFETY
SHUT-OFF
VALVES
OIL INLET
OIL RETURN
2 LEVEL PRESSURE
SOLENOID
LOW/HIGH
MODULATION WITH
2 LEVEL PUMP
PRESSURE
OIL INLET
OIL RETURN
LIGHT
OIL
PUMP
S
S
NOZZLE
SAFETY
SHUT-OFF
VALVES
LOW/HIGH
MODULATION
S
N. O.
OIL
VALVE
PRESSURE
RELIEF VALVE