IC-SA-1511 (02/2014)
V/LNV Series Manual
2-15
Installation
LOW-HIGH-OFF OPERATION - OPEN DAMPER PURGE
Combustion Air
Gas
Oil
COMPONENTS
DESCRIPTION:
A two blade damper 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) A
second external switch ensures
the damper has returned to the
low fire position before ignition is
initiated.
Safety shut off valve(s) are
provided to initiate the flow of gas.
The primary is a diaphragm or
motorized type valve which have
delayed opening rates to prevent
an "in rush" of gas. A butterfly type
gas metering valve is linked
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:
From its closed position the
damper is driven open by the
flame safeguard control where it
remains for the duration of the
pre-purge cycle.
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 returns to the low fire
position which is proven through
the external switch. The burner is
now ready for startup.
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 valve’s 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