Profire V Burner Chapter 2
750-177 2-15
FULL MODULATION - OPEN DAMPER PURGE
Combustion Air Gas Oil
COMPONENTS
DESCRIPTION
A two blade damper is controlled by a
proportional modulating actuator (or
motor) with mechanical linkage. The
modulating actuator is capable of
stopping at any point along its 90
degree stroke based on a signal from
a remotely connected modulating
control or from a burner mounted
manual potentiometer which is
selected through an auto/manual
modulation selector switch. The
actuator also contains two internal
switches that ensure the damper
reach the high fire and low fire
positions during purge and 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 relative to the actuators
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 a return flow nozzle. In the return
line from the nozzle an adjustable oil metering valve
limits the amount of oil allowed to return to the pump.
The metering valve is connected to the damper
actuator with mechanical linkage.
Operating Sequence
PRE-PURGE
From its closed position the damper
is driven open by a signal from the
flame safeguard control where the
high fire air switch is proven. The
damper will remain open 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 internal low
fire air proving 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 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 pressure setting less the volume of oil
returning through the metering valve.
RUN,
MODULATE
Damper is driven by the modulating
actuator to a firing rate position as
determined by the modulating control or
manual potentiometer. Actuator can
complete full travel to high fire in 30
seconds. Actuator will then continue to
adjust firing rate position based on signals
from the modulating control until demand
is satisfied.
The gas valves remain in their open
position. As the actuator begins it's travel
to the firing rate position it is also
adjusting the butterfly gas metering valve
increasing the flow of gas to the manifold.
The burner will continue to modulate as
described under the combustion air
heading until demand is satisfied.
The safety shut-off oil valves remain open. As the
actuator begins it's travel to the firing rate position it is
also adjusting the oil metering valve decreasing the
amount of oil allowed to return to the pump. This in
turn is increasing the pressure and volume of oil at the
nozzle. The burner will continue to modulate as
described under the combustion air heading until
demand is satisfied.
SHUT DOWN,
POST-PURGE
Damper returns to its starting position
based on the 30 second closure speed of
the mechanical actuator during post purge.
On shut down all gas valves close within 1
second. The butterfly valve closes in 30
seconds with the damper actuator.
All valves immediately close. The metering valve
opens to it's low fire position in 30 seconds with the
damper actuator. The oil pump is operating with post-
purge, but oil is flowing through an internal relief valve
and returning to the supply system.
VARIATIONS:
Options are available for 4-20amp
modulating signal conversion or 4-20
proportional modulating actuators.
Also optional is an actuator with dual
low fire start switch positions for
improved "turn down" in dual fuel
situations.
None
On models with a simplex nozzle oil is diverted
from the supply line through the meter and
back to the pump before the first safety shut-off
valve.
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