Safety And Controls; Automatic Ignition - CleaverBrooks 5 Manual

Section 2 — Profire Burner
A
Figure 2-5 Panel Open, Flame
Safety and Fuel Selector Switch
.
PILOT TUBE
GAS ASPIRATING HEAD
ELECTRODE ASSEMBLY
1/8" GAP
Figure 2-6 Gas Pilot Assembly
2-6
F. SAFETY AND CONTROLS
Flame Safety (Figure 2-5, A): The flame safeguard controls
the operating sequences of the combustion system
(prepurge, pilot, firing, and shutdown). The control also
monitors the flame, using a scanner which is sensitive to
specific flame frequencies. The flame safeguard also
automatically shuts down the burner when the flame signal
becomes too weak. Different types of flame safeguard
B
devices can be installed in the combustion systems. Check
the wiring diagram for your burner for information on the
specific unit installed on your burner.
Fuel Selector Switch (Figure 2-5, B): Allows the operator to
select either gas or oil as the active fuel on combination
burners.
Combustion Air Proving Switch (Figure 2-1). The combustion
air proving switch provides confirmation to the flame
safeguard that the combustion air fan is providing air flow.
The fuel supply valves will not open if this switch does not
sense adequate air pressure.
Modulating Motor (Figure 2-3). The modulating motor is
coupled to the jack shaft that operates the main air shutter
and the fuel valve linkages. The modulating motor produces
the torque and rotary positioning required for firing rate
control.
Rear Cap (Figure 2-3). The rear cap contains the locking
setscrew for adjustment of the diffuser relative to the air
baffle, and also the flame scanner for the flame safeguard.
The rear cap must be removed to enable removal of the oil
gun assembly.
The actual controls furnished with any given boiler will
depend upon the type of fuel for which it is equipped.
Boilers having optionally ordered features may have control
components not listed here.
G. AUTOMATIC IGNITION
The burner is ignited by an interrupted type gas pilot
The gas pilot flame is ignited automatically by an electric
spark. Fuel for the pilot is supplied from the utility mains or
from a tank (bottle) supply. Flow rate (flame size) is
regulated by a pressure regulator.
At the beginning of the ignition cycle, the pilot gas solenoid
1/4"
valve and ignition transformer are simultaneously energized.
The ignition transformer high voltage current for the igniting
spark which arcs between the single electrode within the
pilot tube and the wall of the tube itself. The gas pilot
solenoid and transformer are de-energized after main flame
is ignited.
Part No. 750-215