Cleaver-Brooks CBH 40 - Automatic Ignition; Combustion Air; Oil Fuel Flow

line when the gas valves are de-energized. The
vent valve closes when the gas valves are
energized.
MAIN GAS COCK (Figure 1-4)
For manually opening and closing the main fuel
gas supply downstream of the main gas line
pressure regulator. A second shut-off cock, down-
stream of the main gas valve(s), may be installed
to provide a means of shutting off the gas line
whenever a test is made for leakage across the
mam gas valve.
LOW GAS PRESSURE SWITCH (Figure 1-4)
A
pressure actuated switch that is closed whenever
main gas line pressure is above a preselected
pressure. Should the pressure drop below this set-
ting, the switch contacts will open a circuit causing
the main gas valve(s) to close, or prevent the bur-
ner from starting. This switch is usually equipped
with a device that must be manually reset after
being tripped.
HIGH GAS PRESSURE SWITCH (Figure 1-4)
A
pressure actuated switch that is closed whenever
main gas line pressure is below a preselected pres-
sure. Should the pressure rise above the setting, the
switch contacts will open a circuit causing the
main gas valve(s) to close, or prevent the burner
from starting. The switch is usually equipped with
a device that must be manually reset after being
tripped.
LEAKAGE CONNECTION
The body of the gas valve has a plugged opening
that is used whenever it is necessary or desirous to
conduct a test for possible leakage across the
closed valve.
D. AUTOMATIC IGNITION
A gas burner (and an oil burner on a combination
unit), is ignited by an interrupted type gas pilot.
Some insurance regulations require that a light oil
burner (Model 100) be ignited with a gas pilot al-
though standardly this model has spark ignition.
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 (Figure 1-4 ). The burner is designed to
have combustion air flow into and mix with the
pilot gas stream to provide a suitable flame.
At the beginning of the ignition cycle, the pilot gas
solenoid valve and ignition transformer are
simultaneously energized. The ignition trans-
former supplies high voltage current for the
igniting spark which arcs between the single elec-
trode 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.
Chapter 1-General Description and Principles of Operation
On a Model 100 boiler with spark ignition, the low
fire oil
nozzle is ignited by a spark arcing between
two electrodes supplied with high voltage current
from the ignition transformer. At the beginning of
the ignition cycle, the low fire oil solenoid valve
and ignition transformer are simultaneously ener-
gized. The ignition transformer is de-energized af-
ter low fire is established and proven.
E. COMBUSTION AIR
Air for the combustion of fuel, (also called "sec-
ondary" air) is furnished by the forced draft fan
(Figure 1-3) mounted in the front head. In oper-
ation, air pressure is built up in the entire head
and forced through a diffuser plate for a thorough
mixture with the fuel for proper combustion.
The supply of combustion air is governed by auto-
matically throttling the output of the fan by
regulating the air damper to furnish the proper
amount of air for correct ratio of air to fuel for ef-
ficient combustion at both low and high firing
rates.
F. Oil FUEl FlOW
An oil fired boiler is equipped with a belt driven
fuel pump (Figures 1-1 & 1-5) that withdraws fuel
oil from a storage tank. The pump has a greater
capacity than the maximum burning rate and all
oil not delivered to the burner nozzles is returned
to the storage tank.
The pump has an integral pressure regulator that
can be adjusted to provide the necessary atomizing
SUPPORT FROM BUILDING
CONSTRUCTION
Discharge opening
MUST be larger than
inlet
TO STEAM
VENT
WATER LEVEL
NOTE: Back-pressure of steam exhaust system MUST
be less than 10% of safety valve setting-!--
FIGURE 1-7. RECOMMENDED
SAFETY VALVE INSTALLATION PROCEDURE
1-9