750-96 (revised 2010)
Model CB Packaged Boiler Manual
5-9
5.6 — Gas Pilot Flame Adjustment
5.6 — Gas Pilot Flame Adjustment
The size of the gas pilot flame is regulated by adjusting the gas flow through the pilot gas regulator and the adjust-
ing cock. The flame must be sufficient to ignite the main flame and to be seen by the flame detector but an
extremely large flame is not required. An overly rich flame can cause sooting of the flame detector. Too small a
flame can cause ignition problems.
8. Combustion air Proving
Switch: Honeywell C645A
Air pressure against the diaphragm actuates the switch which, when made, com-
pletes a circuit to prove the presence of combustion air. Since the pressure of the
combustion air is at its minimum value when the damper is full open, the switch
should be adjusted under that situation. It should be set to actuate under a condition
of minimum pressure, but not too close to that point to cause nuisance shutdowns.
The test switch on the program relay should be set to TEST. Turn the burner switch
on. The blower will start (provided that all limit circuits are completed) and the pro-
grammer will remain in the low fire (damper closed) portion of the pre-purge.
To have the modulating damper motor drive to high fire (damper open), remove the
cover from the motor and remove the wire from terminal W.
Slowly turn down the air switch adjusting screw until it breaks the circuit. At this point
the programmer will lockout and it must be manually reset before it can be restarted.
Add a half turn or so to the adjusting screw to remake its circuit.
Recycle the program relay to be sure that normal operation is obtained. Replace the
wire on terminal W and reinstall the cover. Return the test switch to the RUN position.
NOTE: On an oil fired boiler, the atomizing air proving switch (AAPS) must also be
made. On a combination fuel fired burner, the fuel selector switch could be set at
“gas” to eliminate the atomizing air proving switch from the circuitry.
9. Atomizing Air Proving
Switch: Dietz 162 P15
Air pressure against the diaphragm actuates the switch which, when made, com-
pletes a circuit to prove the presence of atomizing air. Since the pressure of the atom-
izing air is at its minimum value when there is no fuel present at the nozzle,
adjustment of the switch should be done while the unit is running but not firing. The
control should be set to actuate under a condition of minimum pressure, but not too
close to that point to cause nuisance shutdowns.
The control adjustment may be made during the pre-purge period of operation by
stopping the programmer during the pre-purge period through the use of the TEST
switch. Refer to the control instruction bulletin for details.
The adjustment screw of the atomizing air proving switch can then be adjusted until it
breaks the circuit. At this point, the programmer will lockout and it must be manually
reset before it can be restarted. Turn the adjusting screw up a half turn or so to
remake the circuit.
Since the adjustment of the air switch may be made either during the damper closed
or open positions or pre-purge, it is also possible to make the adjustment with the
relay stopped in the damper open position in a similar manner to the adjustment of
the combustion air proving switch described in the previous section.
After making the adjustment, recycle the control to be sure that normal operation is
obtained. The TEST switch must be set to the RUN position.
Control Setting
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