Adjustment Procedures
6-10
750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual
6.12 — Low Water Cutoff Devices: Steam & Hot Water
No adjustment is required since LWCO controls are preset by the original manufacturer. However, if the water
level is not properly maintained, inspect the devices immediately and replace as required.
6.13 — Combustion Air Proving Switch
Air pressure against the diaphragm actuates the switch which, when made, completes a circuit to prove the pres-
ence 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 slightly below the minimum pressure, but
not too close to that point to cause nuisance shutdowns.
The run/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 programmer will remain in the low-fire (damper closed) por-
tion 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 Combustion Air Proving Switch (CAPS) adjusting screw until it breaks the circuit. Here the
programmer will lock out and must be manually reset before it can be restarted. Add a half turn or so to the adjust-
ing screw to remake its circuit.
Recycle the program relay to be sure that normal operation is obtained. Replace the wire on terminal W and re-
install the cover. Return the test switch to the RUN position.
6.14 — Atomizing Air Proving Switch
The air pressure against the diaphragm actuates the switch which, when closed, completes a circuit to prove the
presence of atomizing air. Since the pressure of the atomizing air is at its minimum value when there is no fuel pres-
ent at the nozzle, adjustment of the switch should be done while the unit is running but not firing. The control
should be set slightly below the 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. Here, the
programmer will lock out and must be manually reset before it can be restarted. Turn the adjusting screw up a half
turn or so to remake the circuit.
NOTE: On an oil fired boiler, the atomizing air proving switch (AAPS) must also be closed.
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.
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