Chapter 6 — Adjustment Procedures
6-10 Part No. 750-184
L. LOW WATER CUTOFF DEVICES (STEAM AND HOT
WATER)
No adjustment is required since LWCO controls are preset by the
original manufacturer. However, if the water level can not be
properly maintained, inspect the devices immediately and replace
as required.
M. COMBUSTION AIR PROVING SWITCH (CAPS)
Air pressure against the diaphragm actuates the switch which,
when made, completes a circuit to prove the presence of
combustion air. The pressure of the combustion air is at its
minimum value when the damper is full open. The Combustion Air
Proving Switch should be adjusted with the damper fully open. 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) portion of the prepurge.
Note: On an oil fired boiler, the atomizing air proving switch
(AAPS) must also be closed.
Note: 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.
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
, 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 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.
N. 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. The pressure of the atomizing 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 slightly below the minimum pressure, but not too
close to that point to cause nuisance shutdowns.
The control adjustment may be made during the prepurge period of
operation by stopping the programmer during the prepurge period
through the use of the TEST switch. Refer to the control instruction
bulletin for details.
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