Gas Control Valve - L.B.White Sentry ST60 Manual Del Propietário

Air diff erential switch:
The air differential switch is a normally open, critical
safety device. See Fig. 21 for location. Its purpose is
to prove to the ignition control that there is a suffi cient
difference in pressure within the burner box before the
ignition control sends power to open the gas control
valve.
FIG. 21
Its electrical contacts close based on the difference
between pressures between the air inlet and the
burner box compartment. If the switch does not close
after the fan motor starts, the igniter will not spark
nor will the gas control valve open. A rapid fl ash will
occur on the red fault diagnostic light. The ignition
control will lock-out for 60 seconds before another trial
attempt. After three (3) fail attempts, a 2-time fl ash
pattern will occur. The same will occur if the fan motor
does not start on a call for heat.
If the switch is already closed from a past ignition
trial, and stays closed prior to a call for heat, the fan
motor will not start, nor will the igniter spark or the
valve open. A rapid fl ash will occur on the red fault
diagnostic light. The ignition control will lock-out for 60
seconds before another trial attempt. After three (3)
failed attempts, a 1-fl ash pattern will occur.
The air differential switch orifi ces should be free of
dirt. If cleaning is needed, use pressurized air:
• Remove the respective orifi ce from the switch.
• Hold up to light. If blocked, clean with air.
• Ensure the orifi ces are pushed back into the proper
location on the switch. See Fig. 22.
• Green orifi ce into black stem
• Blue orifi ce into white stem on switch.
Sentry Tube Heaters
FIG. 22

Gas Control Valve

1. Remove the hose from the sediment trap
2. Remove the two (2) nuts that secure the gas con-
trol valve's mounting bracket to the center partition
of the burner box. See Fig. 23.
FIG. 23
3. Remove the four (4) screws from the gas valve
door. See Fig. 24.
FIG. 24
Owner's Manual • Sentry
21
GREEN
BLUE