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Idiomas disponibles
Idiomas disponibles
Motor and Fan Assembly
A. Motor/Fan wheel removal.
1. Disconnect motor leads.
2. Remove motor mount screws. See Fig. 17
3. Remove motor/fan wheel assembly from the
burner box.
FIG. 17
Air Differential Pressure
Switch, Tubing and
Orifices.
Pressure switch tube: See Fig. 18. Check for
blockage. Clean with compressed air after removing
the tube from the switch and the brass fittings.
FIG. 18
Sentry Tube Heaters
Air differential switch:
The air differential switch is a normally open, critical
safety device. Its purpose is to prove to the ignition
control that there is a sufficient difference in pressure
within the burner box before the ignition control sends
power to open the gas control valve.
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 flash 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 flash
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 flash 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-flash pattern will occur.
The air differential switch orifices should be free of
dirt. If cleaning is needed, use pressurized air:
• Remove the respective orifice from the switch.
• Hold up to light. If blocked, clean with air.
• Ensure the orifices are pushed back into the proper
location on the switch. See Fig. 19.
• Green orifice install into negative (grey) barb.
• Blue orifice install into positive (black) barb.
FIG. 19
Owner's Manual • Sentry
21
BLUE
GREEN
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