5
69-0780
Action
System Response
Primary limit switch string closes.
• Circulating fan turns off after the selected heat fan off delay timing.
• LED stops flashing.
• Normal operation resumes.
Primary limit switch string is open
• Combustion air blower, circulating fan and ignition system are de-energized.
for more than 150 seconds (on each
• Control goes into lockout mode.
of three consecutive cycles).
• LED flashes four times.
• Control remains in lockout until 24V power is removed and reapplied (control
is reset).
• LED stops flashing.
• Normal operation resumes.
Burner limit opens.
• Thermostat and ignition system are de-energized and gas valve closes.
• Combustion air blower and circulating fan heat speed are energized.
• LED flashes once.
Burner limit closes.
• Combustion air blower remains energized for postpurge timing.
• The circulating fan remains energized for the selected delay off timing.
• LED stops flashing.
• Normal operation resumes.
Electronic air cleaner is connected.
• Electronic air cleaner is energized when the circulating fan heat or cool speed
(Connector to 120 Vac electronic
is energized.
air cleaner.)
Humidity control is connected.
• Humidifier is energized when combustion air blower is energized.
(Connector to 120 Vac humidifier.)
ST9141A1002 Operating Sequence (Continued)
