Bard W24G2DA, Installation Instructions Manual

Page: 40 / 69

Manual 2100-592C
Page
40 of 69
FIGURE 17
Sequence of Operation
Electronic Blower Control
Action System Response
Thermostat calls for heat
(W terminal is energized). • Combustion air blower is energized.
• Air proving switch makes. Airflow is established.
• Ignition system is energized.
• Gas valve opens and main burner lights.
• Heat fan on delay timing begins. When timing is complete, the circulating fan is
energized at heat speed.
Thermostat ends call for heat. • Ignition system is de-energized and gas valve closes.
• Combustion air blower is de-energized after postpurge timing.
• Heat fan off delay timing begins. When timing is complete, the circulating fan is
de-energized.
Thermostat begins call for cool
(G and Y1 terminals re-energized). • Cooling contactor is energized.
• Circulating fan is energized on cool speed after cool fan on delay timing.
Thermostat begins call for fan
(G terminal is de-energized). • Circulating fan is de-energized
Limit (flame rollout) opens. • Thermostat and ignition system are de-energized and gas valve closes.
• Combustion air blower and circulating fan heat speed are energized.
Limit (auto reset) or flame rollout
(manual reset) circuit closed. • Combustion air blower remains energized for postpurge timing.
• The circulation fan remains energized for the selected delay off timing.
• Normal operation resumes.