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NORA Oilheat Technicians Manual

Action System Response Thermostat calls for heat. • ST9103A closes oil primary control T-T connections. • Ignition system and oil primary control start the furnace. Oil flows as long as oil primary control senses flame. • Burner motor is energized and heat fan on delay timing begins. When timing is complete, the circulating fan is energized at heat speed and warm air is delivered to the controlled space. Thermostat ends call for heat • Oil primary control is de-energized, terminating the burner cycle. • Heat fan off delay timing begins. When timing is complete, the circulating fan is de-energized. • ST9103A returns to standby mode (oil primary control and circulating fan are off. Burner fails to light • Oil primary control locks out within lockout timing (timing depends on oil primary control). • Burner motor is de-energized. • If heat fan has started, it continues through the selected delay period. Established flame fails • Burner motor is de-energized and oil primary control goes into recycle mode. • If selected heat fan off delay is longer than the recycle delay timing, the heat fan continues to run through the next trial for ignition. Thermostat begins call for cool • Circulating fan is energized at cool speed. • Cooling compressor turns on immediately. Thermostat ends call for cool • Circulating fan and cooling compressor turn off immediately. (G and Y terminals are de-energized) Thermostat begins call for fan • Circulating fan is energized immediately at cool speed. • ST9103A may be factory-configured to operate heat speed in this mode. Thermostat ends call for fan • Circulating fan is de-energized. (G terminal is de-energized) Limit switch string opens • Oil primary controls shuts off burner. • Circulating fan is energized immediately at heat speed. • ST9103A opens oil primary control T-T connections. • Circulating fan runs as long as limit string stays open. • If there is a call for cooling or fan, the circulating fan switches from heat speed to cool speed. Limit switch string closes • ST9103A begins heat fan off delay sequence. • Circulating fan turns off after the selected heat fan off delay timing. • ST9103A recloses oil primary control T-T connections. • Oil primary control is energized, initiating burner light off. Continuous circulating fan is connected • Circulating fan is energized at low speed when there is no call for heat, cool or fan. • If fan operation is required by a call for heat, cool or fan, the ST9103A switches off the continuous fan speed tap before energizing the other fan speed. Electronic air cleaner is connected • Electronic air cleaner (EAC) connections are energized when the heat or cool (Optional connectors are available speed of the circulating fan is energized. EAC connections are not energized for 120 Vac electronic air cleaner) when the optional continuous fan terminal is energized. Humidity control connected • Humidifier connections are energized when burner motor is energized. (Optional connectors are available for 120 Vac humidifier) Chapter 12—Limit Controls and Thermostats 12-13 (W terminal is energized) (G and Y terminals are de-energized) (G terminal is energized) Table 12-1 Chapter 12 Limit Controls/Thermostats


NORA Oilheat Technicians Manual
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