Nordyne O4HD-091A-14-FA-DV Installation, Operation And Maintenance Manual page 23

Table C-1" 1158-120 ELECTRONIC FAN TIMER BOARD (EFT) DETAILED SEQUENCE OF
OPERATION
Mode Action
H EAT
Thermostat calls for heat. ("W"
terminal is energized).
Thermostat ends call for heat.
CW" terminal is de-energized).
Burner fails to light.
Established flame fails.
Thermostat begins call for cool, Cooling contactor is energized immediately,
(G and Y terminals are Circulator fan is energized at cool speed,
COOL energized),
Thermostat ends call for cool, (G Cooling contactor is de-energized immediately,
and Y terminals are de-
Circulator fan turns off immediately,
energized),
Thermostat begins call for fan.
Circulator fan is energized immediately at cooling speed,
FAN (G terminal is energized),
Thermostat ends call for fan. (G
terminal is de-energized). Circulator fan is de-energized immediately,
Limit switch string opens.
System Response
EFT closes the oil primary control T - T connections).
Ignition system and the oil primary control start the furnace. Oil flows as long as the oil
primary control senses flame.
Burner motor is energized and heat "fan on" delay timing begins. When timing is
complete, the circulator fan is energized at heat speed.
The oil primary control is de-energized, terminating the burner cycle.
Heat "fan off" delay timing begins. Length of delay depends on EFT dipswitch settings.
When timing is complete, the circulator fan is de-energized.
EFT returns to standby mode, (Oil primary control and circulator fan are off, unless
continuous fan operation is selected at the thermostat).
Oil primary control locks out within lockout timing, (30 seconds).
Burner motor is de-energized. (Even though thermostat is still calling for heat).
If circulator fan has started, it continues through the selected heat "fan off' delay
period.
Burner motor is de-energized and oil primary control goes into recycle mode.
If the selected heat "fan off" delay timing is longer than the recycle delay timing, the
circulator fan continues to run through the next trial for ignition.
Oil primary control shuts off burner.
Circulator fan is energized immediately at heat speed.
EFT opens the 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 heating to cooling
speed.
LIMIT EFT begins heat "fan off" delay sequence.
Limit switch string closes (with Circulating fan turns off after the selected heat "fan off" timing.
existing call for heat). EFT re-closes the oil primary control T - T connections.
Oil primary control is energized, initiating burner light off.
Circulator fan turns off when heat "fan off" delay time is complete.
Limit switch string closes
Normal operation resumes; EFT control is in standby mode awaiting next thermostat
(without existing call for heat), command.
Continuous circulating fan is Circulating fan is energized when there is no call for heat, cool, or fan.
FAN connected. If fan operation is required by a call for heat, cool, or fan, the EFT switches off the
continuous fan speed tap before energizing the other fan speed.
Electronic air cleaner (EAC) connections are energized when the heat or cool speed of
Electronic Air Cleaner is
EAC connected, the circulator fan is energized. EAC connections are not energized when the optional
continuous fan terminal is energized.
HUM Humidity control is connected. Humidifier connections are energized when the oil burner motor is energized.
1168-1 ELECTRONIC FAN TIMER BOARD (EFT) DETAILED SEQUENCE OF OPERATION
Thermostat Input LEDs (LED1-5, LED8)
Six green LEDs are placed behind their respective thermostat connections (Y1, Y/Y2, G, DH, O, and W) and operate whenever a
call is present.
Thermostat calls for heat "W". The 24VAC input signal is passed to pin 2 of P1 and wilt drive the K1 relay that provides
dedicated contacts to the T-T input of the Oil Primary Control. Thermostat calls for cool "YI". The 24VAC input signal is passed
to pin 6 of PI. Thermostat calls for fan "G". The 24VAC input signal is passed to pin 15 of PI. Thermostat calls for
dehumidification "DH". The 24VAC input signal is passed to pin 10 of PI. Thermostat calls for reversing valve "O". The
24VAC input signal is passed to pin 9 of PI.
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