Field Controls WML-C - Manual (Page 25)

30318 R4 9/9/2005
25
Table C-1: ELECTRONIC FAN TIMER BOARD (EFT) DETAILED SEQUENCE OF OPERATION
Mode Action System Response
Thermostat calls for heat. ("W"
terminal is energized).
a. EFT closes oil primary control T - T connections).
b. Ignition system and R7184 oil primary control start the furnace. Oil flows as long as
the oil primary control senses flame.
c. Burner motor is energized and heat "fan on" delay timing begins. When timing is
complete, the circulator fan is energized at heat speed.
Thermostat ends call for heat.
("W" terminal is de-energized).
a. R7184 oil primary control is de-energized, terminating the burner cycle.
b. Heat "fan off" delay timing begins. Length of delay depends on EFT dipswitch
settings. When timing is complete, the circulator fan is de-energized.
c. EFT returns to standby mode, (Oil primary control and circulator fan are off, unless
continuous fan operation is selected at the thermostat).
Burner fails to light.
a. Oil primary control locks out within lockout timing, (30 seconds).
b. Burner motor is de-energized. (Even though thermostat is still calling for heat).
c. If circulator fan has started, it continues through the selected heat “fan off” delay
period.
HEAT
Established flame fails.
a. Burner motor is de-energized and oil primary control goes into recycle mode.
b. 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.
Thermostat begins call for
cool. (G and Y terminals are
energized).
a. Cooling contactor is energized immediately.
b. Circulator fan is energized at cool speed.
COOL
Thermostat ends call for cool.
(G and Y terminals are de-
energized).
a. Cooling contactor is de-energized immediately.
b. Circulator fan turns off immediately.
Thermostat begins call for fan.
(G terminal is energized).
a. Circulator fan is energized immediately at cooling speed.
FAN
Thermostat ends call for fan.
(G terminal is de-energized).
a. Circulator fan is de-energized immediately.
Limit switch string opens.
a. Oil primary control shuts off burner.
b. Circulator fan is energized immediately at heat speed.
c. EFT opens oil primary control T - T connections. Circulating fan runs as long as
limit string stays open.
d. If there is a call for cooling or fan, the circulating fan switches from heating to
cooling speed.
Limit switch string closes
(with existing call for heat).
a. EFT begins heat “fan off” delay sequence.
b. Circulating fan turns off after the selected heat “fan off” timing.
c. EFT re-closes oil primary control T - T connections.
d. Oil primary control is energized, initiating burner light off. LIMIT
Limit switch string closes
(without existing call for heat).
a. Circulator fan turns off when heat “fan off” delay time is complete.
b. Normal operation resumes; EFT control is in standby mode awaiting next
thermostat command.
FAN
Continuous circulating fan is
connected.
a. Circulating fan is energized when there is no call for heat, cool, or fan.
b. 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.
EAC
Electronic Air Cleaner is
connected.
• Electronic air cleaner (EAC) connections are energized when the heat or cool
speed of 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.