20
Table C-1: ST9103 DETAILED SEQUENCE OF OPERATION
Mode Action
System
Response
Thermostat calls for heat. ("W"
terminal is energized).
a. ST9103 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 (30 seconds), 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 ST9103 dip-
switch settings. When timing is complete, the circulator fan is de-energized.
c. ST9103 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 tim-
ing, the circulator fan continues to run through the next trial for ignition.
Thermostat begins call for cool.
(G and Y terminals are ener-
gized).
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. Circulator fan is energized immediately at heat speed.
d. ST9103 opens oil primary control T - T connections. Circulating fan runs as
long as limit string stays open.
e.
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. ST9103 begins heat “fan off” delay sequence.
b. Circulating fan turns off after the selected heat “fan off” timing.
c. ST9103 re-closes oil primary control T - T connections.
d. Oil primary control is energized, initiating burner light-off.
LIMIT
Limit switch string closes (with-
out existing call for heat).
a. Circulator fan turns off when heat “fan off” delay time is complete.
b. Normal operation resumes; ST9103 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 ST9103
switches off the continuous fan speed tap before energizing the other fan
speed.
EAC
Electronic Air Cleaner is con-
nected.
•
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.
Summary of Contents for P2HMX12F08001
Page 16: ...16 APPENDIX B WIRING DIAGRAM ...
