Heating Sequence; Troubleshooting - Lennox SIGNATURE SLO185BV Series Installation Instructions Manual

Heating Sequence - Actions & Responses
1. Action: Thermostat calls for heat (W terminal is en­
ergized)
Response:
ST9103A control (A15) closes oil primary control
D
TR-TW contacts.
After 15-second prepurge, power is sent to the oil
D
delay valve, ignition occurs and flame is
established.
Ignition sequence continues for 10 seconds after
D
flame is sensed. Oil will continue to flow as long as
cad cell senses flame.
Heat fan on ramp timing begins. When timing is
D
complete, the indoor blower is at heat speed and
warm air is delivered to the controlled space.
2. Action: Thermostat ends call for heat (W terminal is
de-energized)
Response:
After the thermostat is satisfied, the thermostat
D
circuit opens. The oil delay valve and burner are
de-energized.
Burner is de-energized.
D
Heat fan off ramp timing begins. When timing is
D
complete, indoor blower is de-energized.
Blower control returns to standby mode (oil prima­
D
ry control and indoor blower are off).
3. Action: Burner fails to light
Response:
Oil primary control enters soft lockout after ignition
D
failure (15 seconds without flame being sensed).
Push reset button on primary control for one sec­
ond to reset soft lockout.
D After soft lockout reset, oil primary control allows
second ignition attempt. Primary control enters
hard lockout after second ignition failure (15 sec­
onds without flame being sensed). Push reset but­
ton on primary control for 15 seconds until light on
control turns yellow to reset hard lockout.
Burner motor is de-energized.
D
4. Action: Established flame fails
Response:
Burner motor is de-energized and oil primary con­
D
trol goes into recycle mode.
If the fan off delay is longer than the recycle timing,
D
the indoor blower continues to run on heating
speed through the next trial for ignition.
5. Action: Limit Switch Opens
Response:
Oil primary control de-energizes burner.
D
Indoor blower is energized immediately at cool
D
speed.
A15 control opens oil primary control TR-TW con­
D
tacts.
Indoor blower runs as long as limit stays open.
D
6. Action: Limit Switch Closes
Response: If there is a heating demand, A15 control
energizes oil primary control and ignition sequence be­
gins.

Troubleshooting

Burner failure or improper operation can result from a num­
ber of different causes. Often the cause can be pinpointed
by observing the different types of failure or by the process
of elimination. The following troubleshooting charts list
some failures, causes and a sequence of steps to isolate
the point of failure. Check the simplest and most obvious
items before progressing to other items.
Page 24