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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.
Troubleshooting: Fan operating sequence
Action
Thermostat calls for heat.
(W terminal is energized.)
Thermostat ends call for heat.
(W terminal is de-energized.)
Burner fails to light.
Established flame fails.
Thermostat begins call for cool.
(G and Y terminals are energized.)
Thermostat ends call for cool.
(G and Y terminals are de-energized.)
Thermostat begins call for fan.
(G terminal is energized.)
Thermostat ends call for fan.
(G terminal is de-energized.)
Limit switch string opens.
Limit switch string closes.
Continuous circulating fan is connected.
(Optional connectors are available for separate circulat
ing fan speed tap.)
Humidity control is connected.
(Optional connectors are available for 120 Vac humidifi
er.)
The following troubleshooting charts list some failures,
causes and a sequence of steps to isolate the point of fail
ure. Check the simplest and most obvious items before
progressing to other items.
Oil primary control is energized.
Ignition system and oil primary control start the furnace. Oil flows as long as cad cell
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.
Oil primary control is de-energized, terminating the burner cycle.
Heat fan off delay (60 to 120 seconds) timing begins. When timing is complete, the circulat
ing fan is de-energized.
Oil primary control and circulating fan are off.
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 delay off period.
Burner motor is de-energized and oil primary control goes into recycle mode.
If heat fan off delay is longer than the recycle delay timing, the heat fan continues to run
through the next trial for ignition.
Circulating fan is energized at the cool speed.
Cooling compressor turns on immediately.
Circulating fan and cooling compressor turn off immediately.
Circulating fan is energized immediately at cool speed.
Circulating fan is de-energized.
Oil primary control shut off the burner.
Circulating fan is energized immediately at heat speed.
Oil primary control is de-energized.
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.
Heat fan off delay (60 to 120 seconds) begins.
Circulating fan turns off after the selected heat fan off delay timing.
Oil primary control is energized, initiating burner light off.
Circulating fan is energized at low speed when there is no call for heat, cool or fan.
Humidifier connections are energized when the burner motor is energized.
Page 19
System Response
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