750-204
Profire D/LND
3-7
3.9 — Normal Operation
4. Observe the primary atomizing air pressure gauge on the air/oil tank. The gauge reading should be approxi-
mately 10 psi during pre-purge.
5. When the pilot flame is proven, the programmer will proceed to the main flame position. Allow the burner to
operate in low fire, to warm the boiler before moving to high fire.
Typically, for No. 2 through No. 4 oil, CO
2
is 8% to 11% and No. 5 and No. 6 oil is 8% to 13% at low fire.
6. Turn the manual potentiometer switch to the high fire position. Check high fire combustion at this point. Do
not disturb previously established low fire adjustment. Allow the burner to return to low fire position before
adjusting high or intermediate settings. The primary atomizing air pressure will increase automatically with
the oil flow rate.
Typically, for No. 2 through No. 4 oil, CO
2
is 10% to 13% and No. 5 and No. 6 oil is 11% to 15% at high fire.
7. When conditions covered above are assured, refer to sections 3.9 and 3.10.
3.9 — Normal Operation
Normal operation must be with the “MANUAL-AUTO” switch selector on “AUTO.”
In automatic operation, the operating cycle always proceeds sequentially through pre-purge, pilot ignition, main
flame ignition, run, and post-purge. The length of purge and ignition trial vary according to the type of program-
mer used.
During the run cycle, burner input is regulated to the load demand by the modulating pressure or temperature
control on the boiler. The burner will continue to modulate until the operating pressure or temperature is reached.
Programmer control operation should be tested when the burner is initially placed into service, when a control is
replaced, and at scheduled intervals in the maintenance program.
Refer to adjustment procedures and maintenance instructions given in Chapters 4 and 5.
3.10 — Shutdown
When the operating limit control setting is reached or the burner switch is turned “OFF,” the following sequence
occurs:
1. The fuel valve(s) de-energize and flame extinguishes. The blower motor continues running during post-purge.
2. At the end of the post-purge, the blower motor is de-energized. The programmer returns to its starting position
and stops. the unit is ready to restart.
Abnormal shutdown might result from motor overload, flame outage, low water, current or fuel supply interrup-
tion, combustion or atomizing air pressure below minimum level, tripped circuit breakers, blown fuses, or other
interlock devices. Check for cause and correct before restarting the burner.
Safety shutdown caused by ignition or flame failure will actuate a red indicator light and energize an audible
alarm (if so equipped). If the programmer has a non-recycling interlock circuit, any interruption in this circuit
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