Sequence of Operation
3-6
750-96 (revised 2010)
Model CB Packaged Boiler Manual
The control will prevent startup or ignition if limit circuit controls or fuel valve interlocks are open. The control will
lockout upon any abnormal condition affecting air supervisory controls wired in the running interlock circuit.
3.4.1 — No Pilot Flame
The pilot flame must be ignited and proven within a 10-second period after the ignition cycle begins. If not proven
within this period, the main fuel valve circuit will not be powered and the fuel valve(s) will not be energized. The igni-
tion circuit is immediately de-energized and the pilot valve closes, the reset switch lights and lockout occurs imme-
diately.
The blower motor will continue to operate. The flame failure light and the alarm bell (optional) are energized 10
seconds later.
The blower motor will be de-energized. The lockout switch must be manually reset before operation can be
resumed (see above Caution).
3.4.2 — Pilot But No Main Flame
When the pilot flame is proven, the main fuel valve circuit is energized. Depending upon the length of the trial-for-
ignition period, the pilot flame will be extinguished 10 or 15 seconds later. The flame detecting circuit will respond
to de-energize the main fuel valve circuit within 2 to 4 seconds to stop the flow of fuel. The reset switch lights and
lockout occurs immediately. The blower motor will continue to operate.
The flame failure light and alarm bell (optional) are energized 10 seconds later.
The blower motor will be de-energized. The lockout switch must be manually reset before operation can be
resumed (see above Caution).
3.4.3 — Loss of Flame
If a flame outage occurs during normal operation and/or the flame is no longer sensed by the detector, the flame
relay will trip within 2 to 4 seconds to de-energize the fuel valve circuit and shut off fuel flow. The reset switch
lights and lockout occurs immediately. The blower motor continues operation. The flame failure light and alarm
bell (optional) are energized 10 seconds later.
The blower motor will be de-energized. The lockout switch must be manually reset before operation can be
resumed (see above Caution).
If the burner will not start, or upon a safety lockout, the troubleshooting section in the operating manual and the
technical bulletin should be referred to for assistance in pinpointing problems that may not be readily apparent.
The program relay has the capability to self-diagnose and to display a code or message that indicates the failure
condition. Refer to the control bulletin for specifics and suggested remedies. Familiarity with the program relay
and other controls in the system can be obtained by studying the contents of the manual and bulletin. Knowledge
of the system and its controls will make troubleshooting much easier in the event it is necessary. Costly downtime
The lockout switch must be manually reset following a safety shutdown. The cause for loss of flame or any unusual
condition should be investigated and corrected before attempting to restart.
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