Sequence of Operation Chapter 4
750-177 4-5
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. Failure to follow these
instructions could cause damage to the equipment.
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 ignition circuit
is immediately deenergized and the pilot valve closes, the reset switch lights and lockout occurs immediately.
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 deenergized. The lockout switch must be manually reset before operation can be resumed.
(Refer to the previous caution.)
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 deenergize
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 then deenergized. The lockout switch must be manually reset before operation can be resumed.
(Refer to the previous caution.)
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 deenergize the fuel valve circuit and shut off the 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 deenergized. The lockout switch must be manually reset before operation can be resumed.
(Refer to the previous caution.)
If the burner will not start, or upon a safety lockout, the trouble shooting 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 this bulletin.
Knowledge of the system and its controls will make troubleshooting much easier. Costly down time or delays can be
prevented by systematic checks of the actual operation against the normal sequence to determine the stage at which
performance deviates from normal. Following a routine may possibly eliminate overlooking an obvious condition, often
one that is relatively simple to correct.
Remember, a safety device, for the most part, is doing its job when it shuts down or refuses to operate. Never attempt
to circumvent any of the safety features.
Preventive maintenance and scheduled inspection of all components should be followed. Periodic checking of the relay
is recommended to see that a safety lockout will occur under conditions of failure to ignite either pilot or main flame, or
from loss of flame.
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