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R7795A,B,C,D
DETAILED OPERATING SEQUENCE
Detailed Operating Sequence
Fig. 2—Operating sequence for the R7795A,B, with intermittent pilot.
The R7795A,B provides the following operational se-
quence when used with the appropriate flame detector. (See
Figs. 2 and 3.)
STANDBY
The R7795 Primary Control is ready to start up when
the burner controller closes (limits are closed).
NORMAL START-UP
1. With power applied (limits and controller closed,
terminal L1 to 16, and no flame signal present) the 3K re-
lay pulls in and the burner motor (terminal 8) is energized.
2. As soon as the airflow switch closes (terminal 3 to
8), the ST795A Prepurge Timer starts to time out (pre-
purge begins).
NOTE: The ST795A Prepurge Timer returns to zero any
time the airflow switch opens. The prepurge restarts
when the airflow switch recloses.
3. PILOT FLAME ESTABLISHING PERIOD.
At the end of prepurge (ST795A timed out), the 1K
relay pulls in, energizing the ignition transformer (termi-
nal 18) and the intermittent pilot valve (terminal 5). This
starts the ten or four second pilot flame establishing
period. Safety shutdown and lockout will occur if pres-
ence of flame is not proven within:
• Ten seconds if the ORANGE jumper is not clipped.
• Four seconds if the ORANGE jumper is clipped.
4. MAIN FLAME IGNITION TRIAL
At the end of the pilot flame establishing period (ten or
four seconds), and with pilot flame present, the main valve
(terminal 6) is energized.
The R7795 is now in the normal burner run mode of
operation and will remain so until an external command
directs it to do otherwise.
5. NORMAL SHUTDOWN
When the burner controller opens, the pilot valve (ter-
minal 5), the main valve (terminal 6) and the burner/
blower motor (terminal 8) are immediately de-energized.
The R7795 goes into the standby mode, terminating the
operating cycle.