Operation - Honeywell 7800 Series Manual

Sequence of Operation
The operating sequence for the RM7885A follows, see
Figs. 17, 18, and Table 3.
NOTE: The alarm will sound until a flame is sensed.
INITIATE
The RM7885A enters the INITIATE sequence when the
Relay Module is powered. The RM7885A can also enter the
INITIATE sequence when the Relay Module verifies voltage
fluctuations of +10/-15% or frequency fluctuations of +/-
10% during start-up or run sequences. The INITIATE se-
quence lasts for ten seconds unless the voltage or frequency
tolerances are not met. When the tolerances are not met, a
hold condition will be initiated and will be displayed on the
optional VFD for at least five seconds. When the tolerances
are met, the INITIATE sequence will restart. If the condition
is not corrected and the hold condition exists for four minutes,
the RM7885A will lockout. Causes for hold conditions in the
INITIATE sequence are:
• AC line dropout is detected.
• Brownouts caused by a low line voltage.
• AC line noise that can prevent a sufficient reading of
the line voltage inputs.
• AC line frequency error caused by using a 60 Hz device
on a 50 Hz line or vice versa.
STANDBY
The RM7885A will be in the STANDBY mode after it has
completed the INITIATE startup or the Stop Switch has been
pressed. The POWER LED will blink every four seconds,
signifying an internal hardware check has been completed.
The ALARM LED will also be lit and an external alarm will
be activated.
Fig. 17—RM7885A sequence.
LED
DISPLAY
POWER
PILOT
FLAME
MAIN
ALARM
BURNER
START
LIMITS, STOP
STATION AND
SILENCING SWITCH
FLAME
SIGNAL
1 MAIN FUEL VALVE WILL BE ENERGIZED DURING PFEP IF FLAME IS PROVEN.
00
SAFE-
INITIATE STANDBY START
POWER POWER POWER
ALARM
LIMITS, STOP STATION AND ALARM SILENCING SWITCH CLOSED
SAFE START CHECK
NORMAL START-UP
When the Start Switch is pressed, the Ignition Trans-
former is energized and power is applied to terminal 10 of the
RM7885A. If all microcomputer monitored circuits are in the
correct state, the RM7885 will initiate a Safe-Start Check and
Ignition Trials.
SAFE START CHECK (TWO SECONDS)
The RM7885A conducts a two-second Safe-Start Check
as it verifies that critical loads are in the proper state prior to
start-up and that no flame is present in the combustion
chamber.
IGNITION TRIALS
After completing a successful Safe-Start Check, the
RM7885 will provide power to the Intermittent Pilot Valve,
terminal 8 and turn on the PILOT LED.
When flame is proven, the FLAME LED will light, the
ALARM LED will shut off and the RM7885 will bring on the
Main Valve and turn on the MAIN LED.
The Start Switch can now be released, which will shut off
the Ignition Transformer.
NOTE: The Pilot Valve will follow the Start Switch until the
flame is proven. Then it will be in control of the RM7885
(for example, pushing and releasing the Start Switch will
bring on and shut off the Ignition Transformer and the
Pilot Valve until the flame is proven.)
RUN
The RM7885A is now in RUN and will remain in RUN
until the Stop Switch is pressed or a Limit opens terminal 6.
RM7885
00 15 MINUTES
RUN
PFEP
POWER POWER
PILOT PILOT
FLAME FLAME
MAIN MAIN
START SWITCH
10
8
INTERMITTENT PILOT
MAIN VALVE 9
FLAME PROVING
19
RM7885A

OPERATION

Operation
STANDBY
POWER
ALARM
1
L1 6
TO
M5194
65-0107