Sequence Of Operation - Honeywell 7800 SERIES Installation Instructions Manual

RM7838A 7800 SERIES RELAY MODULES
5. RUN Period
a. Intermittent pilot valve/1st stage oil terminal is not
energized.
b. Main valve terminal is not energized.
c. No flame is present.
d. Main valve terminal is de-energized.
e. Internal system fault.
f. Purge card is removed.
g. Purge card is bad.
OPERATION

Sequence of Operation

The RM7838A has the operating sequence listed below; see
Fig. 2. The RM7838A LEDs provide visual indication of the
program sequence: POWER, PILOT, FLAME, MAIN and
ALARM and are displayed on the Keyboard Display Module.
Initiate
The RM7838A enters the INITIATE sequence when the relay
module is initially powered. The RM7838A can also enter the
INITIATE sequence if the relay module verifies voltage
fluctuations of +10/-15% or frequency fluctuations of ±10%
during any part of the operating sequence. The INITIATE
sequence lasts for ten seconds unless the voltage or
frequency tolerances are not met. When the tolerances are
not met, a hold condition is initiated and displayed on the
KDM for at least five seconds. When the tolerances are met,
the INITIATE sequence restarts. If the condition is not correct
and the hold condition exists for four minutes, the RM7838A
locks out.
Causes for hold conditions in the INITIATE sequence include:
a. AC line dropout is detected.
b. AC line noise that can prevent a sufficient reading of the
line voltage inputs.
c. Brownouts caused by low line voltage.
The alarm, terminal 3, is energized during INITIATE.
Standby
The RM7838A is ready to start an operating sequence. When
the Burner Switch is closed, the Blower/Combustion Fan is
powered. The Airflow Switch closes and provides power to
terminal 7 through any additional limits or interlocks.
After terminal 7 is energized, "Safe Start Check" is displayed
on the KDM as the RM7838A transitions from Standby to
Purge. During safe start check, the RM 7838A verifies that
the flame detection system and all components are not in a
flame simulating condition. On applications using a shutter,
the shutter is energized to make sure no flame is present.
The alarm, terminal 3, is energized all the time the system is
in standby.
Normal Start-Up Purge
Closing the burner control switch energizes the combustion fan
and provides power to terminal 7 through all limits and
interlocks. Powering terminal 7 with all the microcomputer
monitored circuits in the correct state, the relay module begins
the PURGE sequence.
Selectable PURGE timing from two seconds to 30 minutes is
available for the RM7838A.
66-1087—2
Purge Hold T19 (High Fire Switch) is displayed until the High
Fire Switch is proven.
PURGE timing begins when the damper motor is manually
driven to the High Fire Purge position and the High Fire Switch
is energized. Four minutes and 15 seconds are provided to
drive the damper to the fully open position. A jumpered or
welded High Fire Switch adds a 30 second hold to the
beginning of purge timing. When PURGE timing is complete,
"PILOT:HOLD:T6 (Start Switch)" is displayed on the KDM.
Ignition Trials
1. Pilot Flame Establishing Period (PFEP):
a. With the damper motor manually driven to the Low
Fire position:
(1) Press the START pushbutton and the ignition
transformer is energized with power from
terminal 10. Power is also applied to terminal 6
through the Start/Stop Switch internal jumper.
The STOP Switch and the Alarm Silencing
Switch. The RM7838A then energizes the
Intermittent Pilot valve (terminal 8).
(2) During PFEP, the Low Fire Switch and the
START switch must remain closed. If one
opens before the flame is proven, the pilot
valve shuts off , but the pilot flame establishing
timer continues to time.
b. Flame must be proven by the end of the ten-
second PFEP (four if configuration JRI jumper is
removed) to allow the sequence to continue. If
flame is not proven by the end of PFEP, a safety
shutdown occurs.
c. With flame proven, terminal 21 outputs line voltage
to maintain the input to terminal 6, which allows the
Start Switch to be released and the ignition to be
shut off.
NOTE: Terminal 10 verifies that the Start Switch is
released. If the Start Switch is not
released, a shutdown occurs.
d. Alarm LED and terminal 3 are turned off when
flame is detected.
Run
1. When the flame is proven, the FLAME LED lights and the
ALARM LED turns off. Release the Start push-button and
the ignition transformer shuts off. At the end of PFEP, the
RM7838A proceeds to the RUN period by energizing the
main valve, terminal 9, and the MAIN status LED on the
relay module.
2. The firing rate damper motor can now be positioned to
meet the setpoint of the process controller.
3. The RM7838A is in RUN and remains in RUN until the
STOP pushbutton is pushed, or a limit opens terminal 7.
4. The alarm, terminal 3, is de-energized during RUN and
energized when shutdown occurs.
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