a. Intermittent pilot valve/1st stage oil terminal is
b. Main valve terminal is not energized.
c. No flame is present.
d. Main valve terminal is de-energized.
e. Internal system fault.
Purge card is removed.
g. Purge card is bad.
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
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
Causes for hold conditions in the INITIATE sequence
a. AC line dropout is detected.
b. AC line noise that can prevent a sufficient read-
ing of the line voltage inputs.
c. Brownouts caused by low line voltage.
The alarm, terminal 3, is energized during INITIATE.
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
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.
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.
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 ter-
minal 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 ener-
gizes 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 establish-
ing timer continues to time.
b. Flame must be proven by the end of the ten- sec-
ond 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
c. With flame proven, terminal 21 outputs line volt-
age 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
2. Alarm LED and terminal 3 are turned off when flame
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 ter-
7800 SERIES RELAY MODULES