RM7800E,G,L,M; RM7840E,G,L,M 7800 SERIES RELAY MODULES
11 66-1085—3
g. Lockout Interlock opens during PREPURGE
(RM7840E,L).
h. Ignition/pilot valve/intermittent pilot valve terminal is
energized.
i. Main valve terminal is energized.
j. Internal system fault occurred.
k. Purge card is removed.
l. Purge card is bad.
4. PILOT FLAME ESTABLISHING Period (PFEP):
a. Low Fire Switch opens.
b. Lockout Interlock opens (RM7840E,L).
c. Ignition/pilot valve/intermittent pilot valve terminal is
not energized.
d. Early spark termination terminal is energized after
five seconds.
e. No flame is present at the end of PFEP.
f. Main valve terminal is energized (RM7800G,M).
g. Internal system fault occurred.
h. Purge card is removed.
i. Purge card is bad.
5. MAIN FLAME ESTABLISHING Period (MFEP):
a. Low Fire Switch Opens.
b. Lockout Interlock opens (RM7840E,L).
c. Ignition/pilot valve/intermittent pilot valve terminal is
not energized.
d. Main valve terminal is not energized.
e. No flame is present at the end of MFEP.
f. Internal system fault occurred.
g. Purge card is removed.
h. Purge card is bad.
6. RUN Period:
a. No flame is present.
b. Lockout Interlock opens (RM7840E,L).
c. Interrupted pilot valve terminal is energized
(RM7840G,M).
d. Main valve terminal is not energized.
e. Internal system fault occurred.
f. Purge card is removed.
g. Purge card is bad.
7. POSTPURGE Period:
a. Preignition Interlock does not close in five seconds
and opens after five-second time period.
b. Ignition/pilot valve/intermittent pilot valve terminal is
energized.
c. Main valve terminal is energized.
d. Internal system fault occurred.
e. Purge card is removed.
f. Purge card is bad.
OPERATION

Sequence of Operation

The RM7800/RM7840 has the following operating sequences,
see Fig. 2, 3, 4, and Table 6. The RM7800/RM7840 LED
provide positive visual indication of the program sequence:
POWER, PILOT, FLAME, MAIN and ALARM.

Initiate

The RM7800/RM7840 enters the INITIATE sequence when
the Relay Module is powered. The RM7800/RM7840 can also
enter the INITIATE sequence if the Relay Module verifies
voltage fluctuations of +10/-15 percent or frequency
fluctuations of +/-10 percent 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 VFD for at least five seconds. When the
tolerances are met, the INITIATE sequence restarts. If the
condition is not corrected and the hold condition exists for four
minutes, the RM7800/RM7840 locks out. Causes for hold
conditions in the INITIATE sequence:
a. AC line dropout is detected.
b. AC line frequency error occurs caused by using a
60 Hz device on a 50 Hz line, or vice versa.
c. AC line noise prevents a sufficient reading of the
line voltage inputs.
d. Low line voltage brownouts occur.
The INITIATE sequence also delays the burner motor starter
from being energized and de-energized from an intermittent
AC line input or control input.

Standby

The RM7800/RM7840 is ready to start an operating sequence
when the operating control determines a call for heat is
present. The burner switch, limits, operating control and all
microcomputer monitored circuits must be in the correct state
for the RM7800/RM7840 to continue into the PREPURGE
sequence.

Normal Start-Up Prepurge

The RM7800/RM7840 provides a prepurge timing selectable
from two seconds to 30 minutes with power applied and the
RM7800 operating control indicating a call for heat:
a. Running Interlocks, Preignition Interlocks, Burner
Switch, Run/Test Switch, Lockout Interlocks and all
microcomputer monitored circuits must be in the
correct operating state.
b. The blower motor output, terminal 5, is powered to
start the PREPURGE sequence, except for the
RM7800E/RM7840. The firing rate motor is driven to
the high fire position. The PREPURGE timing for the
RM7800/RM7840E,L does not begin until the
Lockout Interlock String and High Fire Switch are
both closed. The blower motor output for the
RM7800E is not energized until the High Fire Switch
is closed.
c. The Preignition Interlock input must remain closed
throughout PREPURGE; otherwise, control returns
to the STANDBY state and holds (30 seconds) for
the RM7800/RM7840G,M or safety shutdown for
the RM7800/RM7840E,L occurs.
d. The Lockout Interlock or Running Interlock inputs
(interlock circuit including Airflow Switch) must close
by ten seconds into PREPURGE; otherwise, a
recycle to the beginning of PREPURGE for the
RM7800/RM7840G,M will happen or a safety
shutdown for the RM7800/RM7840E,L occurs.
e. When PREPURGE timing is complete, the firing rate
motor drives to the low fire position,
RM7800/RM7840E,G,L.
f. When the firing rate motor r eaches low fire position,
the Low Fire Switch, terminal 18, input must be
energized before entering the Ignition Trial state.