1. The Airflow Interlock, burner switch, Run/Test switch
and all microcomputer-monitored circuits must also be
in the correct operating state.
2. The motor output, terminal 4, is powered to start the
3. The Airflow Interlock input closes ten seconds into
PREPURGE or within the specified purge card timing;
otherwise, a recycle to the beginning of PREPURGE or
lockout occurs, depending on how the Airflow Switch
selectable jumper (JR3) is configured.
1. Pilot Flame Establishing Period (PFEP):
a. When the PFEP begins:
(1) The pilot valve and ignition transformer,
terminals 8 and 10 (also terminal 21, RM7897A),
are energized. The RM7897A has an intermittent
pilot valve, terminal 8, and interrupted pilot valve
on terminal 21. The RM7897C has an
interrupted pilot valve, terminal 8.
(2) Flame must be proven by the end of the ten
second PFEP (four seconds if Configuration
Jumper JR1 is clipped) to allow the sequence to
continue. If a flame is not proven by the end of
PFEP, a safety shutdown occurs.
(3) the Pre-Ignition Interlock is ignored throughout
the Trial for Ignition State.
2. Main Flame Establishing Period (MFEP):
a. After PFEP, and with the presence of flame,
the main fuel valve, terminal 9, is powered. If a
flameout occurs, the relay module locks out or
recycles (depending on status of jumper JR2) within
0.8 or 3 seconds, depending on the Flame Failure
Response Time (FFRT) of the amplifier.
b. The RM7897A (terminal 21) and RM7897C
(terminal 8) have a ten second MFEP. After the
Ignition Trials, the interrupted pilot valve, terminal 8
or 21, is de-energized. If a flameout occurs, the
relay module locks out or recycles (depending on
status of jumper JR2) within 0.8 or 3 seconds,
depending on the Flame Failure Response Time
(FFRT) of the amplifier.
1. The RM7897C has a delayed main valve that is
energized once the RUN period is entered.
2. The relay module is now in RUN and remains in RUN
until the controller input, terminal 6, opens, indicating
that the demand is satisfied or a limit has opened.
After demand is satisfied or a limit opens, de-energizing
terminal 6, the Ignition/Pilot valve, main valve and delayed
main valve, terminals 8, 9 and 21, are de-energized. The
blower motor, terminal 4, remains powered during the
specified programmed time. The Pre-Ignition Interlock closes
within the first five seconds of Post Purge.
RM7897A1002, RM7897C1000 7800 SERIES RELAY MODULES
The Run/Test Switch is located on the top side of the relay
module, see Fig. 12. The Run/Test Switch allows the burner
sequence to be altered as follows:
1. In the measured PREPURGE sequence, the Run/Test
Switch, placed in the TEST position, causes the
PREPURGE timing to stop.
2. In the Pilot Flame Establishing Period, the Run/Test
Switch, placed in the TEST position, stops the timer
during the first eight seconds of a ten-second PFEP
selection or during the first three seconds of a
four-second PFEP selection. It also allows for pilot
turn-down test and other burner adjustments. This
activates a fifteen-second flameout timer that permits
pilot flame adjustment without nuisance safety
shutdowns. The Run/Test Switch is ignored during
PFEP for the C relay module if terminals
8 and 9 or 9 and 21 are jumpered.
When the relay module is switched to the TEST
mode, it stops and holds at the next Run/Test Switch
point in the operating sequence. Make sure that the
Run/Test Switch is in the RUN position before
leaving the installation.
Fig. 14. Sequence Status LEDs.
SETTINGS AND ADJUSTMENTS
Selectable Site-Configurable Jumpers
The relay module has three site-configurable jumper options,
see Fig. 13 and Table 7. If necessary, clip the site-configurable
jumpers with side cutters and remove the resistors from the
SERVICE NOTE: Clipping and removing a site-configurable
jumper enhances the level of safety.
Clipping and removing a jumper after 200 hours of
operation causes a nonresettable Fault 110. The
relay module must then be replaced.