Greenheck 7800 Series Relay Modules - Manual (Page 11)

RM7895A,B,C,D/EC7895A,C; RM7896A,B,C,D 7800 SERIES RELAY MODULES
11 66-1090—2
4. PILOT FLAME ESTABLISHING PERIOD (PFEP)
a. Airflow lockout feature is enabled and the airflow
switch does not close after ten seconds or within
the specified purge card timing.
b. Flame signal is detected after 30 seconds.
c. Ignition/pilot valve/intermittent pilot valve terminal
is energized.
d. Main valve terminal is energized.
e. Delayed (2nd stage) main valve terminal is
energized (RM7895C,D/EC7895C; RM7896C,D).
f. Internal system fault occurred.
g. Purge card is removed.
h. Purge card is bad.
5. MAIN FLAME ESTABLISHING PERIOD (MFEP)
(RM7895C,D/EC7895C; RM7896C,D)
a. Airflow lockout feature is enabled and the airflow
switch opens.
b. Ignition terminal is energized.
c. Ignition/pilot valve terminal is not energized.
d. Main valve terminal is not energized.
e. Delayed main valve terminal is energized.
f. No flame present at end of MFEP.
g. Internal system fault occurred.
h. Purge card is removed.
i. Purge card is bad.
6. RUN PERIOD
a. No flame present.
b. Airflow lockout feature is enabled and the airflow
switch opens.
c. Interrupted pilot valve terminal is energized
(RM7895C,D/EC7895C; RM7896C,D).
d. Main valve terminal is not energized.
e. Delayed (2nd stage) main valve terminal is not
energized (RM7895C,D/EC7895C; RM7896C,D).
f. Internal system fault occurred.
g. Purge card is removed.
h. Purge card is bad.
OPERATION
Sequence of Operation
The RM7895A,B,C,D/EC7895A,C; RM7896A,B,C,D has the
operating sequences listed below; see Fig. 2 and 3. The
RM7895A,B,C,D/EC7895A,C; RM7896A,B,C,D LED provide
positive visual indication of the program sequence: POWER,
PILOT, FLAME, MAIN and ALARM.
Initiate
The RM7895A,B,C,D/EC7895A,C; RM7896A,B,C,D Relay
Module enters the INITIATE sequence when the relay module
is powered. The RM7895A,B,C,D/EC7895A,C;
RM7896A,B,C,D 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 not met, a hold condition is initiated and displayed
on the optional KDM for at least five seconds; when met, the
INITIATE sequence restarts. If the condition is not corrected
and the hold condition exists for four minutes, the
RM7895A,B,C,D/EC7895A,C; RM7896A,B,C,D locks out.
Causes for hold conditions in the INITIATE sequence:
a. AC line dropout detection.
b. AC line noise that can prevent a sufficient reading of
the line voltage inputs.
c. Low line voltage brownouts.
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 RM7895A,B,C,D/EC7895A,C; RM7896A,B,C,D is ready
to start an operating sequence when the operating control
input determines a call for heat is present. The burner switch,
limits, operating limit control and all microcomputer-monitored
circuits must be in the correct state for the relay module to
continue into the PREPURGE sequence.
Normal Start-Up Prepurge
The RM7895A,B,C,D/EC7895A,C; RM7896A,B,C,D Relay
Module provides PREPURGE timing selectable from two
seconds to thirty minutes with power applied and the
operating control indicating a call for heat.
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
PREPURGE sequence.
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.
Ignition Trials
1. Pilot Flame Establishing Period (PFEP):
a. When the PFEP begins:
(1) The pilot valve and ignition transformer,
terminals 8 and 10, are energized. The
RM7895A,B, EC7895A, and RM7896A,B have
an intermittent pilot valve, terminal 8. The
RM7895C,D, EC7895C, and RM7896C,D
have 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.
b. With flame proven, the ignition, terminal 10, is de-
energized.
2. Main Flame Establishing Period (MFEP):
a. After the Ignition Trials, 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 RM7895C,D/EC7895C, and RM7896C,D have
a ten second MFEP. After the Ignition Trials and
with the presence of flame, the main fuel valve,
terminal 9, is powered. If a flameout occurs, the
relay module locks out within 0.8 or 3 seconds,
depending on the amplifier FFRT.