32-00156-03 12
RM7895A,B,C,D/EC7895A,C; RM7896A,C,D7800 SERIES Relay Modules
f. No flame signal at end of Flame Failure
g. Response Time.
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,
RM7896C,D; EC7895C).
d. Main valve terminal is not energized.
e. Delayed main valve terminal is not energized (RM7895C,
RM7896C,D; EC7895C).
f. Internal system fault occurred.
g. Purge card is removed.
h. Purge card is bad.
i. Ignition terminal is energized.
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 EC7895A,C/RM7895A,B,C,D;RM7896A,B,C,D Re-
lay Module enters the INITIATE sequence when the relay
module is powered. The EC7895A,C/RM7895A,B,C,D;
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 oper-
ating 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 INITI-
ATE sequence restarts. If the condition is not corrected and
the hold condition exists for four minutes, the EC7895A,C/
RM7895A,B,C,D; RM7896A,B,C,D locks out. Causes for hold
conditions in the INITIATE sequence:
1. AC line dropout detection.
2. AC line noise that can prevent a sufficient reading of the
line voltage inputs.
3. 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 EC7895A,C/RM7895A,B,C,D;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, lim-
its, 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 EC7895A,C/RM7895A,B,C,D/RM7896A,B,C,D Relay
Module provides PREPURGE timing selectable from two sec-
onds 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 PRE-
PURGE sequence.
3. The Airflow Interlock input closes ten seconds into PRE-
PURGE or within the specified purge card timing; other-
wise, 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 EC7895A, RM7895A,B,
and RM7896A,B have an intermittent pilot valve,
terminal 8. The EC7895C, RM7895C,D, 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-ener-
gized.
NOTE: For the RM7895C1020/2020 and
RM7896C1036/2036, during the first 8 seconds of
PFEP, when a flame signal is detected, terminal 10 is
de-energized. If the flame signal is lost, terminal 10
will re-energize.
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, depend-
ing on the Flame Failure Response Time (FFRT) of the
amplifier.
b. The EC7895C, RM7895C,D and RM7896C,D have a ten
second MFEP. After the Ignition Trials, the pilot valve,
terminal 8, is de-energized. If a flameout occurs, the re-
lay 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.
Run
1. The EC7895C, RM7895C,D, RM7896C,D has a delayed
main valve that is energized once the RUN period is en-
tered.
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.
Post Purge (RM7896A,B,C,D Only)
After demand is satisfied or a limit opens, de-energizing ter-
minal 6, the Ignition/Pilot valve, main valve and delayed main
valve, terminals 8, 9 and 21, are deenergized. The blower mo-
tor, terminal 4, remains powered for 15 seconds.
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