Principal Technical Features; Sequence Of Operation - Honeywell 7800 Series Installation Instructions Manual

Relay modules
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RM7890A,B/EC7890A,B 7800 SERIES RELAY MODULES

PRINCIPAL TECHNICAL FEATURES

The RM/EC7890 provides all customary flame safeguard
functions as well as significant advancements in safety,
annunciation, and system diagnostics.
Safety Shutdown (Lockout) Occurs if:
1. INITIATE PERIOD
a. AC line power errors occurred, see Operation.
b. Configuration jumpers have been changed (after
200 hours).
c. Four minute INITIATE period has been exceeded.
2. STANDBY PERIOD
a. Flame signal is present after 240 seconds.
b. Ignition/intermittent pilot valve terminal is ener-
gized.
c. Internal system fault occurred.
d. Main valve terminal is energized.
e. 3.0 second (2.0 seconds for RM7890A1064/A2064,
RM7890B1055/B2055 and
EC7890B1028/B2028) Flame Failure Response
Time (FFRT) Amplifier is installed and configuration
jumper is selected for relight (see Table 3).
3. SAFE START CHECK
a. Ignition/intermittent pilot valve terminal is ener-
gized.
b. Internal system fault occurred.
c. Main valve terminal is energized.
4. PILOT FLAME ESTABLISHING PERIOD (PFEP)
a. Ignition/intermittent pilot valve terminal is not
energized.
b. Internal system fault occurred.
c. Main valve terminal is energized.
d. No flame present at end of PFEP.
5. RUN PERIOD
a. Ignition terminal is energized.
b. Internal system fault occurred.
c. Main valve terminal is not energized.
d. No flame present and configuration jumper is
selected for lockout.
e. Pilot valve terminal is not energized.
OPERATION

Sequence of Operation

The RM/EC7890 has the operating sequences listed
below; see Fig. 2. The RM/EC7890 LED provide positive
visual indication of the program sequence: POWER,
PILOT, FLAME, MAIN and ALARM.
Initiate
The RM/EC7890 enters the INITIATE sequence when the
relay module is powered. The RM/EC7890 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 is
displayed on the optional KDM for at least five seconds.
32-00157-03
When the tolerances are met, the INITIATE sequence
restarts. If the condition is not corrected and the hold
condition exists for four minutes, the RM/EC7890 locks
out. Causes for hold conditions in the INITIATE sequence:
a. AC line dropout detection.
b. AC line noise that can prevent a sufficient read-
ing of the line voltage inputs.
c. Brownouts caused by a low line voltage.
NOTE: If a 3.0 second flame failure response amplifier is
installed (2.0 seconds for RM7890A1064/A2064,
RM7890B1055/B2055 and EC7890B1028/B2028)
and configuration jumper JR2 is intact, the
RM/EC7890 locks out. JR2 must be clipped.
Standby
The RM/EC7890 is ready to start an operating sequence
when the operating control input (terminal 6) recognizes a
call for heat. The burner switch, limits, operating limit
control and all microcomputer monitored circuits must be
in the correct state for the RM/EC7890 to continue into
the Safe Start Check.
Normal Start-Up Safe Start Check
The RM/EC7890 verifies that a flame or flame simulating
condition does not exist and proceeds into the Ignition
Trial. If a flame or flame simulating condition is present,
the RM/EC7890 remains in the STANDBY period.
Ignition Trials
a. Pilot Flame Establishing Period (PFEP):
(1) The pilot valve and ignition transformer, ter-
minals 8 and 10, are energized. The
RM/EC7890 has an intermittent pilot valve,
terminal 8.
(2) Flame must be proven by the end of the four-
or ten-second PFEP (30 seconds for
RM7890A1031/A2031) or a safety shutdown
occurs.
(3) Once flame is proven, the ignition, terminal
10, is de-energized and the main valve, termi-
nal 9, is energized.
(a)The RM7890B1030/B2030 finishes the 4-
or 10-second PFEP before the main valve is
energized.
(b)The RM7890A1064/A2064 and
RM7890B1055/B2055 with JR1 intact
completes 10 second PFEP, shutting off
ignition (Terminal 10) at 6 seconds. When
the JR1 clipped these devices complete a 4
second PFEP, shutting off ignition (termi-
nal 10) at 2 seconds.
Run
The RM/EC7890 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.
10

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