Principal Technical Features; Operation - Honeywell 7800 Series Operating Instructions Manual

5 PRInCIPAL teCHnICAL FeAtURes

The RM/EC7890 provides all customary flame safeguard functions
as well as significant advancements in safety, annunciation, and
system diagnostics.
5.1 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 energized.
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) 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 energized.
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.

6 oPeRAtIon

6.1 sequence of operation
The RM/EC7890 has the operating sequences listed below; see
page 8 (4.2.3 Fig. 2. Wiring subbase and operating sequence
chart for RM/EC7890). The RM/EC7890 LED provide positive
visual indication of the program sequence: POWER, PILOT,
FLAME, MAIN and ALARM.
6.1.1 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 dis-
played on the optional KDM 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 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 reading of the line
voltage inputs.
c Brownouts caused by a low line voltage.
➔ NOTE: If a 3.0 second flame failure response amplifi-
er is installed (2.0 seconds for RM7890A1064/A2064,
RM7890B1055/B2055 and EC7890B1028) and configuration
jumper JR2 is intact, the RM/EC7890 locks out. JR2 must be
clipped.
6.1.2 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 microcom-
puter monitored circuits must be in the correct state for the RM/
EC7890 to continue into the Safe Start Check.
6.1.3 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.
6.1.4 Ignition trials
a. Pilot Flame Establishing Period (PFEP):
1 The pilot valve and ignition transformer, terminals 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 fouror 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, terminal 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 devic-
es complete a 4 second PFEP, shutting off ignition (terminal
10) at 2 seconds.
6.1.5 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.
EN-10