Sequence Of Operation - Honeywell 7800 Series Installation Instructions Manual

EC7820A 7800 SERIES RELAY MODULES
OPERATION

Sequence of Operation

The 7800 SERIES Relay Module has the operating
sequences listed below. See Tables 2 and 4.
Initiate
The 7800 SERIES Relay Module enters the INITIATE
sequence when the Relay Module is powered. The 7800
SERIES Relay Module can also enter the INITIATE
sequence if the Relay Module verifies voltage fluctuations
of +10/-15 percent or frequency fluctuations of ±10
percent during any part of the operating sequence. The
INITIATE sequence lasts for two seconds unless the
voltage or frequency tolerances are not met. When the
tolerances are not met, a hold condition is initiated and
displayed on the 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 7800 SERIES Relay Module locks out.
Causes for hold conditions in the INITIATE sequence:
a. AC line dropout detection.
b. AC line noise prevents a sufficient reading of the
line voltage inputs.
c. Low line voltage brownouts.
d. L1 and N are incorrectly wired, causing incorrect
ac line phase.
Standby
The 7800 SERIES Relay Module is ready to start an
operating sequence when the operating control
determines a call for heat is present. The burner switch,
limits, operating control and all microcomputer-
monitored circuits must be in the correct state for the
relay module to continue into the PURGE sequence.
Normal Start-Up Purge
The 7800 SERIES Relay Module provides PURGE timing
selectable from two seconds to thirty minutes with power
applied and the operating control indicating a call for
heat.
a. Preignition Interlocks, Limits and Burner Con-
trol, Run/Test Switch, Airflow Switch input, Lock-
out Input and all microcomputer-monitored
circuits must be in the correct operating state.
b. Blower motor output (terminal 4) is powered to
start the PURGE sequence. PURGE timing does
not begin until the Airflow Switch Input (terminal
7) is closed.
c. Preignition Interlock input must remain closed
throughout PURGE; otherwise, a safety shut-
down occurs.
d. The Airflow Switch input must close by ten sec-
onds into PURGE; otherwise, a safety shutdown
occurs.
32-00197—01
Ignition Trials
1. Preignition:
a. The ignition transformer, terminal 10, are ener-
gized for three seconds.
2. First Safety Time (SAFETY1):
a. With the Low Fire Switch input closed:
(1) The pilot valves and ignition transformer, ter-
minals 8, 10, and 21, are energized. Terminal
8 is an interrupted pilot valve, while terminal
21 is an intermittent pilot valve.
(2) During SAFETY1, the Low Fire Switch Input
must be closed. If it opens, a safety shutdown
occurs.
(3) The Preignition Interlock Input is ignored
during MAIN TRIAL and RUN.
b. Flame must be proven by the end of five or ten
seconds to allow the sequence to continue. A
safety shutdown occurs if there is no flame.
Some devices allow five ignition attempts. The
number of attempts is indicated on the first line
of the display during SAFETY1.
3. Pilot stabilization (PILOT STAB.). With flame proven,
the ignition, terminal 10, is de-energized. The dura-
tion of this state is 5 seconds.
4. Main Trial (MAIN TRIAL):
(a)The MAIN TRIAL time is selectable as five
or eight seconds. After PILOT STAB., and
with the presence of a flame, the main fuel
valve, terminal 9, is powered. If a flame out
occurs, the relay module will lock out within
one or two seconds, depending on the
Flame Failure Response Time (FFRT) of the
amplifier. Thus, second safety time is
defined as MAIN TRIAL time plus FFRT of
the amplifier. Note that some devices allow
three ignition attempts
(b)During MAIN TRIAL, the Low Fire Switch
input must be closed. If it opens, a safety
shutdown occurs.
(c)After five or eight seconds of MAIN TRIAL,
terminal 8 is de-energized for main stabili-
zation. Flame must remain proven during
this period.
Run
1. The firing rate motor releases to modulation.
2. The relay module is now in RUN and remains in RUN
until the controller input, terminal 6, opens, indicat-
ing that the demand is satisfied or a limit has
opened.
NOTE: 7800 SERIES Relay Module LEDs. POWER,
PILOT, FLAME, MAIN and ALARM provide posi-
tive visual indication of the program sequence.
See Fig. .
Run/Test Switch
The Run/Test Switch is located on the top side of the 7800
SERIES Relay Module, see Fig. 5. The Run/Test Switch
1. In the measured PURGE sequence, the Run/Test
Switch, when placed in the TEST position, causes the
PURGE timing to stop.
2. During the PILOT STAB. period, the Run/Test Switch,
when placed in the TEST position, stops the timer,
allowing for pilot turn-down test and other burner
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