Honeywell 7800 Series Installation Instructions Manual page 16

EC7830A, RM7830A, EC7850A, RM7850A 7800 SERIES RELAY MODULES
Normal Start-Up Purge
The relay module provides PURGE timing selectable from
two seconds to thirty minutes with power applied and the
operating control indicating a call for heat.
1. The Preignition Interlocks, Limits and Burner Con-
trol, Run/Test Switch, Airflow Switch Input, Lockout
Input, and all microcomputer-monitored circuits
must also be in the correct operating state.
2. The blower motor output, terminal 5, is powered to
start the PURGE sequence. The firing rate motor is
driven to the high fire position (EC/RM7850A). The
PURGE timing does not begin until the Airflow
Switch Input and High Fire Switch (EC/RM7850A)
are both closed.
3. The Preignition Interlock Input must remain closed
throughout PURGE or a safety shutdown occurs.
4. The Airflow Switch Input must close by ten seconds
into PURGE or a safety shutdown occurs.
5. After the firing rate motor reaches the PURGE rate
position and PURGE timing is completed, the motor
drives to the low fire position (EC/RM7850A).
Ignition Trials
1. Preignition: With the firing rate motor at the low fire
position (EC/RM7850A), the ignition transformer,
terminal 10, is energized for three seconds.
2. First Safety Time (SAFETY1):
a. With the firing rate motor at the low fire position
(EC/RM7850A):
(1) The pilot valves and ignition transformer,
terminals 8, 10 and 21, are energized.
Terminal 8 is an interrupted pilot valve and
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 (EC/RM7850A).
(3) The Preignition Interlock Input is ignored
during SAFETY1, PILOT STAB., MAIN TRIAL,
RUN and POSTPURGE.
b. Flame must be proven by the end of the First
Safety Time to allow the sequence to continue. A
safety shutdown occurs if there is no flame.
3. Pilot stabilization (PILOT STAB.): With flame proven,
the ignition, terminal 10, is de-energized. The dura-
tion of this state is five seconds.
4. Main Trial (MAIN TRIAL):
a. The MAIN TRIAL time is selectable as three or
five seconds. After PILOT STAB., and with the
presence of a flame, the main fuel valve, terminal
9, is powered. If a flameout occurs, the relay
module locks out within one or two seconds,
depending on the amplifier Flame Failure
Response Time (FFRT). Thus, the second safety
time is defined as MAIN TRIAL time plus the
amplifier FFRT.
b. During MAIN TRIAL, the Low Fire Switch Input
must be closed (EC/RM7850A). If it opens, a
safety shutdown occurs.
c. After three or five seconds of MAIN TRIAL, termi-
nal 8 is de-energized for main stabilization.
Flame must remain proven during this five-sec-
ond period.
32-00198—01
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.
Postpurge
The relay module (model specific) provides a two-, 15- or
30-second POSTPURGE following the completion of the
RUN period. The blower motor output is powered to drive
all combustion products and any unburned fuel from the
combustion chamber. It also supplies combustion air to
burn fuel being purged from the fuel line downstream
from the fuel shutoff valve.
1. The main fuel valve and the intermittent pilot valve,
terminals 9 and 21, are de-energized and the firing
rate motor is commanded to the low fire position
(EC/RM7850A) to begin the POSTPURGE period.
2. The Preignition Interlock Input is ignored during
POSTPURGE.
3. After the POSTPURGE period is completed, the relay
module re-enters STANDBY.
Run/Test Switch
The Run/Test Switch is located on the top side of the relay
module, see Fig. 5. The Run/Test Switch allows the burner
sequence to be altered as follows:
1. In Purge Drive to High Fire position, the Run/Test
Switch, when placed in the TEST position, holds in
PURGE with the firing rate motor in the High Fire
position (EC/RM7850A).
2. In the measured PURGE sequence, the Run/Test
Switch, placed in the TEST position, causes the
PURGE timing to stop. The firing rate motor is in the
High Fire position.
3. In Purge Drive to Low Fire position, the Run/Test
Switch, when placed in the TEST position, holds the
burner in PURGE with the firing rate motor in the
Low Fire position (EC/RM7850A).
4. 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
adjustments. This activates a 15-second flameout
timer that permits pilot flame adjustment without
nuisance safety shutdowns.
5. During Run, the Run/Test Switch, when placed in the
TEST position, drives the firing rate motor to the Low
Fire position.
IMPORTANT
When the relay module is switched to the TEST
mode, it stops and holds at the next Run/Test
Switch point in the operating sequence. Make sure
that the Run/Test Switch is in the RUN position
before leaving the installation.
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