Honeywell 7800 Series Manual page 10

RM7800E,G,L,M
SAFETY PROVISIONS
An AMPLI-CHECK™ Amplifier is energized continually
through STANDBY and PREPURGE to detect any possibil-
ity of a runaway detector or a flame. If either situation
happens, a safety shutdown occurs. A standard amplifier is
energized continually through STANDBY and PREPURGE.
If either situation happens, a safety shutdown occurs.
PREIGNITION OUTPUT CIRCUIT CHECK
At the end of PREPURGE, the Dynamic Safety Relay
operation is checked. Also, all safety critical loads, terminals
8, 9, 10 and 21 are checked to verify the terminals are not
powered. If the Dynamic Safety Relay operation is faulty, or
if any of the safety critical loads are powered, safety shut-
down occurs and is annunciated.
TAMPER RESISTANT TIMING AND LOGIC
Safety and logic timings are inaccessible and cannot be
altered or defeated.
VERIFIED SPARK TERMINATION
The ignition terminal is monitored to verify early spark
termination (five seconds ignition and pilot and five seconds
pilot only).
FIRST-OUT ANNUNCIATION AND
SELF-DIAGNOSTICS
Sequence Status Lights (LEDs) provide positive visual
indication of the program sequence: POWER, PILOT,
FLAME, MAIN and ALARM. The green POWER LED
blinks every four seconds to signify the RM7800 hardware is
running correctly.
Multi-function Keyboard Display Module shows elapsed
time during PREPURGE, PILOT IGN, MAIN IGN, and
POSTPURGE. As an additional troubleshooting aid, it pro-
vides sequence timing, diagnostic information, historical
information and expanded annunciator information when a
safety shutdown or hold or normal operation occurs.
First-out Annunciation reports the cause of a safety shut-
down or identifies the cause of a failure to start or continue the
burner control sequence with an English text and numbered
code via the Keyboard Display Module. It monitors all field
input circuits, including the Flame Signal Amplifier and
Firing Rate Position Switches. The system distinguishes 118
modes of failure and detects and annunciates difficult-to-find
intermittent failures.
Self-Diagnostics adds to the First-out Annunciation by
allowing the RM7800 to distinguish between field (external
device) and internal (system related) problems. Faults asso-
ciated within the flame detection subsystem, RM7800 or
plug-in Purge Card, are isolated and reported by the Key-
board Display Module, see Troubleshooting section and
7800 SERIES System Annunciation Diagnostics and
Troubleshooting, form 65-0118.
INTERLOCK REQUIREMENTS
The following interlock inputs are provided:
Low Fire Interlock (RM7800 ALL)
This interlock verifies the firing rate motor is in the low
fire position before and during ignition trials.
High Fire Interlock (RM7800E,L)
This interlock verifies the firing rate motor is in the high
fire position prior to and during PREPURGE. If the High Fire
Switch is jumpered on the RM7800E, the Energy Saving
function will not be performed.
Running Interlock (RM7800G,M)
This interlock (ILK) input signifies a Running Interlock.
If a Running Interlock is open at the beginning of
PREPURGE, a 30 second hold condition is initiated. If
30 seconds elapse and the Running Interlock still has not
closed, a lockout will occur. After entering PREPURGE, if
the Running Interlock opens during the first ten seconds, the
purge timer will be reset. This provides a continuous PURGE
to occur without interruption before the Pilot Flame Estab-
lishing Period. If the Running Interlock opens after 10
seconds into PREPURGE, it will recycle back to the begin-
ning of PREPURGE. If it opens anytime during the Ignition
Trials or Run, it will proceed to POSTPURGE.
A typical Running Interlock string contains an airflow
switch (see Figs. 9 and 11). The Interlock Check is a site
configurable option (see Table 6). If this feature is enabled,
the RM7800 will lockout after 120 seconds, whenever con-
trol terminal 6 is energized, and the Running Interlock string
(including airflow switch) is closed during STANDBY.
Lockout Interlock (RM7800E,L)
This interlock (ILK) input signifies a Lockout Interlock.
If the Lockout Interlock is open for more than ten seconds into
PREPURGE, the RM7800E,L will lockout*. After entering
PREPURGE, if the Lockout Interlock opens during the first
ten seconds, the purge timer will be reset. This provides a
continuous PURGE to occur without interruption before the
Pilot Flame Establishing Period. If a Lockout Interlock opens
anytime after ten seconds into PURGE, during the Ignition
Trials or Run, it causes a lockout.
A typical Lockout Interlock string contains an airflow
switch (see Figs. 8 and 10). The Interlock Check is a site
configurable option (see Table 6). If this feature is enabled,
the RM7800 will lockout after 120 seconds whenever control
terminal 6 is energized, and the Lockout Interlock string
(including airflow switch) is closed during STANDBY.
*NOTE: For the RM7800E, the ten second time frame does
not begin until the blower motor is energized.
Preignition Interlock (RM7800 ALL)
The Preignition Interlock input is typically connected to
proof-of-closure switches for fuel valve(s). The Preignition
Interlock must be energized throughout PREPURGE. If the
Preignition Interlock opens during STANDBY, it causes a
hold (30 seconds). The RM7800 will lockout if the interlock
does not close within 30 seconds during STANDBY. If the
Preignition Interlock opens during PREPURGE, it will re-
cycle to STANDBY (RM7800G,M) or will lockout
(RM7800E,L). If the Preignition Interlock is open after five
seconds into POSTPURGE, the RM7800 will lockout. The
Preignition Interlock is ignored during the ignition trials
state and during RUN.
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