Principal Technical Features; Safety Provisions - Honeywell 7800 Series Installation Instructions Manual

RM7890, RM7895 100 Vac
Device Initiate
RM7890 10 sec.
RM7895 10 sec.
a
Standby and Run can be an infinite time period.
b
Purge is determined by the ST7800 Purge Timing Card selected (RM7895 only).

PRINCIPAL TECHNICAL FEATURES

The RM7890 and RM7895 Relay Modules provide all custom-
ary flame safeguard functions while providing significant ad-
vancements in the areas of safety, annunciation and system
diagnostics.
Safety Shutdown (Lockout) Occurs If:
1 . INITIATE PERIOD
a . AC line power errors occurred; see Operations section.
b . Configuration jumpers are changed after 200 hours of
operation.
c . Four minute INITIATE period has been exceeded.
d . Purge card is not installed or was removed (RM7895
only).
e . Purge card is faulty.
2 . STANDBY PERIOD
a . Flame signal is present after 240 seconds.
b . Ignition/intermittent pilot valve terminal is powered
when it should be off.
c . Internal system fault occurred.
d . Main valve terminal is powered when it should be off.
e . Three-second flame failure response time (FFRT) ampli-
fier is installed and configuration jumper is selected for
relight (RM7890); see Table 8.
f . Purge card is not installed or was removed (RM7895).
g . Purge card is faulty.
3 . SAFE START CHECK
a . Ignition/intermittent pilot valve terminal is energized
when it should be off.
b . Internal system fault occurred.
c . Main valve terminal is energized.
4 . PREPURGE PERIOD (RM7895 Only).
a . Airflow lockout feature is enabled and the airflow switch
does not close after ten seconds or within the specified
purge card timing.
b . Flame signal is detected after 30 seconds.
c . Ignition/pilot valve/intermittent pilot valve terminal is
energized when it should be off.
d . Main valve terminal is energized when it should be off.
e . Internal system fault occurred.
f . Purge card is not installed or was removed.
g . Purge card is faulty.
5 . PILOT FLAME ESTABLISHING PERIOD (PFEP).
a . Ignition/intermittent pilot valve terminal is not ener-
gized.
b . Internal system fault occurred.
c . Main valve terminal is energized when it should be off.
d . No flame present at end of PFEP.
e . Airflow lockout feature is enabled and the airflow switch
opens (RM7895).
f . Purge card is not installed or was removed (RM7895
only).
32-00216-01
Table 6. Sequence Timing for Normal Operation.
a b
Standby Purge
— N/A
— —
Pilot Flame Establishing Period
4 or 10 sec.
4 or 10 sec.
g . Purge card is faulty (RM7895 only).
6 . RUN PERIOD.
a . Ignition terminal is energized when it should be off.
b . Internal system fault occurred.
c . Main valve terminal is not energized when it should be
on.
d . No flame is present and configuration jumper is select-
ed for lockout.
e . Pilot valve terminal is not energized.
f . Airflow lockout feature is enabled and the airflow switch
opens (RM7895).
g . Purge card is not installed or was removed (RM7895
only).
h . Purge card is faulty (RM7895 only).

SAFETY PROVISIONS

Internal Hardware Status Monitoring
The RM7890; RM7895 Relay Modules analyze the integri-
ty of the configuration jumpers and internal hardware. The
RM7895 checks the purge card for correct parity to prevent
purge timing shifts and circuitry failures. The POWER LED
will blink every four seconds, signifying an internal hardware
check.
Closed Loop Logic Test
The test verifies the integrity of all safety critical loads, termi-
nals 8, 9 and 10. If the loads are not energized properly— that
is, the main valve terminal is powered during STANDBY— the
relay module locks out on safety shutdown. The relay mod-
ule must react to input changes but avoid the occurrence of
nuisance shutdown events. Signal conditioning is applied to
line voltage inputs to verify proper operation in the presence
of normal electrical line noises such as transient high voltage
spikes or short periods of line dropout. Signal conditioning is
tolerant of synchronous noise (line noise events that occur at
the same time during each line cycle).
Dynamic AMPLI-CHECK
Dynamic AMPLI-CHECK
amplifier during burner operation and shuts down the relay
module if the flame amplifier fails.
Dynamic Input Check
All system input circuits are examined to assure that the relay
module is capable of recognizing the true status of external
controls, limits and interlocks. If any input fails this test, a
safety shutdown occurs and the fault will be annunciated.
6
a
Run
—
—
TM
Circuitry
TM
circuitry tests the flame signal