Principal Technical Features; Safety Provisions - Honeywell 7800 Series Manual

RM7838B
PRINCIPAL TECHNICAL FEATURES • SAFETY PROVISIONS
The RM7838B provides all customary flame safeguard
functions while providing significant advancements in the
areas of safety, annunciation and system diagnostics.
SAFETY SHUTDOWN (LOCKOUT) OCCURS IF:
1. INITIATE Period
a. Purge card is not installed or removed.
b. Purge card is bad.
c. Configuration jumpers were changed after 200 hours
of operation.
d. AC line power errors, see Operation.
e. Four minute INITIATE period is exceeded.
2. STANDBY Period
a. Flame signal is present after 40 seconds.
b. Preignition Interlock is open after 30 seconds.
c. Ignition/pilot valve/intermittent pilot valve termi-
nal is energized.
d. Main valve terminal is energized.
e. Internal system fault.
f. Purge card is not installed or removed.
g. Purge card is bad.
h. Flame detected during the last two seconds.
3. PURGE Period
a. Preignition Interlock opens anytime during PURGE.
b. Flame signal detected during PURGE .
c. High Purge Rate Switch fails to close within four
minutes, fifteen seconds after the firing rate motor
is commanded to drive to high fire position.
d. Low Fire Start Switch fails to close within four min-
utes, fifteen seconds after the firing rate motor is
commanded to drive to low fire position.
e. Lockout Interlock does not close within five seconds.
f. Lockout Interlock opens during PURGE .
g. Ignition/pilot valve/intermittent pilot valve termi-
nal is energized.
h. Main valve terminal is energized.
i. Internal system fault.
j. Purge card is not installed or removed.
k. Purge card is bad.
4. Purge Hold: T21
a. Preignition Interlock opens.
INTERNAL HARDWARE STATUS MONITORING
The RM7838B checks the purge card for correct parity
to prevent purge timing shifts and circuitry failures. It also
analyzes the integrity of the configuration jumpers and
internal hardware. The POWER LED blinks every four sec-
onds, signifying an internal hardware check.
CLOSED LOOP LOGIC TEST
The test verifies the integrity of all safety critical loads,
terminals 8, 9 and 10. If the loads are not energized prop-
erly; i.e., the main valve terminal is powered during PURGE,
65-0120—1

Principal Technical Features

b. Flame is detected.
c. Lockout Interlock opens during Hold.
d. Ignition/pilot valve/main valve is energized.
e. Internal system fault.
f. Purge card is removed.
g. Purge card is bad.
5. PILOT FLAME ESTABLISHING Period (PFEP)
a. Low Fire Switch opens.
b. Lockout Interlock opens .
c. Ignition/pilot valve/intermittent pilot valve termi-
nal is not energized.
d. No flame is present at end of PFEP.
e. Internal system fault.
f. Purge card is not installed or removed.
g. Purge card is bad.
6. MAIN FLAME ESTABLISHING Period (MFEP)
a. Low Fire Switch opens.
b. Lockout Interlock opens .
c. Ignition/pilot valve/intermittent pilot valve termi-
nal is not energized.
d. Main valve terminal is not energized.
e. No flame is present at end of MFEP.
f. Internal system fault.
g. Purge card is not installed or removed.
h. Purge card is bad.
7. RUN Period
a. No flame is present.
b. Lockout Interlock opens.
c. Main valve terminal is de-energized.
d. Internal system fault.
e. Purge card is not installed or removed.
f. Purge card is bad.
8. Pilot Valve Hold
a. Low Fire Switch opens.
b. Lockout Interlock opens.
c. Ignition/pilot valve terminal is not energized.
d. No flame is present at end of PFEP.
e. Internal system fault.
f. Purge card is not installed or removed.
g. Purge card is bad.
h. Non Shutter Check Amplifier/Detector used.

Safety Provisions

the RM7838B will lockout on safety shutdown. The RM7838B
must react to input changes but avoid the occurrence of
nuisance shutdown events. Signal conditioning is applied to
the line voltage detection circuit inputs to ensure proper
operation in the presence of normal electrical line noise 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).
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