Dynamic Ampli-Check; Dynamic Input Check; Dynamic Safety Relay Test; Tamper Resistant Timing And Logic - Honeywell 7800 SERIES EC7895A Product Data

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Dynamic Ampli-Check®
Dynamic AMPLI-CHECK® circuitry tests the flame signal
amplifier during burner operation and shuts down the EC7895
or RM7895 if the flame amplifier fails.
Dynamic Flame Amplifier and Shutter Check
Self-checking circuitry tests all electronic components in the
flame detection system and amplifier 10 to 12 times per
minute and shuts down the EC7895 or RM7895 if the
detection system fails.

Dynamic Input Check

All system input circuits are examined to assure that the
EC7895 or RM7895 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 is annunciated.

Dynamic Safety Relay Test

Checks the ability of the dynamic safety relay contact to open
and close. Verifies that the safety critical loads, terminals 8, 9,
10 and 21, can be de-energized, as required, by the Dynamic
Self-Check logic.
Dynamic Self-Check Safety Circuit
The microcomputer tests itself and related hardware, and at
the same time, the safety relay system tests the
microcomputer operation. If a microcomputer or safety relay
failure occurs and does not allow proper execution of the self-
check routine, safety shutdown occurs and all safety critical
loads are de-energized.
Expanded Safe-Start Check
The conventional safe-start check, which prevents burner
start-up if flame is indicated at start-up, is expanded to
include a flame signal check during STANDBY, an airflow
switch check and a safety critical load check.
Off Cycle (Standby or Prepurge) Flame
Signal Check
The flame detection subsystem (flame detector and amplifier)
is monitored during STANDBY. If a flame simulating condition
or an actual flame exists, a system hold occurs and start-up is
prevented. If the flame signal exists at any time after the first
40 seconds of STANDBY, a safety shutdown occurs and is
annunciated. A shutter-check amplifier and self-checking
detector are energized for the first 40 seconds during
STANDBY and the last two seconds before exiting STANDBY.
If a flame exists, a safety shutdown occurs. An AMPLI-
CHECK® Amplifier is energized continually through
STANDBY and PREPURGE to detect any possibility of a
runaway detector or a flame. If a flame exists, a safety
shutdown occurs. A standard amplifier is energized
continually through STANDBY and PREPURGE; if a flame
exists, a safety shutdown occurs.

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 assure early spark
termination (ten seconds ignition and pilot and ten seconds
pilot and main 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, signifying that the RM7895 hardware is
running correctly.
Optional multi-function Keyboard Display Module shows
elapsed time during PREPURGE, PILOT IGN and MAIN IGN.
As an additional troubleshooting aid, it provides sequence
timing, diagnostic information and historical information when
a safety shutdown or hold or normal operation occurs.
First-out Annunciation reports the cause of a safety shutdown
or identifies the cause of a failure to start or continue the
burner control sequence with text and numbered code via the
optional Keyboard Display Module. It monitors all field input
circuits, including the flame signal amplifier. The system
distinguishes 43 modes of failure and detects and
annunciates difficult-to-find intermittent failures.
Self-Diagnostics add to the First-out Annunciation by allowing
the EC7895 or RM7895 to distinguish between field (external
device) and internal (system related) problems. Faults
associated within the flame detection subsystem, EC7895 or
RM7895 or Plug-in Purge Card are isolated and reported by
the optional Keyboard Display Module. See the 7800 SERIES
System Annunciation Diagnostics and Troubleshooting,
form 65-0118.
Airflow Switch Interlock
This interlock is typically connected to an airflow switch. The
Airflow Interlock (ILK) input must close ten seconds into
PREPURGE or within the specified purge card timing;
otherwise, a recycle to the beginning of PRE-PURGE or
lockout will occur, depending on how the airflow switch
selectable jumper is configured (see Table 3 in Operation


To prevent possible hazardous burner operation,
verification of safety requirements must be performed
each time a control is installed on a burner.

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