Product Overview

RM7890; RM7895 100 VAC 7800 SERIES RELAY MODULES
7 66-1195—01
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.
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
and 10 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 will be de-energized.
Expanded Safe-Start Check
The conventional safe-start check, which prevents burner
startup when flame is indicated at startup, is expanded to
include a flame signal check during STANDBY and a safety
critical load check.
Off Cycle (Standby) 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 for 240 seconds in STANDBY, a
system hold occurs and startup is prevented. If the flame
signal exists at any time after the 240 seconds during
STANDBY, a safety shutdown occurs and is annunciated. An
AMPLI-CHECK™ Amplifier is energized continually through
STANDBY (and PREPURGE in the RM7895) to detect any
possibility of a runaway detector or a flame. When a flame
exists, a safety shutdown occurs. A standard amplifier is
energized continually through STANDBY (and PREPURGE in
the RM7895). When 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 spark termination.
First-Out Annunciation and Self-
Diagnostics
Sequence Status Lights (LED) 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 relay module hardware is running
correctly.
The optional multi-functional KDM shows elapsed time during
PILOT IGN. As an additional troubleshooting aid, it provides
sequence timing, diagnostic information, historical information
and expanded annunciator information during normal
operation or when a safety shutdown or hold occurs.
First-out Annunciation reports the cause of safety shutdown or
identifies the cause of a failure to start or continue the burner
control sequence with text and numbered code using the
optional KDM. It monitors all field input circuits, including the
flame signal amplifier.
Self-Diagnostics add to the First-Out Annunciation by allowing
the relay module to distinguish between field (external device)
and internal (system related) problems. Faults associated
within the flame detection subsystem or relay module are
isolated and reported by the optional KDM. See the 7800
SERIES Relay Modules Checkout and Troubleshooting, form
65-0229.
Interlock Requirements (RM7895
Only)
The Airflow Switch Interlock input provided in the RM7895 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 PREPURGE or lockout occurs, depending on
how the airflow switch selectable jumper is configured (see
Table 5 in the Operation section).
INSTALLATION
WARNING
Fire or Explosion Hazard.
Can cause severe injury, death or property
damage.
To prevent possible hazardous burner operation, verify
local safety requirements are observed each time a
control is installed on a burner.
WARNING
Electrical Shock Hazard or Equipment Damage
Hazard.
Can cause severe injury, death or equipment and
control damage.
Disconnect the power supply before beginning
installation.
When Installing this Product…
1. Read these instructions carefully. Failure to follow them
could damage the product or cause a hazardous
condition.
2. Check the ratings given in the instructions and marked
on the product to make sure the product is suitable for
the application.
3. Installer must be a trained, experienced, flame
safeguard service technician.
4. After installation is complete, check out the product
operation as provided in these instructions.