Product Overview

RM7890; RM7895 100 VAC 7800 SERIES RELAY MODULES
66-1195—01 24
To Eliminate Ignition Interference
1. Make sure there is enough ground area.
2. Be sure the ignition electrode and the flame rod are on
opposite sides of the ground area.
3. Check for correct spacing on the ignition electrode:
a. 6,000V systems 1/16 in. to 3/32 in. (1.6 mm to 2.4
mm).
b. 10,000V systems 1/8 in. (3.2 mm).
4. Make sure the leadwires from the flame rod and ignition
electrode are not too close together.
5. Replace any deteriorated leadwires.
Flame Signal with Hot Combustion
Chamber (All Installations)
1. After all initial start-up tests and burner adjustments are
completed, operate the burner until the combustion
chamber is at the maximum expected temperature.
2. Observe the equipment manufacturer warmup
instructions.
3. Recycle the burner under these hot conditions and
measure the flame signal.
4. Check the pilot alone for non-DSI (Direct Spark Ignition)
applications or the main burner flame for DSI
applications.
5. Check the FFRT of the flame amplifier.
6. Lower the setpoint of the operating controller and
observe the time it takes for the burner flame to go out.
This should be within 0.8 or 3 seconds maximum,
depending on the amplifier selected.
7. If the flame signal is too low or unsteady, check the
flame detector temperature.
8. Relocate the detector if the temperature is too high.
9. If the response time is still too slow, replace the Plug-in
Flame Signal Amplifier.
10. If the detector is relocated or the amplifier is replaced,
repeat all required Checkout tests.
Safety Shutdown Tests (All
Installations)
Perform these tests at the end of Checkout, after all other
tests are completed. If used, the external alarm should turn
on.
1. Press the relay module reset pushbutton to restart the
system.
2. Open the Airflow Interlock during PREPURGE, PILOT
IGN, MAIN IGN or RUN period (RM7895).
a. Safety shutdown occurs if the Airflow ILK Switch
Failure configuration jumper (JR3) is clipped
(RM7895).
3. Detect flame 240 seconds after entry to STANDBY.
a. Simulate a flame to cause the flame signal voltage
level to be at least 1.25 Vdc for 30 seconds after the
initial 40 second entry into STANDBY (PREPURGE
for RM7895).
b. Safety shutdown occurs.
4. Observe that pilot does not ignite.
a. Close the pilot and main fuel manual shutoff
valve(s).
b. Depress the reset pushbutton.
c. Start the system.
d. Automatic pilot valve(s) should be energized but the
pilot cannot ignite.
e. Safety shutdown will occur.
5. Observe loss of flame during RUN (if Flame Failure
Action configuration jumper, JR2, is selected for
Lockout, see Tables 6 and 7).
a. Open the main fuel manual shutoff valve(s) and
open the manual pilot shutoff valve(s).
b. Depress the reset pushbutton.
c. Start the system. Startup should be normal and the
main burner should light normally.
d. After the sequence is in the normal RUN period for
at least ten seconds with the main burner firing,
close the manual main and pilot fuel shutoff valve(s)
to extinguish the main burner flame.
e. The flame signal drops below 1.25 Vdc within 0.8 or
3 seconds (depending upon the FFRT of the
amplifier) after the main flame goes out.
f. Safety shutdown occurs.
IMPORTANT
1. If the relay module fails to shut down on any of these
tests, take corrective action (refer to the Trouble-
shooting section or RM7890, RM7895 diagnostics)
and return to the beginning of all checkout tests.
2. When all Checkout tests are completed, reset all
switches to original states.
TROUBLESHOOTING
RM7890, RM7895 System
Diagnostics
Troubleshooting control system equipment failures is easier
with the relay module self-diagnostics and first-out
annunciation through the optional KDM. In addition to an
isolated spdt alarm relay (audible annunciation), the relay
module provides visual annunciation by displaying the ALARM
LED.
Self-diagnostics of the relay module enable it to detect and
annunciate both external and internal system problems.
External faults such as flame failures and false flame signals
are annunciated by a lockout of the relay module that
energizes the ALARM LED. Refer to the 7800 SERIES Relay
Modules Checkout and Troubleshooting, form 65-0229 for
additional information.
The relay module provides diagnostic information to aid the
service mechanic to obtain information when troubleshooting
the system. See Table 13.
The optional KDM displays sequence status messages
indicating INITIATE, STANDBY, PREPURGE, PILOT IGN,
MAIN IGN and RUN. The selectable messages also provide
visual indication, current status and historical status of the
equipment such as Flame Signal, Total Cycles, Total Hours,
Fault History and Diagnostic Information. With this information
most problems can be diagnosed without extensive trial and
error testing. Information available in the Diagnostic
Information file includes: Device Type, Device Suffix, Software
Revision, Manufacturing Code, Flame Amplifier Type, Flame
Failure Response Time, Selectable Jumper Configuration
Status and Terminal Status.