Specifications

22 IM 685-2
Troubleshooting Chart
The RM7897A flame safeguard is equipped with an LED to
aid in the diagnosis of burner operation and problems.
Fault
identification is a series of
fast- and slow-blinking LED lights.
The fast blinks identify the tens portion of the fault code (two
fast blinks is 20), while the slow blinks identify the units por-
tion of the fault code (two slow blinks is 2). Two fast blinks
followed by two slow blinks would be fault code 22. This
identifies a flame signal absent at the end of the pilot flame
establishing period. (See Table 6 for Blinking Fault Code
List.) The LED code repeats as long as the fault exists. To
clear the fault, press the RESET button.
In addition, a Keyboard Display Module is available and is a
valuable aid for indicating flame signal DC volts, fault mes-
sages, sequence status, etc. See “Flame Safeguard” on page 20
for additional information on the Keyboard Display Module.
Some of the steps listed in this troubleshooting chart will be
unnecessary if a Keyboard Display Module is used, as that
module will pinpoint many problems.
Voltage checks can be accomplished without removing the
Flame Safeguard by removing the Electrical Access Slot
Covers on the side of the sub-base and then using those elec-
trical access slots.
Table 5. Troubleshooting chart
BURNER MOTOR DOES NOT RUN (AFTER 10 SECOND “INITIATE” PERIOD AND WITH SWITCH AT AUTO):
1.1 Power LED is off. Power is not getting to burner.
1.2 Entire unit seems to be off.
Burner power comes from the main control panel which has a main disconnect switch, a stepdown transformer with primary
winding fuses, a 120V secondary winding fuse, and an on-off service switch. If any of these were open, the burner as well as the
supply fan would be inoperative. The control system also has firestat type temperature sensors which will shut down the entire
unit if supply or return air temperatures exceed set points. On some control systems, the firestats only lock out the supply and
return fans. Check main control schematic, as these would not be burner problems.
1.3 Supply fan will operate.
a. Check the manual reset limit control located between the filters and the supply fan and reset if required.
b. Check that the control system has energized relay R20 located in the main control panel.
1.4 Power LED is on. Push the reset button on the flame safeguard.
1.5 Resetting flame safeguard
does not start motor after the 10
second “Initiate” period is com-
pleted.
a. Check Table 6. The LED code may diagnose the problem.
b. Push the reset button on the burner motor.
(Note: If motor is hot and probably tripped, it has to cool sufficiently before it can be reset.)
c. Remove the left side electrical access cover on the flame safeguard sub-base and test for line voltage at terminal 4 and L2. If
powered, the problem is with the burner motor or its associated controls. On Models 1100-2000, terminal 4 only controls a
contactor and burner motor power comes from its own circuit breaker. If terminal 4 is dead, check for power to terminals 6 and
L2.
d. IF VOLTAGE IS ZERO: The power is being interrupted by the limit control, the manual reset high or auto reset low gas pres-
sure switches (if included), the low fire end switch on the modulating operator (if included), or relay contact in the main control
system. Consult the schematic and determine the interruption.
e. If voltage is satisfactory at terminals 6 and L2 and terminal 4 does not become energized after 10 seconds, and pressing the
safety reset button has no effect, replace the RM7897A.
BURNER MOTOR RUNS, BUT...
2.1 Burner motor runs valve actu-
ator travels to the maximum
rate position and stays there,
the Keyboard Display Module
indicates "Purge Hold".
a. Switch LS2 is not being actuated by the collar on the control rod when at the maximum rate position.
b. The air proving switch AS is not sensing burner fan pressure. Check the connecting tube, setpoint, and wiring. If LS2 and AS
are functioning, 120 volts can be measured across terminals 7 and L2 on the flame safeguard when the burner fan is running.
2.2 Burner motor runs, valve actu-
ator travels to the maximum
rate position and stays there,
the Keyboard Display Module
goes through the prepurge
countdown. At approximately
20 seconds, Relay (R21) does
not energize.
a. Timer TD10 is not 'making' after 20 seconds. Check that there is 120 volts on TD10 tab 1 when the actuator is at the maxi-
mum rate position. TD10 tab 2 should become energized 20 seconds after tab 1 is powered.
b. Relay R21 is not being energized by TD10, check for power across C1 and C2 after TD10 has become energized and replace
R21 if indicated.
2.3 Burner motor runs, prepurge
appears normal, LED marked
PILOT comes on for 10 sec-
onds, then the flame safe-
guard locks out on flame
failure.
a. Check Table 6. The LED code may diagnose the problem.
b. Flame is not igniting or is not being detected by the flame safeguard. Check that the manual gas valves are open. Check for
manifold pressure at Tap (1), Figure 16, during the 10 seconds the LED marked Pilot is on:
1. If zero, verify that there is pressure at Tap (2), Figure 16, during the same 10 second period. If so, check that LS1 is being
actuated by the collar on the control rod when at the low fire position. Check that the manual knob on GV1 is not closed
and power is supplied to valve.
2. If manifold pressure is normal, check for disconnected or shorted flame rod or ignition lead wire. Watch the ignition attempt
through inspection window on burner and check that spark is in the appropriate location. If not, this indicates a short. If
flame is observed but not detected by the flame safeguard, remove the burner gun assembly and check the flame rod,
lead wire, and connections.
3. Check the flame safeguard with a flame simulator:
a. Close main gas test cock.
b. Plug the flame simulator into the flame safeguard.
c. When the LED marked PILOT comes on, touch the simulator G post to ground. If the LED marked FLAME now comes
on, the flame safeguard is working, but it is not receiving an adequate flame signal. If the LED marked FLAME did not
come on, replace the R7847A amplifier and/or the RM7897A flame safeguard.
4. If there is spark but no flame, check for faults that would cause way too much air or too little gas.