In addition, a Keyboard Display Module is available and is a valuable aid for indicating flame signal DC volts, fault messages,
sequence status, etc . Refer to
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 electrical access slots .
Table 6: 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
completed .
a . Check
. 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 pressure 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
continuously, but
burner does not
start (pilot LED)
does not come on
after 30 (60 or 90)
seconds .
a . Check
. The LED code may diagnose the problem .
b . The air switch sensing tube is not in the blower housing and sensing pressure .
c. The air switch or its wiring is defective. 120 volts should appear between terminals 7 and L2 if airflow
switch contacts are made .
2 .2
Burner motor
starts when the
reset button on
RM7897A is
pressed . The
motor runs for
40 (70, 100)
seconds and then
the burner shuts
down and requires
manual resetting .
a . Check
. The LED code may diagnose the problem .
b . If the PILOT LED did not come on for the 10 seconds before shutdown check for voltage between
terminal 10 and L2 during the final 10 seconds before control locks out. If zero voltage, replace the
RM7897A .
c. If the PILOT LED did come on for 10 seconds before shutdown the pilot flame is not igniting or is not
being detected by the flame safeguard. Check that the manual gas valves are open.
d. Check the flame safeguard with a flame simulator.
1 . Close the main gas test cock .
2. Plug the flame simulator into the flame safeguard.
3 . When the pilot indicator light comes on, touch the simulator G post to ground . If the FLAME LED
now comes on the flame safeguard is working, but it is not receiving an adequate flame signal. If
the FLAME LED did not come on replace the R7847A amplifier or/and the RM7897A.
IM 684-6 • ROOFTOP SYSTEMS 26 www .DaikinApplied .com
Troubleshooting