2-12 750-166
TABLE 4—FAULT MESSAGE AND RECOMMENDED TROUBLESHOOTING (Continued).
Fault Code System Failure Recommended Troubleshooting
Fault 24
*Call Service*
The Flame Interlock (relay
module) was on when it should
have been off.
1. Reset and sequence the CB 780/CB 784.
2. If fault persists, replace the relay module.
Fault 25
*Call Service*
The Flame Interlock (relay
module) was off when it should
be on.
1. Reset and sequence the CB 780/CB 784.
2. If fault persists, replace the relay module.
Fault 28
*Pilot Flame Fail*
Pilot flame failure. 1. Check pilot valve wiring and operation. Correct
any errors.
2. Check fuel supply.
3. Check pilot pressure and repeat pilot turndown
test.
4. Check ignition transformer electrode, flame
detector, flame detector sighting, and flame
amplifier.
5. If steps 1 through 4 are correct and the fault
persists, replace the relay module.
Fault 29
*Lockout ILK*
Lockout Interlock fault. 1. Check wiring; correct any errors.
2. Inspect the fan; assure that there is no blockage
of the air intake and that it is supplying air.
3. Assure that the Lockout Interlock switches are
functioning properly and that the contacts are
free from contaminants.
4. Reset and sequence the CB 780/CB 784 to
Prepurge (place the Run/Test Switch into the
TEST position, if available). Measure the voltage
between terminal 7 and G (ground). 120 Vac
should be present.
5. If steps 1 through 4 are correct and the fault
persists, replace the relay module.
Fault 31
*Low Fire Sw. Off*
Low Fire Interlock switch
failure to close during Run.
1. Check wiring; correct any errors.
2. Reset and sequence the CB 780/CB 784.
3. Use either the manual motor position to drive the
motor to the LOW FIRE position, or use the Run/
Test switch option (if available) sequence to Run
Drive to Low Fire and place in the TEST
position. Adjust the Low Fire switch while in this
state to assure that it is closing properly.
4. While in Run Drive to Low Fire state, measure
the voltage between terminal 19 and G (ground).
120 Vac should be present. If not, the switch
adjustment is incorrect and/or the switch is
defective and needs replacement.
5. Reset and sequence the CB 780/CB 784. If
120 Vac was present between the Low Fire
switch and terminal 19 and the fault still persists,
replace the relay module.
(Continued)
To Next Page
Loading...