Honeywell 7800 SERIES Manual page 13

7800 SERIES S7800A1142 KEYBOARD DISPLAY MODULE
Fault Code
Fault 19 Flame was lost during MFEP or
*Main Flame Ign.* the first 10 seconds of the RUN
state.
Fault 20 Low Fire Interlock switch failure
*Low Fire Sw. Off* to close during PREPURGE.
Fault 21 Running Interlock fault during
*Running ILK* PREPURGE.
Fault 22 Lockout Interlock fault during
*Lockout ILK* PREPURGE.
Fault 23 Combustion airflow interlock
*Airflow Switch* fault during PREPURGE.
Fault 24 The flame interlock (relay
*Call Service* module) was on when it should
be off.
Fault 25 The flame interlock (relay
*Call Service* module) was off when it should
be on.
Fault 26 The Manual Open Valve Switch
*Man-Open Sw. Off* was off when it should be on
(Device specific).
Fault 27 Start Switch was on during
*Start Switch On* PREPURGE (Device specific).
Fault 28 Pilot flame failure.
*Pilot Flame Fail*
65-0288-1
Table 7. Hold and Fault Message Summary. (Continued)
System Failure
1. Inspect the main fuel valve(s) and connection(s).
2. Make sure the fuel pressure is high enough to supply fuel to
3. Make sure the flame detector is positioned to obtain the
1. Check wiring and correct any errors.
2. Reset and sequence the relay module.
3. Use either the manual motor potentiometer to drive the motor
4. Measure the voltage between terminal 18 and L2(N) while in
5. Reset and sequence the relay module. If line supply voltage
1. Check wiring and correct any errors.
2. Inspect the fan; make sure there is no blockage of the air
3. Make sure the Interlock Switches are working properly and that
4. Reset and sequence the relay module to PREPURGE (place
5. If steps 1 through 4 are correct and the fault persists, replace
1. Check for F leadwire routing. Make sure routing is in its conduit
1. Check wiring and correct any errors.
2. Make sure that the Manual Open Valve Switch is fully open.
3. Make sure that the Manual Open Valve Switch is functioning
4. Reset and sequence the relay module.
5. Make sure that the Manual Open Valve Switch provides an
6. If steps 1 through 5 are correct and the fault persists, replace
1. Start Switch held on too long.
2. Check wiring; verify that Start Switch is correctly connected.
3. Make sure that the Start Switch is functioning properly and that
4. Reset and sequence the relay module to PREPURGE; set the
5. If steps 1 through 4 are correct and the fault persists, replace
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
5. If steps 1 through 4 are correct and the fault persists, replace
18
Recommended Troubleshooting
the combustion chamber.
required flame signal strength; reset and recycle.
to the Low Fire position or use the Run/Test Switch option, if
available. Sequence to Prepurge drive to Low Fire and place in
the Test Position. Adjust the Low Fire Switch to make sure it
closed properly.
the Prepurge drive to Low Fire state. Line supply voltage
should be present. If not, the switch adjustment is incorrect
and/or the switch is defective and needs replacing.
was present between the Low Fire Switch and terminal 18, and
the fault still persists, replace the relay module.
intake and that it is supplying air.
all switch contacts are free of contaminants.
the Run/Test Switch in the Test position, if available). Measure
the voltage between terminals 7 and L2(N). Line voltage
should be present.
the relay module.
and isolated from noise-producing circuits.
properly and that the switch contacts are free from
contaminants.
electrical path when closed. Verify that the relay module is
receiving power at terminal 17.
the relay module.
the switch contacts are free of contaminants.
Run/Test Switch to Test. Make sure there is no power at
terminal 6 during PREPURGE.
the relay module.
detector sighting and flame amplifier.
the relay module.