Honeywell 7800 Series Product Data page 15

Table 4. Fault Message and Recommended Troubleshooting (continued) .
Fault Code
Fault 21 Running interlock fault
Running ILK during Prepurge.
Fault 22 Lockout interlock fault
Lockout ILK during Prepurge.
Fault 23 Combustion airflow
Airflow Switch interlock fault during
Prepurge.
Fault 24 The flame interlock (relay
Internal Fault module) was on when it
should have been off.
Fault 25 The flame interlock (relay
Internal Fault module) was off when it
should be on.
Fault 26 The Manual Open Valve
Man-Open Sw. Off Switch was off when it
should be on.
Fault 27 Start Switch was on during
Start Switch On Prepurge.
System Failure
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 Running Interlock switches are functioning properly
and that the contacts are free from contaminants.
4. Reset and sequence the 7800 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 per-sists, replace the
relay module.
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 their contacts are free from contaminants.
4. Reset and sequence the 7800 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 per-sists, replace the
relay module.
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 Airflow Interlock switches are functioning properly
and that their contacts are free from contaminants.
4. Reset and sequence the 7800 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 per-sists, replace the
relay module.
1. Reset and sequence the 7800.
2. If fault persists, replace the relay module.
1. Reset and sequence the 7800.
2. If fault persists, replace the relay module.
1. Check wiring, correct any errors.
2. Assure that the Manual Open Valve Switch is fully open.
3. Assure that the Manual Open Switch is functioning properly and that
the contact is free from contaminants.
4. Reset and sequence the RM7838B.
5. Assure that there is voltage going into the switch and coming out of
the switch when closed. Verify that the relay module is receiving
power at terminal 17.
6. If steps 1 through 5 are correct and the fault per-sists, replace the
relay module.
1. Start Switch held "on" too long.
2. Check wiring, verify that the Start Switch has been connected
correctly. Correct any errors.
3. Assure that the Start Switch is functioning properly and that the
contact is free from contaminants.
4. Reset and sequence the RM7838B to Prepurge, place the Run/Test
switch into the Test position. Assure that there is no power at
terminal 6 during Prepurge.
5. If steps 1 through 3 are correct and the fault per-sists, replace the
relay module.
7800 SERIES S7800B DISPLAY MODULE
Recommended Troubleshooting
15
(continued)
65-0219—1