72
13 - TROUBLE SHOOTING
Shutdown Code Table
Shut-
down
Code
Description
Probable Causes
Checking/Solution
Su:20
(1)
Identification running
---
No action required
Su:21
Communication error with
SU PCB
Bad connection
Check whether SU PCB has been correctly fitted in the
connector on SU PCB
Su:22
No flame during
operation
No ionization current
Purge gas supply to remove air
Check gas valve is fully opened
Check supply pressure
Check operation and setting of gas valve
Check air inlet and exhaust are not blocked
Check there is no recirculation of combustion gases
Su:25
(1)
Internal error on the SU-
PCb
---
Replace the SU PCB
Su:29
(2)
tFG sensor above
maximum setpoint
Non-existent or insufficient
water circulation / sensor
error
Replace flue high limit.
Check circulation (direction, pump,valves)
Check water pressure
Check sensors are operating correctly
Check sensor has been correctly fitted
Check cleanliness of heat exchanger
Su:30
(2)
No tFG sensor connected
/shorted Boiler stop
Flue high limit disconnected /
Sensor error
Replace flue high limit.
Su:33
After 5 times tF>tF Max:
controlled stop
Non-existent or insufficient
circulation / sensor error
Replace supply sensor.
Check circulation (direction, pump,valves)
Check water pressure
Check sensors are operating correctly
Check sensor has been correctly fitted
Check cleanliness of heat exchanger
Su:34
(2)
After 5 times tFG>tfmax:
controlled stop
Non-existent or insufficient
circulation / sensor error
Replace flue high limit.
Check circulation (direction, pump,valves)
Check water pressure
Check sensors are operating correctly
Check sensor has been correctly fitted
Check cleanliness of heat exchanger
Su:35
Insufficient gradient on
T1(supply) or T2(return)
after burner starts
Non-existent or insufficient
circulation / sensor error
Check circulation (direction, pump,valves)
Check water pressure
Check sensors are operating correctly
Check sensor has been correctly fitted
Check cleanliness of heat exchanger
(1)
These lock-outs are not stored in fault memory
(2)
tFG : flue gas sensor
PN 240011662 Rev. H [04/30/2019]