Maintenance
81
MAXXfl o EVO 150/302
6.6 ERROR CODES (CONTINUED)
Error
Code
Error Code Description
Diag.
Code
Notes
110
SLT Lockout
306 431
432 433
434 435
436 756
Electronic temperature limits exceeded. General overheating
issue. Check for pump operation, trapped air and heat ex-
changer blockages. Monitor temperatures of system to estab-
lish problem area.
429 818 Safe reset of the error sub code 433 (see above) has not been
met. Allow the boiler to cool further before resetting.
305 412
550 551
754
Mechanical overheat protection circuit is open circuit (connec-
tion X18 on control PCB). Check connector is fully inserted
426 437
815
Flow temperature heat up gradient exceeded. Check pump
operation and presence of trapped air in the heat exchanger.
Flow through heat exchanger may be restricted.
438
817
Maximum Delta T of system exceeded. Check pump opera-
tion and presence of trapped air in the heat exchanger. Flow
through heat exchanger may be restricted.
428
Maximum Delta T of system exceeded. Initial operation of the
pump before the burner is operated, can cause this error. If
accompanied by code 429 within the same minute, this error
can be disregarded.
429
Safe reset of the error sub code 428 /438 (see above) has not
been met. Allow the boiler to cool further before resetting.
427 816 Safe reset criteria has not been met. Allow the boiler to cool
further before resetting.
420 421
819 820
Return temperature greater than fl ow temperature. Check that
the fl ow and return sensors are operating correctly
419 430
813 814
Flow temperature limit exceeded. Check for overheating is-
sues and fl ow sensor (B2) performance.
809 810
422 423
Flow temperature not plausible - Reading less than 0
O
C or
greater than 124
O
C . Check fl ow sensor (B2) and replace if
necessary.
425
812
Return temperature limit exceeded. Check for overheating
issues and return sensor (B7) performance.
424
811
Return temperature not plausible - Reading less than 0
O
C or
greater than 124
O
C . Check return sensor (B7) and replace if
necessary.
111
Shutdown limit thermostat
264
Heat exchanger temperatures have been exceeded. Inves-
tigate fl ow rates, shutoff valves and controls to determine
causes of temporary fault code.
125
Maximum boiler temperature
exceeded
286 500
740
Temperature supervision lockout. Check pump, shutoff valves,
burner and fl ow rates before resetting
501
Temperature has not increased at fl ow sensor after burner
start. Check fl ow sensor is correctly connected
502
Temperature has not increased at return sensor after burner
start. Check return sensor is correctly connected.
126
DHW charging temperature
not reached
72
Charging temperature not achieved within parameterised time
scale. Check operation and heat up times for heater
127
DHW legionella temperature
not reached
73
Check operation of legionella function and DHW system. Le-
gionella setpoint has not been achieved within 48 hours of the
legionella function operating.
NB: When using a secondary return system and B39 sensor,
do not set the legionella function setpoint too high, as the heat
losses of the hot water pipework may not permit this setpoint
at the return point before the heater.
