Strebel S-CB Px 120, Installation Operating & Maintenance Manual

Page: 96 / 118

S-CB Px 120 Manual 96
16.2. Blocking codes
The display is not blinking, but is lightened up during the blocking period.
The boiler is blocking an action, because of an extraordinary situation. This action will be
continued after stabilisation of this situation.
Display message
F l o w t e m p h i g h
9 9 9 , 5 h r s
Reason Flow temperature has exceeded the blocking temperature, but it
has not exceeded the lock-out value.
Cause:
The water flow is restricted.
Corrective action:
Check functioning of the pump.
Check/open all valves that might restrict the water flow through the unit.
Check for an external system pump that influences the flow through the unit.
Check if the system resistance exceeds the spare capacity of the unit pump.
Display message
R e t u r n t e m p h i g h
9 9 9 , 5 h r s
Reason Return temperature has exceeded the blocking temperature, but it
has not exceeded the lock-out value.
Cause:
Systems that pre-heats the boiler return temperature too much/high.
Corrective action:
Reduce pre heat temperature of external heat source.
Cause:
The need for heat in the system suddenly drops causing hot return water to the boiler.
Corrective action:
Dampen external heating system control to prevent sudden boiler temperature rise.
Display message
F l u e t e m p h i g h
9 9 9 , 5 h r s
Reason Flue gas temperature has exceeded the limit.
Cause:
Heat exchanger polluted and not able to transfer enough heat to the system water.
Corrective action:
Check and clean heat exchanger.
Cause:
Bad flue gas sensor or sensor connection (partly shorted.)
Corrective action:
The sensor is of the type NTC. This means when the temperature rises, its resistance
decreases. A partly shorted sensor will drop its resistance and therefore ‘measure’ a raise
in temperature when actually there is none.
Check for moist in the sensor connections or replace the sensor.
´Flue temp high´ message continues p.t.o.
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