Smeg CW 420 User Manual page 22

Err23 Boiler does not heat up as expected
Err24 Boiler temperature probe malfunction
Err25 Boiler water filling malfunction
Err26 Boiler emptying malfunction
Boiler emptying malfunction – with
Err27
tank full
Boiler heating
Err28
(overheating)
- CW 420/430
The problem might occur because water is
continually entering the tank (the causes are as for
Err5 – see above)
If it persists, check in this order:
- damaged boiler heating element
- contactor failure,
- boiler safety thermostat failure,
- boiler temperature probe faulty or incorrectly
positioned
- motherboard relay failure,
Important: if the boiler heating element is damaged,
this might be due to operation with no water in the
boiler - the pressure switch is indicating full even with
the boiler empty: check and if necessary replace the
boiler air trap and/or the relative pressure switch:
the problem is generally preceded by "boiler
overheating E28"
boiler temperature probe disconnected or not
working
The boiler does not fill within the allowed time: check
water intake tap, dynamic pressure in intake system,
cleaning of water intake filter, possible damage to
water intake hose
Or check in this order:
- boiler pressure switch has failed (continuous empty
reading)
- pipe leaking/disconnected (water entering pipe)
- check that rinsing spray arm nozzles are clean
- boiler pressure switch has failed (continuous full
reading)
- pipe leaking/disconnected (water entering pipe)
- rinsing pump not working
Boiler pressure switch has failed (continuous full
reading)
First check:
- boiler pressure switch has failed (continuous full
reading)
- pipe leaking/disconnected: water entering pipe
malfunction
connected to air trap, pressure switch continues to
give full reading even with boiler empty, heating
element operating dry. Or:
- circuit board relay failure, or
- contactor failure
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