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4.8 Servicing and system messages
The newly-developed electronic controls unit with microcontroller continuously monitors the operations of the AT 3000
humidifiers. Any deviations from the operating condition (U codes) are shown on the display.
Code U1 Servicing signal
The steam cylinder can no longer attain the nominal output and needs, therefore, to be cleaned or perhaps replaced.
A visual inspection of the inside of the cylinder is necessary to be able to decide whether it needs replacing. Code U1 is
purely a servicing code; the unit does not switch off automatically. The humidifier continues to function at a reduced
output. Acknowledgement is effected by pressing T6 SET button (cf. Item 4.7).
Code U2 Excess current
Whenever there is excess current (140% of the nominal value) during normal operations, the humidifier switches
itself off automatically for safety reasons. After the fault has been rectified, the humidifier is put back into operation
by pressing T6 SET button (cf. Item 4.7).
Code U3 The humidifier fills continuously
Either there is no heating phase or no water in the cylinder due to the water supply having been cut off. The humidifier
switches itself off automatically after 30 minutes and is put back into operation by pressing T6 SET button (cf. Item 4.7).
Code U4 Microcontroller uncoded
This signal appears if a replacement electronic controls unit has been fitted to the humidifier without being coded.
The humidifier is prevented from operating. The signal disappears as soon as the electronic controls unit has been coded.
Code U5 Preset number of operating hours attained
This signal can appear only if the number of operating hours for the steam cylinder has been pre-programmed. This
is of benefit, for example, if regular servicing periods have been prescribed in accordance with hours run. U5 is purely a
servicing code; acknowledgement is effected by pressing T6 SET button (cf. Item 4.7).
The standard, potential-free relay output enables either collective alarms or just one «U» signal (which can be chosen in
the programming level) to be displayed remotely.
5. Servicing and maintenance
5.1 Cleaning and replacing the steam cylinder
Before commencing, switch off all power to the humidifier and disconnect the unit from the mains.
The serviceable life of the steam cylinder depends on both the hours run and the hardness of the tap water used.
The cylinder should be replaced when the electrodes have become insulated so much (because of calcification) that the
required steam output cannot be reached. At the same time, the water level in the cylinder continuously touches
the Niveau max. sensor. In this case, the specially-constructed water filling cup offers additional protection by feeding
excess water directly into the overflow facility, allowing it simply to drain away.
Whenever U1 appears in the display, you should proceed as described on this page. However, the humidifier can still be
run for some time before you need to replace the steam cylinder.
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