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RCMB300-series_D00372_01_M_XXEN/06.2019
5.2 Offset calibration
The residual current monitoring module must be calibrated to the system to be moni-
tored so that the selected protective function can be fulfilled. Each RCMB30… electron-
ic module must be individually calibrated to the CTBC… built-in measuring current
transformer. Calibration can be carried out by means of the "T" button or via the Mod-
bus interface.
A calibration must always performed in case of:
• New installation
• A replacement of a CTBC… measuring current transformer
• A replacement of an RCMB30… electronic module
• A modification of the response value
In case of response values > 300 mA, no offset calibration is required.
If the device is not calibrated, the LED lights red permanently, commissioning is not
possible. Note that during the offset calibration the system is switched off and no cur-
rent flows through the measuring current transformer.
If a current flows through the measuring current transformer despite the system being
switched off, this indicates a device error. Replace the measuring current transformer imme-
diately.
The alarm relays switch to safe state during offset calibration (system is
switched off).
For measuring current transformers with an internal diameter > 119 mm, an
offset calibration must be carried out.
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