If a 3 pole NSX MCCB is fitted with a Micrologic 5 or 6 trip unit the neutral conductor can be protected with an external CT.

If the neutral protection is enabled before the CT is connected the MCCB will trip.
The display will either have "ENCT" or "STOP" on it.

The trip unit has a function that checks the continuity of the external CT and wiring.
If this cannot be detected the MCCB will trip.

To resolve this problem -

The front cover of the MCCB needs to be removed and either the CT needs to be connected, or terminals T1 & T2 need to be linked so that the MCCB can be reset.
Please see the attachment for further details.

Released for: Schneider Electric Ireland