Huawei · PV inverters · Huawei SUN2000-KTL-M1 (three-phase inverter, 3–10 kW, battery-ready)
Alarm 4021CT connection abnormal
Name in the manufacturer's documentation (fault list): CT connection abnormal
[1]
In plain words (editorial)
The current transformers (CTs) are connected incorrectly – wrong phase or direction, or a disconnected CT cable.
When to call a service technician: Have your installer check the CT installation.
✎ editorial – written from the cited sources, not a manufacturer statement. Status: draft.
For technicians
Possible causes (source text)
- The ct installation phase or direction is incorrect.[2]
- The ct cable is disconnected.[3]
- Ct reverse or incorrect connection of phase u[4]
- Ct reverse or incorrect connection of phase w[5]
- Ct reverse or incorrect connection of phases u and w[6]
- The ct of phase u or w is disconnected or connected to phase o.[7]
- The cts of phases u and w are disconnected, or one ct is connected to phase o and the other ct is disconnected.[8]
Steps given by the manufacturer (source text)
- Check whether the ct is installed in the correct direction.[9]
- Check whether the cable between the ct and the device is disconnected.[10]
- Check whether the ct of phase u is installed in the correct direction.[11]
- Check whether the cts of phases u and w are correctly connected.[12]
- Check whether the ct of phase w is installed in the correct direction.[13]
- Check whether the cts of phases u and w are installed in the correct direction.[14]
- If no fault is found in the preceding steps, power on the device and check whether the alarm is generated. if the fault persists, contact the vendor or technical support.[15]
⚠ Work on refrigerant circuits, mains electricity and PV DC wiring is for qualified technicians only.
The Polish page has more detail (plain-language explanation, safe checks, guides): Read in Polish →
Sources
Every statement has a footnote to the document and PDF page. “Quote verified” means the quote was found automatically in the text of that page.
- [1] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 118 official manufacturer document quote verified
4021 CT connection abnormal
- [2] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 118 official manufacturer document quote verified
the ct installation phase or direction is incorrect.
- [3] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 118 official manufacturer document quote verified
the ct cable is disconnected.
- [4] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 118 official manufacturer document quote verified
ct reverse or incorrect connection of phase u
- [5] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 118 official manufacturer document quote verified
ct reverse or incorrect connection of phase w
- [6] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 118 official manufacturer document quote verified
ct reverse or incorrect connection of phases u and w
- [7] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 118 official manufacturer document quote verified
the ct of phase u or w is disconnected or connected to phase o.
- [8] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 118 official manufacturer document quote verified
the cts of phases u and w are disconnected, or one ct is connected to phase o and the other ct is disconnected.
- [9] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 119 official manufacturer document quote verified
check whether the ct is installed in the correct direction.
- [10] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 119 official manufacturer document quote verified
check whether the cable between the ct and the device is disconnected.
- [11] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 119 official manufacturer document quote verified
check whether the ct of phase u is installed in the correct direction.
- [12] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 119 official manufacturer document quote verified
check whether the cts of phases u and w are correctly connected.
- [13] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 119 official manufacturer document quote verified
check whether the ct of phase w is installed in the correct direction.
- [14] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 119 official manufacturer document quote verified
check whether the cts of phases u and w are installed in the correct direction.
- [15] Inverter Alarm Reference (Issue 14, 2026-06-15) (EDOC1100345192 Issue 14) , p. 119 official manufacturer document quote verified
if no fault is found in the preceding steps, power on the device and check whether the alarm is generated. if the fault persists, contact the vendor or technical support.