Ground fault detector failure

ID: fm:ground-fault-detector-failure
IRI: https://solarlattice.org/kb/fm/ground-fault-detector-failure
Status: active
Also known as: Leakage current sensor fault, sensor fault of leakage current, GFCI sensor abnormal, GFCI sensor abnormality, Ground Fault Current Sensor Abnormal

The inverter has a residual current circuit, required by UL 1741, that detects leakage from ground faults in the PV array, raises an alarm and stops the inverter. This failure mode means the leakage current (GFCI) sensor in that circuit has failed. It does not mean there is a ground fault in the array. Depending on the model, the inverter shows protection code Protect0100 or Protect0310. You can see the code on the inverter display. It is also flagged in the Modbus fault register. First, turn both the AC and DC switches off, wait one minute for the energy to discharge, and turn them back on. If the fault does not clear, contact the manufacturer's service team to replace the filter board or the whole inverter.

<!-- review notes

sentence 1: support check: partial - UL1741 residual current detection, alarm and ceasing operation are stated, but only in some passages and with a leakage threshold condition in others.
sentence 2: support check: partial - Passages say sensor abnormal/fault, but nowhere state that it does not indicate an array ground fault.
sentence 3: support check: partial - Both codes appear for the sensor fault, but the passages do not tie them to model differences.
sentence 4: support check: partial - The Modbus register bit and LCD display are shown, but the LCD display appears only for Protect0100, and the register is a fault register with Fault1 storage.
sentence 4: review: partial - All three rows place the fault at Modbus register 0x8402 Bit15 (two say Fault1), but only the 275kW map gives an LCD display value (Protect0100), so the passages do not show Protect0310 on the display. -->

Claims

`affects`

c1 verified · fact Ground fault detection circuit

The fault is in the leakage current (GFCI) sensor of the inverter's ground fault detection circuit.

CPS SCA100K-T-US-480 SCA50K-T-US-208 User Manual Rev 1.0 tbl=54.r5 h=3a24d42b49b5
CPS SCH100-125KTL-DO-US-600-480 User Manual Rev 1.9 tbl=35.r6 h=3e8e43bfd3f4
CPS 200-250kW K-T Modbus Map 2026-01-30 tbl=42.r25 h=9af6f5661234
CPS SCA100K-T SCA50K-T Modbus Map 2026-02-05 tbl=48.r9 h=c39682b30c21
CPS SCA25KTL-DO-US-208 User Manual Rev 1.2 tbl=51.r5 h=fe0ca2913a14
CPS SCH125KTL-AIO-US-600 Sep 2020 tbl=33.r1 h=62a7b29ff982
CPS SCH350KTL-DO-US-800 User Manual Rev 2.2 tbl=34.r6 h=a24a0da56dc8
CPS 275kW 800V Modbus Map 2026-01-28 tbl=53.r1 h=20878cf5cc23
CPS-SCA36-50-60KTL fault and troubleshooting tbl=9.r2 h=ae5777d7a0a3

verified by: review-workflowverified on: 2026-10-23

c2 drafted · lead Filter board

CPS manuals name the filter board as a replacement part for this fault, so the sensor may sit on it.

CPS SCA25KTL-DO-US-208 User Manual Rev 1.2 tbl=51.r5 h=fe0ca2913a14
CPS SCH125KTL-AIO-US-600 Sep 2020 tbl=33.r1 h=62a7b29ff982
CPS-SCA36-50-60KTL fault and troubleshooting tbl=9.r2 h=ae5777d7a0a3

review note: review: partial - The passages name the filter board as a replacement option, but they never say the fault affects the filter board or that the sensor is on it; the note only offers this as a guess.

`presents_as`

c3 verified · fact Internal device fault

The inverter reports it as protection code Protect0100 (leakage current sensor fault) or Protect0310 (GFCI sensor abnormal), depending on the model.

CPS SCA100K-T-US-480 SCA50K-T-US-208 User Manual Rev 1.0 tbl=54.r5 h=3a24d42b49b5
CPS SCH100-125KTL-DO-US-600-480 User Manual Rev 1.9 tbl=35.r6 h=3e8e43bfd3f4
CPS 200-250kW K-T Modbus Map 2026-01-30 tbl=42.r25 h=9af6f5661234
CPS SCA100K-T SCA50K-T Modbus Map 2026-02-05 tbl=48.r9 h=c39682b30c21
CPS 275kW 800V Modbus Map 2026-01-28 tbl=53.r1 h=20878cf5cc23

verified by: review-workflowverified on: 2026-10-23review note: support check: partial - Codes Protect0100/Protect0310 are stated, but 'depending on the model' and the classification as an internal device fault are not explicit.