PCS Export Control and Fail-Safe Operation Application Note

PCS Export Control and Fail-Safe Operation

Solis S6-EH2P Series | North America | Application Note | V1.0 review draft | October 29, 2026

Subject: This application note explains meter-based Power Control System (PCS) configuration, system-wide export limiting, Fail-Safe operation in meter and supported direct-CT modes, parallel communication-loss protection, settings access, and commissioning verification for applicable Solis S6-EH2P hybrid inverters.

Purpose and intended use

Use this note with the attached UL 3141 Certificate of Compliance, the current model-specific installation manual, and the Solis meter/sensor compatibility list. It is intended for installers, system designers, customers, utility reviewers, and authorities having jurisdiction (AHJs). It describes supported behavior and required verification, not approval of a particular service or completed installation.

Essential requirements

Guide contents

Certification and scope • Metering architecture • Settings and screenshot • Fault-response matrix • Backup loads and recovery • Parallel operation • Commissioning tests • Access and troubleshooting • Utility handover and field record.

Certification, Scope, and Supporting Evidence

Applicable products

This note addresses the S6-EH2P(9.6–16)K-SV-YD-L-US hybrid series, using the following exact model identifiers listed on the supplied certificate:

S6-EH2P16K03-SV-YD-L-US; S6-EH2P16K03-SV-YD-L-US-E; S6-EH2P14K03-SV-YD-L-US; S6-EH2P12K03-SV-YD-L-US; S6-EH2P12K03-SV-YD-L-US-E; S6-EH2P11.4K03-SV-YD-L-US; S6-EH2P10K03-SV-YD-L-US; S6-EH2P9.6K03-SV-YD-L-US.

For other families, regional variants, larger parallel arrays, external generation, or third-party controls, confirm model and configuration applicability with Solis Service.

Certification documents supplied separately

What these documents establish

The certificate identifies listed products and standards; the report records test conditions and results. This note adds manufacturer-confirmed application guidance. Its field instructions and timing declarations are not all direct report quotations.

The designated, evaluated, and supported field metering device for PCS is the CHINT DTSU666. The HIOKI CT6873 in the laboratory test setup was calibrated measurement equipment, not the designated field CT. PCS installations require the approved meter-kit sensors. The manual identifies CHINT CTF24-5K-250 as the direct-connected field CT; its Fail-Safe functionality does not make direct-CT mode PCS-certified.

Boundaries of approval

An export limit does not change the inverter nameplate rating or independently approve service ampacity, conductors, overcurrent protection, panelboards, interconnection, or an external bypass. The utility and AHJ must accept the complete design. Keep the full certificate attached rather than replacing it with an excerpt.

Report page 165 identifies UL 2808 requirements for monitoring equipment in another manufacturer’s panelboard/switchboard and UL 61010-1 for externally located equipment used with specific equipment. Verify the applicable requirement and approved assembly for the installation.

Metering Architecture and Normal Export Control

Required field equipment

Purchase the approved CHINT DTSU666 meter kit, without the -H suffix, through a Solis distributor. Manual V3.2 identifies a kit with CHINT NCTK-36 CTs (600 A/5 A) and a kit with MEATROL NRC-60 Rogowski coils (1000 A). Use the approved meter and its matched kit sensors; do not substitute the inverter’s direct-connected CTs or assume sensor interchangeability.

PCS requires Meter mode: sensors connect to the approved external meter, which communicates with the inverter or parallel master over RS-485. Outside PCS applications, supported direct-CT mode uses CHINT CTF24-5K-250 CTs (250 A, 5000:1 ratio, 5 m / 16.4 ft leads that cannot be extended) and supports export control and Fail-Safe. Direct-CT functionality is not PCS certification.

Shipment transition: Beginning December 1, 2026, all inverters will ship with a CHINT meter and a set of CTs. The bundled CT type is TBD. The CTF24-5K-250 and meter-kit models above describe the current manual, not a commitment to the future bundled sensor type. Final packaging and compatibility details must be locked before publication.

Normal Export Control and Measurement Boundary

Measurement boundary

Measure net power flow at the approved export-control boundary, normally the PCC, and show the measurement location on the single-line diagram. Grid-port power can supply grid-side local loads before reaching the utility, so Grid-port output and utility export are not necessarily equal.

Follow the current approved wiring instructions for voltage references, sensor location and phase association, communication connections, addresses, sensor settings, and cable requirements. This note is not a terminal-level wiring diagram; do not guess pin assignments or communication parameters.

What the export limit controls

Normal export control uses meter feedback to regulate net power exported at the control boundary. It is not simply a fixed ceiling on gross PV production or total energy supplied to on-site loads and batteries. Export regulation and protective grid-relay opening are separate responses.

Example: two inverters, one 15 kW limit

For two supported parallel inverters with a utility-required 15 kW aggregate limit, enter 15 kW at the master. That value governs the full system; do not enter 15 kW independently on each unit as separate export allowances, and do not assume separate 7.5 kW limits are required.

The setting does not promise equal power sharing or continuous availability of 15 kW. Actual power depends on available PV/battery energy, loads, equipment limits, and other active settings. Use the actual utility-approved value for each project; 15 kW is an example, not a default.

Generation outside the controlled system

Obtain design review for AC-coupled PV, other inverters, generators, external bypasses, or additional sources. Do not assume opening a Solis Grid-port relay isolates separately connected equipment or guarantees zero total site export from uncontrolled sources.

Required Settings and Commissioning Configuration

Metering mode

For PCS installations, select Meter mode and install the approved CHINT DTSU666 meter with its matched sensors. Direct-CT mode may support export control and Fail-Safe in supported non-PCS applications, but does not satisfy the PCS requirement.

Export limit

Navigate to Storage Mode > Self-Use (or Selling First). Set Allow Export to ON and Max. Export Power to the utility-approved value. For a supported parallel system, enter the full system limit at the master; a 15 kW system limit means a 15 kW master setting.

Zero export

Set Max. Export Power to 0 W when zero export is required. The manual specifies Export Calibration of −30 W for zero-export applications; this is measurement compensation, not a replacement for the export-limit setting or Fail-Safe protection.

Parallel synchronization

Set Parallel Sync to Lock in the Parallel Settings menu on every inverter. With all units configured this way, enable FailSafe Switch on the master only.

Sensor verification

Auto CT Correction applies only to direct-connected CT mode (manual Section 5.12.2.1). For meter-based PCS installations, verify and correct meter voltage references, sensor direction, and phase association using the meter-kit instructions. Independently verify power-flow readings in either configuration.

Enabling and Verifying FailSafe Switch

Fail-Safe activation

The factory default is OFF. Enable FailSafe Switch using the confirmed path below. Measurement loss does not provide the declared protective Grid-port shutdown when the function is OFF.

Exact FailSafe Switch path

Settings > Professional Settings > Function Settings > Function Setting > FailSafe Switch > Change to ON > Click Save

After saving, read back or refresh the current value and verify ON. Selecting ON in the set-value field alone does not prove the saved setting has changed. Capture the saved configuration for the commissioning record.

Figure 1. Supplied control-screen example: select ON and click Save. The example shows a current value of OFF before saving; it is not evidence of completed commissioning. Plant identifiers have been excluded.

Commissioning evidence

Record the saved export limit and Fail-Safe setting, plus Parallel Sync on every parallel inverter. The supplied screenshot shows OFF before saving and is a configuration example, not proof of completed commissioning.

Fault Detection and Response Matrix

Fail-Safe requires ON and supports the approved meter or direct-CT configuration; PCS still requires the meter. Meter-loss rows apply to meter mode; open-lead protection also applies to direct CTs. Parallel protection requires Parallel Sync = Lock on every unit. Measure timing from the physical interruption, not the alarm.

Short-circuit limitation: do not confuse it with an open lead

A disconnected sensor lead and a short-circuited sensor lead are different faults. Do not claim that a shorted lead opens the grid relays or guarantees anti-backflow protection. SGS report page 90, current sensors S1/S2, records that the short-circuit condition prevents current collection and that the anti-backflow function cannot be achieved.

Incorrect data is not necessarily missing data

Reversed polarity, incorrect phase association, and other invalid readings can compromise export control without triggering Fail-Safe. Use Auto CT Correction only for direct-CT mode; verify and correct meter/sensor wiring in meter mode. Independently verify actual power-flow readings.

A Fail-Safe alarm appears on the inverter LCD when the function activates. Absence of this alarm does not prove sensor wiring or measurements are correct.

Grid Isolation, Backup Loads, Passthrough, and Recovery

What Fail-Safe disconnects

Fail-Safe opens the inverter grid relays and stops all outgoing current and power through the Grid port. Inverter power cannot feed grid-side loads or the utility through that port, including through the inverter’s own internal bypass path.

This is not a blanket statement that the whole inverter stops generating or that all AC terminals become de-energized. The Grid-port supply-side conductors can remain energized by the utility. Zero outgoing power is not proof that equipment is safe to touch or that a disconnect is open.

What can continue

PV generation can continue supplying connected batteries and backup-side loads, subject to available generation and applicable operating limits. A live Backup port therefore does not mean that Fail-Safe has failed. Do not require Backup-port voltage to disappear as the acceptance criterion.

In a PV-only installation with no battery and no Backup-port connection, these remaining energy paths are not present. The key Fail-Safe result is still cessation of outgoing Grid-port current and power, not a claim about battery operation.

Grid passthrough is a separate function

When available PV and battery power are insufficient to support loads, utility power supplies the shortfall through the inverter’s passthrough function. Passthrough is not inverter-generated export and is not evidence of backfeed. Loads remaining energized alone do not identify whether the source is PV, battery, or utility.

Automatic recovery after metering is restored

Once the interrupted CT/meter measurement or meter communication connection is restored, grid-side operation recovers automatically in approximately 3 seconds, without a manual reset. During the described Fail-Safe event the inverter remains synchronized to the grid; it has stopped outgoing Grid-port output rather than undergone a grid-loss event.

The approximately 3-second recovery is not a universal reconnection rule after an actual utility outage, other protective trip, complete shutdown, or grid-code event. Do not substitute a five-minute delay for the described metering-restoration case, or promise this recovery time for slave communication-loss shutdown.

Parallel Systems and Communication-Loss Protection

Normal operation

The master uses shared-meter feedback to enforce the configured system-wide export limit. For the two-inverter example, a 15 kW master setting governs combined export. All parallel units must have Parallel Sync set to Lock, with FailSafe Switch enabled on the master.

Loss of shared-meter feedback

If shared-meter feedback is lost while master–slave communication remains intact, both inverters open their grid relays within 3 seconds. Output to both Grid ports stops. This is grid-side isolation, not necessarily complete loss of PV-to-battery or backup-side operation.

Loss of master–slave communication

If the slave loses communication with the master, the slave shuts down completely, with zero output, in under 3 seconds. It remains shut down until communication with the master is restored. Do not describe this as only a Grid-port cutoff; it is a complete slave shutdown.

The master raises an alarm but continues operating and enforcing the system export limit, provided its own meter feedback and operating conditions remain valid. Loss of the slave does not turn the remaining master’s limit into half the original setting.

Distinct tests and limitations

Interrupting meter RS-485 communication and interrupting the master–slave communication link are different tests with different expected outcomes. Identify which link is being tested and monitor the relevant outputs of both units. Restoration of one link does not prove the other is healthy.

No specific slave restart time, master power-loss sequence, or simultaneous multiple-fault response is declared here. Obtain Solis Service confirmation for those cases, additional parallel units, AC-coupled generation, or other arrangements outside this two-inverter example.

Commissioning evidence for a parallel system

Normal Export-Control Testing and Timing Evidence

Agree acceptance criteria before the witness test

Obtain the utility-approved export value, test conditions, permitted transient behavior, measurement uncertainty, and witness requirements. Normal regulation has a dynamic response; do not promise that a load step can never produce any transient excursion.

Measured SGS results: not Fail-Safe opening times

SGS report GZES250400796301, page 165, explicitly identifies the DTSU666 meter in the test summary. For Power Export Limiting (PEL), it records a maximum open-loop response time of 1.5 seconds and average of 1.2 seconds, and a maximum stabilization time of 6.0 seconds and average of 5.8 seconds.

The manual defines open-loop response as the time for controlled current to complete 90% of its change toward the new steady-state value. Stabilization is the time until controlled current remains within the permitted steady-state band. Neither measurement is a Fail-Safe relay-opening time.

Pages 47–48 provide detailed step-load results. These measurements apply to the tested equipment and conditions, not every installation or a separately certified two-inverter arrangement. Manufacturer-declared Fail-Safe timing is separate.

Suggested normal-operation verification sequence

Keep the measurements separate

For normal export control, assess net export at the PCC. For Fail-Safe isolation, verify no outgoing current and power at the applicable Grid port(s). A low PCC export reading alone does not prove relay opening because site loads may be consuming inverter output.

A configured zero-export limit is a normal regulation mode, not the same condition as opened grid relays. Agree the applicable measurement tolerance and transient criteria; do not confuse a zero-export setting with physical isolation.

Fail-Safe Witness Testing and Safe Restoration

Safety and test preparation

Only qualified personnel may perform the tests using the current Solis-approved procedure and applicable electrical safety controls. This note defines test intent and acceptance criteria; it does not authorize energized terminal work, opening an energized CT secondary, shorting sensor leads, or bypassing protective devices.

Confirm the safe interruption method for the exact sensor circuit. Verify healthy communication, correct readings, saved export and Fail-Safe settings, and Parallel Sync = Lock on every parallel unit. Notify occupants and protect critical loads, especially before complete slave shutdown.

Test A: loss of meter RS-485 communication

Establish measurable outgoing Grid-port power before the fault. With FailSafe Switch ON, interrupt meter-to-inverter/master RS-485 using the approved method. Measure from the physical interruption: a single inverter opens its grid relays in under 3 seconds; both parallel units open within 3 seconds while master–slave communication remains intact.

Test B: open sensor connection

An approved interruption of a sensor signal lead at the DTSU666 meter is an alternative trigger test. In supported non-PCS direct-CT mode, an approved direct-CT disconnection also demonstrates Fail-Safe operation. Verify cessation of outgoing Grid-port current and power. Do not substitute a short-circuit test.

What to observe and record

Use suitable independent instruments to record fault time, each Grid-port response, outgoing current and power, LCD alarm, and continued battery charging or backup-load supply. Record utility import separately. Dashboard refreshes and alarm timestamps alone do not precisely measure relay response.

Restoration

Restore the approved meter/sensor connection and verify approximately 3-second automatic recovery for the described metering-loss event. Confirm valid readings, normal operation, the saved export limit, and FailSafe Switch ON. Re-run normal export verification if settings or wiring changed.

Test loss of master–slave communication separately: expect complete zero-output slave shutdown in under 3 seconds, while the master alarms and retains export control with healthy metering. Restore communication and verify normal system operation; no exact slave restart time is specified.

Restore every temporary interruption and retain the test results. Do not hand over a system with unresolved faults or failed acceptance criteria.

Access Control, Troubleshooting, and Release Checks

Installer-controlled settings access

The homeowner must be registered to their plant by the installer, who controls the plant role and permissions. Register the homeowner as a guest rather than an owner to prevent settings access. This restricts settings generally, not only the export limit. Coordinate protected changes with the installer.

The Professional Settings password can be changed, but that password does not protect the Storage Mode export-power settings. Changing it alone does not secure the export limit. Confirm actual permissions at handover; a plant-role restriction is not a claim of independent physical/LCD tamper protection or a substitute for utility-required access controls.

Troubleshooting guide

Document and firmware control

Use model-specific instructions, current compatibility information, and the firmware combination approved by Solis Service. Record every inverter’s installed versions and follow the service team’s upgrade recommendation. The report’s A3 identifier is not a universal update target. Do not assume unverified correction-menu paths, sensor ratios, or meter communication parameters.

Older guidance for other inverter families, Acrel meters, or EPM systems does not replace this application’s DTSU666 PCS requirement. Do not carry over older in-box equipment statements into the December 2026 packaging arrangement; confirm current kit contents with the distributor.

Utility Handover and Commissioning Record

Customer and utility submission package

Provide this note with the complete applicable UL 3141 Certificate of Compliance. Where requested, include the meter-configuration attestation, Fail-Safe compliance letter, and a project-specific aggregate export-limit statement. Supply the full SGS test report only through Solis’s approved release process and applicable NDA requirements.

Include the approved single-line diagram, control/metering boundary, equipment and firmware schedule, saved settings, sensor-verification results, access-control arrangements, and commissioning/witness records. A capability letter does not substitute for proof that the actual site was commissioned.

Reusable field record: complete for each installation

Release criteria

Release the installation only after saved settings and readings are verified, normal export control and agreed protective tests pass, temporary interruptions are restored, and utility/AHJ requirements are resolved. Retain signed commissioning results.

Review draft: Do not publish until the future bundled CT type and remaining product details are finalized. Preserve the confirmed corrections to the manual’s Fail-Safe description throughout.

Technical assistance

For applicability, firmware, meter kits, safe testing, or utility documentation, contact Solis US Support.

Email: usservice@solisinverters.com | Phone: +1(866)438-8408