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Supplemental Guide: Second System Configurations and Eligibility

Overview

This article details eligibility criteria for add-ons & 2nd systems based on manufacturer's installation guidance & LightReach policy. Following this criteria is required on all LightReach sales.
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Existing generation sources on site (existing PV, battery, generator, etc.) add additional complexity to interconnection, monitoring installation, & configuration of settings.

Installation guidance varies by manufacturer, as some allow for additional sets of CTs to be installed on the AC feeders to "offset" the existing production to normalize home consumption readings, though this is not permitted by all OEMs (See Section F). Always confirm design solutions and permissions with the manufacturer to ensure monitoring accuracy.
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Failure to follow these criteria, or intentional misuse of them, may result in termination of access to the LightReach product.

Add-Ons

Policy Status: Not Acceptable

Definition:

  • Additional solar panels that are tied directly into the customer's same existing inverter, combiner, gateway, and utility meter.

  • These setups require separate equipment and configuration corrections to be considered for approval.

Examples

System Expansion

  • A homeowner who purchased an 8-module system a few years ago now has increased energy demands. They want to add 5 new modules directly onto the existing inverter and stringing.

Home Additions

  • A customer building a new home addition wants to add microinverters to the new roof section, but intends to route them through the existing junction box, combiner, and reporting gateway without installing any additional isolating equipment.

Plan Set:

Second Systems

Policy Status: Allowable with conditions

Definition:

  • A completely separate PV inverter or gateway system, with its own independent stringing, that interconnects into a utility service alongside an existing, separate system.

  • The new system must not physically "touch" or utilize the balance-of-system equipment of the original installation.

Examples

Opposite Roof Arrays

  • A customer requests a new Enphase PV system installed on the opposite side of their roof from an older, existing Enphase PV-only system. The installer isolates the new system by installing an in-line filter to prevent AC line noise interference, meeting all NEC requirements.

Hybrid Storage Upgrades

  • A homeowner wants to add a robust PV + Storage system to pair alongside an existing, older PV system. The original system is left intact and connected upstream of the new equipment, keeping the two systems completely independent.

Plan Set:

Separate Systems

Policy Status: Fully Acceptable

Definition:

  • A brand-new solar system connected to a different electrical meter and a different utility account, completely unrelated to any existing solar setup.

  • Permitted up to a maximum of 3 separate systems per applicant. This is ideal for customers with multiple properties, duplexes, or secondary units.

  • Policy Note: Always refer to the Site Eligibility Article for specific qualification details.

Examples

Multi-Unit / Duplex Properties

  • A landlord owns both sides of a duplex. They installed a Palmetto LightReach system on Side A in 2024. Pleased with the energy savings, they now want to install a completely separate system on Side B, which is tied to its own independent utility meter and account.

California ADUs (Accessory Dwelling Units)

  • In California, regulations allow a new PV system to be installed on a secondary living unit (like a backyard ADU), provided it has separate utility metering. This separate-meter setup is one of the few ways to run multiple systems on a single parcel without violating CA Net Energy Metering (NEM) eligibility.

Plan Set:

Installation requirements

  • The project location is restricted to areas outside of California, with the exception of projects within California that use the LADWP utility. Furthermore, any secondary system requires utility approval; installers are responsible for confirming and adhering to all utility requirements and policies.

  • The new system shall not interfere or impact any pre-existing system NEM or value proposition for the customer in any way.

  • Any code violations or installation irregularities associated with the 1st system are fully addressed by the Certified Installer under their own liability & risk.

  • Some configurations of CTs, such as branch circuiting, may limit the ability of a system to utilize Power Control Systems (PCS) in situations where necessary. Palmetto Lightreach will always ensure the safety of the system is prioritized, so please ensure CT configurations do not disqualify systems from utilizing PCS when necessary.

  • ALL battery functionality requires correct home consumption data, please ensure CT configuration is properly planned for all sites utilizing storage.

  • The Existing System cannot exist within the PLR systems Back up circuit, it cannot interact with the New Palmetto Energy Plan owned PV and Storage when in Back up mode.

    • The reverse is also applicable: PLR systems may not interconnect into existing PV + Storage backup circuits and must be upstream of such

  • All new Palmetto Lightreach systems require new and independent monitoring sites reporting the contracted and installed equipment, excluding any pre-existing equipment in the OEM portal(s)

Consumption Current Transformer (CT) Exceptions: All Palmetto LightReach sites are required to monitor home consumption. If site configurations do not allow for CT installation due to space, distance, or panel configuration, please clearly document the inability to install CTs to provide evidence for QC when processing exceptions.

This table is intended to highlight situations in which the site would be eligible for a second system while meeting system segregation guidelines.

New PV Only

New PV + Storage

No Existing PV

YES

YES

Existing PV Only

YES

YES

Existing PV + Storage

YES

NO

Existing Storage Only

YES

NO

System Configuration

A) Existing PV Only & New PV Only specific:

  • The new PLR-owned system and the existing system must each be independently interconnected, while ensuring total interconnection backfeed abides by all NEC requirements.

    • A combiner/sub-panel is an acceptable location for both systems to join the service.

    • See Section F for specific configuration limitations by OEM, as there are instances where monitoring may be compromised.

General Example schematic:

  • Example: Both the existing PV (Enphase) and the new PV (SolarEdge) interconnect into the home service via an electrical subpanel, both without storage. In this subpanel, the systems will share separate DER breakers abiding by NEC 705.12, but will also need SolarEdge CTs to account for the energy produced by existing PV.

B) Existing PV & New PV + Storage:

  • Must be a new system, separate from any pre-existing solar on site.

  • Existing PV systems must have a separate point of interconnection, outside of the PLR system's backup circuit.

    • The existing system must not be a part of the backup circuit of the new PLR system (Solar Program).

      • Tesla Backup Switch installations, cannot have (E) systems within the backup circuit. These setups should be designed and installed with a Gateway device instead, to allow the (E) system to be installed upstream of the backup circuit.

    • The existing PV-only system must remain grid-dependent

    • How is this achieved? The existing PV-only system must be interconnected upstream of the new PLR-owned system's ATS device or backup circuit.

General Example schematic:

Examples of ATS devices

  • Tesla Backup Gateway

  • Tesla Backup Switch

  • Enphase IQ System Controller

  • Enphase IQ Meter Collar

  • SolarEdge Backup Interface

Equipment specific key points

  • The Tesla Backup Switch and Enphase IQ Meter Collar are ATS devices that are installed at the utility meter base. These devices effectively turn the utility meter into the ATS, and the entirety of the customer's electrical system downstream becomes the backup circuit.

For the long-term integrity of the Palmetto Energy Plan and to allow for future energy generation or storage expansion, it is recommended to design the system using ATS devices such as the Tesla Backup Gateway, Enphase IQ Controller, or SE Backup Interface, as these methods do not prevent new systems from being introduced into the main panel.

C) Existing PV + Storage & New PV-Only -OR- Existing Storage-Only & New PV-Only

  • Ensure the new PV system interconnects line-side of all existing backup circuits.

    • The new PV system must remain grid-dependent. In the event of a power outage, the new PV system will enter its rapid shutdown mode and remain inoperable until grid supply is restored.

    • To properly capture home consumption, parallel sets of CTs may be necessary depending on configurations.

    • Some OEMs do not allow paralleling CT devices. Please ensure all projects are aligned with OEM install guidelines.

    • Backup load panel note: home loads should not be "measured twice" by the same consumption monitoring system.

      • Exercise caution capturing conductors to backup load panels, as capturing the same load multiple times will lead to incorrect consumption data!

See Section F below for further details regarding what is possible and what may not be.

Installing new PV with existing-storage systems on site, may disrupt the monitoring for existing-battery function. It is the responsibility of the new PV installer to ensure all monitoring discrepancies are rectified for existing-battery functionality. Any code violations or installation irregularities associated with the 1st existing system must be fully addressed by the Certified installer, at the installer's own risk!

  • A homeowner has requested additional solar to be added to their residence, stating their original PV + Storage system (purple) covers most of their home needs, but they want to save more money on electricity.

  • A new PV-only system (red) is installed, and the interconnection for the new PV is made on the line-side of the service entrance to the existing Gateway 3. This will allow the new PV to remain isolated from the backup circuit of the existing Gateway 3.

  • New LR PV system CTs are installed on only the battery & existing-PV backfeed conductors (CRITICAL LOADS WILL NOT BE CAPTURED A SECOND TIME).

D) Existing PV + Storage & New PV + Storage -OR- Existing Storage Only & New PV + Storage:

Currently, Palmetto Lightreach does not permit PLR contracted PV systems with storage to be installed on the same meter as existing-storage systems. Existing 3rd party storage devices are not permitted to be tampered with and functionality would be compromised, prohibiting these sites from qualification.

OEM Specific Guidance

Enphase 2nd Systems:

Summary

New Lightreach system (Enphase) + Existing System (Enphase)

  • An additional set of CTs are needed only if existing-PV is interconnected downstream of the primary site CTs (see section below).

  • An In-line filter is a requirement for all multi-system configurations with at least 2 Enphase systems on the same utility transformer.

    • The filter needs to be installed in its own enclosure on the (N) Enphase system after combiner and before POI.

    • Contact Enphase to ensure the correct filter is utilized.

    • Ensure all install instructions are followed and filters are properly grounded.

    • Input & output channels into the filter enclosure must be separate entry points.

  • (N) AC conductors from microinverters on roof to (N) combiner must have > 3.3 feet of separation from (E) Enphase AC conductors (micros to combiner). This distance requirement is to be maintained at all points, including the attic runs.

    • Cannot use the same conduit for (N) + (E) AC conductors (micros to combiner)

    • (N) Modules installed cannot use the same rail & roof attachments as (E) system.

    • Sharing of (E) & (N) Jboxes between systems is not permitted.

Please reference the OEM guidance found in Enphase Energy System planning guide as necessary.

Example schematic:

EnphaseSecondSystem.png

Additional Set of CTs required for Enphase 2nd systems

When installing a new Enphase system:

  • An additional set of CTs are needed only if existing-PV is interconnected downstream of the primary site CTs (see section below).

    • Install these on the existing system backfeed conductors with source arrows facing towards the PV breaker. Double lug these CTs on appropriate Envoy terminal lugs, or splice sets of CT leads together.

      • Ensure phases are not mixed up between CT devices.

      • Do not use more than 3 pairs of CT devices in parallel with Enphase.

      • Ensure CT leads are spliced together according to polarity (- with -, + with +)

  • If existing PV is interconnected upstream of the LightReach site CTs, an additional set is not required.

  • Use this CT video guide for more details

QCells 2nd Systems:

QCells PV-Only

  • Very similar to Enphase CT requirements with CT directionality, placement, & configuration settings.

    • One notable difference to be aware of: Only 2 pairs of CT devices can be paralleled.

  • INSTALLER ALERT - QCells PCS interconnection is incompatible with spliced CT devices.

    • EPCs should be aware of these limitations and refrain from utilizing this configuration.

  • INSTALLER ALERT - Multiple Q.Home Combiners cannot be installed on the same LightReach account, as only one Q.Home is assigned per monitoring site.

    • EPCs should be aware of these limitations and refrain from utilizing this configuration.

Tesla 2nd Systems:

Tesla PV-only

  • When a pre-existing PV system is present on site Tesla Inverter (PVI-45), Neurio metering cannot account correctly for existing system generation due to the way Grid consumption is represented by the Tesla customer app & Powerhub monitoring.

  • INSTALLER ALERT - ”2nd system” Tesla Inverter (PVI-45), Neurio, Solar-only projects are incompatible with PCS interconnection, as existing generation cannot be accounted for when both systems are tied into the same busbar or conductor.

    • EPCs should be aware of these limitations and refrain from utilizing this configuration when PCS is needed for interconnection.

Tesla PW

  • An additional Tesla Remote Meter is to be used if a Gateway 3 or Backup Switch is installed with existing generation or 3rd party solar on site.

  • All existing solar, loads, & generation sources should be captured by monitoring. See references from Tesla HERE for guidance of CT placement.

    • Reminder: Existing PV systems may not be interconnected into new LR backup circuits.

  • CT device cable extensions are available through Tesla.

    • For details about Tesla Remote Meter installation, see the OEM guide HERE

SolarEdge 2nd Systems:

SolarEdge PV-Only & SolarEdge Arbitrage Battery

  • An additional set of CT devices is required if new LR PV is interconnected downstream of the primary site CTs.

  • These devices should have “Source” arrows facing the inverter of the existing system!

  • CT amperage rating must be increased for each additional set of CTs run in parallel. (225A + 225A = 450A), reference below:

  • CT devices in parallel must be the same amperage rating & device model.

  • Ensure phases are not mixed up between CT devices.

  • Ensure CT leads are spliced together according to polarity (- with -, + with +).

    • Double lugging at the phoenix connector is recommended by SolarEdge

    • Example:

  • LightReach suggests Wago or similar style connectors if CT leads are not double lugged.

  • If existing PV is interconnected upstream of the LightReach site CTs, an additional set is not required.
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  • INSTALLER ALERT - SolarEdge BCM PCS interconnection is incompatible with spliced CT devices.

    • EPCs should be aware of these limitations and refrain from utilizing this configuration.

SolarEdge Backup battery & SolarEdge PCS

  • Additional Modbus Meter device installation is required to account for existing generation sources interconnected downstream of the primary site CTs to provide corrected metering.

    • Ensure PCS set point value entered in SolarEdge Go factors the existing system backfeed.

    • Please see the following ModBus Energy Meter guide for details for installation:

  • CT arrow directionality for Modbus meter CTs is towards the utility meter! (this differs from parallel CT device direction with 2nd system)

  • If existing-PV is interconnected upstream of the LightReach site CTs, an additional set is not required.

    • Consider existing PV interconnected upstream of all home loads & the LightReach PV as “service energy” in order to achieve accurate consumption monitoring.

  • INSTALLER ALERT - The Existing System cannot exist within the PLR system’s backup circuit, it cannot interact with the new Palmetto owned PV/storage.

    • EPCs should be aware of these limitations and refrain from utilizing this configuration.

Appendix of Common Rejections and Challenges

The following section of this article contains examples of common violations encountered during the LightReach review process. This section illustrates unacceptable Second System Configurations ONLY. It is not a grading scale for acceptable conditions. The photos and examples included represent the most extreme documented cases and are intended to set a clear floor for what will be rejected.

This is a living document and will be updated as new examples are identified.

Disqualified Configurations for Second Systems

Palmetto Lightreach requires new system functionality and ensures all existing systems follow all electrical guidelines. Here are some configuration examples that will be considered unacceptable and would require changes for financing qualification:

  1. Add-on configurations that utilize existing PV equipment

  2. Missing required equipment for dual-system functionality:

    1. Additional CTs to account for existing PV generation

    2. In-line filters for multi-system Enphase projects

    3. Combining the existing racking with the new system racking

    4. Modbus device for SolarEdge storage/PCS installs

  3. Existing PV System is in new LR backup loads circuit

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