Skip to main content

Add On, Second System eligibility & CTs

Overview

This article details eligibility criteria for add on, 2nd systems based on manufacturer’s installation guidance. Following this criteria is required on all LightReach sales.

Existing generation sources on site (existing PV, battery, generator, etc.) add additional complexity to CT monitoring installation & configuration. Troubleshooting steps vary by manufacturer, as some allow for secondary sets of CTs to be installed on the AC feeders to "offset" the existing production to normalize home consumption readings. This is not permitted guidance from all OEMs (See Section F) though, so always confirm design solutions and permissions with the manufacturer to ensure success in monitoring accuracy.

Failure to follow or intentional misuse of criteria, may result in the termination of access to the LightReach product.

Definition

Examples

Add Ons

  • Additional Panels tied into the same inverter/combiner/gateway and meter

  • These are considered UNACCEPTABLE and would require separate equipment and configuration corrections to qualify for Palmetto Lightreach

Examples

  1. A homeowner purchased an 8 module system a few years ago, but has increased energy demands now and wants to add modules to an existing system’s inverter and stringing

  2. The customer asks to add solar to their new home addition, saying they previously used micros and would want added strings of micros to their new roof space. You intend to use the existing roof junction box, combiner and reporting gateway to minimize additional equipment

Second Systems

  • Separate PV inverter or gateway equipment, stringing, and interconnecting into a service with an existing, but separate system

  • These are allowable by Palmetto Lightreach, but these configurations require proper planning and execution. Please continue reading below for considerations and planning advice

Examples

  1. The customer requests a new (Gen 3) Enphase PV system to be installed on the other half of his roof, opposite of their existing Enphase PV only system from a few years ago. Installer plans to install an in-line filter to reduce noise in the AC lines and ensures the interconnections both abide by NEC requirements.

  2. Homeowner is now ready for a more robust PV + Storage system to pair alongside their initial, existing PV system with no storage. The existing PV system will be re-connected to the home service upstream of a new Tesla Gateway 3 to ensure no existing PV is located in the backup circuit of the new Palmetto Lightreach system

Separate Systems

  • A separate/new system connected to a different electric meter, on a different utility account, unrelated to any existing solar systems.

  • These are acceptable, up to 3 systems per applicant. These are effectively new customers for Palmetto LightReach, who may have multiple units/properties and want solar on each.

Examples

  1. A family owns both sides of a duplex, they purchased a Palmetto Lightreach system in 2024 and were so pleased with their savings, they wanted to add another system to their other half of the building they own completely.

  2. In California, a notable exception allows for the installation of a new Photovoltaic (PV) system on a secondary living unit, provided the unit maintains separate energy metering. This configuration is one of the limited ways to establish multiple PV systems in close proximity without jeopardizing eligibility for Net Energy Metering (NEM) qualification in CA. Therefore, it is essential to always verify that the system's design fully complies with all regulatory requirements to prevent the loss of available PV incentives.

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 installations based on space, distance or panel configuration, please clearly document inability of CT installation to provide evidence for QC on processing exceptions for CTs as needed.
​
NOTE: This is to begin the conversation only, this is not a guarantee of exception being able to be granted.

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

Existing PV Only & New PV Only specific:

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

  • Must have a separate point of interconnection.

  • If utility does not allow a 2nd Point of Interconnection, then:

    • Permitted to have a single point of interconnection, only if existing and new systems are coupled outside of the first disconnecting means.

      • i.e. a new secondary sub panel has to be installed to have breakers from existing and new system landed.

Click here for Example Scenarios

  • Example 1: Both the existing PV (Enphase) and the new PV (SolarEdge) are interconnecting into the home service via an electrical sub panel, both without storage. In this sub panel, the systems will share separate DER breakers to ensure they are abiding by NEC 705.12, but will also need SolarEdge Current Transformers to account for the energy offset by the existing energy source parallel with our new solar.

  • Example 2: A new QCells PV only system (Red) is installed to help cover more energy demand for a home with an existing Enphase PV only system (purple). The Enphase system is connected upstream of the new QCells interconnection with no further loads upstream, allowing for the existing PV to not need QCells CTs to “offset” any extra source production.

    • Tesla Storage differs in guidance for similar configuration for upstream PV sources, as they are needing to be captured as Solar, so ensure to review the OEM specific guidance in continued sections.

Existing PV + New PV & Battery specific:

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

  • Existing PV have a separate point of interconnection - upstream of PLR system ATS.

    • i.e. Existing system must not be a part of the back up circuit of the new LR system.

      • Systems like Tesla Backup Switch that have meter collars for ATS cannot have (E) systems within backup. These setups will need to be designed and installed instead with Gateway so that the (E) system can be installed upstream out of the backup circuit.

    • The existing PV only system must remain grid dependent meaning that in the event of a power outage the existing system will enter its rapid shutdown mode and remain inoperable until grid supply is restored

    • How is this achieved? - The existing PV only system must be interconnected upstream of the New PLR owned systems ATS device.

Examples of ATS devices

  • Tesla back up gateway

  • Tesla backup switch

  • Enphase IQ controller (4th gen)

  • Enphase meter collar (5th Gen)

  • SE Back-up Interface.

Equipment specific key points

  • The Tesla Backup switch and Enphase Meter collar (5th Gen) are ATS devices that are installed at the utility meter base. These devices effectively turn the Utility meter into the ATS and thus the entirety of the customers electrical system is considered the back up circuit.

For the long term integrity of the Palmetto Energy Plan and to allow for future Energy Generation or Storage expansion, it is encouraged to design the system using ATS devices such as Tesla Backup gateway, Enphase IQ controller, or SE Backup interface. These methods do not limit new systems from being introduced into a primary main panel.

Existing PV + Storage or Existing Storage Only & New PV Only

Summary

  • Following similar guidance above, ensuring the new PV system is not “locked” behind the backup circuit for the existing Storage on site.

    • The new PV system must remain grid dependent meaning that 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, multiple sets of CTs may be necessary and in some scenarios, not allowable by OEM SOP. Please ensure all projects are aligned with OEM guidelines, see section F below for further details regarding what is possible and what may not be.

This may affect the existing system’s consumption readings, in turn it’s performance if in a partial load backup configuration. Palmetto Lightreach is not responsible for the performance of existing 3rd party systems, so ensure the homeowner is aware of this if necessary

Click here to further expand examples:

  • 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 wants to save more money on electricity. A new PV only system (Red) is installed, and the interconnection for the new PV is made line side of the service entrance to the existing Gateway 3. This will allow for the new PV to stay isolated from the backup circuit of the Gateway 3.

    • Although Lightreach will be satisfied with ensuring the new system operation is function and meeting expectations from the contract, we would advise to be cognizant of the requirements for monitoring for the existing system for the homeowner's satisfaction.

Existing PV + Storage & New PV + Storage / 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 an existing storage system. 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:

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

  • Additional set of CTs (see section below) - if interconnected downstream of the site CTs

  • 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. Also, 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.

    • No sharing of (E) & (N) Junction boxes between systems.

  • Please reference the OEM guidance found in TECHNICAL BRIEF - North America as necessary

Additional Set of CTs required for Enphase 2nd systems

  • When using a new Enphase system:

    • Use a 2nd set of CTs - these shall go on the existing systems wires with arrows facing towards the PV breaker. Double lug these CTs on combiner terminal lugs, or splice 2 sets of CT wires into one. This is required for accurate consumption data.

      • Please be VERY careful and ensure phases are not mixed up. Proper tagging, line tracing or continuity tests are needed to ensure correct L1/L2 CTs are spliced together.

    • Do not use more than 2 pairs of CT devices in parallel with Enphase.

    • 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

Click for Example

Tesla 2nd Systems

Tesla PV only

  • When a pre-existing generation system (all manufacturers) 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 - This makes ”2nd system” Tesla Inverter (PVI-45), Neurio, Solar-only projects incompatible with PCS interconnection as existing generation cannot be accounted for when both systems are tied into the same busbar or conductor AND in violation of Consumption monitoring requirements - A core requirement of ALL Palmetto Energy Plan projects. EPCs should be aware of these limitations and refrain from utilizing this configuration.

Tesla PW

  • Tesla guidance states an additional Tesla Remote Meter is to be used if a Gateway 3 or Backup Switch is installed with existing generation. All existing solar, loads, & generation sources on site should be captured by monitoring. See references from Tesla HERE for guidance of CT placement.

    • Reminder: Existing PV systems may not be interconnected into backup circuits. A separate PV meter may be utilized to create a partial backup circuit to avoid concern, but most likely will complicate monitoring data requirements for battery integrity and performance, so proceed with weighed caution.

  • CT device Y-splice & cable extensions are available through Tesla, as useful additional tools to help capture all conductors needed.

  • Up to 2 CT devices can be installed per TRM port, however they are explicitly intended to measure that port’s phase (L1 or L2).

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

Click for Example

SolarEdge 2nd Systems

SolarEdge PV Only & SolarEdge Arbitrage Battery

  • An additional set of CT devices is required if interconnected downstream of the primary site CTs as another generation source.

    • 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. (connecting at the phoenix connector is ALWAYS recommended)

Click for Example

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

INSTALLER ALERT - SolarEdge 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 SetApp/SE Go factors the existing system backfeed.

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

  • 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 systems Back up circuit, it cannot interact with the New Palmetto Energy Plan owned PV and Storage when in Back up mode. EPCs should be aware of these limitations and refrain from utilizing this configuration.

QCells 2nd Systems

QCells PV Only

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

  • Multiple Q.Home Combiners cannot be installed on the same LightReach account, as only individual combiners are assigned per monitoring site.

INSTALLER ALERT - QCells PCS interconnection is incompatible with spliced CT devices. 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 Palmetto Energy Plan 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. Can include in line filters for multi-system Enphase projects

    2. Combining the existing racking with the new system racking

  3. Existing PV System is in Backup Loads circuit

Did this answer your question?