CT Configuration Overview

A Lumin Smart Panel ships standard with one pair of 200-amp CTs. Most Lumin installations use these as the Main CTs and clamp them on the feeders between the Microgrid Interconnect Device (MID) and the load center.


Installers can contact Lumin to purchase an additional pair of 200-amp CTs for enhanced monitoring. This second set can be connected to the Lumin Auxiliary (Aux) CT leads and used to measure the combined PV and battery output. In this Main + Aux CT configuration, the Main CTs should be moved to the feeders or service wires between the meter and the MID.


Currently, no Rogowski coils are compatible with Lumin.

The diagrams below illustrate the most common Lumin CT configurations. Systems incorporating certain inverter or battery solutions may require slightly different CT placement; see the bottom of this article. If applicable, also consult the article titled Wiring for Multi-LSP Locations.


Note that for simplicity, the following diagrams do not show placement of the Grid Detection Circuit (GDC). The GDC is an essential element of a Lumin Smart Panel installation. Please refer to documentation in the installation manual and GDC installation article for placement requirements.

Two sets of diagrams that show the most common Lumin CT configurations: the Main CT-Only Configuration (left diagram) and the Main + Aux CT Configuration (right diagram). The Main CT-Only Configuration includes: a Lumin Smart Panel, Electrical Panel, MID/ATS, Meter, Main CTs, PV and Battery. The Main + Aux CT Configuration includes: a Lumin Smart Panel, Electrical Panel, MID/ATS, Meter, Main CTs, Aux CTs, PV and Battery.


Note: Ensure that CTs are clamped on the correct feeders, respecting Lumin convention for identifying A/B phase. Refer to the Lumin Installation Manual, steps 9-18 for more information.


Manufacturer-Specific CT Configurations


Enphase IQ-Series Storage System

Two diagrams of the Lumin CT configuration for an Enphase IQ-Series Storage System. The diagram on the left is for a Main CT-Only Configuration. The diagram on the right is for a Main + Aux CT Configuration. The Main CT-Only Configuration includes: a Lumin Smart Panel, Electrical Panel, IQ System Controller, Main CTs, Meter, Grid Detection Circuit, IQ Battery, IQ Combiner + IQ Gateway, Enphase IQ-Series Microinverters, and PV. The Main + Aux CT Configuration includes: a Lumin Smart Panel, Electrical Panel, IQ System Controller, Meter, Grid Detection Circuit, Main CTs, Aux CTs, IQ Battery, IQ Combiner + IQ Gateway, Enphase IQ-Series Microinverters, and PV.

Note: When utilizing the Main + Aux CT Configuration, Lumin CTs should be installed in the IQ System Controller, ensuring the following:

  1. Main CTs are on the feeders from the main or service. The side of the CTs reading This side toward grid should face the utility meter.
    • Main CTs should read positive wattage when solar and battery are disconnected. If this reading is negative, swap each CT to the opposite leg feeder.
  2. Aux CTs should clamp around both the PV inverter output circuit and the battery circuit. Extra wire length may be required to accommodate CTs on these circuits inside the IQ controller. Alternatively, the CTs can be clamped on these wires in a nearby pass-through box installed for the purpose. Ensure that both wires in each CT are of the correct phase/leg and that the side of the CT reading This side toward grid faces the utility meter (away from the PV and battery).
    • Aux CTs should read negative wattage when power is flowing out of the PV or battery. Unless grid charging of the battery is enabled, these CTs should not display significant positive wattage (it is normal to notice some standby power consumption by the Enphase equipment at night). Lumin Aux CTs in this configuration read the net power supplied by the PV and battery together. Note that if all PV output is charging the battery (not supplying other loads in the home or back feeding the grid), the Aux CTs will read 0 Watts as the outflow of the PV and the inflow of the battery charging will cancel each other out.
    • If using Aux CTs in this configuration, use the Lumin app to edit the Aux CT circuit so that it is descriptively named. Change the category to Solar and Storage.

Sol-Ark

Standard Sol-Ark Partial-Home Backup CT Configuration Using Only Lumin Main CTs

Diagram of the Lumin CT configuration for a Standard Sol-Ark Partial-Home Home Backup. It includes: a Lumin Smart Panel, Protected Loads Panel, Main CTs, Load Out, Grid In/Out, Service Disco/Main Panel, Meter, two PV’s, Sol-Ark and a Battery.

As is true for other Main-CT-only Lumin configurations, this arrangement only measures consumption on the protected loads panel. It does not measure total home consumption or solar export to the grid. 


Notes:

  • All CTs should be phased with respect to Lumin phasing convention (steps 9-18 in the installation manuals).
  • In this configuration CTs should be oriented so that the This side towards grid sticker is facing toward the Sol-Ark inverter.


Sol-Ark Enhanced Data CT Configuration (Requires Two Sets of Lumin CTs)

Diagram of the Lumin CT configuration for a Sol-Ark Enhanced Data CT Configuration, which requires two sets of Lumin CTs. It includes: a Lumin Smart Panel, Protected Loads Panel, Main CTs, Aux CTs, Load Out, Grid In/Out, Service Disco/Main Panel, Meter, Sol-Ark, Battery, two PVs and a DC-coupled PV or AC inverter output.


This configuration provides detailed power flow information about:

  • Grid import
  • Grid export
  • Total home grid consumption
  • Net export of PV power
  • Net consumption of PV and battery power


Aux CTs are placed around both the grid and load lines of the Sol-Ark inverter. When the protected loads panel consumes grid power, the Aux CTs register no wattage as the power flows in both directions through those CTs, with a net reading of 0 watts. When solar or battery power is consumed by either the main or protected loads panels or exported to the grid, power will only flow through one direction on the Aux CTs, causing a non-zero Aux CT wattage reading. This configuration requires a second set of Lumin CTs (available for purchase from Lumin).

Notes:

  • All CTs should be phased with respect to Lumin phasing convention (steps 9-18 in the installation manual).
  • All CTs should be oriented so that the This side towards grid sticker faces away from the Sol-Ark inverter.


Sol-Ark Whole Home Backup (Commonly Seen on Sol-Ark 15k Systems)

Diagram of the Lumin CT configuration for a Sol-Ark Whole Home Backup. It includes: a Lumin Smart Panel, Protected Loads Panel, Main CTs, Aux CTs, Load Out, Grid In/Out, Meter Sol-Ark, Battery, two PV’s and a DC-couple PV or AC inverter output.

This configuration provides detailed power flow information about:

  • Grid import
  • Grid export
  • Total home grid consumption
  • Net export of PV power
  • Net consumption of PV and battery power


As the Sol-Ark 15k is capable of 200-A pass-through, both the grid-in and load-out lines will often be 2/0 AWG. It is not possible to fit two conductors of this size in a single Lumin CT. The recommended approach is to acquire two pairs of Aux CTs (in addition to the one pair of Main CTs that comes standard with a Lumin Smart Panel). Splice both A-phase Aux CTs to the Lumin Aux CT A wire lead and splice both B-phase Aux CTs to the Lumin Aux CT B wire lead. WAGO connectors are ideal for this purpose. After the CTs have been spliced together and connected to the Lumin Smart Panel, place one pair of CTs on the Sol-Ark grid line and the other on the Sol-Ark load line.


Notes:

  • All CTs should be phased with respect to Lumin phasing convention (steps 9-18 in the installation manual).
  • All CTs should be oriented so that the This side towards grid sticker faces away from the Sol-Ark inverter.


Sonnen

Diagram of the Lumin CT configuration for a Sonnen. This includes: a Lumin Smart Panel, Electric Panel, two Aux CTs, Backwards Aux CT, Main CT, Meter, Sonnen batteries and a PV.

Systems integrating Sonnen batteries are unique in that they typically feature PV feeding into an electrical panel separately from the grid + battery feeder. This presents a monitoring challenge whereby it is essentially impossible to correctly measure all power flowing through the system with a single pair of CTs. Full measurement of the power flows in an energy storage system with Sonnen requires four pairs of Lumin CTs: one pair of Main CTs, and three pairs of Auxiliary CTs, all spliced together and feeding the "Aux CT" leads of the Lumin Smart Panel. The Aux CT pair placed between Sonnen and the protected loads panel should be oriented "backwards", with the stickers reading This side towards grid facing away from the utility meter.


Tesla Powerwall

Two sets of diagrams that show the standard Lumin CT configurations with a Tesla Powerwall. The Main CT-Only configuration is on the left, and the Main + Aux CT configuration is on the right. The Main CT-Only Configuration includes: a Lumin Smart Panel, Main Panel, Main CTs, Backup Gateway 2, Meter, Powerwall 2 and a PV. The Main + Aux CT Configuration includes: a Lumin Smart Panel, Main Panel, Backup Gateway 2, Meter, Powerwall 2, Aux CTs, Main CTs and a PV.

Powerwall systems should have CTs configured in the standard Lumin configurations. If utilizing Aux CTs, please note that they can either be clamped around both the inverter and Powerwall conductors inside the Tesla Gateway. Alternatively, if using the optional internal panelboard in the Gateway as a PV and battery combiner, the Aux CTs may be placed around the U-shaped rigid conductors supplied with the panelboard, as these carry the combined current of PV and Powerwall. 


Note: Tesla CTs and Lumin CTs are inter-compatible, so unused Tesla CTs can be repurposed as Lumin Aux CTs, if desired.

Note that the Lumin GDC can be landed on the non-backed-up terminals in the Gateway. Ensure that proper overcurrent protection is used to protect the GDC.


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