CTs

1. Key Principles of CT Installation

1.1 Polarity Matters in CTs

• Why Polarity is Important:

  • CTs (Current Transformers) have a polarity marking. When installed in the wrong direction, CTs give incorrect meter readings.

  • The arrow on the CT indicates direction and should point toward the loads. For production CTs, the arrow points away from the PV (solar) source. For consumption CTs, it points away from the grid.

• Consequence of Incorrect Polarity:

  • If installed backward, readings will be reversed, causing inaccurate energy monitoring and potentially incorrect billing or system control.

1.2 Phase Consistency

• Voltage and Current Phase Matching:

  • For accurate power readings, voltage and current must be measured on the same phase.

  • Check that each phase is consistent from the start to the end of the path.

• Voltage Verification:

  • Between two points on the same phase: the voltage should read 0 volts.

  • Between points on different phases: the voltage should read 240 volts.

  • Use these checks to confirm phase consistency across CTs and wiring paths.

2. Installation Techniques and Troubleshooting

2.1 Double-Check CT Orientation

• Always Verify:

  • Before powering up the system, visually inspect each CT to ensure that the arrow aligns correctly with the load.

  • Production CT: Arrow toward loads, away from PV.

  • Consumption CT: Arrow toward loads, away from the grid.

2.2 Dealing with Inaccessible Main Service Conductors

• Bundling Conductors:

  • If main conductors are inaccessible, group multiple circuit conductors and pass them through a single CT.

  • Correct Bundling: Ensure all Line 1 conductors go through the same CT and all Line 2 conductors go through a separate CT.

• Parallel CT Wiring:

  • If necessary, wire multiple CTs in parallel to maintain phase alignment and proper readings.

3. Practical Example: Correct Wire Placement for Production and Consumption CTs

3.1 Production CT Wire Placement

• Wiring Production CT Leads: Connect leads to terminal P1.

• White Wire: Connects to the top row, terminal one.

• Blue Wire: Connects to the top row, terminal two.

3.2 Consumption CT Wire Placement

• Wiring Consumption CT Leads: Connected to terminals C1 (for CT1) and C2 (for CT2).

  • CT1 White Wire: Top row, terminal four.

  • CT1 Blue Wire: Bottom row, terminal four.

  • CT2 White Wire: Top row, terminal five.

  • CT2 Blue Wire: Bottom row, terminal five.

4. Verifying Phase Consistency Using a Voltmeter

• Using a Digital Voltmeter:

  • Measure voltage between Envoy terminal L1 and phase L1 at the main load center.

  • If voltage reads 0, phases match (L1 to L1, L2 to L2).

  • If voltage reads 240 volts, there’s a phase inconsistency that needs correction.

• Why This Matters:

  • Inconsistent phase readings lead to inaccurate power monitoring, which can affect system performance and accuracy.

5. Next Steps: Setting Up Consumption Meters with the Installer Toolkit App

In the next lesson, we’ll cover how to use the Installer Toolkit app to configure and set up consumption meters, ensuring accurate monitoring and data management.

Summary and Key Takeaways

• Correct polarity is critical for accurate CT readings.

• Voltage and current measurements must be phase-matched.

• Troubleshoot and verify wiring with a voltmeter before system activation.

• When in doubt, double-check CT direction and wiring placements to prevent common errors.

CT installation 

The CT measurements provide valuable system information to the installers and homeowners about PV production, home consumption, and IQ Battery charging/discharging. This information is also crucial for remote maintenance and management of the Enphase system. The CT information also enables a site to support the following applications: 

1.  Main panel upgrade (MPU) avoidance: The MPU avoidance feature of PCS uses production and Consumption CTs installed on-site to limit the total current backfed to the main panel to meet the NEC requirements to avoid having to upgrade the main panel. 

2. Aggregate power export limiting (PEL): The aggregate PEL feature of PCS uses the Consumption CTs installed on a site to limit the total power exported to the grid to the limit defined by the user to meet local code requirements on export power limiting. 

3. Generator metering: On grid-forming sites with a generator installed, a pair of CT-200-CLAMP CTs (same as the Consumption CTs) can be used for metering the generator power. NOTE: There may be other local jurisdiction requirements that may mandate energy measurement. Hence, Enphase recommends the installation of current transformers on all sites. 

Recommended installation location for current transformers 

The following section provides the recommended installation location for current transformers based on the type of system installed at a site. Current transformer installation for PV-only sites Based on the site requirement, consumption meters can be installed for load-with-solar or load-only metering. 

Load-with-solar configuration 

In this configuration, the Consumption CT is installed between the main load center and the utility meter. All Consumption CTs supported by Enphase are service entrance rated and hence can be installed in this configuration. 

NOTE: For sites with IQ Gateway installed instead of IQ Combiner, the Production CT should be placed in the subpanel used for landing the PV branches onto the PV breakers 

Current transformer installation for grid-tied PV+IQ Battery sites 

Current transformer installation for Enphase Energy System sites Partial home backup (without MPU avoidance) 

Partial home backup (with MPU avoidance) 

Whole home backup 

Polarity correctness 

CTs have a specific polarity, which is determined by the direction of the secondary winding. It is important to maintain proper CT polarity in all installations; otherwise, readings will be negative. Refer to Figure 4 for guidance on the correct polarity. 

• The arrow on the Production CT must point away from the PV and towards the PV breaker. 

• The arrow on the Consumption CT must point away from the utility meter and toward the loads.

 • The arrow on the IQ Battery CT must point away from the IQ Battery and towards the IQ Battery breaker. 

NOTE: Always use the meter wizard in the Enphase Installer App to ensure the CTs have been correctly installed before leaving the site. Refer to this Meter configuration in the Installer App training video to understand how the meter wizard helps ensure error-free CT installation. 

However, if CT was still installed with incorrect polarity, the readings measured by the IQ Gateway can be corrected by flipping the polarity of the meters via the Enphase Installer Portal. Read more on how to do this in this support article. 

NOTE: For general troubleshooting guidance, refer to this CT Troubleshooting with Enphase Installer App training video. 

For IQ Combiner 5/5C/4** Follow the steps to connect CTs to an IQ Combiner 5/5C/4**: 

1. Make sure that the main load center wires are de-energized until the CT wires are secured in the terminal blocks. 

2. Connect the red and black CT wires to the red and black “C1” terminals. 

3. Connect the CT purple and brown wires to the purple and brown “C2” terminals.

4. Tighten all connections to 5 in-lbs. 

5. Clamp the C1 CT on the load center feed wire Line 1 (matching the phase on IQ Gateway’s “L1” voltage terminal) with the CT arrow pointing towards the load (away from the grid). 

6. Clamp the purple and brown C2 CT on the load center feed wire Line 2 (matching the phase on IQ Gateway’s “L2” voltage terminal) with the CT arrow pointing towards the load (away from the grid). 

IQ Battery metering Follow the steps to connect an IQ Battery CT (if IQ Battery 5P, IQ Battery 3/3T, or IQ Battery 10/10T is installed on-site) to any IQ Gateway or IQ Combiner: 

1. If an IQ Battery 5P, IQ Battery 3/3T, or IQ Battery 10/10T is present, clamp the blue and white IQ Battery clamp CT on the Line 2 power wire for all branches of the IQ Battery (matching the phase on IQ Gateway’s “L2” voltage terminal) with the CT arrow pointing towards the load (away from the battery). 

2. Connect the CT lead wires to the C3 section (third consumption metering port) on the IQ Gateway/IQ Combiner 4/IQ Combiner 5’s metering port. 

NOTE: The IQ Combiner 5/5C includes a pre-installed power jumper between the L2 and L3 power terminals of the IQ Gateway, as shown in Figure 10. When installing IQ Battery 5P, IQ Battery 3/3T, or IQ Battery 10/10T on a site with a standalone IQ Gateway or an IQ Combiner 4/4C, L2 and L3 power terminals must be shorted using a power jumper as shown in Figure 10. It is mandatory to do this to ensure correct readings on the battery CT. A power jumper is provided with the COMMS-KIT-02. L3 terminals are normally unused in split-phase (that is, LL 240 V, L-N 120 V) systems. Shorting the L2 power terminal on the IQ Gateway to the unused L3 power terminal allows the third consumption metering channel to be used with IQ Battery, as outlined herein. 

NOTE: When installing IQ Battery 5P with a standalone IQ Gateway or an IQ Combiner 4/4C, ensure that the eSW version used is 8.2.62 or higher. 

NOTE: IQ Battery metering is necessary for IQ Combiner4/4C when using MPU avoidance for grid-tied PV + Storage systems. This is supported with eSW 8.2.121 or higher. 

NOTE: To use IQ Battery 3/3T or IQ Battery 10/10T with the IQ Combiner 5/5C, refer to the How to make the IQ Combiner 5_5C compatible with IQ Battery 3T_10T document. 

Using the Enphase Installer App to complete the meter configuration 

Follow the meter configuration wizard in the Enphase Installer App during system commissioning to validate that the current transformers have been correctly installed. 

Setting up the production meter The steps to configure the production meter are as follows: 

1. Navigate to Meter Configuration. 

2. Tap the Production Meter to set up the production meter in the system. 

3. The Production Meter with the phases is displayed. 

4. Select the required phase and tap YES. 

5. The Enable Production Meter is displayed with the production phase details. 

6. Tap ENABLE PRODUCTION METER or NOT NOW to cancel the setup. 

7. The production meter is enabled in the system. NOTE: As the IQ Gateway is connected to the device, make sure not to move away. 

If the Production CTs are incorrectly installed, the Enphase Installer App highlights the power reading in red and suggests solutions to fix it. Implement the fixes suggested to ensure site metering is set up correctly. 

Extending the CT lead wires 

All current transformers include lead wires for wiring the CT directly into the IQ Gateway terminals. 

Production CT lead wires must not be extended if revenue-grade production metering is required. These CTs are certified for revenue-grade production metering. Extending lead wires voids the certification. 

Consumption meter lead wires can be extended to be installed in panels away from where the IQ Gateway is located. These wires may be extended to a maximum of 1.5 Ohms per wire and 3 Ohms for both wires end to end. Appropriately rated, 0.75 mm2 to 1.5 mm2, twisted-pair wire cable is recommended. Install in accordance with all applicable electrical codes and standards. 

NOTE: We technically can splice more CTs UP TOO 600 amps of loads. 

Multiple system production wiring diagram