MCI Health Check

Correction Code: 230313059

Safety and PPE

  • Safety glasses (ANSI Z87.1 or EN 166)
  • Cut-resistant gloves (ANSI Cut Level 3 or EN 388 Level C)

Overview

The following tests are used to confirm MCIs are functioning as expected.

  1. Before removing MCIs from an array to test them, confirm MCIs have been installed per the Powerwall+ / Tesla Solar Inverter installation manual to comply with RSD code requirements (1 MCI per every X modules, or 1 MCI on ends of strings, depending on the system being installed, refer to manual for details).
  2. When identifying which MCI(s) are faulty, remove all MCIs from the array and perform the MCI health tests listed below. Replace any faulty MCI with a known healthy MCI when installing the MCIs in the array again.
    Warning IconA warning icon, calling your attention to a possibly risky situation
    CAUTION
    If an array has faulty MCI(s) and there are not sufficient healthy MCIs to replace them, ensure the system is left OFF until the return visit has been completed and the required number of MCIs has been installed.
Informational PurposesAn informational icon, calling your attention
Note
Take photos of all readings while troubleshooting.If Install Support is required, they will use these screenshots to verify the steps that have been completed and can be skipped during the call.

MCI Diode Test

The MCI diode test is used to ensure the diode in the MCI is functioning as expected.

To perform a diode test:

  1. Follow Tesla PV Inverter (PVI) LOTOV or Powerwall 3 LOTOV to shut down the solar system.
  2. Remove the PV leads from the MCI.
    • To remove the MC4 leads from the MCI, use a MC4 spanner tool.
  3. Set a multimeter to diode testing mode.
  4. Connect the red lead of a digital multimeter to the MC4+ lead of an MCI.
  5. Connect the black lead of the digital multimeter to the MC4- lead of the MCI.
  6. The reading on the digital multimeter should be between 0.25 V and 0.5 V.
    • If the reading is greater than 0.5 V, replace the MCI.
    • If the reading less than 0.25 V, replace the MCI.
    • If the reading indicates 'OL', ensure the leads are securely connected to the MCI's terminals.
      • If the reading still indicates 'OL', replace the MCI.
  7. Unplug both connector leads.

If a suspected non-functional MCI is found in the field, confirm the MCI is the issue by replacing the MCI and confirming the issue has been fixed. Swap the original unit back in again to see if the issue remains fixed, or if the issue occurs again with the original MCI installed.

Informational PurposesAn informational icon, calling your attention
Note
Avoid excessive stress to wires when performing the diode test. Faulty connection of press fit pins will result in an 'OL' reading in the multimeter. If this occurs, manipulate the wires and measure again. For an optional additional check, if the diode test initially failed and now passes, try it again to see if wire management did indeed fix the issue.

MCI Resistance Test

To perform an MCI resistance test:
  1. Set the multimeter to measure resistance. The mode is shown as an omega symbol.
  2. Connect the red lead of a digital multimeter to the MC4- lead of an MCI.
  3. Connect the black lead of the digital multimeter to the MC4+ lead of the MCI.
  4. The reading on the digital multimeter should be greater than 1 MΩ or Open Loop (OL).
    • If the reading is less than 1 MΩ, replace the MCI.

MCI Visual Inspection

Perform a visual inspection of the MCI and conductors, looking for deformation, physical damage, and/or damage to connector integrity. If any issues are found during the visual inspection, or if the MCI fails the resistance test, replace the MCI.