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SOLARDESIGN LAB

Roof wiring · Step-by-step guide

Place and adjust Tesla MCIs

Let SDL place mid-circuit interrupters as you draw strings, then adjust individual locations when needed.

Before you start

  • A self-designed project with roof faces and panels already placed.
  • Your panels, supported Tesla inverter or Powerwall DC input, and compatible module-level device selected in Equipment. This example uses Powerwall 3 and Tesla MCI-2.
  • The project’s site conditions loaded so SDL can check the string limits.

1. Connect your panels into a string

Open Roof layout, then Wiring. An MCI is a Tesla mid-circuit interrupter; SDL calculates its locations from the selected equipment and string layout.

  1. Choose Draw string and click the panels in connection order. Press Enter to finish.
  2. Select the circuit in the right-hand list. Check its Inverter / MPPT input and the displayed panel limit.
  3. Look for MCI layout and the purple device markers. Placement is automatic; there is no separate apply-MCI button.

Already have strings? Select one and continue below. Resolve any string-limit warning before treating its MCI layout as ready.

2. Find the automatic locations

With a string selected, scroll the right-hand panel to MCI locations.

Selected seven-module string with four automatic MCI locations and module-level Auto controls.
Selected seven-module string with four automatic MCI locations and module-level Auto controls. Enlarge screenshot ↗
  1. Match the numbered modules in the list to the selected string on the roof.
  2. MCI here identifies a device location. No MCI means that module currently has none.
  3. Leave the choices on Auto unless you need to adjust a location.

This example has four devices on the selected string. Your count depends on your equipment and layout.

3. Adjust a location

Use the dropdown beside the module you want to change.

Module 2 set to Place here, with the remaining MCI locations redistributed on the selected string.
Module 2 set to Place here, with the remaining MCI locations redistributed on the selected string. Enlarge screenshot ↗
  1. Choose Place here to request an MCI at that module, or Keep clear to avoid that location.
  2. Watch the purple markers and device count update. SDL adjusts the other automatic locations around your choice.
  3. Check any warning that appears. A location preference does not override an equipment limit.

Here, placing an MCI at module 2 moved the remaining automatic locations and kept the count at four.

4. Return to automatic placement

You can change your mind without redrawing the string.

  1. Set an individual module back to Auto to remove only that preference.
  2. Choose Reset to automatic to clear the selected string’s location preferences.
  3. Use the toolbar’s Undo and Redo buttons to compare your latest change. Wait for Saved before leaving the project.