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How to Configure Partial-Home Backup

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This article pertains to EI Residential (EU) installations only.

Whole-Home and Partial-Home Backup

A typical Tigo EI Residential Solar Solution installation provides whole-home backup. The EI system connects between the grid and the service entrance panel. If the grid drops, the EI system provides solar and battery backup power to all residential loads via the service entrance panel.

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Alternatively, an EI system can connect between the service entrance panel and an essential-load panel to provide partial-home backup. If the grid drops, the EI system connects solar and battery backup power only to the essential-load panel. For example, backup power may sustain essential lights, refrigeration, and medical equipment while not powering a non-essential air-conditioning load.

How It Works

The EI Inverter uses a current transformer (CT) located in the EI Link component to monitor solar and battery power export to the grid and enable efficient self-consumption.

To enable a partial-home backup configuration, an essential-load panel is added to the residential service wiring. This panel includes breakers for all circuits that the EI system will power if the grid drops. You then add a current transformer (CT) to the service entrance panel and connect it to the EI Inverter. If the grid drops, this lets the EI system power essential loads while not powering the service entrance panel or exporting power to the grid.

Installation – EU Systems Only

To enable partial-home backup, you will install one CT (for single-phase systems) or three CTs (for three-phase systems) in the service entrance panel, connect the CTs to the inverter, and configure the setup in the mobile EI app.

Obtain a CT:

  • Tigo has tested the YUANXING split core CT #CTSA016-100A/33.33mA.
    CTs with similar capacities may also work.

To create a CT-inverter cable for a single-phase system:

  1. Obtain an RJ-45-terminated, T-568B, straight-through CAT5/6 cable.
  2. Splice the white CT lead to the #1 wire (white/orange).
  3. Splice the black CT lead to the #8 wire (brown).
    1P CAT.png

    1P CT.png

To create a CT-inverter cable for a three-phase system:

  1. Obtain an RJ-45-terminated, T-568B, straight-through CAT5/6 cable.
  2. Splice the phase-R/L1 white CT lead to the #1 wire (white/orange).
  3. Splice the phase-R/L1 black CT lead to the #8 wire (brown).
  4. Splice the phase-S/L2 white CT lead to the #2 wire (orange).
  5. Splice the phase-S/L2 black CT lead to the #7 wire (white/brown).
  6. Splice the phase-T/L3 white CT lead to the #3 wire (white/green).
  7. Splice the phase-T/L3 black CT lead to the #6 wire (green).
    3P CAT.png

    3P CT.png

Install the CT(s):

  • For a single-phase system, attach the CT around the phase wire between the service entrance main breaker and the grid meter.
    Ensure the arrow on the CT points towards the grid.
  • For a three-phase system, attach CTs around the phase R/L1, S/L2, and T/L3 wires between the service entrance main breaker and the grid meter.
    Ensure the arrows on the CTs point towards the grid.

Connect the CT(s) to the inverter:

  1. Remove the CAT5/6 cable from the Meter/CT port on the bottom of the EI Inverter. This cable is no longer required and can be tied off.
  2. Attach the waterproof RJ-45 connector found in the EI Inverter Accessories bag to the Meter/CT port.
  3. Connect the CT CAT5/6 cable to the Meter/CT port.

Configure the setup in the EI app:

  1. In the EI app, open the system and tap the Settings icon.
  2. Tap Edit System > Select Equipment > Inverters/VIEW DETAILS > CONNECT > Inverter Settings > Advanced Options > Backup Type
    app screenshot.png
  3. Tap Partial and SAVE.

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