This checklist is a companion article to the more detailed information found here:
Repowering a PV System with a Tigo Inverter: The Definitive Guide
1. Assessment of Existing System
- Inspect the condition of the existing solar modules for physical damage (cracks, delamination, discoloration).
- Check wiring for wear, loose connections, or corrosion.
- Verify module degradation—calculate expected performance loss based on age.
- Identify any changes in shading (grown trees, new structures, etc.).
- Check the grounding configuration of the old inverter (transformer-based vs. transformerless).
- Determine if the existing array meets updated code requirements.
- Identify the number of strings, module ratings, and array configuration.
- Note the existing inverter’s max voltage, current, and MPPT specs for comparison.
2. Voltage and Current String Checks
- Measure and record each string's open-circuit voltage (Voc) during the coldest part of the day.
- Ensure string Voc does not exceed the Tigo inverter’s maximum DC input voltage (550V), even under cold temperatures.
- Measure and record the short-circuit current (Isc) under sunny conditions.
- Confirm Isc does not exceed the inverter’s max input current (16.9A).
- Verify the temperature coefficient impact on voltage and current readings.
- Ensure the string Vmp falls within the Tigo inverter’s MPPT range (80-550V).
- Check that all strings are producing similar voltage and current values.
3. Compatibility with the Tigo Inverter
- Check that the EI Inverter has sufficient MPPT terminals for the string configuration.
- Assign strings logically to MPPT inputs (e.g., different orientations).
- Decide if Module-Level Power Electronics (MLPE) like TS4 optimizers are needed for shading/mismatch.
4. Regulatory and Code Compliance
- Check if the jurisdiction requires NEC 2017+ module-level rapid shutdown.
- If rapid shutdown is required, install Tigo TS4 units.
- Verify that all disconnects, breakers, and fuses meet the latest NEC and local codes.
- Confirm that the system is compliant with utility interconnection standards.
- Check the existing labels and replace or update system placards as needed.
- Ensure the system is permitted and interconnection agreements are updated.
5. System Efficiency and Performance Gains
- Compare the efficiency ratings of the old and new inverters.
- Ensure the system is appropriately utilizing multi-MPPT inputs for optimization.
- If applicable, recommend DC oversizing to increase production (up to 200% DC:AC).
- Enable and test module-level monitoring if TS4 optimizers are installed.
- Verify that the existing array voltage allows for early-morning and low-light operation (80V).
6. Removal and Replacement Best Practices
- Shut down AC and DC power, and verify zero voltage before handling wiring.
- Remove old inverter carefully, labeling wires as needed.
- Reference the Tigo EI Inverter quick start guide (included in packaging) during this process.
- Mount the new Tigo inverter securely, ensuring adequate ventilation and clearances (>12 inches).
- Properly land and tighten DC input wiring, checking polarity before connecting.
- Connect AC wiring to the correct terminals (L1, L2, Ground, Neutral).
- If using TS4-O/S units, install the TAP (Tigo Access Point) in the center of the array. Multiple
- TAPs may be necessary, depending on the roof layout.
- Ground all components correctly, ensuring a continuous ground path.
- Install surge protection devices (SPDs) if necessary.
- Check DC disconnect placement and operation.
- Ensure conduit and wire management is neat, secure, and code-compliant.
7. Warranty and Manufacturer Support
- Register the Tigo EI inverter for warranty coverage.
- Verify the inverter’s standard and extended warranty options.
- Confirm the warranty claim process and installer support options.
- Inform the customer about warranty coverage and service procedures.
- Ensure all installation and commissioning records are documented.
8. Final Testing and Commissioning
- Test and confirm internet connectivity for remote monitoring. Strong internet is required!
- Perform a final wiring check, ensuring all terminations are torqued to spec.
- Energize the DC input first, verifying proper startup sequence.
- Close the AC breaker and allow the inverter to sync with the grid.
- Use the Tigo EI app to configure and commission the inverter.
- Verify power production and MPPT tracking in the monitoring portal.
- Conduct a rapid shutdown test by cutting AC power and checking voltage drop.
- Walk the customer through inverter operation and monitoring access.
- Document and submit any required paperwork to AHJ and utility.