This article describes supported electrical testing methods for Tigo TS4-O and TS4-S systems, including voltage, current, and insulation resistance testing.
NOTE: This article applies to TS4-O and TS4-S products. For testing TS4-F and TS4-A-F/2F rapid shutdown systems, see Testing TS4-F and TS4-A-F/2F Rapid Shutdown Systems.
Applicable Products
- TS4-A-O, TS4-A-S
- TS4-A-O (725W), TS4-A-S (725)
- TS4-X-O, TS4-X-S
Visit the Tigo Downloads page to view datasheets, quick start guides, and installation manuals.
Before Testing
Before performing electrical testing:
- Identify the TS4 model installed on the system.
- Determine whether the TS4s have been commissioned.
- Follow all applicable electrical safety procedures.
- Use test equipment rated for the voltage and current being measured.
- Confirm that conductors and connectors are rated for the applied test voltage. The voltage rating is printed on Tigo PV cables.
- Follow the test equipment manufacturer's instructions.
Only qualified personnel should perform electrical testing.
Contact Tigo Support with any questions about TS4 testing methods.
What to Expect During Testing
The operating state of a TS4-O or TS4-S affects the voltage and current measurements available during testing.
Before Discovery: TS4-O and TS4-S units pass full module voltage. They do not need communication from the TAP to remain active, so you can perform supported voltage and current measurements without it.
After Discovery: TS4-O and TS4-S units need communication from the TAP to remain active and pass module voltage. If rapid shutdown is initiated or that communication is lost, the units enter the rapid shutdown state.
Before taking measurements that require active TS4s, confirm that the CCA and TAP are powered and communicating with the units.
Supported Testing Methods
The following tests can be performed on TS4-O and TS4-S systems:
| Test | Supported |
|---|---|
| Open Circuit Voltage (Voc) | ✓ |
| Safety Voltage | ✓ |
| Operating Voltage (Vmp) | ✓ |
| Operating Current (Imp) | ✓ |
| Insulation Resistance | ✓ |
| Short Circuit Current (Isc) through TS4 | ✕ |
| IV Curve Tracing through TS4 | ✕ |
✓ Open Circuit Voltage (Voc)
Measure open-circuit voltage when the TS4s are active but not in rapid shutdown. Turn on the inverter and wait for the CCA and TAP to bring the TS4s out of rapid shutdown. Measure the string voltage during the inverter’s five-minute startup period, before it starts producing power. Once the inverter starts producing, the voltage reading is no longer Voc.
You may take the measurement at the individual TS4/module or at the string level using standard DC voltage measurement methods.
For a commissioned system, the CCA and TAP must be operating, and the TS4s must be active before measuring Voc.
What the Measurement Tells You
A Voc measurement can help confirm that the expected module or string voltage is present.
When troubleshooting multiple strings with the same module count and similar conditions, compare the measured voltages between strings. A significant difference may indicate that you need to investigate further.
✓ Safety Voltage
Safety voltage is measured while the TS4-O or TS4-S units are in rapid shutdown. When rapid shutdown is initiated, TS4-O and TS4-S units reduce their output to 0 V.
A string in rapid shutdown should therefore measure approximately 0 V at the string output.
If voltage is present when the system should be in rapid shutdown, verify that rapid shutdown has been initiated and confirm that the TS4s are communicating properly with the Tigo system.
✓ Operating Voltage (Vmp)
Measure operating voltage while the PV system is operating normally, and the TS4s are active.
Measure DC voltage at the appropriate location while the inverter operates and performs maximum power point tracking.
The measured value represents the module or string operating voltage under the conditions present at the time of the test.
✓ Operating Current (Imp)
Measure operating current while the PV system is operating normally.
Use a properly rated DC clamp meter around a single current-carrying conductor.
Current measurements can be useful when comparing:
- Similar strings connected to the same inverter
- Modules within the same string
- Expected and actual string performance
Environmental conditions such as irradiance, shading, module orientation, and temperature can affect current. Consider these conditions when comparing measurements.
✓ Insulation Resistance Testing
Insulation resistance testing can evaluate PV conductors and circuits for insulation faults.
Follow the insulation resistance tester manufacturer's instructions and use a test voltage appropriate for all equipment and conductors connected to the circuit.
When testing a TS4-O or TS4-S system:
1. Testing from negative (–) to ground evaluates the negative homerun conductor.
2. Testing from positive (+) to ground evaluates insulation integrity through the connected PV circuit.
Insulation resistance testing evaluates the PV circuit's electrical insulation. It does not determine whether an individual TS4 is operating correctly.
✕ Short Circuit Current (Isc)
Do not perform an Isc test through a TS4-O or TS4-S.
TS4-O and TS4-S products include short-circuit protection. Applying a short circuit to the TS4 output causes the unit to enter rapid shutdown, resulting in a zero-current measurement.
If required, test the PV module independently according to the module manufacturer's instructions after safely disconnecting it from the TS4.
✕ IV Curve Tracing
Do not perform IV curve tracing through a TS4-O or TS4-S.
An IV curve tracer sweeps the circuit through operating conditions that cause the TS4 to shut down. As a result, an IV curve measured through the TS4 does not accurately represent module performance.
If you need to perform IV curve testing of the PV module, follow the module and test-equipment manufacturers' instructions for testing the module independently of the TS4.
Testing Summary
| Test | TS4 State | Purpose |
|---|---|---|
| Voc | Active | Confirm open circuit voltage |
| Safety Voltage | Rapid shutdown | Confirm expected rapid shutdown voltage |
| Vmp | Active and operating | Measure operating voltage |
| Imp | Active and operating | Measure operating current |
| Insulation Resistance | Follow test procedure | Evaluate circuit insulation integrity |
| Isc through TS4 | Not supported | TS4 short-circuit protection causes shutdown |
| IV Curve through TS4 | Not supported | Test causes TS4 shutdown |
Additional Resources
- TS4-F/TS4-2F: String Voltage Testing and Troubleshooting
- TS4 PV Module Compatibility
- Using SunPower positively grounded modules with Tigo TS4s and Inverters
Contact Tigo Support with any questions about TS4 testing methods.