PV modules installed on different roof surfaces may have different orientations, tilt angles, or irradiance conditions. These differences can cause modules within a string to operate at different power levels.
TS4-O can reduce mismatch losses caused by different orientations, tilts, and shading. However, optimization does not replace proper PV system design. The PV array must remain within the electrical operating requirements of the inverter, PV modules, and TS4.
Use the following requirements when designing systems with TS4-O.
1. Partial TS4-O installation
TS4-O may be installed only on the modules that require optimization when all of the following conditions are met:
- All modules in the string have the same orientation.
- All modules in the string have the same tilt.
- The string is connected to its own MPPT.No other string is connected in parallel to that MPPT.
If any of these conditions are not met, do not use partial TS4-O deployment.
Example: Partial TS4-O deployment
A string contains 6 modules with the same orientation and tilt and is connected to a dedicated MPPT. Two modules experience localized shading.
TS4-O may be installed on the two modules requiring optimization.
2. Mixing TS4-O and TS4-S in the same string
When the entire string requires monitoring and rapid shutdown, you may use TS4-O and TS4-S together when the partial-installation requirements above are met.
Install:
- TS4-O on modules that require optimization.
TS4-S on the remaining modules.
TS4-S provides monitoring and rapid shutdown but does not provide optimization.
Example: Mixed TS4-O and TS4-S deployment
A string contains 6 modules with the same orientation and tilt and is connected to a dedicated MPPT. Three modules require optimization.
Install TS4-O on the three modules requiring optimization and TS4-S on the remaining seven modules.
3. Different orientations or tilts within the same string
If modules within the same series string have different orientations or different tilt angles, install TS4-O on every module in the string.
Do not use partial TS4-O installation or a mixed TS4-O/TS4-S configuration in a string containing modules with different orientations or tilts.
Example: Different orientations within one string
A single series string contains modules facing south and modules facing west.
Because the modules have different orientations, install TS4-O on every module in the string.
The same requirement applies when modules within the string have different tilt angles.
4. Use separate MPPTs for independent strings with different orientations or tilts
When possible, connect independent strings with different orientations or tilts to separate MPPTs.
For example, connect an east-facing string to one MPPT and a west-facing string to another MPPT. This allows each MPPT to independently track the operating point of the connected string.
5. Parallel strings connected to the same MPPT
When parallel strings share the same MPPT and require optimization, install TS4-O on every module in every string connected to that MPPT.
Do not use partial TS4-O installation or mix TS4-O and TS4-S on parallel strings sharing the same MPPT.
For additional parallel-string design requirements, see Design Considerations for Uneven Parallel Strings.
6. Keep string voltage within the inverter operating range
Verify that string voltage remains within the inverter's MPPT operating range and maximum DC input voltage under the expected site temperature conditions.
TS4-O cannot compensate for a string that does not meet the inverter's electrical operating requirements.
7. Maintain sufficient voltage for MPPT operation
When modules within the same series string have different orientations or tilts, consider how irradiance changes throughout the day.
Modules receiving significantly less irradiance may contribute little or no power during certain periods. The remaining producing modules must provide sufficient voltage for the inverter MPPT to start and remain within its operating range.
Quick Reference
Use these rules when selecting the type of TS4-0 and TS4-S installation:
| What do I have? | What do I install? |
| One string, same orientation and tilt, no parallel strings on the MPPT | Install TS4-O only on the modules that need optimization |
| Same as above, but monitoring and rapid shutdown are needed on every module | Install TS4-O on modules that need optimization and TS4-S on the remaining modules |
| Modules in the same string have different orientations or tilts | Install TS4-O on every module in the string |
| Two or more strings are connected in parallel to the same MPPT and optimization is needed | Install TS4-O on every module connected to that MPPT |
| Separate strings have different orientations or tilts | Connect the strings to separate MPPTs when possible |
Design Assistance
For additional design assistance, contact Tigo Support.
Additional Information:
Design Considerations for Uneven Parallel Strings
How to Verify PV Module Compatibility with a TS4 MLPE
TS4 Compatibility with Bifacial PV Modules