Microinverter AC Branch Circuit Sizing: An EPC Review Checklist

The maximum unit count in a microinverter datasheet is a product boundary, not a complete AC branch design. EPC teams must also check conductor capacity, voltage rise, protective devices, connectors, installation method and the rules at the project location.

Start with rated AC current

Use the exact model's rated output current under the stated grid voltage. For an initial single-phase estimate:

Branch current = number of operating units × rated AC current per unit

Do not divide watts by a convenient nominal voltage if the product documentation already provides rated current. Confirm whether continuous-load factors or design margins are required by the applicable code and responsible engineer.

Check every current-limiting component

The permissible branch quantity is limited by the lowest applicable rating in the path: inverter output lead, connector, branch cable, coupler, disconnect, protective device, distribution terminal or manufacturer-stated maximum unit count. The PV connector and cable guide helps turn these into a controlled BOM.

Calculate voltage rise at full export

Long AC runs can raise inverter-terminal voltage during export and cause nuisance disconnection. Calculate the complete route from the farthest unit to the connection point using conductor material, cross-section, route length, current distribution, power factor and connection resistance.

A branch with distributed sources is not always represented accurately by placing all current at one end. Use a method appropriate to the actual topology and keep the calculation in the design file.

Coordinate protection and phase allocation

Confirm nominal voltage, frequency, line-to-neutral versus line-to-line connection, neutral availability, earthing arrangement and protective-device type. For multi-phase sites, document allocation of single-phase units and the network operator's imbalance requirements. The broader process is covered in grid voltage and phase verification.

Design input	Required record
Model and quantity	Approved equipment schedule
Rated current per unit	Manual reference
Cable type, size and route	Cable schedule and layout
Connector ratings	Component data and mating statement
Protective device	Rating, poles and coordination note
Voltage-rise result	Calculation with assumptions
Phase allocation	Single-line and phase schedule

For the APHV Series, the published branch quantity applies to the stated 230 V configuration. The final count can be lower when cable, protection, voltage rise or local requirements impose a tighter limit.

Commission the finished branch

Review the rooftop microinverter AC surge-protection checklist alongside the branch layout to document SPD locations, coordination and coverage of the farthest units.

Measure supply voltage before generation and inverter-terminal voltage during meaningful export. Confirm connector locking, protective-earth continuity, phase allocation, branch labeling and the configured country profile. Record readings with time, operating power and measurement point.

Send the single-line diagram, cable schedule, route lengths, model quantities and destination market through TMG Contact. A firm configuration should identify the governing branch limit and every assumption that must be verified on site.