Appendix A: Ampacity Calculations For Iq8 Commercial Microinverter System; Branch Circuit Current Calculations - enphase IQ8 Design Manual

o
Tap
J. Add the new microinverter serial number to the gateway database using the Enphase Installer
App camera scan to scan the IQ8 Commercial barcode and assign the device in the array
builder.
8 Appendix A: Ampacity calculations for IQ8 Commercial
Microinverter system
Enphase IQ8 Commercial Microinverter supports two series connected PV modules and has a four-pin
output configuration (L1, L2, L3, and neutral sense) with Power on two pins and phase sensing on the
other two pins.
IQ8 Commercial Microinverters are connected across the L-L 208 V connection. The single-phase IQ8
Commercial Microinverter achieves the three-phase configuration and phase balancing using the
three-phase QD Cable rotation. The following figure shows the phase rotation of the QD Cable for a
branch circuit of 9 IQ8 Commercial Microinverters. As shown, the QD Cable rotation creates a balanced
three-phase configuration with L1-L2: 3 microinverters, L2-L3: 3 microinverters, and L1-L3: 3
microinverters connected across each phase.
The branch circuit calculations shall involve vector mathematics for current addition as each
microinverter is connected across L-L and shall contribute current to all three lines – L1, L2, and L3
conductors. To simplify the current calculations, refer to the following formulas. We shall use √3
multipliers for converting phase current to line current.

8.1 Branch circuit current calculations

The equation to calculate ampacity for one branch in a 208 V three-phase system is:
Current (amps per branch) = [(Maximum continuous output power of microinverter) × (maximum
number of microinverters per phase L-L) ×√3] ÷ (208 volts)
The equation to determine OCPD sizing for a three-phase system is:
OCPD Sizing = [(Maximum continuous output power of microinverter) × (maximum number of
microinverters per phase L-L)
× √3 ] ÷ (208 volts) × 1.25 (safety factor)
Use these calculations to determine ampacity in three-phase systems, as shown in the following
sections.
NOTE: Each of the three-line conductors in a balanced three-phase system carries this
current. The neutral sense does not carry any current but is used for microinverter
communications and sensing.
NOTE: In case of an imbalanced system where each phase has a different number of
microinverters, consider the largest number of microinverters in a phase for OCPD sizing
calculations.
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to delete the microinverter from the IQ Gateway Commercial 2 database.
Figure 44: QD Cable rotation for IQ8 AC branch circuit
© 2023 Enphase Energy Inc. All rights reserved.
IQ8 Commercial Microinverter grid-tied PV system
November 2023
USG-00026-1.0