enphase IQ8 Design Manual page 65

Example 1: 12 IQ8 Commercial Microinverters (IQ8P-3P) on a single branch circuit for a 208/120
V three-phase system
The ampacity calculation for a branch circuit of 12 IQ8 Commercial Microinverters (IQ8P-3P) at a three-
phase 208 V site is as follows:
Current (A per branch) = [Microinverter power (watts) x Number of microinverters per phase x √3 ] / grid
voltage = 480 × 4 × √3 / 208 = 15.98 A
The ampacity result is 15.98 A
OCPD sizing = 15.98 A × 1.25 = 19.975 A
A branch circuit of 12 IQ8 Commercial Microinverters (IQ8P-3P) requires a three-pole, 20 A circuit
breaker or OCPD.
Plan your AC branch circuits to meet the limits for a maximum number of 12 microinverters (IQ8P-3P)
per branch when protected with a 3-pole 20 A over-current protection device (OCPD).
In case you are skipping a connector, ensure that each branch circuit has a maximum of four IQ8
Commercial Microinverters (IQ8P-3P) per phase connection, that is, L1-L2, L2-L3, L3-L1. You can check
the marking on connectors C1 (L1-L2), C2 (L2-L3), and C3 (L3-L1) to count the number of
microinverters per phase in a branch circuit.
If one exceeds the limit of 4 IQ8 Commercial Microinverters (IQ8P-3P) per phase (L-L) in a branch
circuit, then the current shall be more than QD Cable capacity. Therefore, it is required to have a
maximum of four IQ8 Commercial Microinverters (IQ8P- 3P) per phase in a branch circuit.
Example 2: 84 IQ8 Commercial Microinverters (IQ8P-3P) in a 208/120 V three-phase system
Calculating the ampacity for other wire sections is the same as for a single circuit, but you must know
the total number of microinverters per phase on the combined wire run.
In this example, a microinverter subpanel feeds a total of 84 microinverters divided into seven branch
circuits with 12 microinverters per circuit with 28 microinverters each for L1:L2, L2:L3 and L3:L1.
The calculation for the main breaker size is as follows:
Current (A per branch) = [480 Watts/microinverter × 28 microinverters × √3 ]÷ 208 volts = 111.9 A The
ampacity result is 111.9 A
OCPD sizing = 111.9 Amps × 1.25 = 139.8 A
A PV system with 84 IQ8 Commercial Microinverters requires a 150 A (minimum) circuit breaker or
OCPD.
NOTE: The above methodology is used only for ease of calculations for an unbalanced system.
The real current calculations shall involve vector mathematics for current addition as each
microinverter is connected across each phase and shall contribute current to all three lines:
L1, L2, and L3 cables.
65 © 2023 Enphase Energy Inc. All rights reserved.
IQ8 Commercial Microinverter grid-tied PV system
November 2023
USG-00026-1.0