enphase IQ8D-72-E-US Design Manual page 79

• Example: 9 IQ8D Microinverters on a Single branch circuit for a 208/120V Three-Phase System
The ampacity calculation for a branch circuit of 9 IQ8D Microinverters at a three-phase 208V site is as follows: Current
(A per branch) = [633 watts/Microinverter × 3 Microinverters × √3] ÷ 208 volts = 15.8 A
The ampacity result is 15.8 A
OCPD sizing = 15.8 A × 1.25 = 19.8 A
A branch circuit of 9 IQ8D Microinverters requires a three-pole, 20A circuit breaker or OCPD.
Plan your AC branch circuits to meet the limits for a maximum number of 9 Microinverters per branch when protected
with
a 3-pole 20A over-current protection device (OCPD).
In case you are skipping a connector, ensure that each branch circuit have a maximum of 3 IQ8D Microinverters
per phase connection i.e. 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 number of Microinverters per phase in a branch circuit.
If one exceeds the limit of 3 IQ8D Microinverters per phase (L-L) in a branch circuit then current shall be more than QD
Cable capacity. Hence it is required to have maximum 3 IQ8D Microinverters per phase in a branch circuit.
• Example: 126 IQ8D Microinverters in a 208/120V Three-Phase System
Calculating the ampacity for other wire sections is 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 126 Microinverters divided into 14 branch circuits with 9
Microinverters per circuit with 42 Microinverters each for L1:L2, L2:L3 and L3:L1
The calculation for main breaker size is as follows:
Current (A per branch) = [633 Watts/Microinverter × 42 Microinverters × √3 ]÷ 208 volts = 221 A
The ampacity result is 221 A
OCPD sizing = 221 Amps × 1.25 = 276 A
A PV system with 126 IQ8D Microinverters requires a 300A (minimum) circuit breaker or OCPD.
• Example: 103 IQ8D Microinverters in a 208/120V Three-Phase System
As number of IQ8D Microinverters in this system are not multiples of 3, this will create an imbalanced three phase
system.
In this example, a Microinverter subpanel feeds a total of 103 Microinverters divided into 9 branch circuits with 9
Microinverters, 2 branch circuits with 8 Microinverters and 1 branch circuit with 6 Microinverters. Each phase has -
© 2022 Enphase Energy Inc. All rights reserved. IQ8D-DG-MKT-00397-02-EN-US-2022-06-10 79