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Planning for a Three-Phase IQ Microinverter System – North America
Β© 2017 Enphase Energy Inc. All rights reserved. September 20, 2017
8
Three-phase, 240V High-Leg Delta System Design
Designing a three-phase, 240V high-leg delta (also known as 240V delta with stinger) system is very simple
with Enphase IQ Microinverters and does not require a transformer. IQ Microinverters do not require a
neutral connection, so can be installed on all three phases in a 240V system.
When interconnecting an IQ Microinverter system to a 240V high-leg delta system, the IQ Envoy (Model
ENV-IQ-AM1-240 M) must be connected to the two hot conductors that are 120V line to neutral. The high-leg
(or stinger leg) will measure 208V from line to neutral. That stinger leg can damage sensitive electronics and
should not be connected to the Envoy.
For 240V delta systems without a neutral, use an inexpensive (~$40) auto-transformer to generate a neutral
for powering the Envoy. Follow the installation recommendations for interconnecting to a 240V delta system.
240V High Leg Delta Electrical Service Conceptual Schematic
Ampacity Calculations for 240V Branch Circuits on Two-Pole Circuit Breakers
Calculate the ampacity of a two-pole branch circuit as follows:
# π‘œπ‘“ π‘€π‘–π‘π‘Ÿπ‘œπ‘–π‘›π‘£π‘’π‘Ÿπ‘‘π‘’π‘Ÿπ‘  βˆ— πΌπ‘›π‘£π‘’π‘Ÿπ‘‘π‘’π‘Ÿ πΆπ‘œπ‘›π‘‘π‘–π‘›π‘œπ‘’π‘  𝑂𝑒𝑑𝑝𝑒𝑑 πΆπ‘’π‘Ÿπ‘Ÿπ‘’π‘›π‘‘ π‘…π‘Žπ‘‘π‘–π‘›π‘” = π΅π‘Ÿπ‘Žπ‘›π‘β„Ž πΆπ‘–π‘Ÿπ‘π‘’π‘–π‘‘ 𝑂𝑒𝑑𝑝𝑒𝑑 πΆπ‘’π‘Ÿπ‘Ÿπ‘’π‘›π‘‘
IQ 6 (240V)
IQ 6+ (240V)
Continuous Output Current Rating
0.96A
1.17A
For a fully populated branch circuit of 13 IQ 6+ Microinverters, the continuous output current rating is:
13 βˆ— 1.17𝐴 = 15.21𝐴
NEC Article 690.9(B) requires a 125% factor be applied to the continuous output current for sizing
overcurrent protection of the branch circuit:
15.21𝐴 βˆ— 1.25 safety factor = 19.0𝐴
A 20A branch circuit overcurrent protection device (OCPD) is required for 13 IQ 6+ Microinverters at 240V.