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Main panel <br />(Back-fed panel) <br />IQ Series Microinverters <br />IQ EV Charger <br />Connect to LC <br />CTs/Cons CTs <br />Connector <br />N <br />N13 <br />RS+GNDRS- <br />NO <br />NC <br />C <br />EIP comm. LED <br />USB1 <br />USB2 RSD LED <br />Status LED <br />Reset <br /> button <br />Main DER <br />breaker <br />AP mode LED <br />AP mode button <br />Power production LED <br />Device comm. LED <br />Device scan button <br />Backfeed lugs <br />with DER relay <br />PV bus DER bus <br />DER centre <br />IQ PV2 <br />IQ PV3 <br />IQ PV1 <br />11 <br />_ <br />N <br />3 4 <br />12 <br />A1 <br />5 6 7 8 <br />910 <br />A2 <br />Combiner controller Board <br />( C C B ) <br />Integrated Production CT <br />Ibattery <br />Integrated Battery CTs <br />Gateway <br />1 2 3 4 D 1 2 3 4 D <br />CT8(L2) <br />IQ PV4 <br />IQ B2 <br />IQ B1 <br />IQ EVC <br />PVA <br />PF <br />CT2, CT3 <br />CT1 <br />CT4, CT5 <br />CT(L1)CT(L1)CT(L2)CT (L2) <br />IQ Combiner 6C <br />Connect to EVSE <br />CT connector on <br />the gateway <br />Utility meter Grid <br />IQ Battery IQ Battery <br />Load Controller <br /> <br />B1 <br />LCB <br />CT6, CT7 <br />1 <br />1 2 3 4 D <br />2 <br />1 2 3 4 D <br />CT9, CT10 <br />(L1,L2) <br />Integrated Backfeed CTs <br />Ibackfeed <br />Iconsumption <br />Consumption CTs <br />Main Panel Upgrade Avoidance <br />with Busbar Overload Control <br />Main Panel Upgrade Avoidance <br />with Feeder Control <br />Additional loads <br />11 <br />8Home loads <br />Figure 6: MPU avoidance using Busbar Overload Control in grid-tied configuration <br />NOTE: Enphase Systems can use Feeder Control on the Main DER breaker along with Busbar <br />Overload Control. This is set automatically if the Main DER breaker is undersized compared to <br />the nameplate, as described in further sections. <br />The following figure shows the diagram for MPU avoidance with Busbar Overload Control in the <br />grid-forming configuration. <br />Enphase Power Control features <br />27 © 2025 Enphase Energy Inc. All rights reserved. August 2025 <br />TEB-00269-2.0-EN <br />IQ EV Charger <br />Ibackfeed <br />Integrated Production CT <br />Integrated Backfeed CTs <br />N13 <br />RS+GNDRS- <br />NO <br />NC <br />C <br />EIP comm. LED <br />USB1 <br />USB2 RSD LED <br />Status LED <br />Reset <br /> button <br />AP mode LED <br />AP mode button <br />Power production LED <br />Device comm. LED <br />Device scan button <br />Backfeed lugs <br />with DER relay <br />PV bus DER bus <br />DER centre <br />IQ PV2 <br />IQ PV3 <br />IQ PV1 <br />11 <br />_ <br />N <br />3 4 <br />12 <br />A1 <br />5 6 7 8 <br />910 <br />A2 <br />Combiner Controller Board (CCB) <br />Gateway <br />1 2 3 4 D 1 2 3 4 D <br />CT8(L2)IQ PV4 <br />IQ B2 <br />IQ B1 <br />IQ EVC <br />PVA <br />PF <br />CT2, CT3 <br />CT1 <br />CT4, CT5 <br />CT(L1)CT(L1)CT(L2)CT (L2) <br />IQ Combiner 6C <br />Load Controller <br /> <br />B1 <br />LCB <br />CT6, CT7 <br />1 <br />1 2 3 4 D <br />2 <br />1 2 3 4 D <br />N <br />Grid <br />Backed up <br />home loads <br />Non-backup <br />heavy loads <br />IQ BatteryIQ Series Microinverters IQ Battery <br />Connect to EVSE <br />CT connector on <br />the gateway <br />Integrated Battery CTs <br />Integrated <br />Consumption CTs <br />Main Panel Upgrade Avoidance <br />with Busbar Overload Control <br />Main Panel Upgrade Avoidance <br />with Feeder Control <br />Main DER <br />breaker Iconsumption <br />11 <br />Main-meter combo <br />with IQ Meter Collar <br />behind the utility meter <br />(back-fed panel) <br />Figure 7: MPU avoidance using Busbar Overload Control in grid-forming configuration <br />NOTE: For MPU avoidance with Busbar Overload Control in either grid-tied or grid-forming <br />configuration, if Consumption CTs and IQ Meter Collar on a pan are used, they must be placed <br />between the main panel and the grid so current from the grid is accurately measured. <br />System sizing for MPU avoidance with Busbar Overload Control <br />With the MPU avoidance option, Busbar Overload Control, the maximum allowed main DER breaker <br />size (backfeed breaker size) is given by the lower rating of (main service breaker in Amperes, 80% of <br />main panel busbar rating in Amperes, 125 A). <br />Enphase Power Control features <br />28 © 2025 Enphase Energy Inc. All rights reserved. August 2025 <br />TEB-00269-2.0-EN