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portsample asked

MultiPlus-II 48/3000/35-50 120V now UL approved in US, seeking advice on configuration.

dual-multiplus-ii-dc-grid-connected-no-ac-2023-04.pngI am interested in configuring a combined AC coupled and DC coupled power generation system for my home that would be connected to the public grid. Last month the Underwriters Laboratory (UL) in the United States found that the MultiPlus-II 48/3000/35-50 120V meets UL 1741 standards for inverters, converters, controllers and interconnection system equipment). It appears that this specific model of Multiplus inverter can now be used in grid connected systems in the US with the approval of the local power company/co-op.Below is a schematic for what I have in mind. The building I am configuring for is 120/240 volt, single-phase, three-wire service. The configuration I am proposing may be familar to many Multiplus users outside of the United States. I would appreciate a constructive critique of this diagram. It appears that the Fronius grid inverter only has one AC out. I'd like to have two hot legs from this system. Thanks in advance.

UPDATE 4/28/2023 Updated schematic to show grid connect per ejrossouw comment.

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ejrossouw answered ·

I cannot comment on your local regulatory etc requirements, which may be different regarding earthing etc. Typically there has to be dual pole isolation, overload and residual current protection between the multi and grid which all has to be on a dedicated circuit. The grid connection is done on ACIN. The inverter is bi-directional. If required, critical loads are done using ACOUT1 with ACOUT2 used for non-critical loads that won't be powered during grid failures. Both ACOUT will require overload etc. protection.

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portsample avatar image portsample commented ·

Interesting. Thanks for the insight and information. I am still curious regarding how and where exactly AC-IN interfaces with the grid for excess power out.

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ejrossouw avatar image ejrossouw portsample commented ·

You will install a CT or ET112 to monitor all loads and depending on your settings, can have zero export etc. If you oversize your array, you can have overloads while exporting, see keep that in mind too.

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