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Non-inverter Generator Transfer Switch Options - MultiPlus vs. Quattro?

I live in the US and recently bought an open frame Champion 7500 generator (non-inverter) to back feed my home through a generator inlet & breaker interlock (edited) at the breaker panel. It works for my needs (well pump, fridge, freezers, lighiting, etc.) but my existing AVR UPSs hate it.

I've looked into getting an online double-conversion UPS or an inverter generator but instead decided to design a critical systems sub panel to be pure sine wave inverter/charger and battery backed. This will act as a single UPS for these systems to work with the non-inverter generator and clean up my frequent brown outs from the local power company. I'm leaning towards starting with either 2x Quattro-II 2x120V or 2x MultiPlus-II 2x120V inverter chargers with 2x SOK 48V 100Ah PRO batteries connected to a dedicated 20-slot breaker panel.

I'm at the point in my design to determine what to do with the transfer switch for the generator. I was initially going with 2x MultiPlus-II 2x120V inverters in a split phase configuration with a manual Eaton transfer switch. My generator currently doesn't support auto-start but a future model may.

I figure using the Quattro-II inverters will eliminate the need for a manual generator transfer switch required for the MultiPlus-II inverters. Is this a correct assumption? The long term solution, and assuming I go with Quattro-II's, would be to install larger, permanent Generac 20kW generator with additional Quattro-II's to manage the loads. I'm not sure if this will ever happen with competing projects.

I don't want to jump into the wrong techonology pool but also am realistic about my budget and timeline for expansion until the rest of the house is remodeled.

Any advice or guidance is appreciated and thank you in advance!

MultiPlus Quattro Inverter Charger
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2 Answers
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Justin Cook answered ·

Neither the MultiPlus-II 2x120 nor the Quattro-II 2x120 is currently available for a 48v battery bank so that may be a determining factor for you, but if you're going to be using 2 of them in split-phase configuration then you wouldn't want the 2x120 versions anyway, since the L2 input/output is disabled when in split-phase config - you'd just use a regular MultiPlus, MultiPlus-II, or Quattro (no Quattro-II in 48v yet either).

The Quattro has 2 separate AC inputs, so would be the solution for having both grid and generator inputs without an external transfer switch.

I will point out however that back-feeding your home can be incredibly dangerous both for yourself and others, so please make sure to consult a reputable and experienced electrician to discuss your needs and develop a safe and workable solution for your system. I think there is most likely a safe and legal method of doing what you want, but the Community here is not the place for establishing what that is - that will be a discussion for you to have with your electrician.

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dissent answered ·

Thanks for the quick response, looking through my notes, I missed that about the 2x120 modules so they would be the non-2x120 versions. Thanks for clarifying that point.

I'm using a breaker interlock (I see I posted as service disconnect, my fault there) so it's safe and as legal, I phoned the local utilities and they have approved this method.

I didn't know that about the 48v not being available yet. Thank you for the heads up there.

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