Whole home backup with 2 split-phase electric panels

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xfaktor asked Sep 22, '23

Whole home backup with 2 split-phase electric panels

I am connected to a grid that experiences regular "hiccups". I would like to create a whole home UPS system using Victron ESS (with solar and batteries). My issue is that I haven't seen or heard of a single person with my same issue: the home is wired with TWO 200A service panels.

I have one meter connected outside that feeds in two 240v cables (one to each panel) in which the various circuit breakers are fairly evenly distributed amongst the two panels. I want to power both panels instead of separating circuits into critical vs non-critical loads.

What would be the best way to implement this? I have two ideas (but I'm open to suggestions):

Purchase four 5kva Multiplus II's and configure 2 in split-phase for each panel
Purchase two 10kva 240v Quattros (one for each panel) and pair each with an AutoTransformer to get the splt-phase.

Is any of this supported Victron and the Cerbo GX?

MultiPlus Quattro Inverter Charger cerbo gx ESS split phase

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Answer 1 · 2023-09-23T16:19:10Z

eric-newton answered · Sep 23, 2023 at 04:19 PM

I’m surprised your two main feeders come out the bottom without any conduit protection at all. This surprised me as to meeting code. IMO I would have those in conduit for bare minimum protection against mower guy clipping it and getting full 200A to ground.

That said, I do believe the four 5kva units would be the better choice. I’d have 4 50 amp breakers in your outside service disconnect panel for each Multiplus-II/Quattro-II unit for what each unit considers AC1.

You’d need to have 2 units per inside panel (basically 10kva available to each panel). I’m unsure of exactly how you’d hook these up, probably need two 50 amp breakers in each panel for backfeeding onto the panel’s busbar. Best to have a knowledgeable installer help recommend proper.

Btw if you want eventual generator input, you’ll want to get the Quattro-II with two AC inputs instead of Multiplus with only a single AC input. You’ll really want the Quattro-II units managing and switching the power and not a slow transfer switch like Generac supplies. It takes about 10-20 seconds for the generac switch to transition and that of course is lights out time. The Quattros can transfer virtually instantly (like 20 ms I think think they have specified)

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xfaktor commented · Sep 25, 2023 at 02:09 AM

Thank you for your input! I never considered the risks of the mains cables not being protected by conduit. It must be ok where I live since the house was built not long ago.

I thought about getting the Quattro's for the generator input, but in my case, I think I'll be better off saving money by connecting a few EG4 Chargeverters to the generator to charge the batteries instead.

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Answer 2 · 2024-01-18T03:09:11Z

dissent answered · Jan 18 at 03:09 AM

Curious if you came to a final resolution on your question @XFaktor. I'm installing the exact same 400A - 2x 200A panel setup and have the same question. I will be adding a generator though. It will be manually operated so the Quattro-II may not help much, was originally planning a manual transfer switch to a 3rd "critical load" panel before starting to look at the Quattro-II. The generator doesn't have an inverter so that's where the Victron equipment comes in to get the pure sine wave to my electronics when on the generator. I've used Victron for years in my mini-RV (LandCruiser) but new to the home products.

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xfaktor commented · Feb 28 at 03:28 AM

I'm still trying to find an adequate solution! I was told it was best to use the same model for all the inverters, so they recommended I use all Multiplus IIs instead mixing them with some Quattros. For the generator, they recommended wiring it directly to one or more "chargeverters" in order to charge the battery bank exclusively.

The issue I'm having now is that I can't get a permit unless I use an inverter that is UL Listed. So I'm considering using four 3k Multiplus II inverters per panel (2 in parallel configured in split phase with another 2 in parallel). I believe this should theoretically allow me to have closer to 200 amps of pass through (to match the panel rating) and an output of roughly 6000kva per 120V line.

Now my question is: With 8 inverters in total, Is this even possible??

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