separate out 110V loads in an 230V split phase system?

[oskaratk]

Howdy,
I am planning a system for my own use - using Victron materials.

Goal is to use stored energy ( 30 kWh batteries) as much as possible, but fall back to grid if the batteries run low. I do NOT want a typical grid-tied system, I need to keep things running when ( not if ) the grid goes out. Hence I am going to use quattros with generator input

reading this : https://diysolarforum.com/threads/2...ictron-multiplus-and-or-autotransformer.69797

seems to confirm my opinion that using an (Victron 100A) auto-transformer behind 2 stacked 5kW quattro inverters would limit my total total 110V load to 28A, no matter whether the 2 legs are balanced or not. Well, that's not going to work

220V, I only need for my heavy loads - well pump, baseboard heater, heatpump etc.

So, I think to separate out all 220V loads into extra subpanel(s) where 1 panel (in my garage) will have "mixed" 220 and low 110 V (lighting). 2 stacked inverters and AT.
For sure not exceeding that 28A limit on neutral

Then have an inverter (110V output) and subpanel for all household 110V loads

It's certainly more expensive, but IMHO a decent solution

Thoughts ?

Thanks
Oskar

 

[ricardocello]

I’ve got lots of posts in the thread you mention, and have the configuration you are discussing.

seems to confirm my opinion that using an (Victron 100A) auto-transformer behind 2 stacked 5kW quattro inverters would limit my total total 110V load to 28A, no matter whether the 2 legs are balanced or not. Well, that's not going to work

Not sure why you would want an autotransformer, it overly complicates neutrals and grounds.

I’ve got one to give me maximum inverter power when inverting only, because that’s how I designed it.
Because all of the loads (240v and 120V) balance out with the AT so the inverters are evenly loaded.
I’ve still never had a 28A imbalance with my setup.

What’s wrong with just using two stacked 5k inverters? Will you pull too much on one of the legs inadvertently?
If so, then yes, the AT can help.

Is your generator 120/240V or just 120V?

 

[Hedges]

That's 28A imbalance, not necessarily 28A total on one leg. But to avoid overloading and having the transformer cut out, 28A per leg it is.

So your idea is a separate, higher wattage 110V inverter?

Your original idea was 2x 5kW inverters, 10kW total, which would be 40A at 240V, 80A at 120V.

If you picked up a 25kVA transformer, 240/480V input and 120/240V output, you could wire the primary in series (480v) and apply 240V to it. Use the center tap of primary as neutral. Don't connect the secondary. It is good for 50A in the primary, will transfer all 50A from one inverter plus 50A from the other, could handle 100A at 120V. So it would handle 100% of your inverter output.

Can you stack two 120V inverters? That would give you 40A per phase, no transformers.

 

[oskaratk]

Not sure why you would want an autotransformer, it overly complicates neutrals and grounds.

What’s wrong with just using two stacked 5k inverters? Will you pull too much on one of the legs inadvertently?
If so, then yes, the AT can help.

Is your generator 120/240V or just 120V?

generator is 120/240V, 11kW.

Yes, my concern is inadvertently pulling too much on one leg.
I envision a situation where someone plugs in an space heater while the hot water kettle is on. Here goes 26A on 1 leg. If it be a complete new electric install/wiring ... I could certainly wire all outlets in a way to minimize chances of imbalance. But in an 1980 built house, I don't have that option.

2 stacked inverters, then I probably go for 2 x 10kW. Monitor ( Don't know whether the Victron software shows imbalance )