Autotransformer vs Paralleled Inverters for 220v

[DrZ123]

I have a Victron Quattro 5000Va 48v unit.

Planning on adding some split unit AC as well as a W/D and dishwasher. Not sure if I will need more power than the Quattro can supply, that is yet to be seen, but I will definitely need 220v for the larger AC unit.

What are the suggestions here for using the Victron autotransformer to achieve 220v, vs adding a second Victron Quattro 5000 and get split phase 220v off of that paralleled with my current unit?

Thanks!

 

[sunshine_eggo]

The AT has a neutral limitation. Even the 100A unit can only handle a 28A imbalance between the legs (32A for a short period), i.e., the maximum you can use on a single leg WITHOUT using something on the other leg is 28A * 120V = 3360W.

With my dual Quattros in 120/240V split phase config, I can use the full 5kVA on each leg as well as surge.

 

[Solar Guppy]

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[DrZ123]

The AT has a neutral limitation. Even the 100A unit can only handle a 28A imbalance between the legs (32A for a short period), i.e., the maximum you can use on a single leg WITHOUT using something on the other leg is 28A * 120V = 3360W.

With my dual Quattros in 120/240V split phase config, I can use the full 5kVA on each leg as well as surge.

Could I put all my 120 volt loads on one leg and then the 220 volts on the other so that they'll always be something on both legs?

 

[sunshine_eggo]

Could I put all my 120 volt loads on one leg and then the 220 volts on the other so that they'll always be something on both legs?

It would seem to make more sense to balance the panel such that neither 120V leg could pull over 28A.

 

[DrZ123]

My thoughts are if the AC units each pull around 800-1500 watts, am I going to max out the single Quattro anyway

 

[sunshine_eggo]

I regularly run 2X RV rooftop units off a single Quattro without issue... other than I usually don't have enough solar to run both without dipping into battery.

While they are in split phase, the 50A to 30A RV Power Cord splitter effectively feeds one quattro to one trailer and the other quattro to the other trailer.

 

[DrZ123]

I regularly run 2X RV rooftop units off a single Quattro without issue... other than I usually don't have enough solar to run both without dipping into battery.

While they are in split phase, the 50A to 30A RV Power Cord splitter effectively feeds one quattro to one trailer and the other quattro to the other trailer.

Those are not 220v AC units though right?

 

[sunshine_eggo]

Those are not 220v AC units though right?

Nope. I'm just saying that a single quattro could likely handle it provided you step up to 240V.

 

[ChrisG]

The AT has a neutral limitation. Even the 100A unit can only handle a 28A imbalance between the legs (32A for a short period), i.e., the maximum you can use on a single leg WITHOUT using something on the other leg is 28A * 120V = 3360W.

I’ve poked this bear a few times on this forum and really not many trying the AT. 3360w imbalance is a good amount for a 5kw inverter. I guess that’s a hair dryer, microwave, and a toaster running on one leg at the same time to hit that imbalance. There have been reports of voltage difference between legs which didn’t seem terrible.

I’m considering trying one until a get another MPII for split phase. Guess if one of the two inverters fail in the future I could wire up AT to mitigate an outage while inverter is repaired.

 

[DrZ123]

The other difference is the 100a Victron Autotransformer is $750 and another Quattro is $2700!

Would just he units themselves be needed plus wiring to get them running?

 

[sunshine_eggo]

I’ve poked this bear a few times on this forum and really not many trying the AT. 3360w imbalance is a good amount for a 5kw inverter. I guess that’s a hair dryer, microwave, and a toaster running on one leg at the same time to hit that imbalance. There have been reports of voltage difference between legs which didn’t seem terrible.

I’m considering trying one until a get another MPII for split phase. Guess if one of the two inverters fail in the future I could wire up AT to mitigate an outage while inverter is repaired.

The other difference is the 100a Victron Autotransformer is $750 and another Quattro is $2700!

Would just he units themselves be needed plus wiring to get them running?

I'm not saying it's not workable or not a good idea. It's just that MANY are "shocked" by:

1) WTF? A 100A transformer with a 28A N limit?
2) WTF? Why are my legs uneven by a few volts?

 

[Solar Guppy]

I'm not saying it's not workable or not a good idea. It's just that MANY are "shocked" by:

1) WTF? A 100A transformer with a 28A N limit?
2) WTF? Why are my legs uneven by a few volts?

The Solis ATR can handle full rated current on a single leg, so it isn't a rule for all, it what you choose to purchase.

 

[ChrisG]

The Solis ATR can handle full rated current on a single leg, so it isn't a rule for all, it what you choose to purchase.

@Solar Guppy , Looks like the Solis has a similar delta limitation between legs like Victron

 

[Solar Guppy]

No, it is not the same, it has 30 amps delta, which means for example you could pull 4500 watts from one phase and 1500 from the other which one could not do from a 3k + 3k ( 6K ) rated split phase inverter.

@sunshine_eggo was showing something that claimed 100 amp but could only do a delta of 30 amp.

 

[ChrisG]

No, it is not the same, it has 30 amps delta, which means for example you could pull 4500 watts from one phase and 1500 from the other which one could not do from a 3k + 3k ( 6K ) rated split phase inverter.

@sunshine_eggo was showing something that claimed 100 amp but could only do a delta of 30 amp.

Seems the same to me. Victron has a 28amp Delta on their 32 amp and 100amp AT. For example, On the 100 you could have 50amp on one leg and 22amp on the other. Any further delta between legs it would trip.

In the dual inverter scenario, a delta isn’t a problem as it can provide max inverter power per leg or 0-100% delta between legs.

 

[zanydroid]

Isn't the Solis going to be rated for imbalance in step-down/neutralforming (because that's what it's intended for?)

But the case under discussion is step-up. I thought the math was different.

 

[ChrisG]

Isn't the Solis going to be rated for imbalance in step-down/neutralforming (because that's what it's intended for?)

But the case under discussion is step-up. I thought the math was different.

You’re right, we are talking about step-up. I didn’t know the math or delta is different for this use case. Thought the Victron ATs still had the Neutral 28A continuous limitation

 

[DrZ123]

I think I'm going to start with the Autotransformer and then if need be get a second inverter later. I can always use the Autotransformer even with the dual inverters it seems, right?

Even if I have both AC units plus the dishwasher on one leg, it likely won't trip that imbalance issue...

 

[zanydroid]

I think starting with AT is fine, I was considering that for a similar application (adapt 120V V2L from an EV to 120/240).

Yeah you can use AT with dual inverters in various ways for extra redundancy.

Keep in mind AT gives you rope to hang yourself with if you have a setup that is sometimes on grid.