What's the reason behind using 240V inverters with transformers when they have split phase ones?

[timselectric]

Dam 8 of those things..wow.

Have to plan for the future. Expecting to have two electric vehicles, in the future.

 

[Rednecktek]

There was also a time when the 240v AIO's were all that was available and affordable at the same time. Back then an autotransformer + a 240v AIO was still cheaper than a 120v split phase unit because only the $RealMoney brands offered the split phase units.

It helped break down some of the solar paywall and drive the development of 120v and 120/240 devices.

 

[Zwy]

Maybe to some degree but I don't think it has to do with just wanting what some youtuber did...which is why I asked the question I did. Doing some research it seems to make sense under certain circumstances. I've noticed that on some of the tier 2 products split phase offerings like mpp you have to buy more than one unit and stack to get split phase. This forces you go buy two units from day one and if one unit goes down you loose one leg.

You miss the point that system capacity is greatly increased with the 2 units. Take the LV6548 for instance, it takes 3 of the 5000ES 240V inverters to equal a pair of LV6548's or EG4's for output.

If you buy a 240 unit you can use one and stack more latter and if one or so goes out you still have full split phase.

No, you have 240V and need a transformer to get split phase. If the transformer fails, what do you have? 240V

Another observation seems to be that the higher kw units are mostly 240V and they seem to be a few hundred cheaper as you mentioned and that adds up for some of us.

Sig Solar shows the 5000ES at $900 x 3= $2700, the EG4 is $1300 x 2= $2600. The 5000ES requires a transformer, additional $350. Where is the savings?

Personally, I'd rather go with split phase right out of the box; I'd also rather get a conext, outback or victron system but that's 3/4x the cost which is another reason I think people weigh their options, research and ask questions. Thanks for your input...you have good points.

Watts247 specifically states, "We do not support the External Auto Transformer Method, as it poses danger of fires when there is a possibility of unbalanced phases, research this topic yourself houses burning to the ground with missing Neutral"

 

[Shimmy]

When you use a transformer like this, auto or isolation, does it help the surge capacity of a HF system since you're adding a transformer after all?

Absolutely not. A LF inverter needs the transformer for harmonics (among other things).

In a perfect world, we would wire up houses where the 240V loads all go to the main panel, and you have a little sub-panel for 120V loads. In that world, you could use a 240:120V isolation transformer sized just for the small loads. This would keep you from using 12/3 Romex for two circuits, but it would greatly help simplify things. (Ok, in a perfect world we might just ditch the 120V altogether, but that is a much bigger change.)

 

[timselectric]

Sig Solar shows the 5000ES at $900 x 3= $2700, the EG4 is $1300 x 2= $2600. The 5000ES requires a transformer, additional $350. Where is the savings

Watts247 has them listed for $588
X3 = $1764
+ transformer $350 = $2114
And you get 15k balanced output, and 300a solar charging. And if one unit goes down, you're still up and running at 60% capacity.

 

[stienman]

Transformers are much, much more reliable than any inverter will ever be and you can install more than one autotransformer to both spread the load and provide redundancy.

I'm not advocating one choice or another, simply pushing against those who are putting unnecessary emphasis on the "dangers" of autotransformers. Understand what the device does, install it properly, make sure it can handle the loads required, and you'll likely never have to touch it again.

All that said, getting permit approval and passing an electrical inspection for a 240V inverter is going to be difficult not because of the autotransformer, but because the inverter is not going to be designed or certified for the US market. Be prepared for a multitude of challenges if you choose to go this route - the cost savings may seem good until you account for all the additional time, inspections, and other hidden costs of going this non-traditional route, not to mention you'll likely have little to no support or warranty for this usage from the inverter manufacturer.

There are few situations where a significant savings will actually occur, taking all things into account, with this design, particularly now as split phase inverters are widely available and dropping in price.

 

[stienman]

Watts247 has them listed for $588
X3 = $1764
+ transformer $350 = $2114
And you get 15k balanced output, and 300a solar charging. And if one unit goes down, you're still up and running at 60% capacity.

A $350 transformer isn't rated to handle 15kW. If you're depending on your superior load balancing skills in the breaker box to keep the load under the 5-6kW the transformer is rated for you're going to have a bad day at some point in the future.

 

[timselectric]

A $350 transformer isn't rated to handle 15kW. If you're depending on your superior load balancing skills in the breaker box to keep the load under the 5-6kW the transformer is rated for you're going to have a bad day at some point in the future.

It's not expected to handle 15kw.
It's a 5kva transformer.
And my imbalance is usually around 3 to 5 amps.
Occasionally surging to 7 amps.
The transformer stays at room temperature.
It will outlast me.

 

[rhino]

What about the high load consumption of the Growatts/MPP inverters or is that not an issue for most? I thought they had a no load consumption of 80-100 watts per inverter which would really add up.. that's about double what a "higher quality" inverter's no load usage is.

 

[stienman]

It's not expected to handle 15kw.
It's a 5kva transformer.

 

[BradCagle]

Think about this with stackable units, especially in split-phase. What happens a few years down the road when one dies, and you can't find the same model, or hardware/firmware version to replace it?

Technology moves fast, and companies are always coming up with new products to replace the old.

 

[timselectric]

What about the high load consumption of the Growatts/MPP inverters or is that not an issue for most? I thought they had a no load consumption of 80-100 watts per inverter which would really add up.. that's about double what a "higher quality" inverter's no load usage is.

As long as you are not limited on space. A few more panels takes care of it.

 

[stienman]

What about the high load consumption of the Growatts/MPP inverters or is that not an issue for most? I thought they had a no load consumption of 80-100 watts per inverter which would really add up.. that's about double what a "higher quality" inverter's no load usage is.

Some report idle consumptions as high as 400w for the growatt 5000ES:

Idle 'no load' Consumption: Specs vs Your Personal Observation

Hello all I have an Off-Grid inverter growatt spf5000 ES and it is connected to 4 655W panels without batteries so far, its idle consumption from the utility is arouns 2 amps, it is making my energy meter spin like crazy, this system was supposed to save money, now it is costing me money, is...

diysolarforum.com

My SPF12000 eats about 150w when on without load and no solar or AC input.

This means it consumes about 3.6kwh per day, which, in the worst case, will require 2 additional solar panels and about 2.4kWH of additional battery capacity. That's about $1,000 more in equipment to support the idle load of the inverter.

It's about 2-3 times more current than more efficient inverters in this power class - 60w or so - so this means you'll be spending about $300 to $500 more to support the idle load of this vs a higher quality inverter.

A solark 12k is $6,500+, a growatt 12k is under $2,500, a savings of $4,000. There are a lot of other features, and the solark is more compelling for a variety of reasons - but purely taking into account the cost of idle consumption vs the output power the savings is still significant with the less efficient inverter. That cost savings covers a lot more than a few solar panels and a few kWH of battery capacity.

But every installation is different, and it's not always going to result in an overall savings, and certainly there are other factors to take into account - there are many competing products because everyone balances their requirements against their costs differently.

 

[rhino]

@stienman Nice informative info. It's good that people become more aware of the idle consumption since these cheaper inverters do not readily provide this information anywhere in their specs.

 

[MichaelK]

Think about this with stackable units, especially in split-phase. What happens a few years down the road when one dies, and you can't find the same model, or hardware/firmware version to replace it?

Technology moves fast, and companies are always coming up with new products to replace the old.

I can relate to this already. I got a Conext 4024 SW inverter as a stand-alone unit, with the idea that I might double capacity at some point to run my well-pump. I bought the 2015 model that "says" is has paralleling capacity. Fast forward to 2020, and paralleling has been taken out of the 4024s features.

As a stand-alone unit it has performed splendedly, and I have not complaints whatsoever, but this change of course bugs me.

 

[MichaelK]

@stienman Nice informative info. It's good that people become more aware of the idle consumption since these cheaper inverters do not readily provide this information anywhere in their specs.

Hmmm, why do you think that is?

 

[timselectric]

Growatt SPF-5000-ES idle consumption is 60w.
Higher than some, but lower than most of its competitors. It adds less than $100 to my total system cost, per unit. But, I'm not designing my system that tight. It's not worth the effort to me, to design and install a system that can barely get by.

 

[Pendrak]

I've been seeing this on youtube with david poz and others and am wondering why this is so alluring? Why buy a bunch of 240V only inverters then have to wire in a transformer to provide the neutral when you can buy inverters already putting out split phase power and just parallel them and combine them at the load center? Wouldn't that be a better option for a few reasons. If the isolation transformer you used to split the phase ever goes out you're without power. If you have five units like in this video and the transformer goes out it's over until you get another one. But if you have five units all running split phase natively you can have all but one go out and still have power..reduced but still have power? A few questions, what's the pull towards doing this? And, does this not turn a HF inverter, or in this case five of them, into LF devices? Does this help with the surge capacity issues HF units have without using a transformer? I looked up the transformer he used and it's between 2500 and 3k. Lastly ...would something like this even pass inspection with or without grid connection?

Cost and expansion, you can put up to 5 units together if you want.

 

[timselectric]

Cost and expansion, you can put up to 5 units together if you want.

Actually 6.

 

[Pendrak]

Sig Solar shows the 5000ES at $900 x 3= $2700, the EG4 is $1300 x 2= $2600. The 5000ES requires a transformer, additional $350. Where is the savings?

Who need 3 5000 ES ? lol i have one with a autotransformer and every is working perfect. My 110v load is max 1000 watts, why i need waste money on 2 units at $2600 and the caliber of cables are bigger, if i have 2 Growaat 5k units and one fail, eveything still working, but if i lost one unit of the EG4 i lost 240v. 5k unit is a good solution for those who want a backup system or a little workshop.