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

[Quattrohead]

a autotransformer for $372 at signature solar

Is NOT a 25kVa ISOLATING transformer.

 

[realpinochet]

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.



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



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 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"

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.



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



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 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"

Aside from a transformer failure you could have multiple 240V units fail and still have split phase power. Not possible with the way mpp and others do this at the moment unless you want to by four units. That's all I was saying. You're right though the transformer is the weak point so I guess double up on those..some are. And, I'd assume capacity is a concern regardless what system you choose with inverter failure.

 

[realpinochet]

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 believe that some vendors have backward compatibility in the firmware but you have a good point. A single unit has its cons to...it goes out you don't have anything.

 

[Pendrak]

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.

Exactly.

 

[Zwy]

Aside from a transformer failure you could have multiple 240V units fail and still have split phase power. Not possible with the way mpp and others do this at the moment unless you want to by four units. That's all I was saying. You're right though the transformer is the weak point so I guess double up on those..some are. And, I'd assume capacity is a concern regardless what system you choose with inverter failure.

It wouldn't have 240V split phase with a pair and one goes down, however one could change the settings and still have 120V on one half of the panel.

The problems with transformer failures are covered in detail in the various 5000ES threads. You have this thread started by Will. https://diysolarforum.com/threads/s...ersion-when-connected-to-american-grid.33975/

only 11 pages. Compared to the 42 pages in the thread started by Sig Solar. https://diysolarforum.com/threads/safe-grid-use-of-the-5000es-and-transformer.34121/

One of the best posts in the thread was this one by HighTechLab. https://diysolarforum.com/threads/safe-grid-use-of-the-5000es-and-transformer.34121/post-429934

in the post, he made this comment. "Let's talk about the practicality though. These units retail at $784. If you are already invested in the inverters, this is a way to fix the issue on your hands if you can't return your inverters, assuming you have the inverter with the neutral-ground bond removed. Take the added after-the-fact cost as a learning lesson that the cheapest solution upfront isn't always the best solution long term."

 

[timselectric]

That's one person's opinion. I have made the correct choice for my situation. Everyone should do the same for themselves. It all depends on what you need your system to do. Weighing all of the options available, to accomplish your goal. Then choose what will work best for you. And what you feel comfortable with doing. (In the end, you are the one who has to live with your system)
The most important thing is to plan out your system before you spend any money. And leave room for possible future expansion.

 

[realpinochet]

It wouldn't have 240V split phase with a pair and one goes down, however one could change the settings and still have 120V on one half of the panel.

The problems with transformer failures are covered in detail in the various 5000ES threads. You have this thread started by Will. https://diysolarforum.com/threads/s...ersion-when-connected-to-american-grid.33975/

only 11 pages. Compared to the 42 pages in the thread started by Sig Solar. https://diysolarforum.com/threads/safe-grid-use-of-the-5000es-and-transformer.34121/

One of the best posts in the thread was this one by HighTechLab. https://diysolarforum.com/threads/safe-grid-use-of-the-5000es-and-transformer.34121/post-429934

in the post, he made this comment. "Let's talk about the practicality though. These units retail at $784. If you are already invested in the inverters, this is a way to fix the issue on your hands if you can't return your inverters, assuming you have the inverter with the neutral-ground bond removed. Take the added after-the-fact cost as a learning lesson that the cheapest solution upfront isn't always the best solution long term."

If the inverter is 240V natively and you're splitting the phase with a isolation transformer and you have multiple units stacked for the only purpose of increased power and redundancy... you would still have split phase power if only one remained. This is assuming the transformer didn't go out. I'm not talking about having to use multiple 120V units in pairs to provide leg 1 and leg 2 like mpp. There's people out there with one 240V inverter with a transformer and split phase. Maybe I'm not understanding you...why would you loose split phase with a single 240V inverter and a working transformer? Most of this safety concern came about due to auto transformers being used from what I'm reading not isolation transformers that seem to be the safe way to accomplish this if one desires. The main issue was loosing the auto transformer and as such the neutral but then having the ground loop from the grid present itself. Practical is subjective to each person. Will seems like a good guy but he's not a electrician. There's seems to be a safe way to do this and legit reasons why people do...which is why I asked.

 

[Zwy]

If the inverter is 240V natively and you're splitting the phase with a isolation transformer and you have multiple units stacked for the only purpose of increased power and redundancy... you would still have split phase power if only one remained. This is assuming the transformer didn't go out. I'm not talking about having to use multiple 120V units in pairs to provide leg 1 and leg 2 like mpp. There's people out there with one 240V inverter with a transformer and split phase. Maybe I'm not understanding you...why would you loose split phase with a single 240V inverter and a working transformer?

Not possible with the way mpp and others do this at the moment unless you want to by four units.

This is what I'm addressing, your comment is claiming that using 2 of the LV6548/EG4 inverters in split phase operation where one inverter goes down, there would not be any power. This isn't true, the settings can be changed in the functioning inverter and 120V would be available in half the panel.

Most of this safety concern came about due to auto transformers being used from what I'm reading not isolation transformers that seem to be the safe way to accomplish this if one desires. The main issue was loosing the auto transformer and as such the neutral but then having the ground loop from the grid present itself.

If the neutral goes open, you will feed 240V out on the 120V circuits; I guess some people like new appliances........

 

[realpinochet]

This is what I'm addressing, your comment is claiming that using 2 of the LV6548/EG4 inverters in split phase operation where one inverter goes down, there would not be any power. This isn't true, the settings can be changed in the functioning inverter and 120V would be available in half the panel.


If the neutral goes open, you will feed 240V out on the 120V circuits; I guess some people like new appliances........

No, I was not saying mpp or eg4 which is why I specifically stated a 240V native unit like the popular growatt. And, yes mpp does have single phase 240V European units. With a isolation transformer and the transformer is lost / neutral lost there's no circuit to complete...where is the 240 coming from? There's nothing to complete the circuit. I believe that was the main concern about the grid neutral getting bonded with a auto transformer.

 

[Quattrohead]

the transformer is the weak point

Actually the transformer is the most reliable part of the system, it just causes the most problems IF it fails.
There is a simple way to mitigate the problem but most seem to not understand it, so I just gave up...not my shit that blows up.

 

[realpinochet]

Actually the transformer is the most reliable part of the system, it just causes the most problems IF it fails.
There is a simple way to mitigate the problem but most seem to not understand it, so I just gave up...not my shit that blows up.

Well, I agree with you 100% but...if it's lost you'd not have a working system. I'd just have two or a spare if cost feasible. It would seem the charger and inverter would be the weakest points.

 

[MajicDiver]

Your truck work with air?

:D

What i mean is that you can get a autotransformer for $372 at signature solar, if you are afraid to have a problem with it just buy 2 and make sure to connect the inverter where the autotransformer say you connect it, if the autotransformer fail and the breaker go down the inverter go down too, so no problem of missing neutral.

The SS auto transformer is only 5kW and no longer available- the one he got was 25 kVa and about same cost. 5 times bigger

 

[Pendrak]

The SS auto transformer is only 5kW and no longer available- the one he got was 25 kVa and about same cost. 5 times bigger

Where do you get a 25k isolated transformer soo cheap? that's a normal price or you get lucky? i want one.

What I mean is that for mere mortals is normal buy stuffs on the shops at normal price.

 

[Zwy]

No, I was not saying mpp or eg4 which is why I specifically stated a 240V native unit like the popular growatt.

This is what you posted,

Not possible with the way mpp and others do this at the moment unless you want to by four units.

Which was not correct. You were referring to split phase operation where pairs of inverters are used for split phase operation at that time and context.

And, yes mpp does have single phase 240V European units. With a isolation transformer and the transformer is lost / neutral lost there's no circuit to complete...where is the 240 coming from? There's nothing to complete the circuit. I believe that was the main concern about the grid neutral getting bonded with a auto transformer.

This is what you posted,

" The main issue was loosing the auto transformer and as such the neutral but then having the ground loop from the grid present itself."

If you lose the neutral on the autotransformer, it will send 240V on the 120V circuits. Now you say isolation transformer because you know you were incorrect.

As it seems you are being evasive once someone points out when you are incorrect, I will no longer continue the discussion. It becomes a waste of time.

 

[Pendrak]

This is what I'm addressing, your comment is claiming that using 2 of the LV6548/EG4 inverters in split phase operation where one inverter goes down, there would not be any power. This isn't true, the settings can be changed in the functioning inverter and 120V would be available in half the panel.


If the neutral goes open, you will feed 240V out on the 120V circuits; I guess some people like new appliances........

There is ways to connect the autotransformer that in the case of fail shut down the inverter at the same time.

Also if you are going to install a offgrid system, tell me if you are not going to BALANCE your connection on the electric board?? that's the basic stuff to do, if you have a good balance on your electric board in the case of a neutral fail nothing will happen, you will not get 240v on a 110v line.

The SS auto transformer is only 5kW and no longer available- the one he got was 25 kVa and about same cost. 5 times bigger,

Where i can get a 25k autotransformer at $400 ??, you get lucky getting one at that price, tell me where a mere mortal like me can get one at that price? is not a good example compare your 25k lucky purchase with other products.

There is availability right now of the autotransformers on Signature solar, not sure why you keep telling that is not longer available, i just buy another one for future expansion (right now I have a DIY battery with 16 cells LF 280k with a JK BMS from docan, Growatt 5000 ES and autotransformer.)

Growatt 5kW Split Phase Transformer | ATS 5000T-US

Signature Solar provides solar panels & components and full kits for off-grid, grid-tie and custom diy solar systems. Providing Solar 101 and hands on experience within the solar industry. Quality inverters, bifacial solar panels, complete solar kits, solar batteries. Holding best in class...

signaturesolar.com

By the way, if you connect the inverter and the autotransformer in the way that Growatt tell you, if there is any problem with the autotransformer (that's is a really weird case, they almost never fail) a breaker will trip, this is the same breaker of the inverter so, is almost impossible to have a problem with lost neutral.

 

[stienman]

Where do you get a 25k isolated transformer soo cheap? that's a normal price or you get lucky? i want one.

What I mean is that for mere mortals is normal buy stuffs on the shops at normal price.

You buy a used one. Transformers are widely available in the industrial power space, and for flexibility many have multiple taps allowing the input and output voltages to be changed as needed. You might get 440VAC three phase from the power company, and need to drive a 220VAC motor - pop a transformer in and you're done.

Generally you'll search for a kVA rating, not kW. Typical sizes available are 15kVA, 25kVA, 30kVA, 45kVA, and if you need much more than that you're going to need a forklift.

Further, they are generally 3 phase transformers, and most have taps for 120v. You can connect them for single phase usage, just be aware the efficiency drops, and you're only using 1/3 the transformer's material. You will have to either understand how to correctly connect it or get help, since the transformer diagram and manufacturer don't supply info on how to connect them for single phase usage.

But they are available used (ebay, craigslist) for $250 - $800, with shipping adding another $200. If you can pick one up locally, so much the better.

And they all hum the same tune.

 

[Pendrak]

You buy a used one. Transformers are widely available in the industrial power space, and for flexibility many have multiple taps allowing the input and output voltages to be changed as needed. You might get 440VAC three phase from the power company, and need to drive a 220VAC motor - pop a transformer in and you're done.

Generally you'll search for a kVA rating, not kW. Typical sizes available are 15kVA, 25kVA, 30kVA, 45kVA, and if you need much more than that you're going to need a forklift.

Further, they are generally 3 phase transformers, and most have taps for 120v. You can connect them for single phase usage, just be aware the efficiency drops, and you're only using 1/3 the transformer's material. You will have to either understand how to correctly connect it or get help, since the transformer diagram and manufacturer don't supply info on how to connect them for single phase usage.

But they are available used (ebay, craigslist) for $250 - $800, with shipping adding another $200. If you can pick one up locally, so much the better.

And they all hum the same tune.

I don't live on USA.

 

[stienman]

I don't live on USA.

They are widely used and available world-wide. The only countries where you might have a hard time finding a 3 phase 25kva transformer are those with little to no industrial sector in their economy.

But that doesn't mean they are easy to find and/or cheap, and I'm sorry if that's the case for your location.

 

[Pendrak]

They are widely used and available world-wide. The only countries where you might have a hard time finding a 3 phase 25kva transformer are those with little to no industrial sector in their economy.

But that doesn't mean they are easy to find and/or cheap, and I'm sorry if that's the case for your location.

I can find isolated transformer used on my country, one with 5kva cost $1000, for me a autotransformer new at $372 (i am including cost of the shipping, the autotransformer cost is $345) is heaven, and most people think the same, this is why people are buying then with the Growatt 5k, easy to install, easy to buy, etc.

 

[Struc]

If the neutral goes open, you will feed 240V out on the 120V circuits; I guess some people like new appliances........

What a drama queen...

This debate and bashing has been going on for well over a year now. Exactly how many transformers have you heard failed during that time?

I know far more stories from friends/family where they lost neutral from a branch falling on overhead power lines or similar. The risk is near zero.

Not to mention, with a few tweaks to the setup, damage from losing neutral is totally avoidable.

I'm also loving everyone's price comparison to the EG4, which has been around - how long?? A few months?? Give me a break. I've had my SPF5000's for over a year now before all these new lower cost 120v inverters came out. Regardless of that fact, knowing what I know today, I think I'd still lean toward the SPF5000.