Safe Grid Use of the 5000ES and transformer

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
10,681
Sunny Boy Storage Automatic Backup Unit similarly has to deal with a 240V floating battery inverter and separate auto-transformer.
On page 12, Q1 isolates L1, L2 from grid and Q5 connects autotransformer.
Ground and Neutral continuity are maintained everywhere.


(Sunny Boy Storage sees neutral, but just for monitoring voltages, can't drive L1/L2 relative to it, only relative to each other.)
 
Last edited:

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
10,681
In Scenario #2, consider no gas line completing the circuit. Ground of circuits powered by GroWatt sit at 12V. Ground rod pulls nearby dirt to same voltage, but at utility entrance earth is at zero volts. You fill your tub, settle in for a nice warm bath (well grounded to earth by waste pipe.) You decide to add some more water, so you reach up and grab the hot water faucet with a soaking wet hand. (Above 30 mA, you can't let go. 12V/30mA = 400 ohms. What is the body's resistance with wet skin?)


... goes to Signature Solar!
 

HighTechLab

Small Business Owner
Joined
Sep 23, 2019
Messages
621
The off-grid system represents a separate system here, like a Generator and an off grid system.
All grounds are combined on each system

See the storedge guide here, maybe we can accept that they got permitting all over the USA


View attachment 80690
I did some more digging onto the original application of the Autotransformer. I am fairly certain you should be referencing this diagram below. Solaredge references their intended use of the autotransformer for phase balancing, NOT deriving a neutral. The Neutral/ground bond from the source feed is kept intact, their inverter circuit has neutral reference, unlike the Growatt. So you are correct, their systems ARE safe and permitted across the country, but they are doing this in a MUCH safer manner with equipment designed for the application. 1642872028818.png
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
10,681
I did some more digging onto the original application of the Autotransformer. I am fairly certain you should be referencing this diagram below. Solaredge references their intended use of the autotransformer for phase balancing, NOT deriving a neutral. The Neutral/ground bond from the source feed is kept intact, their inverter circuit has neutral reference, unlike the Growatt. So you are correct, their systems ARE safe and permitted across the country, but they are doing this in a MUCH safer manner with equipment designed for the application.

Solar Edge schematic shows "Automatic Switchover", "NC" contacts to grid, "NO" contacts to autotransformer.
Never the twain shall meet.

Perhaps it does derive a neutral, or just performs balancing. That depends on what StorEdge outputs.

Hope the "Automatic Switchover" is disabled when "Manual Bypass" is enabled.
 

HighTechLab

Small Business Owner
Joined
Sep 23, 2019
Messages
621
Solar Edge schematic shows "Automatic Switchover", "NC" contacts to grid, "NO" contacts to autotransformer.
Never the twain shall meet.

Perhaps it does derive a neutral, or just performs balancing. That depends on what StorEdge outputs.
Perhaps you are right we can give it the benefit of the doubt. It doesn't magically solve the Growatt issue, because the devil is in the details.

I think we can learn from NEC 450.5; while this article is specifically written for 3 phase systems, the safety aspects DO apply to our single phase system and the diagram provided in the OP has suggestions that don't particularly jive with the NEC and was the reason of concern for my first post in this thread; if the overcurrent protection circuit breaker for the autotransformer is tripped or manually shut off, the neutral is lost.

450.5(A)(1) states that in a 3 phase 4 wire system, that there should NOT be anything between the ungrounded phase conductors and the autotransformer. The same safety issue would occur in a 3 phase system as would a single phase system. A homeowner turning off this breaker accidentally, thinking it went to some other equipment, would start frying stuff in the home due to a lost neutral. In my opinion this is very dangerous and gives me a bad feeling when they included a disclaimer in their diagram.

450.5(A)(2) states that if using this autotransformer as a grounding autotransformer, "an overcurrent sensing device shall be provided". This is NOT a circuit breaker, because a circuit breaker would violate 450.5(A)(1). It needs to SENSE the autotransformer current and then trip the MAIN breaker.

Here is the code language, perhaps I am misinterpreting?

1642872852601.png1642872827845.png
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
10,681
Appears the code (and reasoning) calls for autotransformer to be hardwired to a sub-panel without OCP between them,
and OCP feeding the panel (and therefore autotransformer) should be rated such that transformer can handle full current.

That takes care of loss of phase.

Having a separate 240V-only panel for higher wattage loads and OCP feeding lower amperage split-phase 120/240V panel with autotransformer could be good for newly wired applications.


Using autotransformer in parallel with grid has the issue that it will try to balance grid, which could be so much current as to trip OCP.
Both StorEdge and Sunny Boy Storage applications address that by disconnecting L1/L2 from autotransformer when grid is connected.
(Exactly what happens during the instant of switchover is left as a detail that sensitive devices such as MOV may protest.)


GroWatt could attempt switching of Autotransformer, but I don't think it has enough connections or relay poles to readily bolt on such connections.
For an inverter configuration that generates both 120V phases, autotransformer might help balance phases, and could connect after a delay within their surge capability.

Isolation transformers could be a KISS solution for GroWatt. How many isolation transformers depends on whether "Neutral" terminal and ground are actually well isolated.
 

Cornwallav8r

Solar Enthusiast
Joined
Nov 24, 2021
Messages
65
Driving an 8' ground rod is no big deal, a normal part of some electrical work. I did that when doing a permitted and inspected install of a couple 2500W grid-tie inverters years ago.

Yes, isolation transformer with 120/240V split-phase output would work. I think center tap could either have its own ground rod, isolated from house, or use house's ground system. Or an additional rod and tie to house's ground. Whichever ground was used for the neutral (center tap) bond would also be ground for downstream circuits.

Isolation transformer means no galvanic connection to grid power, and no ground currents produced (except caused by capacitive coupling, typically a few mA.)

I think 240V inverter (across L1/L2) with an autotransformer could be used safely with centertap (which creates neutral) tied in to neutral of house, and ground tied in to ground of the house. What one needs to ensure is that autotransformer doesn't overheat, and if it is disconnected by a breaker, the loads must be disconnected too. (Don't want single-phase loads getting power from L1 or L2 to rely on N when N is no longer defined by the transformer.)
Yes, you have those 2 ground rod options, but it's been my experience it's never a good idea to have separate location isolated ground rods. There will always be some ground current between them, and associated noise possibly affecting electronics. I'd just extend the house ground rod conductor. Don't forget, we're now supposed to drive 2 ground rods at least 6 feet apart (unless you want to test the ground for (I think it is) 25 ohms or less. Most people just drive another one and extend the #6 copper conductor between.
 
Last edited:

Cornwallav8r

Solar Enthusiast
Joined
Nov 24, 2021
Messages
65
Perhaps you are right we can give it the benefit of the doubt. It doesn't magically solve the Growatt issue, because the devil is in the details.

I think we can learn from NEC 450.5; while this article is specifically written for 3 phase systems, the safety aspects DO apply to our single phase system and the diagram provided in the OP has suggestions that don't particularly jive with the NEC and was the reason of concern for my first post in this thread; if the overcurrent protection circuit breaker for the autotransformer is tripped or manually shut off, the neutral is lost.

450.5(A)(1) states that in a 3 phase 4 wire system, that there should NOT be anything between the ungrounded phase conductors and the autotransformer. The same safety issue would occur in a 3 phase system as would a single phase system. A homeowner turning off this breaker accidentally, thinking it went to some other equipment, would start frying stuff in the home due to a lost neutral. In my opinion this is very dangerous and gives me a bad feeling when they included a disclaimer in their diagram.

450.5(A)(2) states that if using this autotransformer as a grounding autotransformer, "an overcurrent sensing device shall be provided". This is NOT a circuit breaker, because a circuit breaker would violate 450.5(A)(1). It needs to SENSE the autotransformer current and then trip the MAIN breaker.

Here is the code language, perhaps I am misinterpreting?

View attachment 80790View attachment 80789
I'd disagree with your first statement. It's been my experience in reading code as a PE (34 years, for what that's worth) that the exact wording is critical, and intended. If they meant it to be for single phase systems, they'd have stated exactly that. It's like saying that certain fire alarm notifications appliances are required in a high rise, so it probably affects other multi-story buildings similarly. Not that your premise is necessarily wrong on its face, we run into this sort of stuff all the time, especially when you're reading past a particular code section's paragraphs into the next section and think you're still in the same section and inapplicable requirements are indicated.
 
Last edited:

Cornwallav8r

Solar Enthusiast
Joined
Nov 24, 2021
Messages
65
Perhaps you are right we can give it the benefit of the doubt. It doesn't magically solve the Growatt issue, because the devil is in the details.

I think we can learn from NEC 450.5; while this article is specifically written for 3 phase systems, the safety aspects DO apply to our single phase system and the diagram provided in the OP has suggestions that don't particularly jive with the NEC and was the reason of concern for my first post in this thread; if the overcurrent protection circuit breaker for the autotransformer is tripped or manually shut off, the neutral is lost.

450.5(A)(1) states that in a 3 phase 4 wire system, that there should NOT be anything between the ungrounded phase conductors and the autotransformer. The same safety issue would occur in a 3 phase system as would a single phase system. A homeowner turning off this breaker accidentally, thinking it went to some other equipment, would start frying stuff in the home due to a lost neutral. In my opinion this is very dangerous and gives me a bad feeling when they included a disclaimer in their diagram.

450.5(A)(2) states that if using this autotransformer as a grounding autotransformer, "an overcurrent sensing device shall be provided". This is NOT a circuit breaker, because a circuit breaker would violate 450.5(A)(1). It needs to SENSE the autotransformer current and then trip the MAIN breaker.

Here is the code language, perhaps I am misinterpreting?

View attachment 80790View attachment 80789
The above is 3 phase only. Inapplicable to our situation. I mean, they specifically define what a "grounding autotransformer" is. And it isn't single phase by their own definition. You have to read the code without inferring other things. It is what it is, and is limited to what they state, for very good reason.
 

Cornwallav8r

Solar Enthusiast
Joined
Nov 24, 2021
Messages
65
We drive ground rods because we are electrical engineers who give a crap, Joe blow turning all green to save the earth on the cheap ain't going to. Nor the guy living on rock ledge lol.
Single phase loads will not get power and be subject to possible loss of neutral and hence unbalanced 120v legs that will blow them up if the circuit breaker kills the voltage to the primary of the transformer.
No different than the cause that got me into this full PV inverter replacement in the first place. Utility opened its neutral upstream twice the past 2 years. We had over 310v at the house, and 155v at the receptacles for like 4 hours. Blew out a ton of stuff, including 24 total Enphase microinverters. Which is why I am isolating now with an off grid setup (financed by insurance payout) that won't exacerbate the issue when it (naturally due to large production) raises the local voltage by another 10v or so in addition when pushing back onto the grid. We lost our central air motor, an air compressor, 10 led lights, the hot tub pump, 24 inverters, the entire control system for the 2-axis PV array trackers, and a few other things. The utility told us each time to pound sand. I should have pursued it with the PUC, but my homeowner's covered the entire loss. I do these type investigations in my sideline forensics work for (4) forensics companies as well. So basically, I'm trading one open neutral risk for another :)
 
Last edited:

Tony Scott

Solar Enthusiast
Joined
Feb 25, 2020
Messages
184
What a cluster f , All this rigging ( ground this, no that, bond this, no bond that) to save a few dollars or make a few dollars. Just buy the products made for our US market and be safe. Or someone will be sorry in the future, I hope it is not you.
The problem is no one knew these were not designed for U.S.
 

Ozark Tinkering

Solar Addict
Joined
Dec 23, 2021
Messages
571
I'd disagree with your first statement. It's been my experience in reading code as a PE (34 years, for what that's worth) that the exact wording is critical, and intended. If they meant it to be for single phase systems, they'd have stated exactly that. It's like saying that certain fire alarm notifications appliances are required in a high rise, so it probably affects other multi-story buildings similarly. Not that your premise is necessarily wrong on its face, we run into this sort of stuff all the time, especially when you're reading past a particular code section's paragraphs into the next section and think you're still in the same section and inapplicable requirements are indicated.
As a retired journeyman who sat for the exam in California (scored 97) as well as the master exam in Arkansas (reciprocated with 13 other states and scored 93) I completely agree with your statement "that the exact wording is critical and intended".

Art. 90.2
(C) Intention. The Code is intended to be used by those skilled and knowledgeable in electrical theory, electrical systems, construction, and the installation and operation of electrical equipment. It isn’t a design specification standard or instruction manual for the untrained and unqualified.
 

Tony Scott

Solar Enthusiast
Joined
Feb 25, 2020
Messages
184
eabyrd:

It seems you are correct. I don't see why there is so much resistance to the idea of a separate loads panel. They are easy to buy, install, etc. But the bigger issue is that this industry (like many others) is relying on influencers to promote their product, and sell them. Those people are being paid in many ways, such as free samples, discounts, affiliate fees based on links, etc.

No one has any means to verify what the background is of the person contributing. Many just follow online advice blindly, and the results may or may not be positive. It may not even be remotely legal. There are a lot of very intelligent, well-meaning people who contribute comments too. How does an average person decide how to proceed?

To my way of thinking, this is on the manufacturers. Why doesn't (for example) Victron get their equipment UL certified. Or Growatt, who sells huge numbers of this equipment here in the US. The excuse that it tedious and expensive is crap. I spent my career going around the world installing equipment that had to be certified for use at its point of installation. Canada, Asia, US, wherever. It requires employees, training, expenses.

But instead, we are discussing modifying a non-certified Growatt, to install and use in the US, with an auto-transformer that might not be certified.

I guess you get what you pay for. Right? I'm still upset that the company who told me my Victron inverter was UL certified were wrong, and I can't send it back and apply the money towards an Outback, SMA, or some other unit that is certified for installation according to US codes. So I won't be buying a Growatt, or anything similar.

All that being said, the last post by Hedges where he comes up with the bath tub scenario...I can actually envision that happening.
The U.S government doesn't require UL certified on all products, I think is the problem. I am surprised Victron is not, seeing as the price they charge for equipment makes people run the other way. So, how can this problem be fixed? I am having a separate loads panel installed and I have two transformers.
 
Last edited:

Tony Scott

Solar Enthusiast
Joined
Feb 25, 2020
Messages
184
Sunny Boy/Sunny Island is a great system.
It has high starting surge for motors, and AC coupling is particularly good for AC loads during the day (e.g. running air conditioner)
Component ratings were optimized for European market, where one 6kW SI and two 6kW SB would work well backfeeding grid.
Here in the US, two 6kW SI and two 6kW SB for on grid, but if strictly off-grid it could handle four 6kW SB. The extra two could be used in a grid-backup system if manually (slowly) switched from direct grid tie to output of Sunny Island.

For now, it is the Sunny Island 6048-US model offered here. That is to be installed indoors (because front panel has openings), and I don't think there are features for peak shaving or backfeeding grid from battery with power stored from earlier.
I would imagine that the European models like 8.0 come to the US eventually, probably have those features and UL-1741-SA listing as well as being sealed for outdoor use.

Plan and price out whatever system you imagine installing eventually (including battery). There are various limits on wattage of inverter, battery charging, pass-through from grid. Depending on the price-point and performance you want, a hybrid of a different brand might fit better.
At $4700 for 5700 watts the price wkuld severely limit people getting into solar. SOL-ARK 12k is a nice option but that price make it difficult to recoup the investment unless you are young, damm



 

Tony Scott

Solar Enthusiast
Joined
Feb 25, 2020
Messages
184
As a retired journeyman who sat for the exam in California (scored 97) as well as the master exam in Arkansas (reciprocated with 13 other states and scored 93) I completely agree with your statement "that the exact wording is critical and intended".

Art. 90.2
(C) Intention. The Code is intended to be used by those skilled and knowledgeable in electrical theory, electrical systems, construction, and the installation and operation of electrical equipment. It isn’t a design specification standard or instruction manual for the untrained and unqualified.
Your rignt about that, which is why I knew I needed an electrician when I watched Mike Holt on YouTube. 👍👍👍👍
 

Cornwallav8r

Solar Enthusiast
Joined
Nov 24, 2021
Messages
65
The U.S government doesn't require UL certified on all products, I think is the problem. I am surprised Victron is not, seeing as the price they charge for equipment makes people run the other way. So, how can this problem be fixed? I am having a separate loads panel installed and I have two transformers.
I wouldn't be too worried about the UL certification, hell half the stuff coming from China has a fake UL sticker on it. Lie, cheat and steal, is China's big deal. I just made that up. Just wire it with a transfer switch, isolating the neutrals. And maintain only one neutral ground bond. Has nothing to do with UL.
 

Ozark Tinkering

Solar Addict
Joined
Dec 23, 2021
Messages
571
This conversation has me also wondering a couple of other things about these non-UL devices...

1. Would that disqualify insurance claims due to fire caused by equipment not UL listed?
2. Would it disqualify you from claiming an energy tax credit if the equipment wasn't UL listed?

This stuff actually matters to me.
 

Tony Scott

Solar Enthusiast
Joined
Feb 25, 2020
Messages
184
This conversation has me also wondering a couple of other things about these non-UL devices...

1. Would that disqualify insurance claims due to fire caused by equipment not UL listed?
2. Would it disqualify you from claiming an energy tax credit if the equipment wasn't UL listed?

This stuff actually matters to me.
The government does not ask about UL for the tax credit. As far as the insurance company goes I don't know.
 

Cheap 4-life

Wanting SolArk/Lifepo4 batteries but I’m CHEAP
Joined
Jan 20, 2021
Messages
411
Location
TN USA
The problem is no one knew these were not designed for U.S.
Some simple beginner research would inform anyone that 240v single phase inverters should not be used with splitphase. Making them work is a hack with an auto transformer. I would spend a few extra hundred and get the inverter that outputs 120v or splitphase..
 
Top