Solar house generator I started DIY back in 2000 - My path from Trace to Xantrex (on FLA battery) to XW Pro inverters on Tesla Model S batteries

Have been playing with a drawing tool called drawio

Created the following diagram for the AC side of my system

"120V Inverter Output"

Do you convert that to 120/240V split phase?
Issues with delivering just 120V to a split-phase panel, must be dealt with appropriately to avoid brown-out to some devices, or overloading shared neutral white wire of some circuits.

Your "special transfer switch" is shown with more than the usual 2 inputs, 1 output. Is inverter able to sit between grid and load panel, acting as a UPS?

I run only 120v circuits on my critical loads panel, no 240v since I only have a 120v inverter at the moment

my critical service panel, 200 amp Square D, has 120v on both sides of the panel and follow a protocol to only install 120v circuits
(this will change when I upgrade to the 240v inverter)

my only 240v loads in the house are the range and un-used electric dryer socket.
these circuits are in the original grid service panel
Only the range is powered and runs only on grid all the time

below are pics of the Inverter Bypass switch I bought in the late 90s
Square D QO load panel. The builder of it in california, I don't think is in busy any longer

Primary critical loads panel on the right
on the left is the Inverter Bypass with an interlock toggle



Close up of the front panel



Interior pics, multiple to get pics of the wiring diagram inside

Hedges said:

"120V Inverter Output"

Do you convert that to 120/240V split phase?

Click to expand...

no, only 120v

Hedges said:

Issues with delivering just 120V to a split-phase panel, must be dealt with appropriately to avoid brown-out to some devices, or overloading shared neutral white wire of some circuits.

Click to expand...

120v only on service panel

Hedges said:

Your "special transfer switch" is shown with more than the usual 2 inputs, 1 output.

Click to expand...

Has 120v circuits

1) Grid Input - from L1 from original grid service panel
2) Grid Output - pass through to Inverter Grid Input to allow for invert bypass when batteries are below Cut off voltage

3) Switched Input 1 - from grid # 1 above
4) Switched Input 2 - from Inverter output

5) Output to Service Panel

Hedges said:

Is inverter able to sit between grid and load panel, acting as a UPS?

Click to expand...

Yes

OK, so you do have 120/240 split phase going through transfer switch to 200A panel as drawing shows, but it was loaded for compatibility with 120V inverter feeding both busbars.

Hedges said:

OK, so you do have 120/240 split phase going through transfer switch to 200A panel as drawing shows, but it was loaded for compatibility with 120V inverter feeding both busbars.

Click to expand...

well only 1 L1 leg 120v going to transfer switch - it what was available 22 years ago, still works today

when I get the 15kw 240v inverter, I won't be using that transfer switch at all.

I will document the next plan later

Nice to see you posting again Doug.

dougbert said:

Will, I love your energy of spirit and what you have done, researched and how you teach it is great. When I build things, I generate a build log of what, how , where, when, who, why questions and answers for that build so that I can have a diary of you will of what I did. This pattern I have used on rebuilding my trucks, one of which is shown in my avatar So I am sharing this log of my system (currently on my local computer) here so it can used for reference by myself and others: This was ALL DIY by myself I began my interest in solar power generation back in 1993 time frame when I came across an issue of the HomePower magazine. I subscribed and received all future issues til the last one that went out in November 2018. An archive of them is located at www.homepower.com At that time I could not buy solar equipment due to cash flow. BUT I could work on reducing my loads in my house. I counted 50 incandescent 60 watt light bulbs located throughout the house. One by one I replaced them all with 13 watt CFL bulbs ($20 each) - I stored the old bulbs so when we moved I would put them back - which I did and took all the CFL bulbs with me. I measured consumption via the electric meter for the months before and after I swapped out the bulbs: Power consumption went down 30% I learned of and bought a load meter for individual devices, but it was expensive $100+. Eventually I learned of the Kill-A-Watt for $25 and have used that ever since. With such metering devices I measured all the pluggable devices in the house. I insulated the refrigerator (floor coils) not side cooler and gained a reduction there. My first purchase was an 18 watt Chinese panel for $150, back in 1996 time frame. I also purchased a Trace 10amp charge controller for $120. - I still have this controller. We had an old 1 car garage that is really just a large shed, in which I setup this system. Starting car battery 18 watt panel 10amp charge controller wires switch and a single 12v light in the shed No other meters, just the above Of course I got the usually wife "What do you want to do?" questions and looks so I kept my mouth shut mostly. Then one night the grid went down and I was not home. My wife went looking for some kind of flashlight and one place she went looking was the shed. As she entered, she just flicked the light on and went looking............(wait for it)...............then she realized that the grid was down (I had taken the old grid light out) but she had lights! She finally saw the vision, er the Light. SOME FOUNDATION There are 4 major components in any power generating system: 1) Generation 2) Processing 3) Storage 4) Loads - or things that consume electricity - the WHY we like electricity

Click to expand...

I got interested in Solar from Richard Perez and his wife Karen.

I too was subscribed to the magazine.

It was fun reading all the articles.

It just wasn’t viable for current residential homes then.
Price per watt was about $5.

Jennifer said:

Nice to see you posting again Doug.

Click to expand...

I just bought module #11, it is waiting for its partner

I have been researching and designing for a new 240v inverter, but have been learning much on various threads and resources on this website
issues on common neutral and inverter bypass operations, along with N=G bonding

sticky issues

Hi Doug
Happy to report that I invested in a small (3) Tesla battery system.
Set up is only temporary while we are building our retirement home. So far works great and haven't had to turn on the genny for 3 weeks now.
System is 8x 320PV, Sigineer 24v 6000w tesla compatable inverter, Midnite DC panel and Midnite charge controller.
Have 3 to 8 guys working with me using 2 tablesaws, air compressor with up to 3 nail guns, chop saws and misc skill saws and Hilti drill.
Inverter has been able to keep up so super happy with the progress and no more dino fuel to build the house.
Fuel up here is CDN $1.98 L. for the low grade, over 4500 hrs on the genny......
Ordered 3 more batteries from the guy that you sent me the link to.
Thanks for posting and your help.

I finally kicked off Phase 3 with my system

After researching the new AIO units out there, I just ordered a Growatt 12kw LF inverter as my new inverter for doing 240v

My goals are:

1) Being able to "handle" the Low Voltage Disconnect of the Tesla batteries. Well, at least lower than other inverters. I have had my batteries LVD currently at 38.6 volts. The 12kw can do 40.0 volts. So I do lose 1.4 volts of capacity on the low end, but I accept that now

2) Be a single unit, not 2 (like the EG4 6.5k inverters), as I don't have space for it

3) be 12kw or greater

4) be cheaper than the Sigineer

5) have better digital monitoring

6) Have US based support - good reviews for Signature Solar

7) Be capable of supporting new tech batteries (like the EG4 and others)

So I am refactoring parts of my system now to support 240v, like pulling new L2 6 gauge wire from here to there, replacing the 120v transfer switch by putting in the 3 pole 240v Transfer switch, bumping upto 80 amp breakers and cleaning up things.

this will support my wife's range (I would have installed a gas range, but she hates gas ranges), and once installed will place the house at 100% stand alone operation, with the system having grid assist for charging on those days when the battery is depleted. Due to monsoon storms in August, I had 2 days where the LVD kicked in for a few hours. Before that, last December LVD events occurred about half of the month due some heavy snow storms. I only produced 51% of my power that month and had to buy the rest. Was glad it was available.

Beyond that, more solar panels to be add and more batteries modules added over time to reach the goal of not needing the grid at all.

My design pattern for my system started 22 years ago, and can be seen by physical layout it is today. If I started today my system would be simpler but due to invested 12 year old designs of the Schneider charge controllers, my system is bigger physically than newer tech would accomplish

Still tinkering and having fun with this productive interest and hobby. It is so rewarding to see just how far the solar tech has proceeded, along with the features we have today compared to 10 and 20 years ago. It's wonderful

PS, will need to consider selling the 5.5kw Xantrex inverter I got back in 2020, or save it. It is 2005 model and I got it due to the fact it could handle the lower LVD. Got it for $2000 then. I wish the Growatt was available then and I knew about, I should have gotten it then. I know people bought them in 2021

Wish the firmware for the Growatt 12kw could handle 38 volt LVD - then I would be truly in heaven. Well maybe

Spent the day re-factoring the AC wiring getting ready for 240v inverter



Here "was" the 120v transfer switch on the left and the solar critical sub panel setup to be run by the inverter. Jerryrig the feed line from inverter to panel for temporary service for a day or two.

lncoming grid is disconnected and about to be torn down and rebuilt



On the left is the 3 pole double throw transfer switch. Grid source from top, inverter source from bottom, Outgoing taps in the center feed the critical loads panel. Got this switch from ebay last year, just been waiting for this

Just screwed to the wall awaiting wires



Here is the incoming grid sub panel. Breaker on left will feed down to the transfer switch for sourcing grid AC, thereby by passing the inverter so it could be worked on

Middle breaker will feed out to the right and down to raceway and then into the inverter for inverter "AC IN"

right breaker is extra, not used at the moment, but filling in the front panel



Here on the left is partial wiring setup
I had to shut the power off to the house totally in order to properly set up the critical panel for temporary powering. Had to schedule with wife to shut things down, and when ready, she took a nap.

The inverter AC IN and AC OUT (hanging down) will be split apart from that bundle and AC IN (ground, L1 and new L2 to be put in and neutral) will be installed in the conduit leaving the grid panel on the right and down to the raceway then to the inverter

AC OUT (L1, new L2 and neutral) will come up from the raceway and enter the bottom of the transfer switch and be connected to the lower 3 taps. Ground from inverter to critical panel will NOT be installed, as a ground (following along side AC IN, to the raceway and then up to the critical panel) from grid panel to critical loads panel will be separately installed to prevent ground loops




There is an undocumented/unexplained operation on the N-G bonding during AC Grid Passthrough and the manufacturers do not explain nor document the issue.

Below are some links talking about this
I am switching neutral with the transfer switch, but neutral is IN COMMON on this 120v only inverter (2 white neutrals in the bundle)

For new 240v inverter, this setup will allow me to:

either setup for
Switching neutral
OR configure for a COMMON neutral with relative ease

Researching the issue in the following thread


Another thread talking about this issue


another thread


FilterGuy made a great post here

here is a great PDF the FilterGuy made and uploaded.
"This document shows diagrams for proper grounding and bonding of either the MPP LV6548 or the EG4 6500EX-48 for several common scenarios."


Growatt confirms the following transformer model:

Another incredible write up, thanks Doug, you should put all this into a book or e-book and sell it, great information . So you like the numbers on this with the Tesla’s I assume. Great research re the bonding issue… well done

Thanks jennifer for the kind words

I just discovered an issue last night

background

the 2 inverters I have had, the Trace and now the Xantrex have a Low Voltage Disconnect program register one can set, to determine at which voltage the inverter will cause the inverter to stop invertering and disconnect from the battery. This can go as low as 36.0 voltage. This prevents draining the battery completely.

Well these 2 inverters do the disconnect AND one more action, they implicitly switch to grid power to power the loads. I have my current one set to power the loads while the solar charges the battery. I do not use the charger to charge the battery

WELL....

after reading the Growatt manual for the 100th time, it finally sinks in.
Their LVD voltage can be set as low as 40.0 as I mentioned in the prior post.

BUT....

it is NOT then that the utility grid is switched to. Doh!

When "Program 01" register is set to SBU (Solar - Battery - Utility mode), the inverter will switch to utility quote:

Solar energy provides power to the loads as first priority.
If solar energy is not sufficient to power all connected loads,
battery energy will supply power to the loads at the same time.
Utility provides power to the loads only when battery voltage
drops to either low-level warning voltage or the setting point in
program 12.

Program 12 reads:

Setting voltage point
back to utility source
when selecting “SBU
priority” or “Solar
first” in program 01

The values for program 12 are

48V model: default 46.0V, 44.0V~51.2V settable

Notice the lowest value is 44.0v - WHAT?

So when the battery reaches a low of 44.0 volts, the "utility" is switched to and I assume inverting from battery ceases - ugh!

Therefore,

normal voltage range is between 42.0v and up. Once voltage hits 42.0v utility is switch to and a warning event can be generated via dry contactor - IF there is utility connected. If there is no utility then the battery will continue to drain until LVD voltage is reached and inverting ceases and the house goes dark.

I missed this and when using tesla batteries could be a waste of tesla capacity.
Of course if the grid goes down anyway, the inverter will still work.

My options:

1) cancel the order
2) build the battery bank up until I reach my max of 110kwh, and add panels thereby avoiding the low voltage warning and the LVD event

So this inverter is like the others, in that they won't allow lower voltage state of charge

The dry contactor is meant to be used to start up a generator. I could use it to trigger a visible or audible alarm.
More to ponder.

Damn…. But good you caught it now, can you trip a normally open relay set (N/O to reduce drain on normal situations) to do an external cutover to grid at LVD?

Jennifer said:

Damn…. But good you caught it now, can you trip a normally open relay set (N/O to reduce drain on normal situations) to do an external cutover to grid at LVD?

Click to expand...

the dry contactor is used as a warning signal only, that battery has only 2 volts of storage left

Since the unit has not yet shipped I might be able to cancel it, but where do I go for a 240v inverter today? The Sigineer is $3600.

when it reaches LVD (some 36.x volts) it switches to grid it runs the loads AND it does a full charge to the battery. Not liking that after understanding what the other AIO units do (more features)

I reckon that’s the price we pay for gettin* the density at that price on those modules, we have to overbuy… or consider the sig an investment at 36

Canceled my order from Signature Solar for SPF 12000T DVM
delayed now to October

SS has 3 models of Growatt 12kw inverters

(1)
SPF 12000T DVM which is the model order I just canceled
(150v Vmax for the MPPT controller)
$1999 + $370 SH

(2)
SPF 12000T DVM MPV
(250v Vmax for the MPPT controller)
$2289 + $370 SH

(3)
SPF 12000T DVM-US MPV
(250v Vmax for the MPPT controller)
$2409 + $370 SH
has UL 1741 certification for US grid connect
but not in stock, might be new unit or in the supply line delays

If I get a Growatt, then the one with UL 1741 certification is the one I would want, it is $410 more
but has the cert and the higher PV voltage input

units 2 and 3 might be the same units, but with unit 3 having the cert UL1741
don't know

awaiting a sales callback with whom I can ask more questions

Inspite of canceling the order, I have gotten the 120v to 240v re-wiring almost complete. been wanting to do that for some time

Why they even bother with 150v pvmax is beyond me, i hit that so fast with just 3 or 4 panels…. I ended up getting a victron mppt RS 450/200. It has 4 totally independent solar charge controllers (trackers) (I’m only using 2 at present, 1 for a small 4 panel string on the roof of the RV, the other for. Large 7 panel string on a building roof), I love it….

I just stumbled across a local dealer for the Sigineer inverters

they carry:

12kw for $2,200
15kw for $2810
18kw for $4200

I called them and he will get back to me on:

1) does their product have the Tesla charging profile available on their Selection #9? I think due to jack they added that to their entire lineup a couple of years ago. Their ad line has:

Works With Lithium or Lead Acid Batteries​

2) does it have an internal N-G Bond switch? He gave me a verbal that it does have an ENABLE/DISABLE switch, but will follow up with an email
if it does, it will work as my 3 pole transfer switch disconnects the grid's neutral when the inverter is selected

The next great thing is, I can do a Will Call pickup and save the shipping. They are located some 50 miles from home

They are a dealer supporting Sigineer and that would be good for future support

If all the answers to my question are GOOD, then the 12kw version would match my needs perfectly as
it is in the ball park price of the Growatt's price, and a 12kw

(also, I think the Growatt 12k transformer IS using a Sigineer transformer, just has different control board and different interface features)

sure I would not have the digital monitoring etc, but would be able to utilize the entire battery capacity down to 38.0v LVD
when LVD occurs they switch off inverting and begins Grid charging of battery and support for the loads until the
battery is charged to 50.5 volts.

50.5 volts would work for me - my solar CC's are set to charge to 49.52, and solar does the bulk of the charging.
The grid charging would only occur infrequently, and less often as I add battery modules

I view the grid AS A BACKUP power source.

this just MIGHT work out