Use Main Panel as Critical Loads Panel?

[Hedges]

It is important to disconnect L1 and L2 if auto-transformer is overloaded or overheated. Can't just protect autotransformer with its own breaker and let loads suffer lost neutral.

If you want a really big autotransformer, you can repurpose the primary windings of an isolation transformer. That could be sized for 100% of inverter output.

 

[zanydroid]

It is important to disconnect L1 and L2 if auto-transformer is overloaded or overheated. Can't just protect autotransformer with its own breaker and let loads suffer lost neutral.

If you want a really big autotransformer, you can repurpose the primary windings of an isolation transformer. That could be sized for 100% of inverter output.

The ATS-US unit here has L1/L2/N going through a ganged 3-pole breaker (presumably configured to common trip). Does this address your concern?

 

[lapsmith]

How much power does your pump use? Mine only uses 82w so to me it's inconsequential.

I do have 57kwh of battery though so there's that ?. (Cost about $7k)

Wow, mine uses 2kw but it has a very low duty cycle for normal household use.

How did you get such a large battery for so little? I got a 75kwh battery for $50k. But it came with a car.

 

[1201]

Wow, mine uses 2kw but it has a very low duty cycle for normal household use.

How did you get such a large battery for so little? I got a 75kwh battery for $50k. But it came with a car.

My aerobic septic has two pumps. The always on aerator pump uses 82w and the pump that goes to the spray heads uses 1kw but only for about 30 minutes a night.

I bought my batteries used like new lol.

David poz did a video on them and he had a 10% off code. It came to like $1280 per 14kwh before shipping and taxes. I should have ordered 10

I took advantage of that deal but didn't order enough
So I ordered another 8 of these

4 New EVE 3.2v 280ah LF280K V3 Lifepo4 Prismatic

You get 4 batteries, 4 2mm copper 250a busbars, and 8 nuts for this price. They are actual grade A EVE 3.2v 280ah cells that are testing around 315ah on average. This is Version 3 model LF280K. 8,000 cycle rated. Click HERE to download the testing data. QR codes are not scratched off. The file...

batteryhookup.com

With two $110 jk bms and a wooden box I'm good to go.

My system is here

I did a thing! Sunny Island, growatt min ac coupled system

hi guys, I finally got my system set up after 1 SOLID year of researching solar PV here there and everywhere and 5 years of solar home building research and planning. I built my passive solar house with pv in mind. No penetrations on the south side. The optimizer said 32° roof angle facing 4...

diysolarforum.com

 

[lapsmith]

It is important to disconnect L1 and L2 if auto-transformer is overloaded or overheated. Can't just protect autotransformer with its own breaker and let loads suffer lost neutral.

If you want a really big autotransformer, you can repurpose the primary windings of an isolation transformer. That could be sized for 100% of inverter output.

OK, they're also the same weight.

I swear there was a bigger, more expensive Growatt AT you could buy. Maybe not in the ATS-US line, or it was a different Chinese inverter company.

I guess another way to do this is to buy any random ATS (even one off Amazon) and buy the Autotransformer separately.

Actually, I don't want an ATS. I want to do the switchover manually so I can manage the critical loads myself.

I'll take a look at the videos but from what I gather, Growatt took all the ATS functionality and the breaker out of the ATS US. At least thats what one youtube video showed...just a transformed and terminal block inside. I'm on my phone so can't post a link now. Will do it tomorrow as well as properly reply to all of the other comments.

 

[lapsmith]

My aerobic septic has two pumps. The always on aerator pump uses 82w and the pump that goes to the spray heads uses 1kw but only for about 30 minutes a night.

I bought my batteries used like new lol.

David poz did a video on them and he had a 10% off code. It came to like $1280 per 14kwh before shipping and taxes. I should have ordered 10

I took advantage of that deal but didn't order enough
So I ordered another 32 of these

4 New EVE 3.2v 280ah LF280K V3 Lifepo4 Prismatic

You get 4 batteries, 4 2mm copper 250a busbars, and 8 nuts for this price. They are actual grade A EVE 3.2v 280ah cells that are testing around 315ah on average. This is Version 3 model LF280K. 8,000 cycle rated. Click HERE to download the testing data. QR codes are not scratched off. The file...

batteryhookup.com

With two $110 jk bms and a wooden box I'm good to go.

My system is here

I did a thing! Sunny Island, growatt min ac coupled system

hi guys, I finally got my system set up after 1 SOLID year of researching solar PV here there and everywhere and 5 years of solar home building research and planning. I built my passive solar house with pv in mind. No penetrations on the south side. The optimizer said 32° roof angle facing 4...

diysolarforum.com

Oops, I was referring to the other pump, the one inside the well. My bad.. Yes, my aerobic also uses about 70 watts continuous. Not sure about the spray head pump, but I'm sure it is similar.

 

[Hedges]

The ATS-US unit here has L1/L2/N going through a ganged 3-pole breaker (presumably configured to common trip). Does this address your concern?

Yes.

I guess another way to do this is to buy any random ATS (even one off Amazon) and buy the Autotransformer separately.

This wouldn't, unless you make ATS and AT work together that way.

 

[Hedges]

Actually, I don't want an ATS. I want to do the switchover manually so I can manage the critical loads myself.

I'll take a look at the videos but from what I gather, Growatt took all the ATS functionality and the breaker out of the ATS US. At least thats what one youtube video showed...just a transformed and terminal block inside. I'm on my phone so can't post a link now. Will do it tomorrow as well as properly reply to all of the other comments.

You just need to make sure you don't overheat the transformer. And if it is disconnected (e.g. by breaker or thermostat) you have to avoid lost neutral to 120v loads.

 

[zanydroid]

I'll take a look at the videos but from what I gather, Growatt took all the ATS functionality and the breaker out of the ATS US. At least thats what one youtube video showed...just a transformed and terminal block inside. I'm on my phone so can't post a link now. Will do it tomorrow as well as properly reply to all of the other comments.

I found three different versions of ATS from Growatt when I was digging around, two with ATS contactors (the 5KVA and 10KVA) + OCPD, and one with terminal blocks.

The only version that makes sense with the wiring diagrams and slide decks Growatt provides, is the two with ATS contactors and OCPD in it.

Actually, I don't want an ATS. I want to do the switchover manually so I can manage the critical loads myself.

OK. You can do a manual transfer off any critical loads output with an appropriate transfer switch or interlocked panel.

And if you want to do it this way and prefer the Victron Autotransformer you can buy that. It would wire in between the 240V critical load output (Growatt calls it EPS) and the 120/240 panel. To prevent burning extra power with the AT being energized and taking some balancing work from the utility transformer / fighting the transformer, you can keep the 3P breaker off until you need the emergency power. Then flip the 3P breaker in the Victron and the transfer switch to the emergency power position.

This wouldn't, unless you make ATS and AT work together that way.

There is no communications line between the inverter and the ATS box in Growatt's manuals, and it looked to me like the ATS is swapped on detecting power loss by the way the contactors are wired up. So you can just copy the way Growatt wired them.

 

[lapsmith]

Probably a good idea to make a sketch and a new thread asking for feedback specifically for the sketch, once you're at that point.

Thanks for posting the sketch. Yes, once I have my design more complete, I will post another thread.

This video includes the rules for equipment disconnects

Interesting that the disconnect must be in sight of the equipment, whereas my utility says it must be readily accessible to their personnel. Hard to do both if the inverter is inside.

Not sure. Which video? Ideally someone would have a closeup shot of what all is on the DIN rail, and from there we can figure out WTF is going on with its logic.

This is the video

And here is a screenshot showing just the xformer.

Is 5kVA enough for you? I think Growatt has a bigger ATS-US as well, 10kVA?

Yes, plenty. I've seen that they do list a 10kva unit, but I've never seen one at any of the typical vendors on line.

Have you seen this PDF with close up pictures of the wiring places?

No, I haven't seen it. Thanks, it is one of the better documents I've seen from them.

 

[Hedges]

Yes, plenty. I've seen that they do list a 10kva unit, but I've never seen one at any of the typical vendors on line.

Is 3kVA (imbalance between L1 and L2) enough?
Because that is all it supports.
Beyond that, transformer would likely overheat, and you need to protect it.

 

[lapsmith]

The way it integrates with Victron equipment is different. It's intended to sit on the 240V output of an inverter. There is no grid connection directly to the Victron AT.

This would be fine with me as I don't want or need the automatic transfer capability. But since there are several versions of the Growatt AT-US, I wonder which one Signature Solar is selling. Price is actually $300 for the 5kw model.

 

[lapsmith]

"Rated unbalanced power(L-N) 3000W"

That is also okay with me as I don't have many loads and can rearrange legs during the installation if necessary.

 

[lapsmith]

I swear there was a bigger, more expensive Growatt AT you could buy.

There is. In fact it is listed here https://signaturesolar.com/growatt-11-4k-split-phase-transformer-ats-11400t-us/ for $500

 

[lapsmith]

You just need to make sure you don't overheat the transformer. And if it is disconnected (e.g. by breaker or thermostat) you have to avoid lost neutral to 120v loads.

Yes, same as if you were using a generator, but I guess the generator would just stall out or the breaker trip if you tried to overload it. I will probably do the same with the output of the transformer if the version that is available doesn't already have a breaker. I would add a 3P breaker.

 

[lapsmith]

OK. You can do a manual transfer off any critical loads output with an appropriate transfer switch or interlocked panel.

And if you want to do it this way and prefer the Victron Autotransformer you can buy that. It would wire in between the 240V critical load output (Growatt calls it EPS) and the 120/240 panel. To prevent burning extra power with the AT being energized and taking some balancing work from the utility transformer / fighting the transformer, you can keep the 3P breaker off until you need the emergency power. Then flip the 3P breaker in the Victron and the transfer switch to the emergency power position.

I will have both, a changeover switch and an interlocked panel. Something like this: https://www.amazon.com/dp/B09994XMD...GAT7V4SM&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

Someone posted that the Growatt ATS-US uses about 30 watts if I'm not mistaken (on battery power no loads).

 

[Hedges]

There is. In fact it is listed here https://signaturesolar.com/growatt-11-4k-split-phase-transformer-ats-11400t-us/ for $500

Smaller.

" The rated power of secondary side L1-N and L2-N could up to 5kVA respectively, and the power difference between the two split phases can not exceed 1.5kW."

I will probably do the same with the output of the transformer if the version that is available doesn't already have a breaker. I would add a 3P breaker.

That is the key - if transformer is overloaded, need to disconnect both L1 and L2 so loads don't suffer lost neutral.
That could be accomplished with various ganged schemes, but the trick is to allow higher current to L1 and L2 so 240V or balanced 120V loads can be powered. Then shut those off it AT carries too much current, or optionally overheats, using thermostat.

Lower amperage breaker on Neutral of AT tripping higher amperage breaker L1 & L2 would be one way. Maybe not kosher to actually interrupt neutral to loads. How neutral wires to grid is one question. Breaker feeding either L1 or L2 of transformer, tripping large L1 and L2 feeding loads from inverter might work.

I think Victron does it with temperature sensor and maybe neutral current sensor.

It isn't trivial to engineer correctly.

 

[lapsmith]

I believe the panel here needs to be unbonded already, so the green screw is probably not all the way in.

Should I post this in another thread?
I checked at the meter where the 400 amp disconnect is and the neutral is bonded to ground and there is a ground rod there. They did not run a ground to the house 300 feet away. The panel at the house has the green screw bonded to neutral as well with another ground rod. Isn't this a no-no and if so, what do I do? There is no way to run a separate ground line to the house, without major expense.

 

[Hedges]

That would seem improper. Except, when multiple customers are fed from single transformer, they each receive L1/L2/N and have their own ground rod. No different it would seem from yours. Have another disconnect at the house? just don't let that combined N/G wire ever get disconnected, or earthworms will complain, and you might too (if touching grounded chassis while standing on the ground.)

The question is semi-related to now derived neutral of auto-transformer is used.

 

[lapsmith]

Have another disconnect at the house?

No other disconnect unfortunately. How would that help?

Yeah, I do want to be kind to the earthworms. Snakes not so much.