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Single inverter + Autotransformer vs Two inverters for split-phase

dapug

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May 17, 2022
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Which would handle more surge from pumps/motors? Two SPF 3000 LVM Growatts (120/240), or a single SPF 5000 ES Growatt with Autotransformer (120/240)?

Loads:
1 hp jet pump 120v 9.6A / 240v 4.5A (estimating 11kW surge)
1 fridge at 120v 1.7A

Panels: 1600W: 4x 400W 9.65A Imp, 50.1Voc (small setup for remote building)
Battery: Eg4 48v 100AH

I suppose I could stick with 120v only, but thought it would be wiser (efficiency?) to run that pump at 240v (but that still leaves me needing 120v for the fridge, hence question about split-phase).

The other factor I am battling is this is for a SMALL setup. 3-4x 400W panels (not maximizing perf/efficiency of the inverters/chargers). The issue here is minimum voltage, so the Growatt SPF 3000 LVM at 60v-115v input is going to be better with fewer panels than any of the more "modern" and "standard" 120v-250v operating input.

Here are some options I've been considering:
  • LVX6048. Pros: 120/240 on a single device, low freq, likely handle the surge. Cons: high idle draw, especially bad when not planning on full/max panel setup.
  • SPF 3000 LVM (2x). Pros: should handle surge, will operate with less panels or low sun (60v input). Cons: need 2 devices to get split 120/240, heck, still need 2 devices to handle surge even on just 120v.
  • SPF 5000 ES + Autotransformer. Pros: might handle surge (pushing it with a 10,000VA limit, maybe transformer will help??). Cons: needs autotransformer to get split 120/240 which also adds idle draw, more wiring/hardware.
  • LV6548 + Soft Start. Pros: LV6548 is awesome, future-proofing. Cons: only gets me 120v (not stacked), soft-start devices are not cheap, also not even sure what to get for that or whether it would work.
Geez. Too many options. I just want to simplify this. It's just an outbuilding! I'm leaning toward two SPF 3000 LVM namely for low 60v min input in this small scale setup (but perhaps its not as critical as I think?), but I cringe at doubling down on "old" tech, lack of future-proofing, etc.

I welcome any input.
 
The reviews that I have seen on YouTube, the Auto transformer is not the way to go if you haven't bought a controller yet. To my understanding is that these Auto transformers are not a true transformer is the since that it at a primary and secondary winds. Because of this, it is easy to get the transformer out of electrical balance and they get extremely hot.
I too am looking for a new controller that puts out both 120vac and 220vac. I do not what to by two 120vac controllers and put them in parallel just to get 220vac.
Growatts have a couple that I'm looking at and Will Powers likes the MPPT LV6048, but things the LV6548 is a better choice.
Besides Will Powers YouTube videos, you might want to watch some YouTube videos of David Poz with respect to controllers.
 
Which would handle more surge from pumps/motors? Two SPF 3000 LVM Growatts (120/240), or a single SPF 5000 ES Growatt with Autotransformer (120/240)?

Loads:
1 hp jet pump 120v 9.6A / 240v 4.5A (estimating 11kW surge)

I think you are estimating surge quite high, if the pump draws 1200w running.

Don't guess, measure.

It might draw upwards of 4000W on starting surge. That I might believe. It should be under 0.5ms https://nooutage.com/start.htm

1 fridge at 120v 1.7A

Panels: 1600W: 4x 400W 9.65A Imp, 50.1Voc (small setup for remote building)
Battery: Eg4 48v 100AH

I suppose I could stick with 120v only, but thought it would be wiser (efficiency?) to run that pump at 240v (but that still leaves me needing 120v for the fridge, hence question about split-phase).

The other factor I am battling is this is for a SMALL setup. 3-4x 400W panels (not maximizing perf/efficiency of the inverters/chargers). The issue here is minimum voltage, so the Growatt SPF 3000 LVM at 60v-115v input is going to be better with fewer panels than any of the more "modern" and "standard" 120v-250v operating input.

Here are some options I've been considering:
  • LVX6048. Pros: 120/240 on a single device, low freq, likely handle the surge. Cons: high idle draw, especially bad when not planning on full/max panel setup.
  • SPF 3000 LVM (2x). Pros: should handle surge, will operate with less panels or low sun (60v input). Cons: need 2 devices to get split 120/240, heck, still need 2 devices to handle surge even on just 120v.
  • SPF 5000 ES + Autotransformer. Pros: might handle surge (pushing it with a 10,000VA limit, maybe transformer will help??). Cons: needs autotransformer to get split 120/240 which also adds idle draw, more wiring/hardware.
  • LV6548 + Soft Start. Pros: LV6548 is awesome, future-proofing. Cons: only gets me 120v (not stacked), soft-start devices are not cheap, also not even sure what to get for that or whether it would work.
Geez. Too many options. I just want to simplify this. It's just an outbuilding! I'm leaning toward two SPF 3000 LVM namely for low 60v min input in this small scale setup (but perhaps its not as critical as I think?), but I cringe at doubling down on "old" tech, lack of future-proofing, etc.

I welcome any input.
Measure first, I think you can then make a better informed decision. I will say if you believe 2 SPF3000LVM's will handle the surge, the LV6548 most likely will but I'd still run 2 LV6548's.

I doubt the EG4 will handle the surge either. With a rated 100A discharge, you will only get 4800W.
 
The reviews that I have seen on YouTube, the Auto transformer is not the way to go if you haven't bought a controller yet. To my understanding is that these Auto transformers are not a true transformer is the since that it at a primary and secondary winds. Because of this, it is easy to get the transformer out of electrical balance and they get extremely hot.
... you might want to watch some YouTube videos of David Poz with respect to controllers.
Very insightful, thank you. This is exactly the kind of info I'm fishing for with this post. David Poz does like the Growatt + Autotransformer, but probably has a lot more time into fine tuning that most people probably shouldn't have to deal with.

I think you are estimating surge quite high, if the pump draws 1200w running.
Possibly. @sunshine_eggo hinted the same. I was basing it off a motor power chart I found here in the forums.
Measure first, I think you can then make a better informed decision. I will say if you believe 2 SPF3000LVM's will handle the surge, the LV6548 most likely will but I'd still run 2 LV6548's.

I doubt the EG4 will handle the surge either. With a rated 100A discharge, you will only get 4800W.
I'm looking at another option here. A 24v DC jet pump with a Victron MPPT charge controller and a panel or two, probably just sit on a couple 12v AGM for now. That should take care of that. And then I can still use my EG4 battery and whatever inverter I want for the fridge and any other 115v items. In which case, I too lean toward LV6548!
 
I can hardly believe how exactly my situation matches yours. The more you described, the more I thought, "Did I adopt and alter ego and write this in my sleep?" So what did you eventually decide?
 
I can hardly believe how exactly my situation matches yours. The more you described, the more I thought, "Did I adopt and alter ego and write this in my sleep?" So what did you eventually decide?
Ha! Awesome. Well, what I settled on was a 24v DC pump on a dedicated little setup with a couple of AGM batteries and Victron MPPT controller.

This decision was not because I could not get it to work with an AC setup, but rather, because the location of the pump in my homestead layout changed, and it didn't warrant running AC power out to it (so, a remote, self-contained dedicated system was better, regardless of power tech type).

If I had opted for AC on that pump, I think I would have run two EG4 inverters and a 240v pump. I've opted for EG4 over the Growatt, the LV6548, and the LVX6048 on my main AC system for the home. This is a fully off-grid homestead in the wilderness, no grid for miles. The main deciding factor was that EG4 has a 500v input limit (double that of LV6548), and I can therefore put more panels in series. I still like the LVX6048 a lot, but I just can't "afford" the constant power draw it takes, at least not for my particular scenario.
 
Ha! Awesome. Well, what I settled on was a 24v DC pump on a dedicated little setup with a couple of AGM batteries and Victron MPPT controller.

This decision was not because I could not get it to work with an AC setup, but rather, because the location of the pump in my homestead layout changed, and it didn't warrant running AC power out to it (so, a remote, self-contained dedicated system was better, regardless of power tech type).

If I had opted for AC on that pump, I think I would have run two EG4 inverters and a 240v pump. I've opted for EG4 over the Growatt, the LV6548, and the LVX6048 on my main AC system for the home. This is a fully off-grid homestead in the wilderness, no grid for miles. The main deciding factor was that EG4 has a 500v input limit (double that of LV6548), and I can therefore put more panels in series. I still like the LVX6048 a lot, but I just can't "afford" the constant power draw it takes, at least not for my particular scenario.
Slight difference in our setups. My well is about 50 feet from my solar shed, which is 20 feet from the cabin, so I'm trying to git'er all done with one product mix. I like the EG4 stuff but their PV voltage input range is too narrow for me. Next year, I'll have space for a good-size array, but right now I only have space for 3 panels.. So I need something with a low minimum PV input voltage but which will grow with me later. The LV6548 has a 90-250V range, so I'm eyeing that one very carefully. We're also fully off-grid, no power for miles.
 
Slight difference in our setups. My well is about 50 feet from my solar shed, which is 20 feet from the cabin, so I'm trying to git'er all done with one product mix. I like the EG4 stuff but their PV voltage input range is too narrow for me. Next year, I'll have space for a good-size array, but right now I only have space for 3 panels.. So I need something with a low minimum PV input voltage but which will grow with me later. The LV6548 has a 90-250V range, so I'm eyeing that one very carefully. We're also fully off-grid, no power for miles.
LV6548 has 2 PV inputs, the EG4 only has one.

The main thing is what panels will be used and what is the specs and how to maximize input for any inverter. In previous threads, if you to max out the PV input as close as possible for the LV6548 per 4Kw input, the 300W to 350W panels usually would work out well for amps and volts.

As for the EG4, I haven't done any comparisons, it may be better suited for 500W panels. I do know in a recent thread

a member was discussing having 3 strings in 8S3P (24 panels) and either need to add a SCC or split the array into 2 strings if using the EG4. With the LV6548, it would have been easy to run 4S2P per input with one input not used. But the LV6548 isn't the "hot new kid" on the block which everyone thinks is much better.

Higher voltage PV isn't always the best solution.
 
Ha! Awesome. Well, what I settled on was a 24v DC pump on a dedicated little setup with a couple of AGM batteries and Victron MPPT controller.

This decision was not because I could not get it to work with an AC setup, but rather, because the location of the pump in my homestead layout changed, and it didn't warrant running AC power out to it (so, a remote, self-contained dedicated system was better, regardless of power tech type).

If I had opted for AC on that pump, I think I would have run two EG4 inverters and a 240v pump. I've opted for EG4 over the Growatt, the LV6548, and the LVX6048 on my main AC system for the home. This is a fully off-grid homestead in the wilderness, no grid for miles. The main deciding factor was that EG4 has a 500v input limit (double that of LV6548), and I can therefore put more panels in series. I still like the LVX6048 a lot, but I just can't "afford" the constant power draw it takes, at least not for my particular scenario.

May I ask what region your cabin is in? I’ve been on the hunt for a long time and am always interested in new areas.
 
LV6548 has 2 PV inputs, the EG4 only has one.

The main thing is what panels will be used and what is the specs and how to maximize input for any inverter. In previous threads, if you to max out the PV input as close as possible for the LV6548 per 4Kw input, the 300W to 350W panels usually would work out well for amps and volts.

As for the EG4, I haven't done any comparisons, it may be better suited for 500W panels. I do know in a recent thread

a member was discussing having 3 strings in 8S3P (24 panels) and either need to add a SCC or split the array into 2 strings if using the EG4. With the LV6548, it would have been easy to run 4S2P per input with one input not used. But the LV6548 isn't the "hot new kid" on the block which everyone thinks is much better.

Higher voltage PV isn't always the best solution.
Isn't the EG still capped at 4000W for each of its PV input? Or can a single PV sink the entire 8000W pv input?
 
Each PV input is 4000W. I first thought these only have one PV input for a total of 8000W but it is 2 PV inputs, 4000W each.

One might do better getting close to the 4000W limit with the 500VOC rating with the EG4. Still 18A per PV input.
 
The reviews that I have seen on YouTube, the Auto transformer is not the way to go if you haven't bought a controller yet. To my understanding is that these Auto transformers are not a true transformer is the since that it at a primary and secondary winds. Because of this, it is easy to get the transformer out of electrical balance and they get extremely hot.
I too am looking for a new controller that puts out both 120vac and 220vac. I do not what to by two 120vac controllers and put them in parallel just to get 220vac.
Growatts have a couple that I'm looking at and Will Powers likes the MPPT LV6048, but things the LV6548 is a better choice.
Besides Will Powers YouTube videos, you might want to watch some YouTube videos of David Poz with respect to controllers.
If you take a gander at the autotransformer from Victron they give specifications for allowed imbalance. This states basically that you can continuously run 28A through the neutral, so some quick math:
  1. 10 kva inverter means ~42ish amps at 240V
  2. This means the maximum continuous difference between L1 and L2 is 28 amps, or if you were drawing 42A from L1 you would need to be drawing 14 amps from L2.
So versus 2x 5KVA inverters, you could draw max of 42 amps on either L1 or L2 but you could draw 42 amps on L1 and 0 on L2 without issues. With a autotransformer you could sustain ~57 amps on either L1 or L2 as long as your opposite phase was at 28 amps.

I think they're assuming that you have a standard split phase panel with a reasonable attempt made to distribute the loads but you want to run a hairdryer on one of the phases without tripping the inverter.
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