How about Using a 1-Phase 120V to 3-Phase 240V Converter Instead of Parallel Inverters?

I think it’s worth it to grab a meter that can record the actual inrush current because that will narrow down what inverter to get.

forbin said:

However, just to be safe, I'll use the highest number on the spec sheet and assume the inrush is 42A, which works out to ~10,000 W. So it seems that an inverter that can handle 10,000 W for a few seconds once a week should do the trick.

Oh, and I forgot to mention one other data point in my challenge. I want to do it with equipment from MPP, Growatt, EG4, or another vendor of similar quality. I cannot afford Schneider, Sol-Ark, or the other big boys who are, shall we say, very proud of their equipment.

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You appear to be wholely absorbed with pen and paper documentation rather than empirical testing. It seems you won't accept suggestions like getting an "inrush current" meter, either because you are very cheap, or very inexperienced. In either case, to be frankly honest, this mentality will guarranty your failure. There is an order of magnitude difference between powering your TV via solar, and powering your well-pump via solar. You need quality equipment to get that done.

You will end up spending more money. Once for the MPP, and again for an inverter that actually works. At this point all I can say is "you'll find out". I really hope you don't end up burning out your well-pump, because replacing one is nothing to look forward to.

MichaelK said:

You appear to be wholely absorbed with pen and paper documentation rather than empirical testing. It seems you won't accept suggestions like getting an "inrush current" meter, either because you are very cheap, or very inexperienced.

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I'm inexperienced, for sure, and certainly cheap, but neither of those are factors in this case. I live in the wilderness, 30 minutes from the nearest paved road and about 1.5 hours from a Home Depot. I leave the mountain about once every 1-2 weeks. The thread was getting old, so I provided at least some empirical information. It sounds like you believe there's a chance my particular model of PenTek pump has an inrush current that is more than 6 times its running load, which would be pretty unusual, from what I've been told, and could mean the pump is drawing up to 150% more than the manufacturer's published LRA spec. I sure hope that's not the case, but I'll confirm with a better clamp-meter when I can.

Surge of 5x rated power is what I expect, and have measured for one or two motors. Sometimes running current below spec.
When a motor has a starting winding, either switched (common for some applications) or through a start/run capacitor (typically for higher torque), maybe it draws additional current beyond what 5x rated would indicate.

In 3-phase applications, LRA is a similarly higher value, and that's just the running windings.

Growatt 5kW rated 2x surge power for 5 seconds, in manual but not spec sheet.

Do you happen to know of an inexpensive ammeter that can record a valid peak amps value @Hedges ? I have a few clamp meters but none of them can capture the peak. There seems to be a lot that list that as a feature, but I don't want to just buy shots in the dark, myself.

It appears watts247 is going to firesale the next shipment of Growatt 5000 ES, if you are okay dealing with removing the screw yourself @forbin
https://watts247.com/product/spf-5000-es/

Look for an inrush feature.

forbin said:

I live in the wilderness, 30 minutes from the nearest paved road and about 1.5 hours from a Home Depot. I leave the mountain about once every 1-2 weeks.

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My place is 60 minutes up a dirt mountain road, twice as far, but I somehow managed to do all the background investigation I mentioned, and installed a quality inverter myself.

forbin said:

It sounds like you believe there's a chance my particular model of PenTek pump has an inrush current that is more than 6 times its running load, which would be pretty unusual, from what I've been told, and could mean the pump is drawing up to 150% more than the manufacturer's published LRA spec. I sure hope that's not the case, but I'll confirm with a better clamp-meter when I can.

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I'm pretty sure I've NEVER mentioned "6 times" to anyone here. In my own case, testing my own pump, I find it runs on 9.5A, but has an inrush of 38A, when ends up being 4X. That is the number I almost always quote when talking about starting surge.

The critical point I'm trying to make is that you shouldn't be asking what the starting surge is, you should be determining what the starting surge is. My concern is if you are not up to that level of expertise, then you really aren't at the level of doing this yourself.

copec said:

Do you happen to know of an inexpensive ammeter that can record a valid peak amps value @Hedges ? I have a few clamp meters but none of them can capture the peak. There seems to be a lot that list that as a feature, but I don't want to just buy shots in the dark, myself.

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I have this one, that has worked well for me. Prices are going up though. I think I got my first one for 58$. I also have a far more expensive Fluke meter with inrush capability, but I find that when used side by side, the UniT matches to within 1% accuracy.

MichaelK said:

My place is 60 minutes up a dirt mountain road, twice as far, but I somehow managed to do all the background investigation I mentioned, and installed a quality inverter myself.

I'm pretty sure I've NEVER mentioned "6 times" to anyone here. In my own case, testing my own pump, I find it runs on 9.5A, but has an inrush of 38A, when ends up being 4X. That is the number I almost always quote when talking about starting surge.

The critical point I'm trying to make is that you shouldn't be asking what the starting surge is, you should be determining what the starting surge is. My concern is if you are not up to that level of expertise, then you really aren't at the level of doing this yourself.

I have this one, that has worked well for me. Prices are going up though. I think I got my first one for 58$. I also have a far more expensive Fluke meter with inrush capability, but I find that when used side by side, the UniT matches to within 1% accuracy.

1PC UNI-T UT216C 600A True RMS Digital Clamp Meters | eBay

Find many great new & used options and get the best deals for 1PC UNI-T UT216C 600A True RMS Digital Clamp Meters at the best online prices at eBay! Free shipping for many products!

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It sounds like you have a great place and I'm not trying to compete with you. I was explaining why I have not had an opportunity to get a better clamp meter in the few days between your original comment and yesterday. Despite the fact that I initially said I was about ready to purchase something, I'm still gathering information. I joined the SolarPanelTalk forum 7 years ago back in 2015 and I've been reading and researching intermittently since then, but only in the past year have I been getting serious, and in the past few months really serious, but I know there is a lot to learn and everyone has to start somewhere.

You did not say anything about "6 times." That's just what the math seems to work out to. I believe I have a PenTek P42B0010A2 pump, which is listed at 21.7 LRA. Since I have not yet confirmed it, I'm assuming for conversational purposes that I have PenTek's highest powered 1HP model, which is listed at 42A LRA. I know, based on testing, that my pump draws 7A when running. If its inrush power is more than 42A, then it would be using more than 6 times it's running Amps, which is uncommon. That's what I was trying to communicate. I get the critical point you are trying to make.

forbin said:

I get the critical point you are trying to make.

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Sorry, I just get so intense! Will try to relax a bit. I try to convey that good solar isn't cheap, and cheap solar isn't good. If you are trying to go off-grid to save money, you are making a mistake. A lot of people miss that completely. I try to advise people on what I know works. That's why I try to push people in a certain direction.

MichaelK said:

Sorry, I just get so intense! Will try to relax a bit. I try to convey that good solar isn't cheap, and cheap solar isn't good. If you are trying to go off-grid to save money, you are making a mistake. A lot of people miss that completely. I try to advise people on what I know works. That's why I try to push people in a certain direction.

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No worries. We've been living 100% off grid for a little over two years. The cabin came with a small 12V solar system and I've been learning some things in the process of using and tending to it. I've had to replace the charge controller twice, the inverter twice, the battery chargers, and re-wire the circuit breaker box, and re-route the panel wires, and replace fuses and cutoffs, and so forth, and install a whole new battery bank. In fact, the only part of the system that I haven't replaced are the panels. Thankfully, 12V is fairly safe for beginners. Our appliances are all propane and the daily water supply comes from a 500 gal. tank that feeds the house through an RV pump. We have no A/C, so our power consumption is low, around 4kWh per day, and a big chunk of that is the inverter's idle consumption. Even so, we end up running the generator way too much. I killed my bank of FLA batteries through abuse and neglect. Lesson learned. Now I want to get a more powerful system that can run more things and give us a few days of autonomy, and I'm trying to fit a lot of priorities into a small space and a small budget. My progress toward a final design is glacial.

forbin said:

The cabin came with a small 12V solar system and I've been learning some things in the process of using and tending to it. I've had to replace the charge controller twice, the inverter twice, the battery chargers, and re-wire the circuit breaker box, and re-route the panel wires, and replace fuses and cutoffs, and so forth, and install a whole new battery bank. In fact, the only part of the system that I haven't replaced are the panels.

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You know, I think people here, including myself, would find it very valuable to hear more about what the failures were? Can you go into more detail as to what went wrong with controllers and inverters? I'm guessing that your battery bank failed from inadequate charging? Big battery banks with small solar arrays were a thing back in the 90s. Why the rewiring?

I'd be happy to share my failures, which are many, and successes, which are fewer, but satisfying. I'll make some comments later today.

MichaelK said:

You know, I think people here, including myself, would find it very valuable to hear more about what the failures were? Can you go into more detail as to what went wrong with controllers and inverters? I'm guessing that your battery bank failed from inadequate charging? Big battery banks with small solar arrays were a thing back in the 90s. Why the rewiring?

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The cabin was built, and the system installed, around the year 2000. When I bought it in 2019, the breaker box was rusty and falling off the wall. Inside it was a tangled mess. I installed a new box, new breakers, and ran the wires cleanly, but didn't do anything new or creative. I just wired everything the way it was already, but neatly. The battery bank is 8 x Trojan T105's in 4 parallel strings of 2. I'm now aware that it's a bad idea, but it's what I inherited from the previous owner. I replaced all the batteries with brand new ones, but I didn't really know how to care for them. I wasn't any good at measuring SOC or knowing how long to run the generator to fill them up. I under-charged, over-charged, partially charged, and subjected them to all manner of un-gentlemanly tortures. Recently, I got so busy at work that I didn't make time to maintain them, and the water levels got too low and exposed the tops of the plates. I filled them, but now the batteries can't handle any significant discharge. We can run our fans and computers, but any time the RV pump kicks in, the voltage drops too low and the transfer switch kicks over to shore power. Since there isn't any shore power, we either reset the switch or start the generator. (Oh yeah, I also replaced the transfer switch once. The original Iota ATS died due to bugs, birds, dirt, and humidity.) The batteries are my biggest failure. The rest of the system is just cheap. The original inverter, a Whistler 2000, just went bad, and the cheap Amazon one we bought to replace it went bad, too. The third one is a PowerMax PMX2000 and seems to work fine. The original charge controller was a $29 special that got blasted by lightning. We replaced it with another cheapo, which had wire holes that were too small for the solar cables, so (cover your ears) I actually snipped off a few of the conductors from the stranded wire to make them fit. That worried me, so I finally put in an Epever controller, re-terminated the cables, and it has worked well. Now I want to grow up and get some real equipment. That's my story.

Now for the pictures.

Supervstech said:

Now for the pictures.

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Oh man, I couldn't. My skin is not that thick, and I'm sober.

Rednecktek said:

Phase sequence. A split phase output from a paralleled set of inverters or an autotransformer gives you two waves of AC at 180deg off, so when one is peaking the other is at bottom.

On 3-phase your waves are 120deg off so when one leg is peaking the other two are only 2/3 of the way to where they're going.

Many people get the 240v versions of AIO's and put the 240v through an autotransformer to split the output into the two opposing wave forms, not uncommon at all.

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There's been debate about this with signature solar selling the 240V growatt and using a auto transformer to provide the neutral; what if the auto transformer fails and you loose the neutral?

copec said:

Do you happen to know of an inexpensive ammeter that can record a valid peak amps value @Hedges ? I have a few clamp meters but none of them can capture the peak. There seems to be a lot that list that as a feature, but I don't want to just buy shots in the dark, myself.

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I bought the Harbor Freight Ames 1000A one.

Key features for me were DC clamp amps, 0.01A resolution, 1000A on highest scale, inrush.


That may be accurate for motor starting surge of multiple cycles, haven't tried comparing to others.

It isn't fast enough for the less than one cycle inrush charging capacitors or starting up a transformer that saturates (For that I use a 20 kHz bandwidth fluke clamp probe and oscilloscope).
And I think "inrush" is only a feature it has on AC range, not DC.

realpinochet said:

There's been debate about this with signature solar selling the 240V growatt and using a auto transformer to provide the neutral; what if the auto transformer fails and you loose the neutral?

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Then bad things happen.
You could use theirs or another stand-alone autotransformer with suitable breaker configuration to avoid the issue.
Signature now sells one with breaker and relay that should fix the problem, OK I think for off-grid.
What I don't believe is that it also fixes the "trying to balance utility grid", "neutral bonding to ground" and "no objectionable current" issues. No schematics I've seen so far would allow connection to grid without some problem I could identify.

Victron appears to address all issues, because they also include a relay to switch neutral and bond it to ground.

Isolation transformer is another solution. Dumb passive big iron, not much can go wrong.

I’ve been putting up this fellow’s install as an example of how it should be done with a grid connection:
There are used 480x240-240/120 transformers all over for relatively cheap.

If you aren’t doing a grid connection, I believe you would be fine with the autotransformer solution from Signature Solar, if going with that - even if passing through a generator at times.

realpinochet said:

There's been debate about this with signature solar selling the 240V growatt and using a auto transformer to provide the neutral; what if the auto transformer fails and you loose the neutral?

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I believe it has been worked out, except when passing through a grid connection. It’s pretty simple, you wire the inverter(s) and autotransformer together before a three pole breaker, so if it flips, it disconnects all power.