diy solar

diy solar

(Really) Off-Grid EVAL with the Sol-Ark 5K - True off-grid is the ONLY place to test Off-Grid ability. (or stay on the grid).

Marketing terms like "a complete off-grid solution" have to be taken carefully. One persons off-grid solution is not another's.

I would not buy the auto transformer if I was you. Consider instead going away from the SolArk. These units are really designed for people that have grid power. Most of the features as you have found are not workable in a true off-grid situation.
I'm very agreeable to that.... I need all the features working for me. I am looking into replacing it later this year. The hybrid and all-in-one design are very attractive for grid power, and I've seen them sell as "used."
 
If you're looking at other inverters such as Schneider, also look at Sunny Island.
Single phase, stackable. They can be had around $2500 or so on eBay.

If Schneider does split-phase by driving transformer primary and having center-tapped secondary, that could be attractive. Should get full wattage on one leg, at least for duration of a surge. (Think they may isolate center tap while fed from split-phase grid.)

Sunny Island doesn't share between phases during startup like that, but it does have 11kW surge.
If PV is AC coupled, that is normally 240V, and with 11 kW coming from PV, all 11kW could be used from a single phase. (half comes from PV inverter, other half transfers between phases by Sunny Island.)
 
If you're looking at other inverters such as Schneider, also look at Sunny Island.
Single phase, stackable. They can be had around $2500 or so on eBay.

If Schneider does split-phase by driving transformer primary and having center-tapped secondary, that could be attractive. Should get full wattage on one leg, at least for duration of a surge. (Think they may isolate center tap while fed from split-phase grid.)

Sunny Island doesn't share between phases during startup like that, but it does have 11kW surge.
If PV is AC coupled, that is normally 240V, and with 11 kW coming from PV, all 11kW could be used from a single phase. (half comes from PV inverter, other half transfers between phases by Sunny Island.)
Just be aware of the BMS requirements for lithium. It’s doable but there’s only 2-3 of the more expensive (but high quality) BMSs like REC that will work. The cheaper rack mount batteries won’t communicate unless SOK got their bugs worked out.

For a larger system I think it’s superior. Or even a medium two Sunny Island system that could be expanded if required. But it’s not inexpensive.
 
If Schneider does split-phase by driving transformer primary and having center-tapped secondary, that could be attractive. Should get full wattage on one leg, at least for duration of a surge. (Think they may isolate center tap while fed from split-phase grid.)
I suspect it does. It’s a direct descendant of Trace/Xantrex as is Outback.
 
It was just tested for the sale, and they rated it a 1 gallon/minute... which I think is very low, but we're getting ( by timing it) about 4.5/5.0 gals a minute though a 100ft hose while filling my water hauler. but in fear of drawing too much, too fast -- I limit my draws to about (90 gals) 350 litres per session and wait and hour or so to do another.
With that idea....( not to abuse the well) we are planning to setup the deep well pump on a timer, so as to run automatically only (perhaps) 10 mins @ every 2 hours only until the 1100 gal storage tank is full....and draw water for the house from the tank with another pump just for the house.
I don't know much about wells but I think for this one, I don't want to draw it down too fast based on the rate the inspector came up with.
That’s a low flowing well and it’s very easy to fry a well pump if they run dry. For any well that has a pump that can pump more water than the well produces, a pump saver device should be installed. They constantly monitor the electrical load and immediately shuts down the pump when it senses the the pump free spinning. There is a setting to determine how long it waits before pumping again (giving the well a chance to catch up). They are called “pump saver plus” and run about $250
 
That’s a low flowing well and it’s very easy to fry a well pump if they run dry. For any well that has a pump that can pump more water than the well produces, a pump saver device should be installed. They constantly monitor the electrical load and immediately shuts down the pump when it senses the the pump free spinning. There is a setting to determine how long it waits before pumping again (giving the well a chance to catch up). They are called “pump saver plus” and run about $250
That's a great idea.... we'll put one of these in the system when we put the rest of it together. THANKS!
 
In retrospect I think you would have had less issues if you had gone larger with the Sol Ark. probably the 8k would have been a better choice. I don’t think you will have any issues with a washing machine. If you can run a mini split you can run a washing machine. I have a 15k and I haven’t had any issues with motors but I don’t have anything major single phase. I have several larger motors but they are all 220v and start and run flawlessly.
 
Are these motors 3-phase?
No 2.5 hp pool pump and 1.5 hp deep well pump both 220v and a 5 ton geothermal. Several single phase motors a smaller shop compressor, a sump pump and a sewage ejector pump. All start and run fine on my 15k. I also have not noticed any LED light flicker.
 
A few quick notes from an installer here. (BTW we use a bit of Sol-Arks and 90% of our installs are off-grid.)

Last year we probably installed 40 or more Sol-Ark inverters, mostly off-grid.

I agree that they are not ideal for off-grid, much better suited for grid-tie and backup for critical loads. We still used a fair amount of them because of how integrated they are with their all-in-one design. But we have learned that we need to upsize them in comparison to what we would install in Schneider or other brands of transformer based inverters. (We would say a Schneider XWpro is more capable than a Sol-Ark 12K when it comes to grunt power.)

-ANY SOL-ARK SMALLER THAN THE 15K WILL STRUGGLE WITH 120V SURGE LOADS!!!! And I believe any high frequency (transformerless) inverter will! They don't have imbalance tolerance, and a transformer based inverter has much more oomph!
-A Schneider SW4048 would run what you have! (Although I would recommend a soft-start pump such as the Grundfos.)
-Transformer based 120/240 split phase inverters (such as Schneider SW and XWpro) generally are rated to handle a 70% imbalanced load.
-Sol-Arks are not configurable for 120v only output! They basically have 2 120v inverter circuits that have a controlled phase angle according to the setting you choose in the menu. (120/240, 120/208, etc.)
-A side note- when configured for 120/208 3 phase, one inverter will only provide 2 of the 3 legs, you need at least 2 inverters to get actual 3 phase output. (We have used single inverter 120/208v configuration in scenarios where there was existing 3 phase but the customer wanted to have some backed up loads- office equipment etc., and so the critical loads panel is 2 legs at 120/208v 180 degrees phase angle.)
-Note* even a Sol-Ark 12K WILL OVERLOAD at times if you have 120v surge loads such as motor starts!
-I personally have Victron inverters stacked to make my 120/240v (because of the endless "tinkering" possibilities with their venus OS), but if you want to have a bulletproof inverter that can handle imbalance and surges, go with a transformer based split phase inverter and a separate charge controller. (personal preference on charge controllers is Midnite Classic or Victron)
-In terms of off-grid and no internet monitoring- I'm not sure that you will find that in any name brand inverter out there. Everything is online anymore seemingly. I will say though, I love Victron when it comes to their GX devices. (I have a Cerbo GX.) Also, Victron has bluetooth on many of their devices, and updates can be pushed through bluetooth, over the internet, or via usb flash drive.
-A load balancing transformer would probably not help much in your scenario, as the high frequency transformerless inverters don't have much voltage sag at all, and voltage difference between the 2 legs is what allows the transformer to "shift" the imbalance across to the other leg.


One more note* the latest firmware on Schneider SW4048 inverters puts out 128/256ish volts, which is very high! The solution is a "hacked" firmware file update. (not really hacked, I guess.... just an older file "re-named" so that it can be loaded onto the newer version SW4048) Just something to keep in mind. Things work at that voltage, but it just feels very high...
 
A few quick notes from an installer here. (BTW we use a bit of Sol-Arks and 90% of our installs are off-grid.)


-ANY SOL-ARK SMALLER THAN THE 15K WILL STRUGGLE WITH 120V SURGE LOADS!!!! And I believe any high frequency (transformerless) inverter will! They don't have imbalance tolerance, and a transformer based inverter has much more oomph!

Have you tried adding a transformer to (at least partially) rebalance 120V loads?
A 25kVA 240/480 to 120/240V transformer can be had sometimes around $500.
Using the two primary 240V + 240V windings as autotransformer, it should handle up to 6kVA continuous transfer from one phase to the other. How much actually transfers would depend on inverter's voltage droop (programming/configuration?)
I might plug it in to a 50A range outlet for testing. (30A dryer outlet probably sufficient for surge loads.)

Of course, as isolation transformer it would perfectly balance. Some additional loss.
 
A few quick notes from an installer here. (BTW we use a bit of Sol-Arks and 90% of our installs are off-grid.)

Last year we probably installed 40 or more Sol-Ark inverters, mostly off-grid.

I agree that they are not ideal for off-grid, much better suited for grid-tie and backup for critical loads. We still used a fair amount of them because of how integrated they are with their all-in-one design. But we have learned that we need to upsize them in comparison to what we would install in Schneider or other brands of transformer based inverters. (We would say a Schneider XWpro is more capable than a Sol-Ark 12K when it comes to grunt power.)

-ANY SOL-ARK SMALLER THAN THE 15K WILL STRUGGLE WITH 120V SURGE LOADS!!!! And I believe any high frequency (transformerless) inverter will! They don't have imbalance tolerance, and a transformer based inverter has much more oomph!
-A Schneider SW4048 would run what you have! (Although I would recommend a soft-start pump such as the Grundfos.)
-Transformer based 120/240 split phase inverters (such as Schneider SW and XWpro) generally are rated to handle a 70% imbalanced load.
-Sol-Arks are not configurable for 120v only output! They basically have 2 120v inverter circuits that have a controlled phase angle according to the setting you choose in the menu. (120/240, 120/208, etc.)
-A side note- when configured for 120/208 3 phase, one inverter will only provide 2 of the 3 legs, you need at least 2 inverters to get actual 3 phase output. (We have used single inverter 120/208v configuration in scenarios where there was existing 3 phase but the customer wanted to have some backed up loads- office equipment etc., and so the critical loads panel is 2 legs at 120/208v 180 degrees phase angle.)
-Note* even a Sol-Ark 12K WILL OVERLOAD at times if you have 120v surge loads such as motor starts!
-I personally have Victron inverters stacked to make my 120/240v (because of the endless "tinkering" possibilities with their venus OS), but if you want to have a bulletproof inverter that can handle imbalance and surges, go with a transformer based split phase inverter and a separate charge controller. (personal preference on charge controllers is Midnite Classic or Victron)
-In terms of off-grid and no internet monitoring- I'm not sure that you will find that in any name brand inverter out there. Everything is online anymore seemingly. I will say though, I love Victron when it comes to their GX devices. (I have a Cerbo GX.) Also, Victron has bluetooth on many of their devices, and updates can be pushed through bluetooth, over the internet, or via usb flash drive.
-A load balancing transformer would probably not help much in your scenario, as the high frequency transformerless inverters don't have much voltage sag at all, and voltage difference between the 2 legs is what allows the transformer to "shift" the imbalance across to the other leg.


One more note* the latest firmware on Schneider SW4048 inverters puts out 128/256ish volts, which is very high! The solution is a "hacked" firmware file update. (not really hacked, I guess.... just an older file "re-named" so that it can be loaded onto the newer version SW4048) Just something to keep in mind. Things work at that voltage, but it just feels very high...
On the internet monitoring front…I think Home Assistant (homebrewed local smart home/IOT controller) could display most or all from various inverters and devices. Problem is, that requires additional complexities, minimally a raspberry Pi and preferably something stronger, and time and tinkering. I know someone has cracked the code (pun intended) for SMA. All of them are probably possible.
 
Have you tried adding a transformer to (at least partially) rebalance 120V loads?
A 25kVA 240/480 to 120/240V transformer can be had sometimes around $500.
Using the two primary 240V + 240V windings as autotransformer, it should handle up to 6kVA continuous transfer from one phase to the other. How much actually transfers would depend on inverter's voltage droop (programming/configuration?)
I might plug it in to a 50A range outlet for testing. (30A dryer outlet probably sufficient for surge loads.)

Of course, as isolation transformer it would perfectly balance. Some additional loss.
We have not tried a load balancing transformer yet, but a local friend of mine who does a bit of "playing around with" Sol-Arks (he works for an alternative energy distributor) has done it. I haven't asked him directly about that but I was told second hand that he didn't have much luck, due to how little voltage drop occurs with a high frequency inverter like a Sol-Ark.

Another thing that I would say regarding that is, whenever you have a transformer "hooked into" an electrical system, you have some parasitic draw, even when it is not 'working". For that reason we have always tried to steer away from using transformers when possible.

Also, to be honest, I think technically if someone were to use a transformer to balance the 2 lines, the transformer could be pretty small. Theoretically, it wouldn't need to be bigger than your largest unbalanced load potential. (Although I always like to stay on the safe side, as it seems loads always increase after a system is installed for a few years, or sometimes after only a few months/weeks.) :sneaky:
 
On the internet monitoring front…I think Home Assistant (homebrewed local smart home/IOT controller) could display most or all from various inverters and devices. Problem is, that requires additional complexities, minimally a raspberry Pi and preferably something stronger, and time and tinkering. I know someone has cracked the code (pun intended) for SMA. All of them are probably possible.
I have looked at Home Assistant and would like to play around with it at some point. Just haven't gotten around to it.

I just got done setting up Solar Assistant though, with our Sol-Ark 12K at our shop. It's a pretty impressive monitoring platform so far! It gives you local monitoring and also logging with no internet connection! (And also remote monitoring with internet, if you want it.) It runs on a Raspberry Pi and can log down to every 2-10 seconds depending on which model you are running it on! I am currently running it on a RPi Zero W and have 10 second interval logging on it.

Not sure if this will work, but I will try to attach a screenshot of the main page, "zoomed in" to a 15 minute log.

EDIT: Sorry I just have it as a PDF right now, I will try to convert it to something that can be viewed without downloading!
 

Attachments

  • SolarAssistant.pdf
    389.6 KB · Views: 2
Another thing that I would say regarding that is, whenever you have a transformer "hooked into" an electrical system, you have some parasitic draw, even when it is not 'working". For that reason we have always tried to steer away from using transformers when possible.

Yes, the current draw by a typical transformer meant for grid use is pretty horrible. It was optimized for cost.
That's why I suggest operating at half rated voltage, 120V applied to 240V rated windings.


Some transformers are much better behaved. Only slight rebalancing here, maybe much shorter wires would have done more.



Also, to be honest, I think technically if someone were to use a transformer to balance the 2 lines, the transformer could be pretty small. Theoretically, it wouldn't need to be bigger than your largest unbalanced load potential. (Although I always like to stay on the safe side, as it seems loads always increase after a system is installed for a few years, or sometimes after only a few months/weeks.) :sneaky:

Which is where your friend didn't see much benefit. Small transformer in parallel doesn't supply much of the current.

The SolArk delivers a good amount of power per phase, I think it was more than half what it could draw from battery (boost converter.) Just allocate loads reasonably. If total 120V load on one phase exceeds max, or if total load at 240V does, it will shut off. Buy more inverter if required.

An isolation or auto-transformer deriving neutral for loads is the only way to let imbalanced 120V loads draw 100% of inverter 240V capability. An auto-transformer has issues, so isolation is better.
 
Something else that I have seen done recently is to use a 120/240V split phase transformer (Doesn't really matter if that is the voltage on primary or on secondary, or even a load balancing specific one [autotransformer?]), then the 2 inverter lines are hooked up to the lines of the transformer, and the neutral is pulled straight off the transformer. This works............. as long as it works........ if the transformer were to fail, you would have an open neutral which usually toasts something from your loads. It's a relatively small risk, but a risk non-the-less. This method will make so that all loads always end up drawing equally off the 2 lines from the inverter, but comes with grounding issues and risks.

Please note* there are a bit of technical details that would need to be done (to make it work on a Sol-Ark) that I won't elaborate on. I really don't recommend it because you end up with an ungrounded electrical system coming off of the inverter. And as soon as you use a generator to charge, that whole electrical system coming from the gen is ungrounded as well! I see it being done using Growatt 230V units that are technically EU units (230V L-N) and have a sticker on the side that literally says not to do it! (All while Growatt literally has and/or had a transformer available to do it!) :rolleyes::oops:

I am mostly mentioning this as a precaution to anyone who might consider doing that! Cheap inverters (or other components, etc.) don't always equal something that you can use safely as a cheap alternative to quality products!
 
Something else that I have seen done recently is to use a 120/240V split phase transformer (Doesn't really matter if that is the voltage on primary or on secondary, or even a load balancing specific one [autotransformer?]), then the 2 inverter lines are hooked up to the lines of the transformer, and the neutral is pulled straight off the transformer. This works............. as long as it works........

Let's say you have a typical transformer, 240/480V primary, 120/240V secondary.

If you drive the secondary from inverter, 240V into two series connected 120V + 120V windings (as auto-transformer to derive a neutral), the current draw no-load will be horrendous (I measured 9A rms). It will go far into saturation and draw multiple amps.

If you were to use it as an isolation transformer, 240V into 240V primary windings (both in parallel, 240V || 240V) it will be much better but still draw an multiple amps ( 4A rms for the VA size I've tested.)

By applying 120V to a 240V primary winding, I got the current down to 0.6A rms. Power dissipated was less than that suggests, because it was a reactive load, and 4-quadrant inverter recovered the stored power.

Not all inverter behave nicely into reactive loads. I tried an isolation transformer on an Eaton UPS at work, and power draw of the UPS more than doubled (tripping a circuit breaker due to a pump also operating on the same circuit.)

There are some transformers made for use with inverters, designed for lower current draw. Expensive and far between, of course, which is why I look for ways to use typical transformers at derated voltage.
 
Let's say you have a typical transformer, 240/480V primary, 120/240V secondary.

If you drive the secondary from inverter, 240V into two series connected 120V + 120V windings (as auto-transformer to derive a neutral), the current draw no-load will be horrendous (I measured 9A rms). It will go far into saturation and draw multiple amps.

If you were to use it as an isolation transformer, 240V into 240V primary windings (both in parallel, 240V || 240V) it will be much better but still draw an multiple amps ( 4A rms for the VA size I've tested.)

By applying 120V to a 240V primary winding, I got the current down to 0.6A rms. Power dissipated was less than that suggests, because it was a reactive load, and 4-quadrant inverter recovered the stored power.

Not all inverter behave nicely into reactive loads. I tried an isolation transformer on an Eaton UPS at work, and power draw of the UPS more than doubled (tripping a circuit breaker due to a pump also operating on the same circuit.)

There are some transformers made for use with inverters, designed for lower current draw. Expensive and far between, of course, which is why I look for ways to use typical transformers at derated voltage.
That is very interesting! I have set up a number of transformers for "standard uses" ?, (Such as 208 primary- 120/240 secondary, and 240/480 primary- 120/240 secondary, always to connect a 120/240v inverter to some "other" power source.) but have never done much experimenting and playing around with "alternative" uses.
 
Standard usage powered from grid will be fine.
Powered from inverter I think the excessive no-load current will reduce system efficiency, best case.

You've connected a transformer to your inverter? Check power output, AC amps, DC amps & volts with/without the transformer connected.
I'm able to distinguish real from reactive power that way. I also do it with an oscilloscope, voltage & current probes. That lets me see phase shift, also distorted current waveform.
I find some transformers are better behaved than others. And that operating typical transformers at reduced voltage makes them closer to ideal, like an order of magnitude reduced no-load current.

To let 3 out of 4 Sunny Island 120V inverters sleep, while still having split-phase, I plan to use a transformer. It needs to not cause excessive additional loss. (Reduction from 100W to 25W, plus about 7W for the transformer.)
 
Back
Top