3kw inverter

[denn]

im a beginner and have yet to discover how to calculate surge.  in building my system i need to know if the 3kw 24vly dc to 220ac would start two 3/4hp 1495 watt 6.5 amp well pumps.  i am building a system using 9 355 watt panels and intend two use 2 s340 on 4 pannels and the 3kw on 4 more, leaving one to go with expansion.  thanks

[Sid Genetry Solar]

Well, off the top...depends on what inverter you're referring to.  It's not clear, as I cannot find anything by searching what you've provided ("24lvy").

If you're looking at the MakeSkyBlue 3KVA-24-230 (https://makeskyblue.com/products/3kva-hybrid-mppt-solar-inverter-24v-dc-to-230v-ac) then the answer is more than likely "definitely not."  I am taking a wild guess that it is the inverter you're referring to, simply because you mention "3kw" and the fact that you posted in the MakeSkyBlue subforum.

 

IF IT IS THE INVERTER you're referring to...

There is a big difference between power measured as VA (volt amps) and W (watts).  Manufacturers like to use VA to rate their inverters, as it makes the number look better--but then you get caught with an inverter that won't do what you need.

The above link rates the inverter at "3000VA/2400W."  In other words, the inverter cannot sustain the running power of both pumps (3000W).

And HF inverters (which the MSB is) are at best very poor at handling surges.  Most cheaper units (i.e. Chinese-made) are horrible at handling surge loads.

 

So in short to the best of my guess: no, that inverter won't run the pumps.  Probably won't be able to start even one of them--and even if it does, trying to start the 2nd one will result in the inverter overloading and stalling the first pump.  Been there, done that with HF inverters.

 

EDIT: You need to provide a LOT more details/links as to what exactly the equipment you're referring to.  I have no idea what you're referring to with "2 s340 on 4 pannels".

[denn]

thanks for reply.  Ok, because of reviews from actual customers i do wish to use sky blue for my system, which currently consists of nothing but 9, 355 watt panels with a voc of 47.45, and 1 3500 watt pure sine wave inverter.  You are correct about the msb 3kw off grid tie inverter being the one i was refering to.  i wish to go with 24vlt battery system and build it in a way that if one charge controler fails it will not stop the entire system.  the two well pumps are my biggest concern and my biggest draw.  the controller i am referring to is the msb 30 amp charge controler which has a 720 watt max pv  input, if i understand the volt rating then it is capable of between 37 and 105 volts.  i am new to solar and would greatly appreciate any info you could provide.  HF vrs LF inverters?  does msb make a LF inverter that would handel the load?  Again thanks for your reply and help in the matter.

[TheButcher]

To be honest seeing someone considering a MakeSkyBlue inverter fills me with all kinds of trepidation.  Whilst their solar battery chargers do work the firmware is shall we say a little 'quirky' and lacks some fairly important items for a battery charger.  For the record I do own 3 of their chargers so I'm not talking out my ... hat ... on this.  If the firmware in their inverter follows the same path in terms of features and quality it's not going to be a smooth ride.  The quality of the program in the device these days really does matter as a lot of what the inverter does, AC waveform, protection systems etc, is all done by/under control of it.  This doesn't even consider the hardware itself, which given MakeSkyBlue, isn't going to be particularly high either.

Do your homework on this before clicking purchase.

[TheButcher]

Worthwhile reading ...

https://diysolarforum.com/threads/feedback-on-make-sky-blue-hybrid-inverter-requested-all-in-one.7400/

[Sid Genetry Solar]

4 hours ago, TheButcher said:

Worthwhile reading ...

https://diysolarforum.com/threads/feedback-on-make-sky-blue-hybrid-inverter-requested-all-in-one.7400/

Definitely interesting--though it was nothing but disgruntled customers reporting there 😉.  Would be interesting to see an honest review of one of those units actually working (if there is such a thing, haha!)

[TheButcher]

Yeah, true, but distilling it down, doesn't meet the specs; didn't have the functionality stated; went bang.  All good enough reasons individually to not buy one, IMO.

[denn]

i am definatly  doing more research, however, it doesnt change the fact that myself, and others like me, simply cannot afford the Rolex time piece and must find a reasonable Timex.  that being said, perhaps i should look at PWM controllers again.  the best defence against this jab war we are in is to get as many as possible off grid and back to an independent lifestyle, and with the economy like it is i truly want my system build to be within a poor mans budget.

[Sid Genetry Solar]

49 minutes ago, denn said:

i am definatly  doing more research, however, it doesnt change the fact that myself, and others like me, simply cannot afford the Rolex time piece and must find a reasonable Timex

Well, if the Timex won't keep time...then it is a total waste of money, and you end up spending a lot more in the end.

I've bought a cheap Chinese HF inverter before (the SwiPower 3kw)--it's real cheap, but completely useless if you run ANYTHING except resistive loads (i.e. heaters).  Try to start a handsaw with the 'fridge running?  The 'fridge compressor is going to stall (which then goes through an overheat thermal protection cycle).  It was a total joke--though in it's defense, I somehow did not burn it up.  Admire the junk here: https://www.ebay.com/itm/124247095731

Let me just say: if you need to run 2 water pumps, you are probably going to be FAR better off with an "8kw" Power Jack inverter (which will overheat much past 3-4kw in the first place...but will handle significant surge startups).

Like someone else posted on a different forum, it is best to "buy once, cry once."

[TheButcher]

A 1000% step up from the MSB would be the MPP Solar range of all-in-ones.  Yes, they cost more and yes they will have trouble starting those water pumps but they do explain that in the documents and recommend a unit with 3 to 7 times the run rating of the motor to cope with the start up and the same thing explained by Sid above will apply if you exceed the instantaneous power rating of the inverter.  It's the nature of these things.  Once you exceed the power rating the AC waveform goes to hell and the inverter also considerably drops the peak voltage of the AC to stop itself from blowing up.  That will likely cause AC line driven motors that are under load to stall.

[dickson]

 if you exceed the instantaneous power rating of the inverter.  It's the nature of these things.  Once you exceed the power rating the AC waveform goes to hell and the inverter also considerably drops the peak voltage of the AC to stop itself from blowing up.  That will likely cause AC line driven motors that are under load to stall.

I  watch the AC votage  of starting a microwve oven  go from  116vac  down to  99 vac  on my  8kw powerjack  and the  rev 11.1  control board  shut down the inverter and save the FETs and not  blowing up  . This happen when the battery  is low  at  49v DC .    

[TheButcher]

Not sure if that's a deliberate effect or just a side effect of the sine being crushed flat under 'high' (high for PJ 😉 ) load due to the 'voltage' of the transformer not being a good match with the battery voltage.  Sid could probably comment about it.

Some HF inverters just produce horrible waveforms, like Sids' example posted elsewhere while others produce a few cycles of distorted sine while they let the HVDC drop to reduce the AC peak voltage and thereby limit current but once the initial distorted cycle or two is past the waveform is pretty sinusoidal.  Once the inverter sees current is more agreeable the HVDC is allowed to slowly rise back to normal (~170VDC for 120VAC, 340VDC for 240VAC) with the sine climbing back to normal instep with that.

Edited November 26, 2021 by TheButcher

[dickson]

Not sure if that's a deliberate effect or just a side effect of the sine being crushed flat under 'high' (high for PJ 😉 ) load due to the 'voltage' of the transformer not being a good match with the battery voltage.

The battery  at 60 v DC the  microwave  oven will  start  and the AC voltage will  drop from 116vac to 106vac .  The  voltage  will  go back up to 116vac and the microwave oven  will run normal .   The  powerjack  will make a warping  noise  for 5 sec  and shut down  if the  AC voltage drop below 99vac  and the red  alarm light  stay on  .   This is a good feature  for the rev 11.1 control board .   The  rev 10.3 cotrol board  will  try  to start  a heavy  surge load  and  blow up the FETs  and then  set the red light  alarm  but it is too late as the damage is done .  

[Sid Genetry Solar]

7 hours ago, dickson said:

I  watch the AC votage  of starting a microwve oven  go from  116vac  down to  99 vac  on my  8kw powerjack  and the  rev 11.1  control board  shut down the inverter and save the FETs and not  blowing up  . This happen when the battery  is low  at  49v DC .    

Sounds to me like a mathematical headroom limitation...low battery + too shallow transformer ratio + very lossy transformer = 99vAC with a pure square wave input.

PJ likes to use a 36v -> 230v ratio for 48v inverters...so mathematically requiring 51vDC minimum (at no load) for a pure sine output.  Well, since the transformers are wound with so little wire, the voltage drop losses will be extreme under heavy loads--meaning that even when the inverter saturates to a pure square wave (to try to bring the voltage up), the losses in the transformer are so high that 99vAC is all that is left over.

 

4 hours ago, dickson said:

The  powerjack  will make a warping  noise  for 5 sec  and shut down  if the  AC voltage drop below 99vac  and the red  alarm light  stay on  .

This "warping" noise is the CPU's SPWM regulator overflowing from 200% throttle back to 0 again...over and over again.

 

4 hours ago, dickson said:

This is a good feature  for the rev 11.1 control board .   The  rev 10.3 cotrol board  will  try  to start  a heavy  surge load  and  blow up the FETs  and then  set the red light  alarm  but it is too late as the damage is done .  

Frankly, these are coincidental results.  The PJ CPU firmware hasn't changed one bit since at least v8...and the 11.1 control board changes from the 10.3 are basically just the addition of the "charge amp limit" circuit.

[dickson]

This "warping" noise is the CPU's SPWM regulator overflowing from 200% throttle back to 0 again...over and over again.

That  warping noise  from   the  rev11.1   control board   is so  loud and  scary  for 5 seconds that  I was  waiting  for the inverter   to blow up  but I know now that  nothing bad will  happen .  

[Sid Genetry Solar]

3 hours ago, dickson said:

That  warping noise  from   the  rev11.1   control board   is so  loud and  scary  for 5 seconds that  I was  waiting  for the inverter   to blow up  but I know now that  nothing bad will  happen .  

This behavior has not changed from at least Rev 7.x through the current Rev 11.1.

[denn]

yes sir, after much more research i decided to go with the 60 amp Epever, wth 4 355 watt panels and a 3500 watt pure sine wave inverter, this part of my build will be to operate fridge, deepfreeze and on sunny days the washing machine.  After i get this all hooked up, i believe ill look into getting a all in one unit for each motor, however i am going to do a lot more research as well as learn how to drive the system i am building.  

[Sid Genetry Solar]

33 minutes ago, denn said:

yes sir, after much more research i decided to go with the 60 amp Epever, wth 4 355 watt panels and a 3500 watt pure sine wave inverter, this part of my build will be to operate fridge, deepfreeze and on sunny days the washing machine.  After i get this all hooked up, i believe ill look into getting a all in one unit for each motor, however i am going to do a lot more research as well as learn how to drive the system i am building.  

A 3500W pure sine wave inverter, care to provide a link?

Do you have the make/model of the solar panels?  It is kinda important to keep in mind the maximum input voltage of the Epever (as they make 150v and 200v versions) vs the highest no-load voltage of the solar panels at the coldest expected temperatures.  (Solar panel voltage/efficiency significantly increases as the ambient temperature goes down.)

If you plan to bump up the size of the system at a later date, you might consider paying a small cost increase for, say, an 80A or 100A Epever--and in the end you might save money over purchasing 2 smaller units.  Food for thought anyway.

[denn]

i have the JA solar 355 watt with a voc of 47.45 and a imp of 9.16.  if i did calculate it right then i should be close to its limit of 150v.  2 daisy chain 2 in paralell.  i like the idea of having several charge controllers and inverters, that way no single device failure  will shut me down.  yes, you and others have changed my timex analogy, what have i saved if it burns my house down?  once i get educated better with this section, then the next part of the build i believe ill go with a charge controller that can handel the entire 3.2kw of panels but only use it on five of the panels, thinking that will work as a system back up.  there or so many options on custom builds it is literally mind blowing.  for now, ill consentrate on the small 1420 watt system i am curently building.  i have been reading threads on grounding lately and that seems confuseing, why so many different answers?  i am turning my back bedroom into my power plant, so everything will be protected, and already installed a ground buss and tied into house ground through a wall socket.  After reading a section about grounding on here i am more confused than when i started, so if you know of a good read about grounding i could use it.   inverter?  is a xwine, only used long enough to know it works under small loads.  they have zero customer support and can not geta reply.  they sent a bag of fuses and a jumper wire that i could supposedly use to make it a 48vlt inverter, but no instructions on how to or fuse installation.  bought it while looking for a timex, however it has a sixteen lb weight so a decent transformer, apparently.  thank sid, youre a big help.

[Sid Genetry Solar]

20 minutes ago, denn said:

is a xwine, only used long enough to know it works under small loads.  they have zero customer support and can not geta reply.  they sent a bag of fuses and a jumper wire that i could supposedly use to make it a 48vlt inverter, but no instructions on how to or fuse installation.  bought it while looking for a timex, however it has a sixteen lb weight so a decent transformer, apparently.

16lbs...that's DEFINITELY a high-frequency inverter.  It should run your 'fridge, freezer and other simple appliances fine...but don't expect it to start the water pumps.  Or an A/C for that matter.

Quick search for "xwine inverter" turned up one "4000W 24v" inverter listing on eBay...but worth noting is that it is a MODIFIED SINE inverter, not a PURE SINE.  Expect the 'fridge and freezer compressors to run noisily.

For comparison, a 6kw GS inverter weighs right around 50lbs...most of that weight being the low-frequency transformer.

 

Doubt a "jumper wire" will be able to adjust the inverter from 24v to 48v...on any inverter, the transformer ratio must be changed for proper operation.  On an HF inverter, you'll likely have 4-6 small HF transformers in a row.

 

26 minutes ago, denn said:

i have the JA solar 355 watt with a voc of 47.45 and a imp of 9.16.  if i did calculate it right then i should be close to its limit of 150v.  2 daisy chain 2 in paralell.

Spec sheet here: https://www.sunwize.com/wp-content/uploads/2020/06/JASolar-JAM72S01-355.pdf

Those are excellent solar panels...I hope you got a good price on them 😉

Module efficiency of 18%...most (including the ones I have!) are 15% efficient.

 

Found a solar panel temperature coefficient calculator, plugged your solar panel info in, and we find the following:

Quote

You entered

• Total string OC voltage: 94.9
• Nominal maximum power: : 1420
• Worst case temperature: 0
• Temperature coefficient (Voc): -0.3
• Temperature coefficient (Pmax): -0.38

For these, your:

• Total worst case differential is: 25
• Your voltage increase (%) is: 7.5
• Your voltage increase (V) is: 7.1175
• Your maximum voltage (V) is: 102.0175
  
• Your Pmax increase is (%): 9.5
• Your Pmax increase is (W): 134.9
• Your total Pmax at this temperature is (W): 1554.9

 

Note that I specified 0C as the minimum expected temperature (for the Carribean area anyway!) 

Using the panels in 2 parallel strings of 2 series panels, at 25C, your panels max voltage will be 94.9v.  At 0C, the same panels will produce 102.0v.  Both well within a 150v MPPT's range.

 

34 minutes ago, denn said:

once i get educated better with this section, then the next part of the build i believe ill go with a charge controller that can handel the entire 3.2kw of panels but only use it on five of the panels, thinking that will work as a system back up.

I personally have 3 MPPT charge controllers (1 Morningstar Tristar, and 2 Epever Tracer 8420AN)...all loaded pretty much to the max rating.  Yes, it is important not to exceed the max power rating...but I don't know that you would gain significant reliability by running a charge controller at 30% output.  What damages equipment is more often surge voltages/spikes caused by either lightning, or electrical connect/disconnect instances.

 

36 minutes ago, denn said:

i have been reading threads on grounding lately and that seems confuseing, why so many different answers?  i am turning my back bedroom into my power plant, so everything will be protected, and already installed a ground buss and tied into house ground through a wall socket.  After reading a section about grounding on here i am more confused than when i started, so if you know of a good read about grounding i could use it.

Don't ask me 😉

I've experienced a number of equipment failures as a result of grounding providing a path for electricity to flow through appliances...so I should not comment further on the subject.

[denn]

haha, i hear you on the grounding.  No, my inverter is the 3500 watt gold series, until i get another one, from an outfit that has a support staff, it will be exclusive to the fridge and df.  once better educated on it ill take it apart and see what i got, i fell pretty sure the fuses will be solder jobs to the mother bord.   on the underpowering of the inverter my goal is to reduce heat stress, after all im steal set on the 24volt system, for now.  i have been toying with the idea of a second battery bank of 48 vlt and two plug and play 48/220 inverters, one for each motor.  panels are two years old and got them for 50 bucks a pop, thats why i jumped in so unprepared, you dont have to be very smart to recognize a deal like that.

[Sid Genetry Solar]

6 minutes ago, denn said:

No, my inverter is the 3500 watt gold series,

You mean this?  https://www.amazon.com/XWJNE-Inverter-Adapter-Converter-Charging/dp/B08T66LR8M?th=1

(XWJNE 3500W inverter?)

They included one partial "stock" photo....

...DEFINITELY a High-Frequency (HF) inverter 😉.

YMMV.  Some are pretty decent, but some are also really shoddy.  I personally had experience with a SwiPower Chinese HF inverter...worked fine for resistive loads (heaters, etc.), but terribly with any sort of surge load.

 

8 minutes ago, denn said:

panels are two years old and got them for 50 bucks a pop, thats why i jumped in so unprepared, you dont have to be very smart to recognize a deal like that.

That is an excellent start to a solar system 😉.  It's comical how many people spend $120-150 for a "100w solar panel", and think they got a good deal...at over $1.00/W.  Your panels come in at a stupendously good $0.14/W...for starting out, you're doing way better than most people!  I purchased my first panels for $0.80/W...thought that was good.