# Inverter Sizing, and Choice



## thestartupman (Jul 25, 2010)

I know everyone get so very opinionated about solar power systems. I know people will say that it isn't economical to run a well pump off solar, or that I should replace the pump with something else. I will tell you my plan, and hopefully I can get some good educated feed back. I am looking to purchase a inverter and have it sized to run my current well pump as efficiently as possible. My well is a 1 HP pump. I want the inverter to be either 24v, or 48v. My plan is to set this up to be a permanent backup, grid down system. I plan to size the inverter to run the well, which I plan to add a couple extra pressure tanks too. The well will only be used during the daylight hours. It will also only be used manually if the grid was down. I plan on using the rest of the power created to run a couple of small freezers (a little less than 1 Kwh per day ea, and other smaller type items on an as needed, and as final system design will allow). Again, my main point to get too is to find the best inverter to run the 1 Hp well pump. Hmmm, I forgot, the other requirement would be to be 120 / 240. I was looking at Conext SW 4024, or maybe even the 2524. I am open to others though. My point is to keep the cost down, and try to get the most efficiency from it. My plan is to set this up to run the well 365 days a year as needed.


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## TnAndy (Sep 15, 2005)

Wasn't familiar with them, but looks good. That's cheaper than you could do with Outback (you'd need two inverters + a "brain" box to do the same thing).


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## Gary in ohio (May 11, 2002)

what are the power requirements for the 1hp pump? What is the current/voltage and what is the max inrush current?


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## Steve_S (Feb 25, 2015)

I have a Deep Well (240') and use a Grundfos SQ5 *Soft Start* 120v, 2 Wire pump. Run to cabin is another 70'. Running off-grid it is essential you use a Soft Start pump so it does not have a massive startup amperage draw on our system lest you want to burn up your inverter & more. 

240v is not necessary unless you must use it for something. You'll need the specs on your existing pump to determine running amps & startup amps. You'll need an inverter that has enough capacity to handle the pump start "while" still supplying 50% of your regular load at minimum. You'll need to do your own power assessment on the loads. Most everything can be run from a 24V Battery Bank but when you get up to 3Kw area or 240V then 48V is more suitable.

There are many Inverters, Inverter/Chargers out there and the prices vary hugely. The better Inverter/Chargers will auto-start your Genny when needed to charge the batteries with their own High Amp charger. Key Points is that you want *Pure Sine* and not Mod or Wave Sine, as this is better for electronics as well as motors (pumps & compressors {fridge/freezer} especially). Do NOT seriously oversize the Inverter as that will waste power unnecessarily.

Hope it Helps


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## JeepHammer (May 12, 2015)

Your starting draw, your 'Start Up' draw problem is solved with Capicators,
Often called 'Hard Start' Capicators.
You will find them hanging off the side of any electric motor that has to start under load,
Air compressors, water pumps, A/C compressors, ect,
Mine set at the top of the well head, the closest you can get to the pump, the better off you are.
For AC induction motors, these are the best way to get things done,
And since they can be added to any voltage supply line,
They are easy to install.

You want an inverter that can 'Surge' to about 1.5 times its rated continous output.
This will also help with hard starts.

At 240 feet, its a REAL good idea to have a check valve just above the pump.
This will stop siphoning, and it will take back pressure off the pump.
Most deep well pumps have a BRASS check valve already installed,
But some of the 'Knock-Off'/Import pumps have a plastic or ceramic check valve that likes to fail...

What ever the MAXIMUM draw (spike) that pump is rated for, you will need at least that much inverter CONTINOUS supply, without counting on the 'Surge' of the Inverter...

This *Should* allow for the freezers to operate while the well pump kicks on without crashing.

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I started out with a DC pump.
My reasoning was with a simple timer or manual switch,
The pump driven directly off the panels would give me water,
No matter what else happened.

I still have the DC pump as a reserve, but since have switched to an AC pump.
After I got away from large panel strings, large battery banks and trying to run most everything on DC,
My wiring/cable sizes got MUCH smaller and cheaper,
I can use common wiring sizes, which are MUCH cheaper,
And you can just do so many more things with common 120/240 AC than you can special ordering everything for DC...

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Now, one bit of trivia,
If you use OVERSIZED wire conductors between circuit breaker and pump,
Use the MINIMUM size breaker for the pump,
The breaker will be your 'Fail Safe' when the inverter/panels/batteries can't produce enough current to start the pump.

If the breaker is too big,
The inverter will 'Scram' or shut down from overload.
When the inverter shuts down, it will usually take a MANUAL breaker reset, a fuse replacment, or a manual restart at the inverter to get things going again.

The PUMP LINE breaker takes the beating off the inverter breaker or fuse circuit,
Your inverter lasts longer and anyone with a finger can reset the pump breaker,
While some inverter fuses/breakers are either located in an odd place on the unit,
Or sometimes inside the case, you have to remove the case to find the circuit protection...
A REAL pain in the butt!

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You are trying to do this for just emergencies,
And yet, I would use a 'Ship To Shore' switch,
Handle 'Up' runs the pump on 'Grid',
Handle 'Down' runs the pump off solar.

And I would run the pump odd solar full time, falling back on the 'Grid' (or generator, or batteries through the inverter).
You are going to lay out all this money, put together the infrastructure,
The faster Pay Back is using the solar every day you can,
Saving you meter money, and paying you back for the outlay of cash.

If I were you,
Once you find out how reliable solar is,
And how much you can extract from it,
You will probably want to expand.

Panels with 'Micro Inverters' attached make things so much more simple,
And in emergency situations, one panel/inverter can go down and NOT cripple the rest of the panel/inverter output.
This is a GREAT thing for people that would rely on thei systems after tornados, ice storms, hurricanes, natural disasters.
You always have automatic redundancy that you do NOT have with panels strings and a single inverter...


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## doc- (Jun 26, 2015)

JeepHammer said:


> -And I would run the pump odd solar full time, falling back on the 'Grid' (or generator, or batteries through the inverter).
> You are going to lay out all this money, put together the infrastructure,
> The faster Pay Back is using the solar every day you can,
> Saving you meter money, and paying you back for the outlay of cash.
> ...


That's an obvious bit of logic that is, amazingly, missed by so many. Excellent post.


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## thestartupman (Jul 25, 2010)

JeepHammer said:


> Your starting draw, your 'Start Up' draw problem is solved with Capicators,
> Often called 'Hard Start' Capicators.
> You will find them hanging off the side of any electric motor that has to start under load,
> Air compressors, water pumps, A/C compressors, ect,
> ...


Yes, I do plan to run this system full time once it is in. The only difference that you didn't catch in my post is that the freezers will never kick in while the pump is running. I plan to only run the pump once I shut down the rest of any other draw on the system. So their shouldn't need to be any reason to over size the inverter beyond what it takes to start the pump, with no other draw. 
I do plan to grow the system, but not really ever to expand this system I am talking about now. The plan is to make this system as balanced, and efficient as possible, then build a separate system for the rest of the house. I will build this next system using as many compatible parts as I can. This will make it so I would have spare parts for the first system that I consider to be an emergency system, even though it would run daily.


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## JeepHammer (May 12, 2015)

It's your system, do what you think is in your best interest!
That's the beauty of having your own grid, you aren't stuck with what someone else _*Thinks*_ you need...

Grid inter-tie will reduce bills, especially with timers or current sensors to run high drain devices during peak sun hours.

With the exception of power source (Solar/Batteries/Generator, in that order),
My well pumps/water system is pretty standard.
15 years ago, with Series Panels & single inverter, nothing more than dirt or a couple leaves on a panel could dramatically reduce available power for the pump.

With panels/micro inverters in Parallel, you maximize output even when one or two panels have 'Issues'.
Running on a 'Standard' pump reduces costs and problems.

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The point I was trying to make,
With a _Slightly_ oversized system, and 'Hard Start' capicators, there is no reason you can't run the pump and freezers at the same time.

Hard Start caps solve the 'Surge' issues on start up,
For both the pump & freezers,
And they will smooth out the occasional surge you see when a high drain device kicks off,
Which is something most people don't think about...

Kick Off line surges won't hurt induction AC motors, but they can be murder on delicate electronics, like power monitoring systems, things with microchips are particularly succeptable.
One case I can directly testify to was my energy star, high efficiency cloths washer,
Three digital control modules later I figured out what was happening and added hard start caps to the well pump, no more fried modules since the hard start caps also work as surge suppression when you wire them BEFORE the pump switch.

I had mine wired AFTER the pump switch, which means they got taken out of the circuit when the pump kicked off...
Leaving them in the circuit dampened the surge when the pump kicked off stopped my surge issues.

I did the same thing with my milling machine & lathe, and big surges dropped off to almost nothing,
Plus I have ZERO problems getting those big, high drain motors started now, they kick right on without throwing breakers, even when power is marginal.

The reason I mentioned Hard Start Caps in the first place was you wanted to get by with the 'Minimum' that would run the well pump,
And when you are at the margins of what you can produce, Hard Start Caps will really extend the capabilities of your system.

The inverters are FULL of capicators,
And Capicators are the reason an Inverter has a 'Surge Capability' in the first place.
Hard Start Caps is just adding an extended capability to the inverter,
Caps they simpl didn't have room for in the case, 
Or their clients simply didnt 'Normally' need the added capacity...


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## JeepHammer (May 12, 2015)

doc- said:


> That's an obvious bit of logic that is, amazingly, missed by so many. Excellent post.


I catch a lot of crap because I 'Automate' so much,
Squeeze the most out of every last drop of water, every electron, ect.

I can maintain 'Systems' well into old age,
But I'm 'Disabled', and my medical issues are getting worse with old age...

And, I paid perfectly good money for the solar, water, ect,
Getting the most out of it only makes sense (and saves a ton of dollar$).

Unless this is some last ditch, SHTF, protected system,
Its not making real good sense to me...

Depending on tank capacity and useage,
The well pump is going to run twice a day,
And with timers, those will be at the beginning of Peak Sun,
And at the end of Peak Sun.

The rest of the time, the system will be idling along, occasionally running a couple of freezers, which will barely regester on the capacity of a system that will run a 240' deep well pump...

That's a LOT of wasted capacity...
With grid inter-tie it could be running the meter backwards, taking MONEY off the electric bill,
OR,
It could be doing a lot of extra work every minute the sun shines.

Either way, there is a BUNCH of capacity that will NOT be wasted.

If this is the 'Sacred Cow' system, the dead last resort backup during a SHTF event,
Then the panels need to be covered when not directly in use.
The Photon to Electron event happens even when the energy potential isn't being used.
The panels are S-L-O-W-L-Y degrading over time when they are in light,
Semi-conductors in the inverters are slowly degrading when power is applied to them.

Every part of the system needs to be backed up, as mentioned by the OP,
Pump, pipes/lines, valves, switches, inverters, panels all need to be backed up.

My SHTF with a deep well started when the second well was drilled.
The existing well was 120', but the casing was too small to add a second pump,
And Common Sense dictates having the redundant system in place and ready to use.

My second well has a larger casing, and a hand pump in place.
The hand pump was expensive, made of brass and food grade stainless steel,
But MUCH cheaper than a redundant solar/electric pump.

The old well still has an electric pump, we still use it for irrigation,
But its demand only, not automated.
It was in a bad location for home use is the only reason we drilled the second well...

The other part of this is,
Once you get the mind set of 'KISS' (Keep It Simple Stupid),
And use as much COMMON switches, valves, voltages & wiring that is easily replaced, the better off you will be with a self maintained system.

They *Might Not* be the 'Latest & Greatest' or the top of efficiency,
But they are rebuildable, well tested through time, and most important, USER SERVICABLE!

Common sense extends to things like pressure switches,
If you don't want to drain the entire water system to change a faulty pressure switch, stick a $5 valve under the switch,
You simply turn the switch 'OFF', replace, turn back 'ON' and you are done.
No mess, no fuss, easy and reliable...


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## thestartupman (Jul 25, 2010)

JeepHammer, I mentioned in my original post that I wanted the freezers and what to run while the well pump is not in use, and I plan to add other items as the system will allow. Yes, my entire design is being planned to get every bit I can out of the system. I guess what I am trying to say is that I want to design a system to run my well as efficiently as possible, (using my current 1hp pump) then I plan to design the rest of my usage around what the critical part (inverter) will be. I know most peoples idea of going off grid is to just make everything to handle larger loads, go bigger. I am just trying to get the inverter for the well, get my next critical items running (Freezers, Fridge, ect), then decide what other items will be useful to be run daily on this system. Later on I will design a separate system to run independently of this system. In my opinion, this whole idea pivots around the best possible inverter and most efficient, to run the well.


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## JeepHammer (May 12, 2015)

The most 'Efficient' pump is an AC Induction motor.
AC requires an inverter since panels produce in DC.

You are looking at 300 feet MINIMUM of large gauge cables to run the pump on DC,
And the DC resistance losses in the cables alone would preclude DC.
Your choice of an AC Induction motor pump puts you ahead of the game already.

With that in mind, AC is the way to go.
Don't get locked into a single DC to AC inverter...

Large inverters are expensive, so a 'Back Up' inverter is going to cost a substantial amount of money to hang there and do nothing until the primary fails.

I've gone that route, it was the only way to do it when I started,
And I'm still running part of my system and until the panels/inverters fail,
I'm going to continue to use them.

There are a couple of things that complicat the single inverter system,
The first is your panel strings.
Since these inverters need more watts input in DC than one or two panels can produce,
You need to wire your panels in Series,
#1 feeds into #2, then into #3, ect.
That drives AMPERAGE potential way up, and some panels have too fine of surface conductor to handle the amperage required to run the pump.

The other problem is you have to periodically disconnect every panel and test it for the load it is currently handling.
Wired in Series, one weak or failed panel reduces the entire string, or stops production entirely.

A weak panel that can only pass 100 watts will cripple the entire string to 100 watts output no matter there might be 16 each, 250 watt panels in the string.

You will need to make Series strings of say, 8 panels in a string to keep the accumulated amperage from cooking the panel surface conductors,
Then parillel the series strings (with heavy diodes to keep a weak string from sucking power from the strong strings) to have a reliable input for the inverter.

Keep in mind that commonly available Diodes (Diode, A one way check valve for electricity)
Have a forward voltage drop that reduces what gets to your inverter,
And they need cooling, some kind of heat sink...

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The second issue is,
The least expensive inverters don't have multiple inputs for current from the panels,
You get ONE DC input, and one AC output.

A better (and more expensive) inverter will have two, three or four DC inputs for your different panel strings...

This is a better situation!
You can keep panel strings reasonable, use three or four strings,
And the inverter does the work of external diodes.

The problem here is, ONE dirty panel, ONE panel with a good size leaf stuck to it will instantly drop your potential output at the inverter by nearly 1/2 with two strings,
1/3 with three strings, or 1/4 with 4 strings of panels...

The same rules still apply, the string is only as good as its weakest panel...
That leaf or blob of bird crap can knock your production to the inverter low enough to kick the system out entirely...
When you are right on the edge to start with, just dust can reduce the strings output below minimum the inverter needs to operate the system...

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This is where Micro Inverters really shine!
An inverter for every one or two panels.
You don't loose production for the entire string,
Just the panel or inverter that is shaded or malfunctioning...

You get a 3% or 5% loss, instead of 25%, 50%, or 75% loss,
Still enough production to operate your pump & freezers...

You simply oversize by 10% for a single bad panel/inverter,
Instead of over sizing 50% AND adding a very expensive back up inverter.

Its MUCH more practical IN REAL WORLD USE, you will have to compair costs and see if it makes economic sense...

These things are automated, expandable, and stupid simple to hook up!
Two weather proof/idiot proof plugs from panel to inverter,
One weather proof plug from inverter to wiring going to the fuse panel.

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I can tell you from years of experence,
Taking strings off line, testing panels to find the 'Weak' one,
Moving panels around to group weak panels together,
Checking connections in 50 places, trying to get everything sealed back up from weather, ect is a lot of work!

And that has to be done MANUALLY,
While the newer Micro Inverters have wire-less transmitters, and will report their current output and any problems they have on the higher end systems.
You don't have to screw with much of anything unless the inverters report a problem...
Even washing/dusting the panels can be dictated by the output...
If all panels drop, its time to clean,
And since the inverter/software tracks the output over time,
You know EXACTLY when the panels are dropping in production.

Its also good to know your peak production times, your peak useage times, and how much the system generates and returns to the grid, stuff like that...

I upgrade as my system ages,
Older, weak panels might get moved to a security light,
Panel, battery, dusk to dawn switch and light.
The panel isn't useless, its just degraded to the point its a restriction in a string,
But the lowered output makes it perfect for charging a battery directly.

My drive enterence is 7/8 mile from the house,
But the drive alarm is powered by older, smaller panels and a weak battery that was no longer fit for the battery strings.

The electric fence is an older, smaller panel, weak battery powering the fence charger.

Security motion detectors & cameras are the same deal.

Don't look at your system as 'SHTF', works or doesn't,
All the stuff can be repurposed... Which adds to its useful life and by extension continues to pay you back even longer...


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## Bellyman (Jul 6, 2013)

I'll show my ignorance by asking, but perhaps I'm not the only one who needs to learn...

I don't quite understand the idea of the "micro-inverters" that you mention. Are these micro-inverters right out at the panels? Are they interconnected with each other? How does it all fit together?


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## TnAndy (Sep 15, 2005)

Bellyman said:


> I'll show my ignorance by asking, but perhaps I'm not the only one who needs to learn...
> 
> I don't quite understand the idea of the "micro-inverters" that you mention. Are these micro-inverters right out at the panels? Are they interconnected with each other? How does it all fit together?


You've pretty much got it. 

A single, small, grid tie only, inverter that converts PV DC to 240v AC at about 1 to 1.1 amp each right at the panel.(depends on inverter and panel size....but they are meant for 250w panels and larger). 

They are wired in parallel so the output voltage stays the same (240v), and the amps build to whatever is allowed on a single string....in the case of Enphase brand (only brand I've used....there is at least one other one out there I know of), that is about 17 on a circuit, max of 20amp. But you can run multiple circuits to whatever you want.

On a 40 panel system I did, for example (10,000w)(max allowed by our utility), we ran 3 circuits....13+13+14.

Here's a pic of my own ground mount rack with 10 inverters bolted in place, and before the panels (10x250w) get mounted on top of them:










You plug the inverters into a special cable you buy along with them (you buy however many "drops" you want, one for each inverter to connect into), then the panel plugs right into the inverter (same connectors).

You run the drop cable to a disconnect, and then into your electrical service, and you're done. It's the easiest system possible for grid tie...really is "plug and play". Plus, unlike central inverters that you must run your strings in series (12-15 panels) (most of them don't even "fire up" until you hit several hundred volts), if you lose a panel with micro inverters, you only lose THAT panel (or inverter)...not the whole string.

And with Enphase, they have real time internet monitoring at no charge. You can look on your personal website you set up with them once you finish your install, and see EXACTLY what you are producing now, or what you did at any time in the past....also quite handy.

For grid tie only systems, I can't recommend these too highly.


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## Bellyman (Jul 6, 2013)

Thanks, Andy!! That really puts it together a lot better for me.

I hadn't been thinking in terms of grid-tie systems. 

Is there anything similar for off-grid setups? I can see how having 240 volts coming right off of the panels could make wiring runs much less expensive but then I'm not sure how the current would be parsed out or how the battery recharging would be handled efficiently.


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## JeepHammer (May 12, 2015)

> I forgot, the other requirement would be to be 120 / 240. I was looking at Conext SW 4024, or maybe even the 2524.


4024, That's a 4,000 watt inverter.
4,000 watts divided by 120 Volts = 33.3 Amps
4,000 Watts divided by 240 Volts = 16.6 Amps

Grundfos 1 and 1.5 HP in well pumps, 240 Volts,
Draw between 11 & 12 Amps (2,880 Watts) on start up,
And 7 to 9 amps (1,920 Watts) running.

This is for reference...
That particular inverter has a built in battery charger, probably for a 24 volt string or bank.
90 amp charger with three steps to charge batteries,
Which would allow you to series batteries for 24 volts,
Then Parallel the strings to make up a fairly large bank.

I'm not a fan of just throwing amperage at batteries, letting them sort out which battery gets what charge, but that's not an issue here...
Charge controllers on each string is a better way, but that's advanced, and we are talking basics.

That inverter has a 5 second, 7,000 Watt Surge capacity (equivalent of Hard Start capacitor bank), exactly what I was talking about before...

Since the propaganda says these are stackable, I would assume they are syncing inverters,
Meaning they synchronize with each other, which is a good thing for adding more panels/power later.

This inverter and a good in well submersible pump would make a pretty good match,
The issue you will see with this inverter, and NO BATTERY BANK is your panels array will have to be WAY oversized to compensate for partly cloudy days.

With a battery bank, the power you banked in the batteries YESTERDAY will compensate for clouds today, and the batteries recharge tomorrow...

If you wanted an off grid inverter, this isn't a bad choice,
The price isn't bad, its got all the basic features,
But that 2 Year warranty bothers me a little...
If it cooks every two years, then that's about $700 a year for just the inverter.
Since I don't have one of these, I can't tell you how long they 'Normally' last.

-------

The grid inter-tie feature is a good deal!
If panels/battery or cloud cover disable the solar/battery part,
The inverter can use grid power to run the pump.

Off grid solar and batteries kind of go together, 
The grid inter-tie just gives you more options, and allows your pump/freezer backup to turn that meter backwards when you aren't consuming the power you make from the panels.

Since you can run it as an off grid system, or a grid inter-tie system,
Kind of gives you the best of both worlds...


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## TnAndy (Sep 15, 2005)

Bellyman said:


> Thanks, Andy!! That really puts it together a lot better for me.
> 
> I hadn't been thinking in terms of grid-tie systems.
> 
> Is there anything similar for off-grid setups? I can see how having 240 volts coming right off of the panels could make wiring runs much less expensive but then I'm not sure how the current would be parsed out or how the battery recharging would be handled efficiently.



No, they are not setup for off grid. They have to sense grid power, or they shut down.

It 'might' be possible to mix them into an off grid system, but I can't say for sure. 

Most off grid systems use 'inverter/charger' combinations, so, in theory, you could fire up an inverter off a battery bank, (with no panels or charge controllers feeding the battery, as a 'normal' off grid system is set up) then cut these type of inverters into the mix, and it 'shouldn't' know the difference as to whether the power turned out by the inverter/charger was grid or not....lot of off grid inverters actually run cleaner power than the grid. As the battery required charging, the I/C unit would siphon some of the power to maintain the batteries.....in theory.....

My own system, for example, is a hybrid of a hybrid . 

The first 6kw I put up is a grid tie with battery backup affair. I use a pair of Outback inverter/chargers, fed via a 1200amp/[email protected] battery bank that turns out true 240vAC. The 6kw of panels that feeds into the battery bank runs thru 3 separate Outback charge controllers. This is normally grid tied, but if the grid drops out, my inverters drop out as well...but a second set of contacts in them close, (feature of the "GTFX" series inverters) and divert the power to a transfer switch. I flip the transfer switch over to Solar, and we keep on operating.

The last 5kw of my system is 20-250w panels and 20 micro inverters...(the pic above is the first 10, I added 10 more after that)...they completely bypass all the Outback system and simply feed straight back to the grid (thru a separate power meter, so I get credit for my production...same meter the Outback system feed thru in grid-up time).

NOW, my thinking is....and this is only theory....that should the grid go down, and look to STAY down long term, AND my mirco inverters were OK (as in not damaged by EMP or Sun Spot), I would rewire their configuration so they also fed into the Outback off grid mode output....because they way they are wired now (same meter as the Outback) wouldn't work with the grid shut down....just be a matter of rerouting some wiring to the off grid side of my inverters.... I sorta think it would work....I don't see why not.....but I can't swear to it.

Of course, you'd ALSO have to change the way you use power.....since your peak production would be in the middle of sunny days, you'd want to use it then, and lighten your loads at night to keep from over using (thus extending life) batteries. You'd wash clothes, or run power tools for example from 11am to 2pm on sunny days....that kind of thing.


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## thestartupman (Jul 25, 2010)

JeepHammer, to start with, I would like to say I really appreciate your feedback. A lot of time the only feedback a person gets is not answers to the questions being asked, but only the thoughts of how they think things should be done. I really like your thoughts on re-purposing items that are not as efficient as they once were. I do plan to have a small bank of batteries. I just don't plan to 2 or three days worth of batteries. I was planning to keep the well capable of running on the grid if need be, but just use manual cutoff switches to switch over if needed. Do you have any other suggestions for inverters that may fit my needs better?


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## JeepHammer (May 12, 2015)

TnAndy,
What you describe is almost exactly what I've done.

Panels feed stand alone charge controllers, charge controllers feed directly from DC output from the panels.
A charge controller for each Series battery string in the battery bank.

The batteries, when properly matched in the strings, and properly charged, those batteries live a LOT longer.
This takes a little more power from the panels than a single charging source,
But I make the power, I can't make my own batteries, so the longer they live the less they cost per year of use.

Now, solar/battery power into a TRUE SINE WAVE INVERTER,
With a true sine wave inverter, the micro inverters will sync up with it and reduce what the big inverter has to do...

One word of caution here, you CAN add so much the stand alone inverter shuts down,
Crashing the entire system... Momentarily.
As soon as the micro inverters shut down, the stand alone inverter will kick back in, but it will take up to 15 minutes for the micro inverters to sync up and produce again.

There are also a couple of 'Hacks', units that will allow the micro inverters to work off grid,
But be aware that those units will void your factory warranty.

I suspect these are sine wave inverters and a 'Load', since micro inverters are designed to operate 'Full Throttle' since they return excess production to the grid.
Excess production would have to be wasted by a load of some sort to work.

I simply don't add more micro inverters than I have load for,
Letting the big inverter scale up/down depending on load.


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## JeepHammer (May 12, 2015)

Not really, you picked a VERY flexible inverter,
It's hard to buy too big, its really easy to buy too small and do it over again.
That inverter works 'Stand Alone', Grid Inter-tie, or ganged with other like inverters.
I wish they made that inverter at that price when I started!

The only thing I would research before I pulled the trigger was DC inputs.
I'm not nuts about 'Combiner' boxes,
Boxes that combine panel Series strings into a Parallel input for the inverter.

From lugs/terminal strips made of steel or worse, aluminum,
To using expensive DC breakers instead of sizing the panel string correctly in the first place.

I'm not happy with single point charging.
Chargers are load sensing, if ONE battery in the string/bank is demanding more charge than the others,
The ENTIRE STRING/BANK gets the charge, overcharging the 'Good' batteries.

The MYTH is you have to charge the battery string, front to back, all together.

The FACT is you could have a 6 or 12 volt charger on every battery,
The most EFFECTIVE (not efficient) way is to charge in 24 volt strings.
In my case, that's a charger/controller for every 4 batteries.

6 volt batteries, 4 each for 24 volt strings,
Add stings and charge controller as you need more reserve.

The deal is,
A charger throws positive current at the batteries,
The first takes a big drink, the rest is passed to the second, it takes a big drink, and so on,
By the time the current reaches the back battery in the string, there isn't as much current,
So often times the 'Middle' and tail batteries are chronically undercharged, 
Which limits the work they do, and their life span.

-------

Now, If we were charging in AC, this wouldn't work,
But DC POSITIVE will seek its OWN DC Negative to complete its Circuit.

DC doesn't care what else is going on, its seeking its polar opposite ONLY to complete the circuit.

I use this for battery charging in the middle of a bigger circuit.
Since the positive from the charger is seeking its specific negative,
You can easily charge SPECIFIC batteries in the middle of a larger string or bank.

This completely escapes people for some reason,
They think AC where a potential current will seek 'Ground' t the first possible opportunity,
Where DC seeks only its SPECIFIC polar opposite.

People don't take advantage of series/parallel battery banks enough,
Keeping Amps down, high amperage is hard on everything from requiring larger conductors with more expensive copper, to frying contacts in switches.

Keep amperage down, drive voltage up, smaller conductors, reasonable/common switches save a bunch of money.


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## thestartupman (Jul 25, 2010)

JeepHammer, thanks again for the great information. I have to say I have to read over yours and others post many times, to try to get a better understanding. Keep the great info coming though. It may take me a while to catch on to everything, but I know I would rather learn from you and others, then learn by making mistakes. Thanks Again


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## JeepHammer (May 12, 2015)

*The guy that doesn't make mistakes isn't doing anything.*

Between LAZY and Internet know it all types, no one gets much done these days,
So I'm glad to help out if I can when a guy shows initiative!

I'll try about anything once if it makes sense...
Common sense is sorely lacking in a lot of cases!

Welders have used high capacity Diodes for years to Rectify AC to DC,
So does every automotive alternator.
A Diode is a one way 'Gate' valve for electricity,
Lets current run one direction, but not the other.
I say 'Gate' valve because there is a forward current drop to get it 'Open' and flowing,
But you simply size the Diode to the amount of current its supposed to handle in your circuit.

Diodes come in handy when you want battery strings to feed an inverter,
But you want that battery string isolated from the rest of the batteries for charging.
All your batteries won't be the same age, size, type or condition/capicity.

You group the stronger batteries together with their own charger, and since they are all the same size, type, age, ect, they charge at the same rate,
So you hang a charge controller on those batteries to maintain them.

Same with the older, weaker batteries since they are going to demand a higher charge rate for a longer period of time, which would cook (overcharge) your newer, stronger, more efficient batteries.

Then you do it again with the really old batteries,
Reaching the end of service life in your battery bank,
Demanding more charge than the rest of the batteries in the bank,
And with that increased demand, your other two sets would be overcharged.

Common, high capicity, 6 volt 'Golf Cart' batteries are common for battery backup systems,
Mostly because they are true 'Deep Cycle', take abuse and are forgiving, and they are cheaper Per Amp Hour since they are 'Common' and not 'Special Purpose' batteries.

A 24 volt string will take 4 batteries wired in Series to produce the 24 Volts.
Series drives Volts Up,
Parellel drives Amps Up.

Say, three strings of 4 batteries in Series, 24 volt strings.
That's 12 batteries total...

'Blemish' batteries, scuffed cases, ect. Will run you about $160 each around here.
$160 battery x 12 batteries = $1,920
Charge controllers are $25 to $75 each.
Pretty cheap insurance to keep a $2,000 investment alive,
And that investment allows you to add batteries as you need them,
Not replace ALL batteries at the same time.

You can wind up paying $250 each for batteries, so short string charging makes even more sense & protects an even larger investment...

Don't forget, properly watered and charged, you can expect another 2 or 3 years of service out of your battery investment!
Charge equalization between batteries is a big deal in solar arrays,
Its automatic with a charger on each short string.

The 24 Volt Series string gets a Diode just before it dumps into the parillel lines to the inverter.
This diode keeps he strings from back feeding into each other,
Weaker battery strings aren't sucking power from stronger battery strings,
And weaker battery strings aren't demanding charge power from a central charger, while hat same central charge power isn't cooking your stronger batteries that charge fully quicker.

---------- 

I don't know your skill/knowledge level on this stuff,
So some basic, then advanced education on this stuff...

Lets say we are working with 6 Volt Deep Cycle Batteries,
For ease on the math end of things, Lets say 1,000 Amps each.

Series Wiring,
Positive of first battery wired to inverter,
Second Battery Positive Wired to first battery negative,
Third battery positive wired to second battery negative,
Fourth battery positive wires to third battery negative,
Fourth battery negative wired to inverter.

This is Series, its still 1,000 Amps,
But Voltage is driven up by 6 Volts with each battery you wire into that Series string.
4 Batteries 6 Volts each, 24 Volts @ 1,000 Amps.

------------

Now, take those same 4 batteries,
Wire all the Positive terminals together in a stright line, then directly to the inverter,
Wire all the negatives together in a stright line, then directly to the inverter,
And you will deliver 6 Volts @ 4,000 amps.

Series drives VOLTAGE up,
Parillel drives AMPERAGE up.

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Now, say you have 3 strings, 24 Volts @ 1,000 Amps each String,
But now you PARILLEL the strings to the inverter,
Each string Positive Connects to a larger cable feeding the positive on the Inverter,
Each string Negative Connects to a larger cable feeding the Positive on the Inverter.

Strings are Series to produce 24 Volts,
24 Volt Strings feeding in Parillel to the Inverter,
This is now a 24 Volt feed at 3,000 amps!
One heck of a lot of power, keeping the amperage potential reasonable...

With Diodes at the junction between string and Parillel feed lines to the inverter,
The strings are isolated in the battery bank as a whole, so you can charge each string for maximum lonjevity,
And yet, each string can throw its full potential at the inverter.

Like I said, large capacity Diodes for Welders work well for this,
They are common and very reasonable priced ($20 to $35),
And a charge controller for each string ($25 to $75),
These are one time costs normally, since they will continue to serve you as you rotate out old batteries, and rotate in new batteries...

I know this sounds confusing, but think of it this way,
You go to expand your battery bank in a year or two,
You CAN NOT put new batteries in a single charging string with 2 year old batteries!
The new batteries will cook while the single charger tries to charge your two year old batteries.

Another thing that's cropped up more than once,
You get a 'Deal' on larger or smaller batteries than the matched set you started with...
Or the manufacturer discontinued the batteries you started with...
Again, a mixed set of batteries just simply will not work together for long.

Small string chargers are cheap, diodes are cheap, and they allow you to use strings of different size, age, type, even voltages of batteries together _'In Banc'_.
A heck of a good deal since you don't have to replace the entire battery bank every time you want to expand, or replace a couple of batteries that aren't 'cutting the mustard' anymore.

---------

This same simple approach lets me use the golf cart batteries, still in the golf cart,
To act as a reserve battery supply for the house.
I simply plug in a LARGE cable connector to the golf cart when I'm not using it,
That cable set has the charger/charge controller hooked up to it inside the shed where the rest of the batteries are,
And connects the golf cart batteries to the home inverter, to power the house.

I couldn't see just having my reserve battery bank just sitting on the floor doing NOTHING waiting for those two overcast days in a row,
So I drive my reserve batteries around, plug them in when I get home...
If we have two overcast, raining days in a row, its an open golf cart, chances are its charged and just sitting there, ready to power the house...

--------

Speaking of RE-purposing things...
When I got the golf cart, I was looking for a 'Cheap' set of reserve batteries.
The local battery supplier didnt have any deals, but told me about a guy that bought a full set of top of the line batteries last year, and got a new golf cart 'This' year...

Since the old golf cart wouldn't run with new batteries,
He might want to sell the batteries...

He sold me the batteries cheap, but the deal was I had to take the old golf cart and junk it for him.

$24 relay got the cart running, I'm not scrapping a running golf cart,
But I still need the batteries....
What to do?.... What to do?....

$20 Diode, $35 charge controller, $20 worth of 'Anderson' connectors.
Short range transportation AND a battery reserve bank!

Mount my very first 2,500 Watt inverter on the golf cart and I've got 120 volt AC power at my job sites without listening to a generator run...

Add on a 12 volt air compressor & tank, I have compressed air at my job sites without listening to a generator run...

Add some LED lights, and its of use after dark.
Keeps me from getting run over when I run back and forth on county roads also...

Take those silly golf bag brackets off, mount an extension cord reel,
And a compressed air hose reel and I'm off to the races with a quite capable work site vehicle that also serves as a back up battery bank!

Hard sun top already on the cart, throw a couple odd solar panels up there and it will actually charge its self a little...

One thing about electricity, if you make your own, the uses are almost unlimited...


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## JeepHammer (May 12, 2015)

The inverter first mentioned, I wasn't clear on how many inputs it has.
Obviously, battery/panel input, 
I wasn't clear if it had Grid AND Generator, or Grid OR Generator.

Anyway, along that common sense line of thinking,
I see people picking up 'Back Up' generators all over the place.
I started with a Briggs & Strattion powered 4,000 Watt generator,
Which is OK for construction tools,
But was sadily lacking for much of anything else except for basic appliances.
The power it produced was 'Dirty', voltage and cycling all over the place,
That's hard on induction motors in refridiration, certain death for sensitive electronics.

I was looking at a 10,000 watt unit when it dawned on me that was about what my big diesel welder produced, 
And the voltage/cycles of the welder are pretty much dead on, clean power.
The welder has 120 Volt, 240 Volt & 240 Volt 3 phase AC taps built in.

My milling machine and lathe are 3 phase, so no phase converters to run them,
I just fire up the welder.

When the welder runs, it makes so much excess power,
I charge the batteries, run the well pump, and I can run an electric cloths dryer in the shop.
(Work cloths, shop towels, rugs, ect.)

Since I run the welder for shop tools at least once a week for paying metal working jobs,
Using that excess power to top off the water tanks, do 'Laundry', ect pays for itself.

If I had it to do over again, the welder would be propane instead of diesel.
The stove, water heater, radiant floor heat is all propane, 
And there aren't any storage issues with propane.

It would be more intergrated with propane, but I'm not going to run out and plunk down cash just to switch to propane,
Maybe switch when the welder engine needs rebuilt...

Another place to get a big, useful generator is an RV salvage yard.
Those RV's have big honkin gensets, and you can pick up low hour genset for 20 cents on the retail dollar.
The local insurance auctions have a dozen every sale,
My portable back up generator is gasoline, 7,500 watts,
Low RPM so it doesn't rattle your teeth when it runs,
And its a name brand (Onan) so parts for it are all over the Internet,
Cheap to buy/maintain, dead reliable.


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