SW+5548 Inverters

[ChrisOlson]

I found some new Xantrex SW Plus 5548 inverters for sale on eBay for only $2,500 each, with free shipping:
http://www.ebay.com/itm/271067957427?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

So I called Schneider Electric to check on the warranty on these units.  They investigated it and called me back.  They said they will honor the warranty on the units pending the seller providing documentation that he is an authorized Xantrex dealer and not just an individual.  And that he provide documentation for the warranty start date that the units have been powered up and tested after sitting for 6-7 years and is not shipping any DOA units.

The guy at Schneider said that the SW+ is one of the most rugged inverters ever built and they don't anticipate one ever having any warranty issues.  But there are components in those inverters that don't like to sit around that long and could possibly have issues if they have not been stored properly and moisture got in.  In the event one does have a problem, it would be my cost to ship it directly to Schneider to have it repaired, and they would pay the shipping cost back to me.  He said with a new XW-series they would send out a replacement unit for a warranty issue and when I receive it I would send the defective unit back - or in some cases that require only a simple board or part replacement they will ship out the parts needed to fix it and walk the owner thru servicing it over the phone.  But he said with the SW Plus that's not possible because they don't have any in stock.

If everything checks out I'm looking at buying two of these units and swapping out our SW Plus 4024's with them.  I already have the AC conduit boxes, ISC-S stacking cable, and Generator Start Module for the SW Plus inverters.  It would be a cheap upgrade to 11 kW of capacity, with a 2 year warranty.
--
Chris

[richhagen]

I have a single SW4048 running.  I bought it used, and have never had an issue with it.  It is a heavy unit and was a lot of fun for me to hang on the wall by myself, but I was too impatient to wait around once I got it.  I routinely run mine to 3kw or more, especially when dumping through a couple of space heaters, the inverter's cooling fans kick on under load, but it has had no problems and will start about anything on 120V for me from welders to motors.  I know Dan has a somewhat similar setup to what you are talking about, and he had that issue with his welder kicking them out that he has since resolved. 

[ChrisOlson]

Yes, our 4024's are pretty awesome units.  The guy at Schneider kind of chuckled when he was telling me about the warranty and what it would entail, as he said those inverters have a reputation of handling anything you can throw at 'em and the chances of one having a warranty issue are almost slim to none.
--
Chris

[OperaHouse]

I guess I would give you the same advice that VFD makers give to people that store their products for a couple years.  Power them up for 48 hours before placing any load on them.  That will give the capacitors time to reform before they have to deal with high currents. 

[ChrisOlson]

Well, so far the guy that's selling those has failed to meet Schneider's requirements for the warranty.  I contacted him and told him what Schneider needs for documentation, gave him my case number that Schneider gave me that they will keep on record for warranty purposes in the event I buy them.  Nothing - now he's failing to respond after 24 hours.

Schneider Electric's Customer Support dept was absolutely superb, BTW, in handling my inquiry.
--
Chris

[Frank S]

Chris looking at the site he states these are new in the box but old stock. My company often buys containers full of merchandise mostly large equipment  as we are sole distributors in this country for many manufactures We sometimes have stuff that is EX-O_ stock the only way we remain sole distributors for the manufacturers is our in house warranty and after sales service. some of our items may be out of shelf life according the the manufactures if so we must sell at a highly reduced rate and still warranty them or sell as is where is but never as new old stock.
  I think it is amazing that  Schneider Electric' would even offer to honor a warranty period simply if he produces the proper documentation That would seem the least he could do if he was a dealer for them at one time
 It tells me that Schneider Electric' is more than a stand up manufacture since they are willing to do this.
 I could but won't name dozens of very large companies that would laugh in your face if you had asked them to stand behind something that had been on a dealers shelf for  as long as he has had those units.
 Offer him 1/4 the amount he is asking just to take them of his hands, tell him that if he won't or can't produce the documents that is all they are worth

[ChrisOlson]

He still has refused to return any replies now after I told him what Schneider Electric is requiring to validate the warranty on those inverters.  I looked back thru his history and he has been selling Xantrex stuff advertised as "new" clear back to 2007.  He probably is not a Xantrex dealer - more than likely just a guy that gets this stuff from someplace and sells it on eBay to turn a buck.

There are still brand new SW Plus inverters out there.  We bought our 4024's brand new, but from an authorized Xantrex dealer that handles all warranty work in house and on-site, and has all the parts in stock and tools to work on them.  There was a very large solar outfit in California not too long ago that had some brand new SW Plus 4024's for sale as well - their price on them was $2,650.

It's almost impossible to find them used.  People that have them won't give them up, and they don't break.

The downside to the SW Plus is that they are damn heavy.  Two men can barely lift one up to the wall and it takes a third man (or woman) to install the screws to hold it there.  And they're noisy - they got three big transformers in there that all work together to generate the sine wave.  Those transformers sound like a big 250 kVA 480/277 utility transformer when the inverter has any significant load on it.  But they also beat the pants off anything Outback ever built or thunk up.  So when a guy finds a deal like this it's rather disappointing when it turns out to (maybe) be not legit.
--
Chris

[boB]

But they also beat the pants off anything Outback ever built or thunk up.  So when a guy finds a deal like this it's rather disappointing when it turns out to (maybe) be not legit.
--
Chris

Yes, they're good inverters...

Fun Fact:  The same guy that designed the SW inverters designed the OB FX inverters.

boB

[ChrisOlson]

LOL!  I wish I could find that guy and tell him he forgot to put the following into the FX:

• dual AC inputs (REALLY handy for off-grid when you got standby and backup generators)
• generator load support
• a bigger battery charger that can at least use the full capacity of a 3.6 kW Honda generator and properly charge a 1,000 ah bank at C/10)
• native support for three-wire generators (without having to buy a crappy Atkinson controller)
• he went and turned a 4024 into a 3524 plus removed a bunch of overload capacity, leaving us all just a few watts short of running many off-grid homes with one inverter.

While this "Outback guy" impressed many, there's a still a few of us that got the Original Deal and remember what real inverters used to be.  We're hoping he reaches back into his file in remembrance of what it took to make an inverter not only good, but legendary, and does it again with a different name on it.

Now, if I could just find that guy to tell him all this.........   
--
Chris

[SparWeb]

If you track him down, and take the 5548, please let me know.  You could send your twin 4024's to a good retirement home, here. 

I already have one, it needs a friend.  And a backup friend.

[ChrisOlson]

Well, our 4024's are Plus models, which are more capable than the old SW Series II.  Is that what you got is a Plus?
--
Chris

[SparWeb]

No, my 4024 is a vintage model from "Trace".  Instead of trying to stack old+new, I'd take your twin 4024+ models to have a matched set for 240v/120v house power.

People that have them won't give them up, and they don't break.

Exactly.
And I don't expect you to part with your 4024's either (but I thought I'd ask first).

[ChrisOlson]

Well, that's the deal - right now I actually got more inverter capacity in our house than I need for most things.  But I have to use generator support to power both the house and machine tools in my shop when I'm working in there.  And use generator support in the house for the heavy draw stuff.  A 5.5 kVA inverter, with generator support, would be plenty for the house with a Outback PSX-240 6 kVA transformer on it.  And I don't have enough inverter capacity, even with gen support, if I get wild in the shop and my wife gets wild in the house at the same time.

I've looked at various scenarios:
One theory I had was that I could step the bank up to 48 volts to run a 5548 for the house.  And split the bank into two 24 volt "halves", putting a 4024 on each bank half.  Use the 4024's dedicated to the shop with my Trace T240 transformer on the output of those to keep them balanced for the 120 volt loads in the shop.

Theoretically this should not affect bank balance at all, and allow me to run anything in the shop without gen support.  And only use the gen support on the 5548 in the house for the heavy draw items like my wife's clothes dryer and range.

That was all just one scenario I dreamed up to get more power on tap.

But this deal on the 5548's appears to be falling thru.  I could "Buy It Now" and get one, but it doesn't appear that he's going to come up with the stuff that Schneider required for the warranty to be effective.
--
Chris

[Frank S]

All A guy would have to do would be be up front and say I'm sorry but I simply do not have the documentation
 Then you could decide to make a counter offer at a reduced price without the possibility of a warranty He could accept and you would be taking a chance.
 I haven't bought much from fleabay because it is so difficult to find a seller who is willing to warranty international shipments. Europe sellers seem to be better informed or possibly more intelligent than US sellers about shipping. Australian, Canadian. British, Dutch & German  appear to be the most honest

[ChrisOlson]

Thing of it is, I can buy a XW6048 from Windsun for only $3,100:
http://www.solar-electric.com/xaxwhyin1.html

Of course, I'd also have to add in the SCP:
http://www.solar-electric.com/xaxwsycopas.html

And the generator starter:
http://www.solar-electric.com/xaxwagsauges.html

We also looked at an Outback GS8048 Radian:
http://www.solar-electric.com/ourags8wain.html

But the Xantrex unit supports three-wire generators directly from the SCP and the Radian requires the use of a CRAPPY Atkinson aftermarket controller.  So I won't buy an Outback because of that reason (hear that "Outback guy" that might build something that can actually compete with the SW/XW someday?)

And then the Radian don't have a PF corrected charger in it.  The XW's PF corrected charger is state-of-the-art.  Why Outback never put a PF corrected charger in their flagship inverter is a mystery that can't be solved (same with three-wire gen support).  I sure hope that "Outback guy" is listening because it appears the Alpha Group is more interested in cutting corners than building what we need   
--
Chris

[boB]

What is it about the Atkinson you don't like ?

Also, the "Outback guy" won't be on any forums.

The VFX inverter/charger is just smaller than the SW and so you don't get as much power out
of it.  But they do parallel stack.  The surge power of at least the 48V VFX is around 6kW for
starting motors etc.

The SW was  better but of course it was bigger and heavier than the FX/VFX.
 The charger really should have been PFC but is somewhat more difficult.

I like the Magnum chargers which are PFC.   That's a pretty fancy trick to make
the inverter circuitry work in reverse AND be PFC !

The SW charger isn't PFC either but might be more towards PFC = 1.0 in many
cases.

boB

[ChrisOlson]

What is it about the Atkinson you don't like ?

It's not integrated.  Say, for instance, that you you have your generator's crank time set at 4 seconds for summer and it fires up every time.  But cold weather comes and you want to change precrank (preheat) seconds and crank time to adjust for more reliable starting in the cold weather, and so it doesn't run the battery down on multiple tries to get it started.  Easy - just go to the inverter's control panel and push a couple buttons and the job is done.  Ooops - not on an Outback.......

Some more of my thoughts on auto gen starting -
Two wire generators are bogus.  I get the distinct impression that the people that designed them live in Florida.  But the people who primarily use off-grid stuff live in the frigid north.  Kohler and Onan generators with no ambient or engine temp sensing will run the battery dead before they'll start at zero F.  Disable that two-wire start and make it three wire so YOU (the inverter) has control over starting parameters and you can get them to fire up every time.

And lastly, it's nice to have the gen controller mounted on the utility room wall with knockouts for the wiring and stuff to make it nice and neat, so you can see the status at a glance and got nice switches for lockout for gen servicing.


Not with an Outback.  You got a Atkinson controller that looks like a porcupine with wires hanging out of the face of it - and one of those wires is a separate AC input from the generator, for pete's sake, so it can sense the voltage and freq from the gen (which should be done in the inverter).

To each his own.  But when I look at spec'ing out an off-grid system where the customer wants auto gen start the first thing I tell them right upfront is, "Well, you won't be buying an Outback then......"
--
Chris

[ChrisOlson]

Got a new SW Plus 5548, brand new still in the box.  But not from the eBay dude.  I got it from an authorized Xantrex/Schneider Electric dealer that had it in stock - with an approved factory 2 year warranty on it.  Traded our almost 2 year old SW Plus 4024's, plus the T240 Xantrex transformer for it, even trade.  This is a 120 volt inverter so I got a Outback PSX-240 Autotransformer for it.  The Outback PSX-240 is much heavier duty than our T240 was - the Outback is rated 6 kVA continuous output and weighs about 50 lbs.

This setup is more power efficient than stacked inverters and has a couple advantages over a split phase inverter - one is zero problems with leg balancing for 120 volt loads.  We rewired our panels and got a 120 volt Load Center and a 240 volt Load Center now.

The 120V Load Center is a 100 amp panel and is fed by the inverter.  The 120V Load Center feeds the 240V Load center thru the transformer.  There is a 30 amp two-pole breaker in the 120V Load Center that feeds the transformer - one leg from that 30 amp two-pole breaker is pass-thru directly to the 240V Load Center.  The other leg from that breaker feeds the transformer input.  The transformer generates the other leg of the 240V split phase and sends it to the 240V Load Center.

The idle consumption on the transformer is only 10 watts - less than half of what an idling inverter uses in a stacked configuration.  And because all loads are fed from one source, there is zero leg balancing issues like you have with a split-phase inverter (or stacked inverters), even with imbalance on the 240V Load Center legs.

So this is something I've been mulling over for quite some time simply because stacked inverters are a power hog when you have to have both of them running 24/7 with a balancing transformer for the 120V loads.  The idle consumption of the whole system was about 60 watts, and the running losses pretty much corresponded with that.  The idle consumption of our new setup is only 30 watts and the operating efficiency at our normal 300-1,000 watt average loads is about 94% instead of in the high 80's from running two inverters off the peak of their efficiency curves.

This is the autotransformer - the wire nut connection is made on AWG 6 wire that passes thru to the 240V Load Center and the other leg goes thru the transformer so it can generate a sine wave that's 180 degrees out of phase with the pass-thru leg.  The PSX-240 was about 450 bucks with shipping cost on it:





The SW Plus 5548 slid right in - didn't even have to remove the ACCB from the wall for the bottom inverter.:



And it delivers the goods.  Full load test, with generator support, with every switch in the house that we could find turned on for 30 minutes:


--
Chris

[Frank S]

this should address some of the12/ 24/48v series parallel bank balancing issues I've been reading about

[ChrisOlson]

I wired our T12-250's four in series, giving me six strings in parallel to the bus.  It rendered my bank balancing meters useless.  I need to sit down and draw a wiring diagram and think it thru - I have a rotary switch that I robbed out of a Jacobs inverter that I can use to connect to various batteries in the bank, in pairs, to check their balance without having to get out a DVOM and check it right at the bank.

But I don't think the way I have it wired will be a problem anyway.

The thermostat in the house, and the fan center relay for our central forced air wood furnace is 24 volt.  So I did have to tap the center point from system ground on one string to supply 24 VDC power for our furnace controls.  If I can find a suitable transformer I could run that on 120 V AC power and eliminate that tap.  I don't think the furnace controls would care if it's 24 VDC from the battery bank, or 24 VAC with a little transformer.
--
Chris

[Frank S]

little 30 to 50 va 120 to 24 v transformers should be common as dirt almost every door chime system has them if your controls were finicky about vac just use a single bridge rectifier

[southpaw]

I wired our T12-250's four in series, giving me six strings in parallel to the bus.  It rendered my bank balancing meters useless.  I need to sit down and draw a wiring diagram and think it thru - I have a rotary switch that I robbed out of a Jacobs inverter that I can use to connect to various batteries in the bank, in pairs, to check their balance without having to get out a DVOM and check it right at the bank.

But I don't think the way I have it wired will be a problem anyway.

The thermostat in the house, and the fan center relay for our central forced air wood furnace is 24 volt.  So I did have to tap the center point from system ground on one string to supply 24 VDC power for our furnace controls.  If I can find a suitable transformer I could run that on 120 V AC power and eliminate that tap.  I don't think the furnace controls would care if it's 24 VDC from the battery bank, or 24 VAC with a little transformer.
--
Chris

I read in some robertshaw (maker of 24 vac gas valves) some time ago that they could be operated on 12vdc. I think 24vdc might let out the "magic smoke".

[bart]

    Coming from an HVAC guy, you can buy, and thats what I carry on the service van, multi-tap transformers w/built in circuit breakers. From 40va to 75va. 120v, 208v, 230v, or up to 460v. If the controls don't specify DC compatibility, I"d stay with AC.

[ChrisOlson]

Actually, the controls on the furnace say 24VAC.  That's what it says on the fan center relay anyhow.  And the thermostat wiring going upstairs is on that same circuit, so I assume that's AC also.

When we got it, it said in the installation manual that 24 VDC could be used for off-grid applications where a 24 VDC system is used.  It has been that way for two years.  It gives a part number in the manual for a transformer that can be ordered for it to supply 24 VAC for on-grid installations.

But really, it doesn't seem to be a problem with the center tap on the bank.  The relay coil only draws like .1 amps and so far it hasn't affected anything on the batteries.  So may leave it as 24VDC.
--
Chris

[bart]

   If you've got the manual and it says you can do it, your good to go. Many boards are AC/DC, but unlike you, many customers don't have one or the installing company did not leave it.

[stratford4528]

Has any one thought of using XXXX inverters. I'm a agent in the UK and use a 5000watt XXXX which are superb. Very quiet and superb operation you don't even notice when the generator cuts in and out to charge  the batteries.


Sorry, too much like a sales pitch for a first post, though thanks for disclosing your position up front.  Damon

[kitestrings]

Hi Chris,

I managed to somehow miss this post as it unfolded.  I have a few questions:

I'd understood that Xantrex was still in business, but I take it that they just don't manufacture the orignal SW Plus units, is that right?

I was having trouble following your battery configuration.  You said you'd wired "four in series, ..six strings to the bus" and the T12 250's are 225 AH(?), so I wasn't sure how you got to 1200 AH, maybe 200AH/ea is nominal.  Anyway, my broader question is why so many parallel strings?  I'd thought it was more desirable to have say longer series strings, but fewer of them in parallel?

What is "generator support", is this the ability to fully load the inverter, plus the generator input?

Lastly, I suspect the 'Outback guy' that did the design work and the folks who determined what would sell, make profit, allow weight to be paired down, etc, etc. where not the same folks.  Just a hunch.

~kitestrings

[ChrisOlson]

Trace Engineering originally built the DR's and SW's.  Trace merged with Xantrex and Xantrex built the SW Plus.  The SW Plus has more surge and overload capacity, non-volatile memory, external GSM (Generator Start Module), and several other improvements over the SW Series II.  Xantrex replaced the SW Plus single phase models with the XW-series split phase models.

Schneider Electric bought Xantrex.  The mobile and marine market is marketed under the Xantrex brand.  The renewable energy models are now called Conext XW's.

Several Xantrex/Schneider dealers still have brand new in the box SW Plus inverters in stock.  I verified with Schneider Customer Support that they will still honor the new product warranty on those units, and they will.  We have a two year factory warranty on our new inverter.

I selected the SW Plus because it has more overload capacity than the XW's.  We paid more for it than I could've gotten a new XW for.  But to this day there is nobody that has matched them for reliability and raw overload capacity.  That's why I wanted it.

Our bank is 24 Rolls T12-250's.  They are 200 ah @ the 20 hr rate.  It takes four of them to make 48 volts.  I have six strings in parallel.  Each string is 200 ah.  Six strings is 1,200 ah or 58 kW.

Generator support is where the inverter can sync with the generator and use both generator and battery power to meet heavy loads.  The overload capacity of the inverter allows you to start a heavy load with the inverter running in overload.  It calls for help from the gen and starts it, the gen comes online and takes over the bulk of the load while the inverter supplies what the gen can't.  When the load goes away the inverter watches it for a time that you program into it and shuts the generator off if the load has remained below the Load Start threshold.

This allows you to use a much smaller and more fuel efficient generator than what you would have to use with an inverter that only do pass-thru transfer.

There are very few inverters ever built that have gen support.  The Trace/Xantrex/Conext line have it.  The Outback Radian, and Magnum Energy will be coming out with one soon.  Reportedly, SMA has some models that can do it but I haven't verified that, nor do I know of anybody who is actually using it on a SMA inverter.

We use gen support, with an automatic start generator, almost exclusively here to operate our big loads.

I just got our ICM/25 Remote installed yesterday in the kitchen where our biggest loads typically are.  We're pretty happy with the new setup.  It handles our loads without even breathing hard.


--
Chris

[kitestrings]

Thanks for the update on the franchise.  I'd lost track.  We still have one of the older, modified sine-wave Trace's (2500 Series?).  Some would say it is a boat anchor now I supose, but you can't say it wasn't a work-horse.  In its day, it was a big improvement - load sensing, 1/3 watt no-load, auto-gen sensing/swithching, (im)pulse-phase shifting meant you could start much larger loads than most inverters.  I still use it out in the garage for some light-duty stuff.

Okay, I had the battery scheme pretty much pegged, but why would you go for say 3-series strings of 6V, 400Ah, or 2-series strings of 600AH?  Oh, and just so you're not confused with a battery sales-person it's 58 kW; about half of it available long-term.

The generator support sounds like a nice feature.  Makes sense.

Nice looking set-up.  ~ks

[ChrisOlson]

I was having trouble following your battery configuration.  You said you'd wired "four in series, ..six strings to the bus" and the T12 250's are 225 AH(?), so I wasn't sure how you got to 1200 AH, maybe 200AH/ea is nominal.  Anyway, my broader question is why so many parallel strings?  I'd thought it was more desirable to have say longer series strings, but fewer of them in parallel?

I'm putting this in a separate post because the other one got pretty long.

Battery amp-hour capacity is really a red herring.  I wish people would use kW or kWh instead.  For instance if you take four 12 volt 200 ah batteries and connect them parallel you have 800 amp hours @ 12 volt.  If you connect them series/parallel for 24 volt you have 400 ah.  If you connect them series for 48 volt you have 200 ah.

In every case above the kW capacity of the four batteries is the same - 9.6 kW.  This gets confusing for folks.  Some people think that because they got 10 batteries at 100 ah each that they have 1,000 ah.  But it depends on what voltage the bank is wired for because two of those batteries in series are still only 100 ah at the new nominal voltage.

On the series/parallel thing, this has been discussed before.  Each string of our T12's can deliver 800 amps from a fully charged state and maintain the voltage above 9.5 volts per six cells, or 38 volts with four in series.  Our new 5548 will deliver 7.2 kW for 10 minutes @ 15C in the utility room, and 7.2 kW for 3 minutes at 25C in the utility room.  However, it will only do it as long as the input voltage is above it's rated nominal, which is 50.4 volts.  If the input voltage drops the inverter is de-rated accordingly because the transformers get hot.

So if you want to get full surge overload capacity from your inverter without having it over heat you have to maintain the rated voltage into it.  And the surge DC amps to a big inverter, when operating it in overload for up to its rated overload time are tremendous.  WAAY beyond what it pulls at full continuous rated load.

So I'm sorry, but most people don't wire their banks to operate their inverter to it's maximum capability.  They say "I got the Big Kahuna Inverter" but they ain't even got CLOSE to enough battery to feed it.  So they may as well have bought a smaller inverter.  You need parallel connections to feed a big inverter because every battery in a series string has to deliver the full amps of the load on that string.  There is only one way to deliver the required amps to a big inverter and keep the voltage at or above rated nominal, and that's using parallel feeds to it.

Edit:
Darn - forgot to finish explaining our system and why I use 6 parallel feeds:

At the 7.2 kW overload that we need from our inverter to meet loads until the generator can get there to help, it pulls 160 amps DC.  The voltage has to stay at or above 50.4 to get the full rated overload capacity from it.  With six strings that's about 26-27 amps per string.  If you try that with just one string the voltage won't even maintain 48.  Two strings might get it right around 48 volts.  Three strings will help if they're fully charged.  With 6 strings it will maintain it even if the bank isn't fully charged.

Our bank spends a lot more time at partial charge states than it does at fully charged.  So it takes a lot of parallel strings to have the power on tap at the correct voltage for the inverter in order to get full power from it.
--
Chris

[kitestrings]

Chris,

Interesting.  The AH rating works fine in the context of a bank or string voltage.  I'm not one of the confused.  I've seen numerous, and recent, articles promoting fewer series strings for the "best long-term battery health", but I've never thought a single series string to be a good compromise.

In your example, at 7.2 kW, I understand in your configuration you've got say 26A; in a 3-series, 6V bank you'd have 50A+ per string; 2-series 4V bank we're probabley 80A.  You've got much higher loading than anything we, or most residential applications, might encounter.  I suspect that is why it is not more of a problem.  It was by design.  That was my basic question.

I'm always interested to see what others are doing with off-grid.  Good discussion.  Sorry if I took it slightly off-topic.  ~ks

[ChrisOlson]

In your example, at 7.2 kW, I understand in your configuration you've got say 26A; in a 3-series, 6V bank you'd have 50A+ per string; 2-series 4V bank we're probabley 80A.  You've got much higher loading than anything we, or most residential applications, might encounter.  I suspect that is why it is not more of a problem.  It was by design.  That was my basic question.

Actually 7.2 kW is low for a residential application.  But for most off-grid systems it's a lot.  If my wife walks up to her range, pushes every button on it and fires up everything in it, it draws 7 kW alone.  And we run that kind of stuff with our inverter (with generator support to help out).  My wife won't allow a gas line into the house.  So we got electric stuff, including our clothes dryer (another big Power Sink).

If we had, for instance, a single series string of twenty four 2V cells the string could easily deliver the required DC amps but the voltage would drop because every battery in the string has to carry the full amps of the load.  We got the T12's almost two years ago because they're famous for being able to deliver amps without voltage drop at the battery posts.  I just got enough in parallel so they'll deliver the amps without voltage drop even with the bank at 60-70% SOC.  That way the inverter doesn't have to be de-rated for overload time and we can pull full overload from it any time we want without the power going out.

It just has to deliver that overload power for the time it takes to get the generator started, warmed up, sync'd and connected to the load.  Then the actual inverter load drops to what the generator can't deliver to meet it.

And example would be like when my wife does laundry.  We have probably 1.2 kW of "normal" loads on in the house.  She throws a load of clothes in the dryer and turns it on.  The dryer draws 5 kW.  Then she throws another load of clothes in the washer and gets a second load going.  The washer draws 7 amps (.85 kW).  Now the total loads are suddenly slightly over 7 kW.  The inverter is only rated for 5.5 kVA continuous up to 104 degrees F ambient temp.  So it's running a full 1.5 kW overloaded.  30 seconds after she started the dryer the generator is already online and delivering 3.6 kVA of the total load.  The inverter only has to handle 3.4 kVA of it and is now only running at 62% of its rated continuous output, which is right in the big fat hump of its efficiency curve instead of on the downside.

Not many people use generator support but I don't know why.  It's way more efficient in the long run than buying the extra batteries and inverter capacity it takes to run those big loads for the relatively short time that they're usually on.  That's the specific reason we went to one inverter instead of two - the whole system is way more efficient with just one, and no leg balancing problems with one unit with a transformer on it.

I learned a lot about running these big inverters at full load to get the most out of them after we bought our previous system.  I was able to "trade up" to a yet more efficient setup without hardly spending a dime on the trade.  So I'm REALLY happy with it.  That 5548 is one hell of an inverter.

What's the old phrase - "They Don't Build 'em Like That Anymore"?
--
Chris

[dbcollen]

"Our bank is 24 Rolls T12-250's.  They are 200 ah @ the 20 hr rate.  It takes four of them to make 48 volts.  I have six strings in parallel.  Each string is 200 ah.  Six strings is 1,200 ah or 58 kW"

KW is an instantaneous measure of power, please don't try to confuse people by using it for capacity, capacity is measured in KWH.