Problem stacking Schneider sw4024 inverters

lost trail · December 2014

Hey guys.

We just "upgraded" our system with a couple conext sw4024 inverters and all necessary components. We run a 24volt system on 12 inline deep cell marine batteries. Outback charge controllers, 2 diesel gen sets for back up. We run a backcountry lodge and have significant draw when guests are here, so we need two of the units to accommodate the usage. 3500w just isn't enough for city folk!

The inverters seem to work fine if we're running on one, but once we stack them, they start throwing all sorts of random fault and warning errors. Lots of "AC Over Current" faults when our actual draw isn't more than 800w.

We've been going around in circles with the tech guys at Schneider, but can't find the problem. The issue is not due to bad installation. We had our electrical engineer buddy come and help with putting them in.

I'm beginning to think these units were originally made to work alone and that the stacking option was an afterthought. Anybody else out there have a problem when stacking these?

It looks like another guy on the forum had similar problems and upgraded to xw4024s. See "fried sw4024." Anybody have experience stacking the xws?

Cariboocoot · December 2014

Re: Problem stacking Schneider sw4024 inverters

I can't help you with the stacking issues (probably yet another programming bug) but I have to comment on this:

12 inline deep cell marine batteries

That is not going to work well right there. You need to get proper deep cycle batteries of large enough capacity to meet the power needs without a lot of parallel wiring. As it is you've just got another type of failure waiting to happen.

Don't know why you bought the SW4024's when you got Outback controllers; you could have bought Radians instead. But that's neither here nor there.

lost trail · December 2014

Re: Problem stacking Schneider sw4024 inverters

Cariboocoot wrote: »

I can't help you with the stacking issues (probably yet another programming bug) but I have to comment on this:

That is not going to work well right there. You need to get proper deep cycle batteries of large enough capacity to meet the power needs without a lot of parallel wiring. As it is you've just got another type of failure waiting to happen.

Don't know why you bought the SW4024's when you got Outback controllers; you could have bought Radians instead. But that's neither here nor there.

We're questioning our decision on Schneider, too. We had Trace and Xantrax in the past, and never had a problem, so we figured they were good enough, and we liked the price. Lesson learned: you get what you pay for! Thanks for the advice on the battery bank.

westbranch · December 2014

Re: Problem stacking Schneider sw4024 inverters

Is that 6 sets of 2 batteries feeding both inverters simultaneously or ??

lost trail · December 2014

Re: Problem stacking Schneider sw4024 inverters

No, they're all inline.

westbranch · December 2014

Re: Problem stacking Schneider sw4024 inverters

So they are individual 2v cells. that sounds like L-16's? Brand?

mike95490 · December 2014

Re: Problem stacking Schneider sw4024 inverters

Do the inverters share the same battery bank, or does each inverter have it's own bank ?

INLINE is not a battery wiring term. Series or Parallel are the terms we need, and how the batteries are wired.

24volt system on 12 inline deep cell marine batteries

does not produce 24V ???

lost trail · December 2014

Re: Problem stacking Schneider sw4024 inverters

both inverters share the same battery bank. We considered splitting the string, but don't want to make things that messy.
As for the batteries, they are NOT marines. They're Hup Solar. 2 volt 2000 amp, 12 batteries in one string.

Cariboocoot · December 2014

Re: Problem stacking Schneider sw4024 inverters

lost trail wrote: »

As for the batteries, they are NOT marines. They're Hup Solar. 2 volt 2000 amp, 12 batteries in one string.

That is much different and much better.

lost trail · December 2014

Re: Problem stacking Schneider sw4024 inverters

ok, so now that we have that out of the way, back to the inverters. Anybody have any problems stacking the sw4024's? They seem to work fine when we have only one hooked up, but as soon as we stack them, there's problems.

mike95490 · December 2014

Re: Problem stacking Schneider sw4024 inverters

Maybe the sync cable is bad ? Maybe it's a special cable, not a standard ethernet cable ?

BB. · December 2014

Re: Problem stacking Schneider sw4024 inverters

Note that there (at least) two standards for RJ based Internet cables... Straight through and cross over. With much of the modern computer equipment today, it does not care (computer will "swap" Tx and Rx pins if needed to match cable).

-Bill

lost trail · December 2014

Re: Problem stacking Schneider sw4024 inverters

BB. wrote: »

Note that there (at least) two standards for RJ based Internet cables... Straight through and cross over. With much of the modern computer equipment today, it does not care (computer will "swap" Tx and Rx pins if needed to match cable).

-Bill

I read this to imply any standard ethernet cable should suffice, correct?

BB. · December 2014

Re: Problem stacking Schneider sw4024 inverters

Saying that there are (at least) two different cable pin outs "standard" for Ethernet RJ cables.

I do not know if one or the other (or both) would work with stacking the inverter or if there is a different pin-out yet for the Context.

I could not find a cable pin-out with a quick web search (or even where to buy such a cable).

Call NAWS (our host) or contact Schneider for details.

-Bill

dexy · December 2014

Re: Problem stacking Schneider sw4024 inverters

I had an issue with stacking them but even worse than yours.

I have a new installation I just completed June 2014 and I have 2 XW6048 inverters stacked with the same battery bank input. They worked ok as master slave for about 2 hrs, and the slave just went dead, as in flat dead, wouldn't turn on for anything, tried all sorts of resets and reboots and so many other tests with the Schneider tech support and nothing worked, wouldn't just come back on.

Schneider ended up sending us a new replacement unit, I still haven't got to install the new unit yet (because this is a remote vacation home in Nigeria I have to get to), but I'm hoping for the best. Right now the system is still running on 1 XW6048 inverter limiting the max output to 6KW vs intended 12KW.

Attachment not found.

jtdiesel65 · December 2014

Re: Problem stacking Schneider sw4024 inverters

see

http://forum.solar-electric.com/showthread.php?21344-Fried-conext-sw4024

AFAIK there was some new firmware to take care of some of the faults. You will also see incorrect load readings although those are harmless.

I was getting random faults too which would cut the power for a second. Nevermind the charging issue. I could never get them to work reliably and that was after 6 different inverters, changing firmware a couple times, changing all the xanbus cables, etc, etc, etc. In my case, they ended up replacing my SW's with XW's and I haven't had a problem since. SW stacking was most definitely an after thought.

edit: oops, just saw that you had already seen this.

jtdiesel65 · December 2014

Re: Problem stacking Schneider sw4024 inverters

lost trail wrote: »

I read this to imply any standard ethernet cable should suffice, correct?

Although there is a stacking port, you don't use it on the SW's. (Why it's there I dunno, perhaps for future uses?) You need to connect the inverters via the xanbus ports which use just a standard ethernet cable. I upgraded all ones that came with the SW's with cat6 cables that I verified as working on my home network, but it didn't help. But having said that, you could have a bad cable. It's not out of the question. You should also probably make sure the bus is properly terminated.

mike95490 · December 2014

Re: Problem stacking Schneider sw4024 inverters

jtdiesel65 wrote: »

..You should also probably make sure the bus is properly terminated.

Yes, Xanbus wants to have BOTH ends terminated with their little load resistor. And i can't remember if you have to use LONG cables between devices or SHORT cables. I know it is very picky about the cables & terminations.

lost trail · December 2014

Re: Problem stacking Schneider sw4024 inverters

jtdiesel65 wrote: »

Although there is a stacking port, you don't use it on the SW's. (Why it's there I dunno, perhaps for future uses?) You need to connect the inverters via the xanbus ports which use just a standard ethernet cable. I upgraded all ones that came with the SW's with cat6 cables that I verified as working on my home network, but it didn't help. But having said that, you could have a bad cable. It's not out of the question. You should also probably make sure the bus is properly terminated.

Bus termination is good. We're running CAT5 cable.
Our buddy is an electrical engineer and helped us with installation. Since then, we've been over all the wiring and connections with Tech Support. There doesn't seem to be anything wrong with the way we have the system set up. Our friend took one of the inverters apart (NOT one of the ones we're currently using) and said it looks like these units were not originally made to stack. Did you ever get Schneider to admit this?
Seeing your original thread helped us know that at least we're not alone. Glad to see that your system is finally running the way it should!

jtdiesel65 · December 2014

Re: Problem stacking Schneider sw4024 inverters

lost trail wrote: »

Since then, we've been over all the wiring and connections with Tech Support. There doesn't seem to be anything wrong with the way we have the system set up. Our friend took one of the inverters apart (NOT one of the ones we're currently using) and said it looks like these units were not originally made to stack. Did you ever get Schneider to admit this?
!

I don't know what their original plans were. I never asked if they were originally made to stack. I was more of "How are you going to fix this?" The whole neutral thing was a fiasco. The manual says two different things. Tech support also told me two different things. It's a new product and they were applying XW knowledge not SW knowledge. The AC panel isn't usable without some extra parts (busses, etc). Even the label for the bypass lockout is backwards. The second level people behind those who answer phone calls know that the product has some flaws. They did alude to the fact that some other stacked units were also throwing some faults, but I also got a sense that there really wasn't much for stacked units in the field.

Setup isn't that hard and the only thing that could easily be screwed up is wiring the neutral because the manual's wiring diagram is wrong and because the AC panel and stacking kit don't give you the parts or instructions to wire it correctly.

I think the core problem with those inverters when stacked is how neutrals are handled. It's not like the XW, the neutrals are switched via relay. So what you have is a classic race condition with each inverter's load/current sense versus the two inverters trying to sync their events across xanbus which IMO is flaky at best. Hence weird faults and charging states where one is charging and the other isn't. That's my take on it anyway.

Not much I can offer for advice except try to get the latest firmware, install it and factory reset both units. There was a firmware update to fix some random faults in the works that was supposed to come out in fall 2014. I actually never installed it because I got the XWs before it came out.

BTW, Sounds like you might just go to a different inverter. One solution might be move to 48v and buy a 6048 and just opt out of having to stack.

Wulfman · July 2015

I too have 2 SW4024s. Been going round and round with tech support at Schneider.
I bought 2 of these to have some redundancy in my power. I have 12 1100AH rolls
2v cell batteries and have plenty of power. This all started one day back on May 18th shortly after installation.
I have both inverters hooked up and my water pump fires off and the slave inverter decides
to have a heart attack. It starts thumping like it's trying to turn on but cant.
I have never had an issue with running only one inverter, my pump just runs fine even as
happened 2 days ago the microwave was turned on at the same time.
This is a 12 amp 120v jet pump pumping from a 500 gallon tank.
It draws about 1300 watts after it's startup current. When I have both inverters enabled
most of the time both inverters share the load. Sometimes only the master inverter supplies the load.
They are not consistent in their operations. When I get this Odd error the lights flicker and some times
the slave inverter tosses an under voltage error. The master keeps right on inverting tossing no errors.
I do notice that the master inverter battery current goes way up like the load has increased a lot.
Tech support has told me to do all sorts of things none of which has helped the issue.
Remove the grounds, remove the input neutrals isolate everything. Replace the brand new shielded Ethernet cables.
Even sent me a replacement inverter and still inverters work the same, nothing has helped.
After a lot of logging and testing on my end I have noticed a few things.
Under load the slave sometimes internally reads 10 volts lower than the master.
This happens even if the slave is not supplying current.
If I measure the voltage on the connector on the inverter its always within 0.5 volts of the master, not agreeing
with the internal measurements. I do not use the switch gear I run liquid tight conduit to regular breaker
boxes using about 3 feet of 8 gauge wiring for each inverter. Each inverter has its own breaker per instructions.
I have never used the AC input for charging and it's never been hooked up to anything other than its own Breaker box.
I have also found out that while looking through the Energy and event logs every time there is an error the slave
reads positive battery current in the DC output.log file.
I am a 35 year electronics engineer. Done years of test engineering and design work. Been living on solar for over 20
of the past 30 years. I am positive when this error happens that the slave inverter is trying to charge the batteries
using the masters supplied power. I cannot *prove* this because I do not have the firmware or the schematics to troubleshoot this.
I have been offered a XW6048 in exchange for these 2 inverters but that would incur another 4000$ plus expense enlarging my battery bank.
Not to mention removing all redundancy I require as my 90 year old father lives here with me and needs his power.
I just do not use that much power to upgrade the bank. I really have no desire rewiring my solar array for the higher charge voltage either.
I have asked for the upgrade to the XW4024 that above poster asked for and got offering to pay the difference at their cost.
That would be much less expensive than doubling my battery bank. I am at a loss. You would think that a mature product
would not have this kind of an issue. Anybody out there also running 2 SW4024s is welcome to send me some mail and we can swap notes.

t00ls · January 2019

from what I read on the install manual, the stacking port is not used on these models....do not connect them

when used together you must make 1 of them 00 and the other 01 on the SCP under multiple device configuration

assign 00 as master and 01 as slave in the same menu for each device....this is important

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

The Input and Output Neutrals are electrically tied at the inverter terminals. Only a

Neutral wire (from the AC Out cable) is necessary from each inverter
-----------------------------------------------------------------------------------------------

so dont put a neutral on the input

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

To configure the system for multiple unit configuration:

1. Apply DC power to both inverter/chargers.

Power up order has no impact. Because there are now two Master units in the

system, the SCP will detect an

F71

fault, a “system configuration fault”.

2. From the SCP

System Status

screen, press

Enter

. The

Select Device

screen

appears.

3. Select the inverter to configure as a Slave unit from the list, then press

Enter

.

4. Bring up the

Advanced Settings

screen by pressing

Enter

, Up, and Down arrow

buttons all together.

5. Select

Advanced Settings

and press

Enter

. The Advanced Settings screen

appears.

6. Scroll down to select

Multi Unit Config

.

At this point all devices in the system will be automatically placed in standby mode.

All three LEDs on the inverter to be configured will start flashing

7. Select

Invtr Mode

and press

Enter

.

8. Select

Slave

and press

Enter

.

9. Press the

Exit

button repeatedly until the

System Status

screen appears.

Search Mode Operation in Multiple Unit Configuration

Search mode is automatically enabled in multiple unit installations with two

paralleled Conext SW units. Only the master Conext SW operates, and the slave

unit comes online only when the load exceeds approximately 60% of the rated

output of the master unit. When the load drops below 20% of the master’s rated

output, the slave unit turns off.

so the slave is not always inverting...it will shut down

t00ls · January 2019

as far as the batteries go

Inverter/chargers can

operate from different battery banks, meaning each unit is connected to its own

battery bank. However, it is highly recommended to use only a single battery

bank.

Jdfearl · October 2023

t00ls said:

The Input and Output Neutrals are electrically tied at the inverter terminals. Only a
Neutral wire (from the AC Out cable) is necessary from each inverter
-----------------------------------------------------------------------------------------------
so dont put a neutral on the input
---------------------------------------------------------------------------------------------
What will happen if there is a connected neutral on the input?

Dave Angelini · October 2023

The old SW Inverters can be stacked! You should not be stacking the CSW inverters. That was an option early on that is not supported by Schneider.

Do not mix these models up!

Jdfearl · October 2023

True you can't stack them but can they be run in parallel? If not I'll sell the second one that was given to me.

Jdfearl · October 2023

t00ls said:

The Input and Output Neutrals are electrically tied at the inverter terminals. Only a
Neutral wire (from the AC Out cable) is necessary from each inverter
-----------------------------------------------------------------------------------------------
so dont put a neutral on the input
---------------------------------------------------------------------------------------------
What will happen if there is a connected neutral on the input?

littleharbor2 · October 2023

Oh boy, I hope I don't get crucified for this....

Are you running any 220 split phase circuits? This is probably totally against code but if all circuits are 110 vac could you run one inverter on one leg and the other on the second leg of the breaker panel? If you clearly label the panel to never use any 220 breakers

Dave Angelini · October 2023

Not going to crucify you, there is plenty of that in the world today.

Do not mix these models up! saying this again about CSW and SW inverter/chargers for others reading this thread.

If you did what littleharbor suggests with a CSW, you would not get near rated output as the inverters each would be imbalanced.

You definitely would be out of warranty if you have one. CSW can log things that are done to it that are not "playing nice"

I spend alot of time training with Schneider XW but I do not use the CSW for clients. You should be good with your due diligence and check with Schneider.

Image: https://us.v-cdn.net/6024911/uploads/editor/2n/ui3o2wsrlmju.jpg

littleharbor2 · October 2023

Oh, I forgot, the CSW is split phase. Doh! I'm still in the 115 vac Trace SW world

Jdfearl · October 2023

great, thanks for responses!! I am gonna switch away from CSW 4024

Problem stacking Schneider sw4024 inverters

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