Conext SW4024 - AC Support Performance

giawa · May 2018

Hi everyone,

I've just set up a Conext SW4024 on a 24V battery bank and 1.6kW of panels. My house normally draws around 700W, and I'm finding that AC support is only covering about 300-400W of that. During full sunlight my panels are generating in excess of 1kW, so I find the inverter is very rarely able to hold the battery voltage at the AC support voltage.

Some reading has shown that I should have checked the fine print a bit better. The AC support for the SW only supplies the common current between L1 and L2, so if the currents are off balance at all then that will be made up by grid power.

I did a firmware update, hoping that new software might be better. No luck there. I was trolling through all of the settings on the combox and found an "Inverter Mode" option, and my inverter is current set to "Split Phase Master". There's an option for "Single Phase Master". I can't find any reference to this setting in my user manual. Does anyone know what this does? Will this change the output to be a single phase? Will this help the inverter with AC support since there is no longer L1 and L2?

Alternatively, does anyone know of any methods to improve the AC support for the inverter? I've already tried to balance L1 and L2 as best as possible by moving around some breakers, but I usually have a 2A or more difference between the phases, resulting in a lot of power being consumed from the grid needlessly. Even if it were possible to disable grid power when the battery voltage is above a certain level, that would be pretty neat, but I don't see any option for that.

Thanks for reading,

Giawa

mike95490 · May 2018

Best suggestion is an autotransformer.

littleharbor2 · May 2018

We have a Schneider pro on the forum. He'll likely chime in in a day or so. Dave Angelini you around?

mcgivor · May 2018

Here is a thread dealing withe the same issue, perhaps it will save you time over ping Pong communication
http://forum.solar-electric.com/discussion/353094/balancing-the-loads-of-my-conext-sw-with-an-autotransformer

giawa · May 2018

mcgivor said:

Here is a thread dealing withe the same issue, perhaps it will save you time over ping Pong communication
http://forum.solar-electric.com/discussion/353094/balancing-the-loads-of-my-conext-sw-with-an-autotransformer

Awesome, thanks for the link. That was a good read! I might have to go down this path if I can't do something in software. I did try out the "Single Phase Master" mode, but the ComBox reported that it was not able to change this setting (even with the inverter in standby), so I'm still not sure what it does yet.

Giawa

mcgivor · May 2018

My understanding is the " Single or split phase master " settings are used when multiple units are configured as master/slave, this may explain why the setting is disabled on a single unit.

giawa · May 2018

mcgivor said:

My understanding is the " Single or split phase master " settings are used when multiple units are configured as master/slave, this may explain why the setting is disabled on a single unit.

Fair enough. Interesting that it does default to "Split Phase Master", which would suggest the other settings are still configurable.

Giawa

mcgivor · May 2018

Probably because it is a split phase, that is what it defaults to, mine is a single phase 230V unit, but since I have neither grid nor a second slave unit, haven't had a need to venture into those settings, but the word "master" would indicate a multi unit configuration setting. The configuration tool manual goes into these settings on page 2.7, attached pdf

Estragon · May 2018

Maybe relevant... I have a pair of Outbacks configurable in a number of ways, two of which are; in series (providing 120/240 split phase), or in master/slave parallel (providing 120v only, with the second inverter in sleep mode unless needed for loads over the 3500w capacity of the master).

Since I need 240v only periodically for a water pump, I set them up as master/slave 120v and run the pump through an autotransformer.

I don't know how a single phase master setup would work in a grid context though. Grid is normally split phase, so the inverter would only work on one half of the panel?

mcgivor · May 2018

@Estragon said, I don't know how a single phase master setup would work in a grid context though. Grid is normally split phase, so the inverter would only work on one half of the panel?

Split phase is used predominantly in North America along with territories associated, Puerto Rico etcetera, but in fact most of the world uses single phase at a higher voltage, 220, 230,240V for domestic power. The designation for Schneider SW series inverter chargers are ended with NA or E, NA being split phase, E being single phase, internally my bet would be the only difference is the output transformer has a center tap grounded neutral to provide the split, 120/240V, which is why perhaps it has difficulty with AC support. Adding an auto transformer to re consolidate the split to re aquire single phase seems like a solution which adds further losses, if a single phase unit were used instead, with an auto transformer on the output to provide the split, it would probably be more efficient, but manufacturers probably design with common practice in mind, hense the North American designation, along with certificates, UL and CSA, which need to be met.
Random thoughts for what they're worth.

giawa · May 2018

mcgivor said:

Split phase is used predominantly in North America along with territories associated, Puerto Rico etcetera, but in fact most of the world uses single phase at a higher voltage, 220, 230,240V for domestic power.

This is actually what I thought single phase might entail, so when I went to test it I disconnected the inverter output from the load and was ready with my multi-meter to measure it. However, I didn't even get the change.

mcgivor said:

internally my bet would be the only difference is the output transformer has a center tap grounded neutral to provide the split, 120/240V, which is why perhaps it has difficulty with AC support.

That makes sense. I'm just disappointed because it obviously has no trouble feeding different currents on L1 and L2 when the grid is unavailable.

Giawa

Dave Angelini · May 2018

It can have issues because it is ridiculous in my opinion to use a small inverter like this for a grid application. It really is an offgrid inverter.

It will take work by someone to make it work acceptably. It still seems like you are going to have to learn all of the ins and outs of advanced support.

As said by others split phase just makes it harder to make this very small inverter work well with unbalanced split phase loads. It is not too bad in non split applications with the grid but again, it really cries for the XW+ line of inverter/chargers when working with the grid.

Just compare the available power of a residence on the grid with the size of a CSW. Talk about imbalance!

giawa · May 2018

Dave Angelini said:

It can have issues because it is ridiculous in my opinion to use a small inverter like this for a grid application. It really is an offgrid inverter.

I went with the SW because I wasn't interested in selling back to the grid, and the documentation would suggest that it had similar capabilities to the XW for being grid interactive (via AC support). It's definitely my fault for not fully understanding the limitations of the SW when in a grid application (versus the XW family), but now I've got it and am hoping to make the best of it.

I am happy with the off-grid performance (and to be honest, that's what I've been doing. When I have good sun I just shut off the AC input and everything is great). I'm even thinking along the lines of a two phase 30A relay that could shut off the grid input when the battery voltage and SoC is over a certain threshold (and perhaps based on the weather reports, who knows). I'm curious if you have any thoughts on that. Two of my concerns are longevity of the relay inside the SW, as well as what effect this would have on my electronics which would be subject to the voltage drop on their AC input during the transition from grid pass-thru (with AC support) to inverter only.

Dave Angelini said:

It will take work by someone to make it work acceptably. It still seems like you are going to have to learn all of the ins and outs of advanced support.

That's going to have to be me. Do you have any suggestions on what I should try to tackle next? I've reached out to MrM1 asking if they had any luck with an autotransformer. Do you have any particular configuration settings or reading you would suggest I take a look at?

Dave Angelini said:
As said by others split phase just makes it harder to make this very small inverter work well with unbalanced split phase loads. It is not too bad in non split applications with the grid but again, it really cries for the XW+ line of inverter/chargers when working with the grid.

I'll look into the possibility of running the inverter in single phase output. That kind of heralds back to my original question about "Single Phase Master" and what that might mean. The user manual is pretty sparse on information regarding that mode, but from reading the Outback manual I'm guessing that the option might only become valid when two Conext SWs exist and each of them are providing a single phase. Any extra information you can provide would be very much appreciated. Thanks,

Giawa

Dave Angelini · May 2018

My advice is read the XW+ manual. Master and slave refer to adding additional inverters (more than one). I bill for my services other than general advice.
I own Outback and Schneider in my IRA and always want the stocks to go higher

giawa · May 2018

Dave Angelini said:

My advice is read the XW+ manual. Master and slave refer to adding additional inverters (more than one). I bill for my services other than general advice.
I own Outback and Schneider in my IRA and always want the stocks to go higher

Fair enough. Thanks for the advice.

MrM1 · May 2018

I also find the Charger of the SW to be Meh

at best

Several things stick out:

1. The SW charger only allows for 32v max for EQ. Trojan batteries call for 32.4v and do not get a good EQ at 32v with the larger L16s

2. The relationship between End Amps (which is set for 2% of bank Ah by Schneider) and Absorb time is pretty useless. The charger will ALWAYS end when it wants to according to Amps. The time you set for absorb will never come close. Thus the timer is useless.

3. That being said, the 2% end amp is supposed to be 2% of the user selected battery bank Ah. (this is not in the documentation, but Schneider will tell you this if you ask) ... So a 400 Ah user set battery bank should terminate absorb charge at 8 amps, a 50 Ah user set battery bank should terminate at 1 amp. NEVER HAPPENS. I have set the Battery Ah setting to 50 and 500 ... it always terminates at 7-8 amps. Never terminates on the timer setting or 2% of the battery bank unless you use a hi Ah setting (I have gotten it to work for 2% using a 1000 Ah setting - but that is too hi for my 435 Ah bank).

4. So because of the above, Absorb only lasts about 30-55 minutes at best. Way to short for a good absorb charge IMHO.

5. AND, The batteries NEVER reach full charge according to SG on the first SW charge cycle. (bulk / absorb / float)

6. There seems to be NO work around that I have found for any of the above yet ... except to ...

- either, restart the charge via changing the recharge volts and charging again to fully change the battery bank.

- or set float to the same as absorb ... this will finish off the charging, but then YOU have to be the timer. There is not charge shut off.

So over all the best way to charge if needing Gen or AC power (as many have stated before about gen charging in general) is to use the SW to do the bulk of charging in the morning. And then use your RE (solar) charge controller for finish charging and EQing at the proper voltage.

I have found the MidNite Solar Charge controller to be far superior in user control and settings than the SW charger.

giawa · May 2018

MrM1 said:

I also find the Charger of the SW to be Meh at best

Awesome, thanks for the detailed information. I've disabled the SW charger for now, instead relying on my Morningstar MPPT charge controller. My hope was to reduce my reliance on grid as much as possible, so I'm avoiding charging my batteries from a grid source for now. In the future I will likely use the charger on the SW during certain hours once my utility implements peak metering (which was just approved and is in their rate schedule, but hasn't actually been rolled out yet).

I just checked out your thread on your setup and installation and it looks great!

Giawa

Horsefly · May 2018

Dave Angelini said:

I own Outback and Schneider in my IRA and always want the stocks to go higher

Hmmm... You own Outback in your IRA? Looks to me like they are privately held. Neat trick if you know how to own privately held stuff in your IRA.

littleharbor2 · May 2018

Outback Steakhouse maybe?

Dave Angelini · May 2018

Horsefly said:

Dave Angelini said:

I own Outback and Schneider in my IRA and always want the stocks to go higher

Hmmm... You own Outback in your IRA? Looks to me like they are privately held. Neat trick if you know how to own privately held stuff in your IRA.

I own Outback in the form of money and equipment they have paid me over the years. Our testing relationship began in 2005. When they became part of the Alpha group I was very happy! Field testing of the MX-60 led to the fact that it really did not have enough memory to track accurately and the FM series solved many problems. The new mppt charger is awesome! When the Skybox comes out it will make my life much nicer.

It is not that hard to own privately held companies in your IRA BTW. If you have prefered shares that are often used as incentives to employees you can sell them and buy other stocks, bonds, ETFs or funds in an IRA and let it grow tax deferred. The same with cash payments of course.

"Private companies may also use stock options to pay vendors and consultants. ... options, giving the holder the right to purchase shares of the company's stock ..."

The problems in this thread with the grid charging on a CSW do not make sense to me. Either the unit is being programmed wrong, or it is defective. Schneider has used this since the XW+ came out in 2004. Does yours do this Horsefly?

giawa · May 2018

Dave Angelini said:

The problems in this thread with the grid charging on a CSW do not make sense to me. Either the unit is being programmed wrong, or it is defective. Schneider has used this since the XW+ came out in 2004. Does yours do this Horsefly?

This thread was me asking a question about peoples experience with balancing loads across L1 and L2 to improve the AC support of the Conext SW. It isn't well advertised, but after searching online Schneider does have some information here about this limitation of the SW: https://www.schneider-electric.ca/en/faqs/FA332947/ It isn't a programming or an installation issue, or even a defective unit. I don't know where we started talking about 'grid charging'. I don't even have the charger of my SW enabled.

Giawa

Dave Angelini · May 2018

I agree with you Gaiwa but charging was mentioned and I responded. Might also be mixing up another thread....

I also responded to you about how hard it is to do this with such a small inverter. As an inverter output "size" increases the balance problem decreases for most residential apps. This is why the XW was invented, not just to sell power but to be effectively sized.

In most of the world where split phase is not used, the CSW works better. What you could do is try and use 240V loads and minimize the issue

Horsefly · May 2018

Dave Angelini said:

The problems in this thread with the grid charging on a CSW do not make sense to me. Either the unit is being programmed wrong, or it is defective. Schneider has used this since the XW+ came out in 2004. Does yours do this Horsefly?

Well, two things: First, I don't think this thread was originally about charging at all, although I have seen the issues that @MrM1 discussed above (End amps is fixed at 2% according to the manual, but for smaller banks it never gets to 2% before going to float). Second, I don't have grid, I only have a generator. Having said that, I've seen some pretty strange behavior of the charging off the generator too. However, since charging wasn't the topic here, I won't further derail.

MrM1 · May 2018

giawa said:
This thread was me asking a question about peoples experience with balancing loads across L1 and L2 to improve the AC support of the Conext SW. It isn't well advertised, but after searching online Schneider does have some information here about this limitation of the SW: https://www.schneider-electric.ca/en/faqs/FA332947/ It isn't a programming or an installation issue, or even a defective unit. I don't know where we started talking about 'grid charging'. I don't even have the charger of my SW enabled.

Giawa

That is the first I have ever seen this link and info. Glad you supplied it. Looks like Schneider is finally admitting what the SW will and will not do. This is a far cry from the owners manual that simply states ...

AC Support ensures that no current comes from the AC Input connection of the Conext SW as long as the battery’s state-of-charge (SOC) or battery voltage conditions allow it. (975-0638-01-01 Rev E p1–7)

This never did happen as stated in the SW. The link you posted looks to be a more clear description of actual performance behavior for the SW.

giawa · May 2018

MrM1 said:

giawa said:
This thread was me asking a question about peoples experience with balancing loads across L1 and L2 to improve the AC support of the Conext SW. It isn't well advertised, but after searching online Schneider does have some information here about this limitation of the SW: https://www.schneider-electric.ca/en/faqs/FA332947/ It isn't a programming or an installation issue, or even a defective unit. I don't know where we started talking about 'grid charging'. I don't even have the charger of my SW enabled.

Giawa

That is the first I have ever seen this link and info. Glad you supplied it. Looks like Schneider is finally admitting what the SW will and will not do. This is a far cry from the owners manual that simply states ...

AC Support ensures that no current comes from the AC Input connection of the Conext SW as long as the battery’s state-of-charge (SOC) or battery voltage conditions allow it. (975-0638-01-01 Rev E p1–7)

This never did happen as stated in the SW. The link you posted looks to be a more clear description of actual performance behavior for the SW.

Yup, I was surprised when I found that link. I'm not 100% sure if that link was available when I actually purchased the SW (I may have missed it). If I had read that link then I would have gone with an XW series (or perhaps a Radian), but I was under the impression that the SW owners manual had the definitive information.

I'm glad that link was useful to you. I'm still embarked on my quest to improve my AC Support performance, and will keep this thread updated if I make any interesting progress. Right now I've just continued to re-balance the L1/L2 current by moving some breakers around. I have a better understanding of what draws constant loads and put those on complimentary breakers. I'm up to around 60-70% of my 700W consumption being supported by solar.

Dave Angelini said:

What you could do is try and use 240V loads and minimize the issue

I'm actually thinking of moving a couple of my 240V loads just for this reason. Currently I only have 120V loads, and left my 240V loads on the main grid panel, not wanting to stress out the inverter. I have a small mini split heat pump that looks like it would be a good contender for running off the inverter.

Giawa

giawa · May 2018

For posterity, I just got a reply from Schneider Support:

Aside from balancing loads the other solution is to disconnect the inverter from Grid input by turning off the breaker when AC support is to be used and reconnecting at the end of the day or when required. Unfortunately this requires manual connect and disconnect which isn't ideal in most cases.

I also asked them about setting up an automated relay to disconnect the grid from the inverter during periods of high SoC/battery voltage, and whether this might cause an issue for the longevity of the SW internals. They didn't see any issue with that, and said connecting/disconnecting the grid 4-6 times a day should be no problem as long as the AC input draw doesn't exceed 30A (which I think is a given - I also have the AC on a 30A breaker in the main panel).

You shouldn't be concerned about damage on the inverter's relay with this setup. Opening/closing about 4~6 times per day shouldn't cause any issues as long as your AC input draw doesn't exceed 30A.

Giawa

Dave Angelini · May 2018

I do have a modbus designer I work with who uses a Raspberry and programs some of the bigger XW system we do. This allows the automation of electrically disconnecting the internal transfer switching for different applications. One is what you are doing but most are for Telcom and bringing up back-up power to the systems and meeting their constraints.

BTW the smaller Radian has the same issues with balance in split phase power. It is about size afterall

MrM1 · May 2018

giawa said:

For posterity, I just got a reply from Schneider Support:

Aside from balancing loads the other solution is to disconnect the inverter from Grid input by turning off the breaker when AC support is to be used and reconnecting at the end of the day or when required. Unfortunately this requires manual connect and disconnect which isn't ideal in most cases.

I also asked them about setting up an automated relay to disconnect the grid from the inverter during periods of high SoC/battery voltage, and whether this might cause an issue for the longevity of the SW internals. They didn't see any issue with that, and said connecting/disconnecting the grid 4-6 times a day should be no problem as long as the AC input draw doesn't exceed 30A (which I think is a given - I also have the AC on a 30A breaker in the main panel).

You shouldn't be concerned about damage on the inverter's relay with this setup. Opening/closing about 4~6 times per day shouldn't cause any issues as long as your AC input draw doesn't exceed 30A.

Giawa

Turning off and reconnecting is basically what I do now. I disconnect from the grid most of the time and reconnect when I
1. have cloudy days and get low
2. Need to charge when there is no sun
3. Need a full tank of super heated hot water if there has been no sun

So far it has worked out very well. It just would have been nice if the SW would have worked as advertised. Imagine, running all your off grid loads until the battery bank hi a certain threshold, the The sw would switch over to grid power, and if you wanted (you could have used charger time blocks) could have recharged the batteries.

As it stands right now, If I run ACS mode, my batteries never dis charge past 90% SOC before the sun comes up and floats them back up. It is more like "battery supports gird" rather than "grid supporting battery"

But an idea I had, maybe some sort of wifi smart box timer like this might work for AC grid in control. Not sure if it would work. I am sure that @Dave Angelini could tell us. But just a quick look at it would allow you to control the AC connection in to the SW with your smart phone and I think it has a timer option too. Looks pretty neat if it will handle the 240v 30amp AC in needs to the SW

MrM1 · May 2018

Dave Angelini said:

I do have a modbus designer I work with who uses a Raspberry and programs some of the bigger XW system we do. This allows the automation of electrically disconnecting the internal transfer switching for different applications. One is what you are doing but most are for Telcom and bringing up back-up power to the systems and meeting their constraints.

BTW the smaller Radian has the same issues with balance in split phase power. It is about size afterall

Thanks Dave for your valuable insights as always. Good to know as the Radian was on my short list for replacement in a few years. (my how is when my first battery bank dies, I will replace the inverter too and step up to 48v). Guess I will keep a close eye on the MidNite Solar is up to with the B-17 Series.

I think the Autotransformer idea might be the best solution, but with a watt draw below 250-350 ... nothing ... no balancing or whatever is going to make the SW 4024 feed off the batteries. at low watts it will be supplied at or near 100% from the grid. And this is the main reason I did not get an autotransformer. Once I go to bed, my loads are so low, I would not draw from the batteries anyway. It is just easier to be off grid ... unless I need grid support.

giawa · May 2018

Dave Angelini said:

I do have a modbus designer I work with who uses a Raspberry and programs some of the bigger XW system we do. This allows the automation of electrically disconnecting the internal transfer switching for different applications. One is what you are doing but most are for Telcom and bringing up back-up power to the systems and meeting their constraints.

Oddly enough, I just ordered a USB->Modbus adapter, so I was actually going to give that a try. I'll keep everyone here informed of how that goes.

Giawa

giawa · May 2018

Just keeping people up to date with my experiments. It turns out ComBox supports ModBus over TCP on port 502, so you don't even need a USB->ModBus adapter or anything like that. Crazy enough, it doesn't even require any authentication, so you can read/write values over ModBus if you have access to port 502 (seems like a major security hole to me, so make sure you don't port forward everything to your ComBox, especially not port 502).

For anyone who wants to follow along, I've attached a C# file that will compile into a program that reports back the battery voltage, battery power, grid power and load power for a Conext SW at ModBus address 90. You can set the IP address of the ComBox on line 11, and you could update the values passed into SendModBus at its different locations to change the ModBus address of your SW. You could even use different addresses for different ModBus devices (for example - you could easily modify this code to work with an XW, a charge controller, or whatever else you have connected to ComBox). Documentation with the memory map for these devices is here: https://solar.schneider-electric.com/product/conext-combox/

I'm waiting for some hardware to arrive so that I can automatically disconnect the AC input from the SW when solar and SoC are good. I'll keep updating for posterity.

Giawa

Conext SW4024 - AC Support Performance

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