Schneider CSW4024 fault

Horsefly

We had something happen yesterday that is concerning, and I'm not sure what would cause it. I'm hoping some folks here with experience in Schneider inverters (@Dave Angelini, @mcgivor, @mike95490, and I'm sure others) would have some thoughts.

Yesterday afternoon my brother called me in a panic. He was at our cabin, and he noticed that his phone charger was not charging. It was daylight (but cloudy and raining), but no other loads were on. He went down to the equipment room and found that the fault light was on on the CSW4024 Inverter. I walked him through seeing what the fault was:  F1, "AC Output Under voltage".  The book says this is caused by the output voltage dropping below 210V (obviously this is across both legs of the split-phase output), and suggests "Removing excessive loads".

With me trying to guide him, I had him first simply try to clear the fault, but it came back in a few seconds. I then had him turn off the main breakers to the rest of the house, so that there was no loads at all, then try again. Same thing: After clearing the fault it came back in a few seconds. Finally I had him shut down three breakers in order: PV to CC, CC to battery, and then the big 250A breaker from the battery to the CSW. After about a minute I had him turn the breakers back on in reverse order. After some time (I'm not sure how long) the inverter came back up and all seemed fine. He then turned the breakers back on to the house wiring, and everything continued to be fine. 

This morning he reported that there had been no more problems. It's now been over 24 hrs, and if anything did happen I'm sure he would have called again.

So here's the questions:

1. Any ideas what would cause this output under voltage fault? Since there was virtually no loads, I'm at a loss.
2. Do I chalk this up as a random event, or does this indicate that perhaps I've got bigger problems with the CSW around the corner?
3. Is there a way to force the CSW to reset / reboot short of they way I did it?  I had my brother use the standby button on the SCP but that never helped. Would disabling and then re-enabling the inverter function from the SCP have done the same thing?

I'm interested to hear the thoughts of you more-experienced folks.

BB.

Here are my guesses, things to look at:

1. There was too many loads on the inverter (hair dryers, well pump and/or fridge starting, etc.). Restarting the loads were still there (starting pump, starting fridge, hair dryers, etc.).
2. Check the battery bus in DC input voltage... Possibly the battery bank was at low state of charge/failing battery cell, or possibly a poor connection from battery bank to inverter DC inputs (low DC input voltage can cause low AC output voltage).
3. Any lightning in the area (within miles of the inverter)?
4. Any Midnite or other surge suppressors (MOV type) on the AC output (including power strips with surge suppressors)... Shorted MOV or using a 120 VAC surge suppressed power strip on 240 VAC (may not happen in USA, but does happen in other countries running 230 VAC buses with US AC plug type computers/equipment that runs on 100-264 VAC input).
5. There could be an inverter output transistor failure (or drive circuit). They (bad diodes/transistors/etc.) generally do not "fix" themselves (open/shorted transistors).

-Bill

Horsefly

BB. said:

Here are my guesses, things to look at:

1. There was too many loads on the inverter (hair dryers, well pump and/or fridge starting, etc.). Restarting the loads were still there (starting pump, starting fridge, hair dryers, etc.).
2. Check the battery bus in DC input voltage... Possibly the battery bank was at low state of charge/failing battery cell, or possibly a poor connection from battery bank to inverter DC inputs (low DC input voltage can cause low AC output voltage).
3. Any lightning in the area (within miles of the inverter)?
4. Any Midnite or other surge suppressors (MOV type) on the AC output (including power strips with surge suppressors)... Shorted MOV or using a 120 VAC surge suppressed power strip on 240 VAC (may not happen in USA, but does happen in other countries running 230 VAC buses with US AC plug type computers/equipment that runs on 100-264 VAC input).
5. There could be an inverter output transistor failure (or drive circuit). They (bad diodes/transistors/etc.) generally do not "fix" themselves (open/shorted transistors).

-Bill

Thanks Bill. 

1. My brother swears there was no big loads on at the time the power went out. However, if the well pump is running the only way to tell is if you are standing in the equipment room and can hear the inverter straining. Based only on the pressure reading on the pressure tank, it appeared that the pump hadn't been running for quite some time. Besides, like I said, I had him turn off the main breakers before we cleared the fault, but the fault came back anyway. So that was with no loads at all.
2. According to the SCP, the battery bank was in Absorption when the power went out. Voltage was showing at 29.1V (24V bank).
3. Not sure about lightning. I'll check with my brother about that. I would think he would have mentioned it though.
4. I do have Midnite surge protection devices. One 300VDC SPD at the panels, and two 300VAC on the e-panel: One on the input from the generator, and one on the output of the inverter. When we finally got the inverter going again, he said that the blue LED was lit in the inverter SPD, so I would guess it's still good.
5. Since the inverter came back up, I would think that means none of the critical components inside failed.

I just remembered something else, but I'm not sure if it means anything. My brother said that he had been running the generator for a while, thinking that because of the rain it would be good to help charge the batteries. He said that in fact it had been running when the power went out. Since the CSW4024 has an automatic transfer switch, the inverter itself should not have been running, and the generator power should have been what was powering the cabin. But the power went out.  Now I'm more confused. 

mcgivor

This is not something I've seen myself, but then again my unit is not a split phase type, it could be that there is an imbalance on one leg causing a voltage drop, it wouldn't take much a microwave and a hair dryer operating together, as an example, could overwhelm the capacity momentarily of a single leg if connected to a common circuit in the distribution. Such an event would be captured in logged data if a ComBox were used, it's so easy to create such a scenario without knowing, one in the kitchen another in the bedroom inadvertently using appliances similtaniously, but this is only speculation.

Having a shared user system will often result in the unknown, particularly if there are more than one user, if this is the case it's likely to be a one off situation. Performing a cold reboot  would have the results of a system reboot via software, perhaps even better if there were an electronic algorithm loop issue. 

Personally I would consider it a random event worthy of investigation when you are on site, thus eliminating the variables, the system are well designed with safeguards incorporated to prevent their self destruction, my suggestion would be to investigate the split  ballance, or lack thereof, before drawing any conclusions.

Yeah its easy being an arm chair quarterback, however simple problems often have logical solutions.

Dave Angelini

Generator, lightning, and loads are what causes these problems usually. As Bill said there could be a fault developing. Take a peak at all of the device faults and warnings along with system faults and warnings. Since this is no longer a new unit I would make sure the inverter is up to date with firmware. 

Ah firmware, there are times when the guys are fixing an issue, they do not list it in the firmware release notes. So just because it is not listed does not mean they did not address an issue. Since you said you are sure there were not loads running that could imbalance a relatively small inverter (my opinion)  then firmware is where I would go.

All of the stuff you did was kind of a waste except the DC power down.  An inverter needs to go to zero vdc to force a hard reset of the device. Some have such good capacitors that Schneider and Outback have recommended below. People mess this up by leaving the solar on, not measuring the terminals, or just not waiting long enough. For me it is usually 5 minutes or less. 

Solution:Power cycle the unit and leave it off until voltage falls below<2 volt on terminals of the inverter(Wait about 20-30 min)
Re power the unit, if fault still persists then the next step is to perform a restore to default
If the fault still ocurrs after power cycle and restore to defaults unit needs to be replaced.

A fault that shuts down power is very serious to me. I never have this and neither do my clients. If it happened again I would replace the unit or at least have a spare. I know this is a cabin but this is unacceptable, to me!

 I hope your brother in law is not like mine. I would leave the home unoccupied before I would leave him there alone unsupervised.

Horsefly

Thanks @Dave Angelini and @mcgivor.  I am going up there next Thursday or Friday for several days. I'll try and look through the faults and warnings.

Dave: My brother-in-law (sister's husband) is fine. He helped me do the install, is really handy, and stays well within the rules. My brother (the one that had this problem) is a retired fighter pilot who seems to sometimes do things just to see what happens. There is a good chance there is something beyond what he has told me.

I don't currently have a way to update the firmware. I only have the MPPT60-150, the CSW4024, and the SCP.  I guess I could buy a combox or gateway if needed, but I'll wait to see what I find when I'm up there.

The fact that the generator was running has added more confusion for me. I don't see how the inverter would fault on it's output voltage if it had been bypassed by the transfer switch. Recall I had the issue where the transfer switch was switching back and forth every few seconds, and it turns out it was because I had the charge controller and the CSW charger both set to the same voltages. Changing those fixed that issue, but my brother told me this morning that he was hearing the same clicking every few seconds when this happened. He rushed over to turn off the generator before going in the equipment room and seeing the fault light on.

Strange stuff. I'll post back here if I find something interesting.

Edit to add: My brother also said that they system has been running fine now since the hard restart on Saturday. He's been using it like usual (which may not be normal usage - I'm not sure). 

BB.

Any way the generator and inverter transfer switches get mixed up (Genset and Inverter outputs tied directly together)?

Some manual/DIY transfer switches don't have interlocks--And somebody could switch the xfer switches in the wrong order?

-Bill

mcgivor

@Horsefly Just a side note you mentioned using a 300V SPD on both the AC and DC, the clamping voltage should be closer to the maximum allowable, I've lost both an inverter and charge controller due to lightning, despite having SPD's which were rated for higher voltage. After supplying specifications of the units to be protected to a manufacturer, these were what were recommend, my inverter is 230V non split so only one is needed, if the generator is hard wired with a long outdoor run it may be a good idea to have one on the input as well.



 

Horsefly

BB. said:

Any way the generator and inverter transfer switches get mixed up (Genset and Inverter outputs tied directly together)?

Some manual/DIY transfer switches don't have interlocks--And somebody could switch the xfer switches in the wrong order?

-Bill

The transfer switch I'm talking about is automatic, and is internal to the inverter/charger. The inverter watches for voltage in, and once it qualifies the input voltage (in this case from the generator) the transfer switch kicks in and switches over to have the output connected to the genset rather than the inverter. If it was wired wrong I would have discovered it long before now, as there have been times when we needed the generator power. It's worked fine, and when the generator is turned off there is a very short (<1 sec) dip in the power before the inverter takes over.

At this point I'm suspicious that the problem is again the same conflict between the charge controller and the inverter charger. That was causing the transfer switch to toggle back and forth every few seconds last year, until @Estragon and @Dave Angelini suggested I set the charge voltages different between the CC and the inverter charger. That seemed to fix it last year.  My brother was reporting the same "clicking" (transfer switch going back and forth). It may be that someone (maybe my brother) experimented some with the charge voltage settings.

I'm not sure how such a conflict as we had last year would cause this inverter fault, but I guess it might be related.

Horsefly

mcgivor said:

@Horsefly Just a side note you mentioned using a 300V SPD on both the AC and DC, the clamping voltage should be closer to the maximum allowable, I've lost both an inverter and charge controller due to lightning, despite having SPD's which were rated for higher voltage. After supplying specifications of the units to be protected to a manufacturer, these were what were recommend, my inverter is 230V non split so only one is needed, if the generator is hard wired with a long outdoor run it may be a good idea to have one on the input as well.

Hmmm...  I got the impression that these SPDs from Midnite were the ones I should use. Can't remember where I read it. 

I do have an SPD on the generator input to the inverter, one on the inverter output, and a DC SPD mounted on the combiner box out at the ground mount ~200 feet away.

The generator is in a shop that is attached to the cabin. The entrance to the shop is outside, but the wiring from the generator to the equipment room is all inside, and only about 30 feet.

rafflec66

Hello, I am having this exact same problem and it just started today.  Any chance since your problem was in 2020 that you figured out the issue?  Any help would be much appreciated.  Off grid Alaska so this system is pretty important LOL

Horsefly

rafflec66 said:

Hello, I am having this exact same problem and it just started today.  Any chance since your problem was in 2020 that you figured out the issue?  Any help would be much appreciated.  Off grid Alaska so this system is pretty important LOL

It's been a while, so my memory of this issue is a bit hazy.  The generator is a pretty cheap Westinghouse 7500W.  Almost no one ever runs it any more, as the solar has been more than enough to keep things going during visits to the cabin. For some reason my brother has always liked to run the generator, so the fact that he was the only one to ever see this error leads me to believe it was something with the generator.  It's hard to justify the expense now, but if we ever decide to get a new generator it is going to be an inverter generator with a more stable pure sine wave, and hopefully a more quiet non-open-frame one.

I remember testing things myself when I went up. I ran the generator and watched the auto transfer switch kick-in as the generator started and stopped, but I never saw any problems.

Last summer I did run the generator again for the first time since 2020, but it was just to make sure it started (it did start, although a bit reluctantly).  I didn't see any issues with the transfer switch or powering loads for a few minutes.

Dave Angelini

rafflec66 said:

Hello, I am having this exact same problem and it just started today.  Any chance since your problem was in 2020 that you figured out the issue?  Any help would be much appreciated.  Off grid Alaska so this system is pretty important LOL



It almost always is the genset !  However, you can do permanent damage to the input relay if this goes on. It is not a replaceable part either. Widen the specs, use another genset to test. The genset needs to be close on frequency, voltage and have a clean waveform. The waveform is very hard to test and so another genset is the way to test.

Good Luck up there !