Two EG4-6500EX in parallel - One unit complaining about low bus voltage

We have had a Schneider system running flawlessly (ish) for a few years now, but are moving that equipment to another house, and so went with the cheap option on the main house. Point being, I'm not totally new to solar installations, but I cannot figure out what's going on here.

I have installed two EG4-6500EX units in parallel, with communications between them, have installed a bank of 6 EG4-LL batteries with communications between them, and have connected the battery bank to both inverters. I have connected our PV array to the slave inverter (Because the conduit was already run, and it's closer to the slave than the master), and have set both inverters to EG4 on setting 05 (Battery Type).

When I start up the master inverter, it is successfully communicating with the battery bank (Battery icon blinking), but after a brief timeout, it faults with error 52. Meanwhile, the second unit does not fault, and begins charging the bank from the PV as you'd expect. The battery bank voltage is 52V as measured at the bank bus bars. The battery cables are identical in length between the two units. AC input and output are currently not connected (Units are grounded, battery rack is gorunded)

I'm unsure of where to go from here. Am I missing something?

Edited to remove reference to Error 03, which is no longer present

I just went and restarted them again, and error 03 is gone but 52 is still present. 52 is the low bus voltage warning. There is no PV input on this primary inverter, which may be why it's complaining about that? How can I tell it that there is no PV input to see? I can't find anything in the manual about that.

One things that jumps out about the set up would be your setting 05. Your slave inverter should be set to USE mode. After placing it in this setting, go check that setting "12" is showing you a % rather than a voltage amount. My next step would be checking into your PV array.

Ah yeah, I do recall reading somewhere that the second inverter needs to be in USE. I will look at that after work.

I would think if there was an issue with the PV array (Which has been in service for 3+ years now), that inverter 2 would be the one complaining, not inverter 1. The array voltage and current all look fine, though - I'm not sure what else to check there.

I think your problem is going to lie in the setting. With the slave not being in USE then they are not going to properly communicate. So, you could see errors like 52 or 61. Your master inverter is most likely just not seeing any PV input.

I appreciate it. I'll report back after work when I've had a chance to look at it.

Even after setting master to EG4 and 2P1 and the slave to USE and 2P2 (180 offset), I still get the error. Thing is, I ONLY get it after I turn on the slave unit.

IE, if I turn on master (With the button on the front) and do NOT turn on the slave (IE just connect PV input so that it turns on, but do not hit the button) it will run indefinitely. As soon as I hit the button on the slave unit and it starts trying to invert, the master unit goes into F52. Any ideas?

timthrifty said:

Even after setting master to EG4 and 2P1 and the slave to USE and 2P2 (180 offset), I still get the error. Thing is, I ONLY get it after I turn on the slave unit.

IE, if I turn on master (With the button on the front) and do NOT turn on the slave (IE just connect PV input so that it turns on, but do not hit the button) it will run indefinitely. As soon as I hit the button on the slave unit and it starts trying to invert, the master unit goes into F52. Any ideas?

Click to expand...

Disconnect the pv to eliminate a potential cause.
See if the problem correlates to pv absence/presence?

timthrifty said:

Even after setting master to EG4 and 2P1 and the slave to USE and 2P2 (180 offset), I still get the error. Thing is, I ONLY get it after I turn on the slave unit.

IE, if I turn on master (With the button on the front) and do NOT turn on the slave (IE just connect PV input so that it turns on, but do not hit the button) it will run indefinitely. As soon as I hit the button on the slave unit and it starts trying to invert, the master unit goes into F52. Any ideas?

Click to expand...

Did you send an email to tech support this morning at 9:55? If so, I'm going to get you a call from a tech to try and get you lined out as soon as possible.

@BenFromSignatureSolar since we are on the subject can you explain why so many user manuals for inverter's that can be run in parallel suggest/require equal path resistance for all the paralleled inverters?
I can't see any reason why they shouldn't work in parallel even if they are connected to completely separate battery banks.

@BenFromSignatureSolar Yes, I did. Just posted here as well because I know you guys are busy and that it might very well be user error.

@John Frum Good idea on disconnecting PV. Unfortunately, same result. If I turn on master just from the battery bank power, it turns on and then eventually times out and turns off (No faults). If I turn on slave alone, same thing. However, if I turn them both on, as soon as slave starts trying to invert, master throws F52.

I did notice in this latest testing the slave starts to invert first when they're both on, and indicates 120V output. However, master never does indicate 120 (At least I didn't see it), it simply faults as soon as it starts to invert.

timthrifty said:

@BenFromSignatureSolar Yes, I did. Just posted here as well because I know you guys are busy and that it might very well be user error.

@John Frum Good idea on disconnecting PV. Unfortunately, same result. If I turn on master just from the battery bank power, it turns on and then eventually times out and turns off (No faults). If I turn on slave alone, same thing. However, if I turn them both on, as soon as slave starts trying to invert, master throws F52.

Click to expand...

Can you post the verbiage that goes with error code F52 please?

From the manual, error 52 is "Bus voltage is too low" with a suggested resolution of "Check to ensure you are getting proper PV voltage to the inverter."

Which is funny since the unit that's actually receiving the PV input throws no faults and has been charging the battery bank all day...

Can you attach the pv to the inverter that is throwing the error and see if it goes away?
Or possibly shifts to the other inverter?

That's a big fat maybe. The space is tight and the conduit is already run - Not sure if I can make it reach to the other unit. I also had thought about changing the 2P1/2P2 assignments as a test, but hadn't gotten to that yet. I think I'll go try that first.

Just went and changed the 2P1/2P2 assignments around. The old master (now slave) faulted again, so it's something specific to the unit, or it's the fact that it doesn't have PV input.

Is there some sort of master reset I can run on the units? I have only changed these two settings, but maybe starting from a fresh slate will correct the issue.

timthrifty said:

Just went and changed the 2P1/2P2 assignments around. The old master (now slave) faulted again, so it's something specific to the unit, or it's the fact that it doesn't have PV input.

Is there some sort of master reset I can run on the units? I have only changed these two settings, but maybe starting from a fresh slate will correct the issue.

Click to expand...

I am just going to get you on the phone with someone so we can try to get this worked out.

There isn't a master reset. But if you are making settings changes, I would advise doing a power cycle on the system. There is a good chance that you have everything right, but it hasn't taken effect.

The units have been turned off and on dozens of times, and between each flip-flop of settings.

ok heard. We're about to call you

So Signature Solar just called and is telling me that both units must have PV input and that the PV input can't be shared between the inverters. IE each unit must have input from a separate array. 6 inverters requires 6 separate arrays. This makes no sense to me. It's not mentioned anywhere in the manual, and the inverters will happily run all day long as long as they're not inverting. I had 2P2 charging the battery bank all day today, no faults.

I'm not saying he's wrong, but that makes no sense to me, and if it truly is the case, that needs to be mentioned in the manual, because it leaves me royally screwed and I'm sure I won't be the last...