PV Voltage Being Limited by my new EG4 12000XP

[Joehaynie]

I’ve had my EG4 12000XP inverter installed for a couple of weeks, but I’ve noticed a troubling trend. The inverter itself seems to be limiting the voltage (and consequently the wattage) of both of my PV strings to 120V. The strings themselves (11 330W panels each) are actually generating over 400V. When the sun comes out every new day the voltage on my PV strings gets limited to 120V until I reset the PV switch at the inverter. Even then the voltage at the inverter is less than the voltage coming from the strings. By the next day it goes back to 120V and I have to reset it again. Here’s a short video demonstrating the problem.

So far it has stumped my friends at Signature Solar, though they are working on it. Anybody here have any idea what may be going on?

 

[jeeptj12]

They did tell me it was governed at 385VDC.

 

[Joehaynie]

They did tell me it was governed at 385VDC.

Well that, at least is good to know. Once I get the 120V limitation solved maybe I can reconfigure my strings to stay under 385VDC and use all my PV. Thank you!

 

[wpns]

Even then the voltage at the inverter is less than the voltage coming from the strings

Where are you measuring the voltage at the inverter and the voltage from the strings? Something doesn't make sense...

The 18Kpv has a "Start PV Volt" setting, maybe the MPPT is starting up and getting wedged at a low voltage and not tracking thereafter? Try setting it higher? IIRC someone said the new software can't be set to less than 200V, though mine (FAAB-1B1C) seems happy with 140, though they do get into the 250-450V range during the day.

 

[Ampster]

I am just speculating but I wonder what would happen if the OP reconfigured the strings now. Maybe the 120v thing is how the inverter protects itself from over voltage?

 

[Mattb4]

First off the Voc voltage will always drop towards Vmp and lower if insufficient sun is available to provide power once you turn on your AIO. You mention being cloudy in your video which could contribute to a low PV voltage under load. One other possibility is a bad connection that is causing high resistance such that as your AIO loads down the solar panels they can not maintain more than a minimum output.

I can not see that your AIO can set a low PV voltage since this is a function of loading the panels. They want to maintain Voc under no load and and max wattage when loaded down to Vmp.

 

[Joehaynie]

Where are you measuring the voltage at the inverter and the voltage from the strings? Something doesn't make sense...

The 18Kpv has a "Start PV Volt" setting, maybe the MPPT is starting up and getting wedged at a low voltage and not tracking thereafter? Try setting it higher? IIRC someone said the new software can't be set to less than 200V, though mine (FAAB-1B1C) seems happy with 140, though they do get into the 250-450V range during the day.

For the inverter I am measuring voltage at the screws that tighten the PV input cables. For the strings I’m measuring at the the DC breaker through which the string is running. The really strange thing (see the brief video) is that when the inverter throttles the string voltage down to 120V it impacts the voltage I am reading upstream at my DC breaker—it also reads 120V. Then, when I shut off the PV switch at the inverter my DC breaker goes back to reading 430V. I’m scratching my head over that one.

I am searching for a “Start PV Volt” setting on the 12000XP but not finding it.

 

[Joehaynie]

I am just speculating but I wonder what would happen if the OP reconfigured the strings now. Maybe the 120v thing is how the inverter protects itself from over voltage?

Thank you. I like the theory that the 120v thing is the inverter’s protection from over voltage. However, the 120v limitation start every morning at first-light so it would be strange for there to be too much voltage at that point. Also, what is the OP (I don’t know that term)?

 

[Quattrohead]

Bypass 1 panel in each string and see what happens. I feel like the inverter is sensing an overvoltage and maybe protecting itself by basically shorting the PV strings and such is the nature of PV panels they are somewhat self-limiting in a short circuit situation.
Do you have any RSD devices on your panels?

 

[Joehaynie]

First off the Voc voltage will always drop towards Vmp and lower if insufficient sun is available to provide power once you turn on your AIO. You mention being cloudy in your video which could contribute to a low PV voltage under load. One other possibility is a bad connection that is causing high resistance such that as your AIO loads down the solar panels they can not maintain more than a minimum output.

I can not see that your AIO can set a low PV voltage since this is a function of loading the panels. They want to maintain Voc under no load and and max wattage when loaded down to Vmp.

That makes sense that there would be a drop if there is insufficient sun. What seems wrong is that it stays at the 120v even when the sun is bright and strong. Also, this morning at first light I saw that the AIO was back to 120V so I reset the PV switch and I was getting 200+ volts even though it wasn’t strong enough yet to power the AIO.

You are right that the 12000XP doesn’t seem to have a setting for low PV voltage.

 

[Joehaynie]

Bypass 1 panel in each string and see what happens. I feel like the inverter is sensing an overvoltage and maybe protecting itself by basically shorting the PV strings and such is the nature of PV panels they are somewhat self-limiting in a short circuit situation.
Do you have any RSD devices on your panels?

I’ll try that. I don’t have any RDS devices.

This is probably unrelated, but during the first few days after installing the inverter I was getting no power out of one of the strings. I finally realized that I had my cables reversed on that string. I reversed the cables and that string started working at the inverter. I wonder if dealing with reversed polarity made the inverter go into some kind of protective mode.

 

[Ampster]

Also, what is the OP (I don’t know that term)?

Original Poster. I used that term to avoid confusion because other comments were between your original post and I did not want them to be confused and think I was responding to their post.

 

[Ampster]

..... Then, when I shut off the PV switch at the inverter my DC breaker goes back to reading 430V. I’m scratching my head over that one.

That is normal. There will always be voltage. In that case you are reading the open circuit voltage. At first light because the panels are cold overnight the voltage could go even higher because of the temperature coefficient. When the panels are connected to the MPPT controller, the voltage is being reduced by the MPPT algorithm.

 

[Mattb4]

I’ll try that. I don’t have any RDS devices.

This is probably unrelated, but during the first few days after installing the inverter I was getting no power out of one of the strings. I finally realized that I had my cables reversed on that string. I reversed the cables and that string started working at the inverter. I wonder if dealing with reversed polarity made the inverter go into some kind of protective mode.

Just a quick definition. Strings form an Array to one SCC. What you have is two Arrays each composed of 11 panels wired in series. So out of both your arrays you have the same issue of low PV voltage. The array that was wired in reverse polarity could have damaged its SCC associated with it but hard to see it would damage both of them.

Are the panels new?

 

[wpns]

Where are you measuring the voltage at the inverter and the voltage from the strings? Something doesn't make sense...

OK, I watched the video. You are not getting different voltages simultaneously, you are getting different voltages with and without the MPPT connected. This is normal.

The 120V is not normal.

 

[wpns]

Can you show the rest of the wiring between the two strings and the MPPT inputs? It looks like some of them are going through your breakers and some are not?

I am wondering, for instance, if the two strings are in parallel and the two MPPT inputs are fighting with each other

 

[Joehaynie]

Just a quick definition. Strings form an Array to one SCC. What you have is two Arrays each composed of 11 panels wired in series. So out of both your arrays you have the same issue of low PV voltage. The array that was wired in reverse polarity could have damaged its SCC associated with it but hard to see it would damage both of them.

Are the panels new?

Yes, new panels, but I’m interested to know in what way used ones might cause this kind of problem.

 

[Mattb4]

Used panels could have faults that cause one or more in series to not be consistent under loading (things heat up and open). If your AIO PVmin is 120vDC the SCC MPPT will attempt to maximize loading down to that voltage.

But with new panels that should not be the problem and certainly not in 2 separate Arrays. As WPNS says double check that you are not connecting the 2 arrays together somehow. Go methodically through all your connections.

 

[Joehaynie]

Can you show the rest of the wiring between the two strings and the MPPT inputs? It looks like some of them are going through your breakers and some are not?

I am wondering, for instance, if the two strings are in parallel and the two MPPT inputs are fighting with each other

I have the 4 cables from the 2 arrays running through a single conduit. The cables from the east array run to the top breaker and the ones from the west pass through to the lower breaker. All four cables then run into the inverter. Here are a couple of photos showing the details.

 

[wpns]

Can you get it to reset if you only open and then close one of the breakers instead of the switch on the inverter?

 

[Aether]

I am also having the same issue with the same inverter. Issue starts in the morning. It stays at 120V until I either turn off PV from EG4 Switch, or turn off PV at breaker. I have 1 series string that sits at 445v open circuit. It then goes to an appropriate ~365v or so on after the "reset".

I did receive an Email from the level 2 tech support team, mostly stating they are aware of the issue and may have a fix. But that was all that was stated for now. I will update here if they give me good advice or changes. Since this is an issue that can only be tested once each day essentially, this problem could take a long time to get figured out, unless i tarp down all my panels lol.

 

[Mattb4]

I am also having the same issue with the same inverter. Issue starts in the morning. It stays at 120V until I either turn off PV from EG4 Switch, or turn off PV at breaker. I have 1 series string that sits at 445v open circuit. It then goes to an appropriate ~365v or so on after the "reset".

I did receive an Email from the level 2 tech support team, mostly stating they are aware of the issue and may have a fix. ...

Hopefully it just involves software and not replacing the hardware.

 

[Aether]

@Joehaynie Since our Open Circuit Voltage is close to the same. I am going to reduce my series string down one panel for tomorrow morning to see how it performs. Worse thing is I just add it back in when I turn the system off, or maybe figure out somewhere the issue could be stemming from. So far I have had 5, out of 5 days since it was put into operation that this has been an issue, so any change could rule out other troubleshooting, even though we are staying well within the spec sheet. It might be worth doing a half string tomorrow on one of your sets to see if there is any change, if you have the wire length ability in your setup to do that.

 

[Robert Ibe]

I think Ampster has the answer , reduce your series string by 1 or 2 panels and see what happens.
I leave a minimum of 20% room for the VOC to account for cold mornings.

 

[Aether]

I think Ampster has the answer , reduce your series string by 1 or 2 panels and see what happens.
I leave a minimum of 20% room for the VOC to account for cold mornings.

This seems a bit odd for me to understand. In the morning, does the voltage not slowly creep up from 0? Also on some of the warmer days this week, I am unsure this is a problem here in Central FL. I could be wrong, and will test it anyways. I am more thinking the voltage is ramping up to 120v then stopping. It sits right at 120.0v Even during the middle of the day before the reset as well. If it was overloaded somehow, I think it would be safer for it to disconnect or not allow current to flow? I guess a lot of speculation there.