Any thoughts on this problem? I just can't win

[foo1bar]

I bet that guy is jacked bc no doubt I'm doing the same thing to him

I doubt the guy 5 miles away who also has a PV system is going to be impacted by you or is going to impact you.
Maybe if it were a utility scale system (ie. 100kW+) it'd have enough impact on the grid, that you would notice it.

What it sounds like is you're still at the edge of being too high of voltage that it's causing your system to disconnect.

What did the POCO say was the voltage range they deliver to your house?
Is 252V within *their* spec?
What did the serviceman find when he came to your house? What was the voltage at that time? Is the POCO going to do anything / make any changes? If so, what?

I'd consider getting a TED5000 or similar system hooking it up and having detailed data on just what the voltages actually are. (If you can get the data from your SMA inverter, great - if not, buy or rent something that can get the data and show you what the voltages are throughout the day.)

After you have answers from the POCO, you'll have an idea on what to do moving forward.

[bcroe]

That happened to me. The pair of 7.5KW inverters took turns knocking the other one
off line, because with both on the line terminals got up to 264VAC. Fix that by getting
the PoCo to lower their voltage, reduce the V rise with bigger wire at your end, or set
the voltage monitors (including line to neutral) to a higher value. Bruce Roe

These are your options. Enough talk already, which are you going to do? I fixed mine.

Bruce Roe

[oregon_phil]

A problem that appears intermittent probably isn't and will take a lot of time and effort to fix. Changes to the system will only confound things. There are so many inverter variables. Take a step back and look at the problem. Don't make any assumptions.

You have line voltage of 252VAC. The inverter has a default upper limit for reconnection to the grid of 127 VAC (254 VAC). As Bruce implies above, you have very little margin even for one inverter.

Theory: One inverter should connect to the grid and run full tilt. Proof: Run one inverter for a week, then run the other inverter for a week. Running an inverter for one day wouldn't be much of a proof for me. This will prove that each system can run on its own without errors/faults.

When two systems are turned on, that's when the problems start. It's the interaction of the two systems that is causing the problems; interaction problems are the most difficult problems to solve.

BUT, as others have said, 2 VAC rise in voltage from the second inverter at your panel is not beyond reason. 2VAC rise between legs or 1 VAC rise on each leg is totally reasonable. You should be able to explain this to a technical geek at the power company.

You can prove the line voltage theory to yourself by renting a data logging meter and hook it to your electrical panel. But the bottom line is that you need more line voltage margin. Get the line voltage lowered.

[Markyrocks69]

These are your options. Enough talk already, which are you going to do? I fixed mine.

Bruce Roe

I'm working on it. The idea of replacing the wiring is a nonstarter. I'd honestly rather revisit the idea of moving the inverters back inside the house. That would be kinda the nuclear option at this point. if I go that route it probably wouldn't be until next spring.

Like I said b4 I called the poco, they didn't seem too interested in doing anything. i applied for a gridguard code end of last week so I'm just kinda twirling my thumbs waiting on that. I know with the code I can change the reconnection limits and timed disconnects ect so I feel like if I get that I should be able to do what I need to get it working right.

Currently the system has been nerfed to 5kw per inverter and it seems to be working as intended at this level

[foo1bar]

Like I said b4 I called the poco, they didn't seem too interested in doing anything.

So what did they say in your followup calls?
I would be calling them once or twice a week until they responded with what they found and what they're going to do to rectify the situation. And I'd try to be as nice as possible to the person answering the phone, since they might be able to escalate it to the proper channels. And they're not the ones that are the decision makers for service calls, etc so it isn't their fault if the POCO doesn't respond..
After about 3 weeks, I'd send a certified letter if they didn't give a response.
And then I'd contact the Public Utilities Commission a few weeks later if they still didn't respond.