String inverter - one array vs multiple arrays (pros vs cons)

[jflorey2]

The optimizers absolutely can except when installed out of specifications. Just like the engine on my bike can move it easily and accelerate it nicely to speed, but if installed in a dump truck will not be able to move it.

Right. But if you install a small electric motor with a good inverter on the dump truck it won't burn out or anything - it will limit the current to the motor, and just not move the truck. It sounded like you were suggesting it could be damaged.

The problem is that the optimizers are limiting devices like a fuse. If you put too many amps on them then you have a problem.

Right - but from your descriptions in the past, they are fully functional and protected DC/DC converters that can create whatever voltage/current is needed by the system. And almost all DC/DC converters incorporate current limiting to prevent damage due to shorts and overloads. (Which I think is what you meant by "limiting device like a fuse." If they do that, then the inverter is protected.

The problem is not the communications but that the rating of the optimizers is exceeded. Why would you expect it to work when installed improperly? would you think you could connect 1 million watts? 1 billion watts? there is a limit that the manufacturer specifies and it has been exceeded by more than a little.

I wouldn't expect it to work and convert 1 billion watts. But if I connected 1 billion watts of solar to an SMA inverter (for example) it would just produce up to whatever it was rated to produce, and then limit. (As long as you keep DC voltages within its operating limits of course.)

In the case of the Solaredge inverter I could see it shutting down in that case, if the optimizers couldn't throttle back enough or something. But where would the damage come in? The optimizers have to be instructed to turn on and produce X volts. Why would the inverter instruct them to provide a damaging voltage or current?

[ButchDeal]

So damage can occur, but how can it be measured?

how can what be measured?

[arf88]

So damage can occur, but how can it be measured?

[ButchDeal]

Doesn't the inverter communicate with the optimizers to set appropriate voltages? Does a long string prevent this communication from working properly? I thought the optimizers defaulted to low or zero output if communications is not seen (to comply with rapid shutdown.)

The problem is that the optimizers are limiting devices like a fuse. If you put too many amps on them then you have a problem.
The problem is not the communications but that the rating of the optimizers is exceeded. Why would you expect it to work when installed improperly? would you think you could connect 1 million watts? 1 billion watts? there is a limit that the manufacturer specifies and it has been exceeded by more than a little.

[ButchDeal]

hmm, one would think the optimizer would have the ability to throttle the output based on feedback from the inverter before it reached that max limit. guess not.

Agree, just passing the message, they agreed to rewire it which is good enough for me for now. But would still like to understand why the damage could occur if there is a constant two way handshake between the optimizer and inverter which is supposed to do limiting.

The optimizers absolutely can except when installed out of specifications. Just like the engine on my bike can move it easily and accelerate it nicely to speed, but if installed in a dump truck will not be able to move it. There are specifications for the installation of a product and equipment and when you exceed the amperage ratting, things go badly.

[arf88]

The fail safe in the inverter controls the optimizers but if the string is out of range then they may likely be unable to limit the power properly.


This makes no since in an optimized system, this statement is talking about non-optimized strings.
The minimum number of optimizers is 8 per string. Earlier we thought that we were talking about a total of 16 which would bring it to minimal string lengths.

hmm, one would think the optimizer would have the ability to throttle the output based on feedback from the inverter before it reached that max limit. guess not.

Agree, just passing the message, they agreed to rewire it which is good enough for me for now. But would still like to understand why the damage could occur if there is a constant two way handshake between the optimizer and inverter which is supposed to do limiting.

[jflorey2]

primarily voided warranty, and potential damage.

Doesn't the inverter communicate with the optimizers to set appropriate voltages? Does a long string prevent this communication from working properly? I thought the optimizers defaulted to low or zero output if communications is not seen (to comply with rapid shutdown.)

[ButchDeal]

The installer responded that they would schedule to rewire it, but "both options 2 strings or one string are acceptable temperature effects on voltage and with fewer panels sometimes you have less voltage"

This makes no since in an optimized system, this statement is talking about non-optimized strings.
The minimum number of optimizers is 8 per string. Earlier we thought that we were talking about a total of 16 which would bring it to minimal string lengths.

[ButchDeal]

Great question, wouldn't the fail safe inside the inverter prevent damage? I assume clipping here would not apply b/c it is post input from the PV system.

The fail safe in the inverter controls the optimizers but if the string is out of range then they may likely be unable to limit the power properly.

[ButchDeal]

What will happen to the system if a string with too much wattage is installed, as in this case? Will it limit to the ratings of that string of the inverter, or will there be damage?

primarily voided warranty, and potential damage.

[arf88]

It doesnt matter if it ever ever ever ever reaches that wattage. It was installed incorrectly with a string that has too much wattage ( potential, stc, solar, whatever) on it.

The installer responded that they would schedule to rewire it, but "both options 2 strings or one string are acceptable temperature effects on voltage and with fewer panels sometimes you have less voltage"

I think it was mentioned earlier in this thread about panel voltage and minimum number of panels.

[arf88]

What will happen to the system if a string with too much wattage is installed, as in this case? Will it limit to the ratings of that string of the inverter, or will there be damage?

Great question, wouldn't the fail safe inside the inverter prevent damage? I assume clipping here would not apply b/c it is post input from the PV system.

[arf88]

It doesnt matter if it ever ever ever ever reaches that wattage. It was installed incorrectly with a string that has too much wattage ( potential, stc, solar, whatever) on it.

Got it, i sent the installer an email asking them to re-wire it. I hope i don't get resistance to this but will let you know what they say.

[jflorey2]

It doesnt matter if it ever ever ever ever reaches that wattage. It was installed incorrectly with a string that has too much wattage ( potential, stc, solar, whatever) on it.

What will happen to the system if a string with too much wattage is installed, as in this case? Will it limit to the ratings of that string of the inverter, or will there be damage?

[ButchDeal]

Even if the system has never reached the 5.7W peak output you are saying this is still a problem correct?

It doesnt matter if it ever ever ever ever reaches that wattage. It was installed incorrectly with a string that has too much wattage ( potential, stc, solar, whatever) on it.